// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/fs/nfs/inode.c
 *
 *  Copyright (C) 1992  Rick Sladkey
 *
 *  nfs inode and superblock handling functions
 *
 *  Modularised by Alan Cox <alan@lxorguk.ukuu.org.uk>, while hacking some
 *  experimental NFS changes. Modularisation taken straight from SYS5 fs.
 *
 *  Change to nfs_read_super() to permit NFS mounts to multi-homed hosts.
 *  J.S.Peatfield@damtp.cam.ac.uk
 *
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched/signal.h>
#include <linux/time.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/unistd.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/stats.h>
#include <linux/sunrpc/metrics.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/nfs4_mount.h>
#include <linux/lockd/bind.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <linux/inet.h>
#include <linux/nfs_xdr.h>
#include <linux/slab.h>
#include <linux/compat.h>
#include <linux/freezer.h>
#include <linux/uaccess.h>
#include <linux/iversion.h>

#include "nfs4_fs.h"
#include "callback.h"
#include "delegation.h"
#include "iostat.h"
#include "internal.h"
#include "fscache.h"
#include "pnfs.h"
#include "nfs.h"
#include "netns.h"
#include "sysfs.h"

#include "nfstrace.h"

#define NFSDBG_FACILITY         NFSDBG_VFS

#define NFS_64_BIT_INODE_NUMBERS_ENABLED        1

/* Default is to see 64-bit inode numbers */
static bool enable_ino64 = NFS_64_BIT_INODE_NUMBERS_ENABLED;

static int nfs_update_inode(struct inode *, struct nfs_fattr *);

static struct kmem_cache * nfs_inode_cachep;

static inline unsigned long
nfs_fattr_to_ino_t(struct nfs_fattr *fattr)
{
        return nfs_fileid_to_ino_t(fattr->fileid);
}

static int nfs_wait_killable(int mode)
{
        freezable_schedule_unsafe();
        if (signal_pending_state(mode, current))
                return -ERESTARTSYS;
        return 0;
}

int nfs_wait_bit_killable(struct wait_bit_key *key, int mode)
{
        return nfs_wait_killable(mode);
}
EXPORT_SYMBOL_GPL(nfs_wait_bit_killable);

/**
 * nfs_compat_user_ino64 - returns the user-visible inode number
 * @fileid: 64-bit fileid
 *
 * This function returns a 32-bit inode number if the boot parameter
 * nfs.enable_ino64 is zero.
 */
u64 nfs_compat_user_ino64(u64 fileid)
{
#ifdef CONFIG_COMPAT
        compat_ulong_t ino;
#else   
        unsigned long ino;
#endif

        if (enable_ino64)
                return fileid;
        ino = fileid;
        if (sizeof(ino) < sizeof(fileid))
                ino ^= fileid >> (sizeof(fileid)-sizeof(ino)) * 8;
        return ino;
}

int nfs_drop_inode(struct inode *inode)
{
        return NFS_STALE(inode) || generic_drop_inode(inode);
}
EXPORT_SYMBOL_GPL(nfs_drop_inode);

void nfs_clear_inode(struct inode *inode)
{
        /*
         * The following should never happen...
         */
        WARN_ON_ONCE(nfs_have_writebacks(inode));
        WARN_ON_ONCE(!list_empty(&NFS_I(inode)->open_files));
        nfs_zap_acl_cache(inode);
        nfs_access_zap_cache(inode);
        nfs_fscache_clear_inode(inode);
}
EXPORT_SYMBOL_GPL(nfs_clear_inode);

void nfs_evict_inode(struct inode *inode)
{
        truncate_inode_pages_final(&inode->i_data);
        clear_inode(inode);
        nfs_clear_inode(inode);
}

int nfs_sync_inode(struct inode *inode)
{
        inode_dio_wait(inode);
        return nfs_wb_all(inode);
}
EXPORT_SYMBOL_GPL(nfs_sync_inode);

/**
 * nfs_sync_mapping - helper to flush all mmapped dirty data to disk
 * @mapping: pointer to struct address_space
 */
int nfs_sync_mapping(struct address_space *mapping)
{
        int ret = 0;

        if (mapping->nrpages != 0) {
                unmap_mapping_range(mapping, 0, 0, 0);
                ret = nfs_wb_all(mapping->host);
        }
        return ret;
}

static int nfs_attribute_timeout(struct inode *inode)
{
        struct nfs_inode *nfsi = NFS_I(inode);

        return !time_in_range_open(jiffies, nfsi->read_cache_jiffies, nfsi->read_cache_jiffies + nfsi->attrtimeo);
}

static bool nfs_check_cache_flags_invalid(struct inode *inode,
                                          unsigned long flags)
{
        unsigned long cache_validity = READ_ONCE(NFS_I(inode)->cache_validity);

        return (cache_validity & flags) != 0;
}

bool nfs_check_cache_invalid(struct inode *inode, unsigned long flags)
{
        if (nfs_check_cache_flags_invalid(inode, flags))
                return true;
        return nfs_attribute_cache_expired(inode);
}
EXPORT_SYMBOL_GPL(nfs_check_cache_invalid);

#ifdef CONFIG_NFS_V4_2
static bool nfs_has_xattr_cache(const struct nfs_inode *nfsi)
{
        return nfsi->xattr_cache != NULL;
}
#else
static bool nfs_has_xattr_cache(const struct nfs_inode *nfsi)
{
        return false;
}
#endif

void nfs_set_cache_invalid(struct inode *inode, unsigned long flags)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        bool have_delegation = NFS_PROTO(inode)->have_delegation(inode, FMODE_READ);

        if (have_delegation) {
                if (!(flags & NFS_INO_REVAL_FORCED))
                        flags &= ~(NFS_INO_INVALID_MODE |
                                   NFS_INO_INVALID_OTHER |
                                   NFS_INO_INVALID_XATTR);
                flags &= ~(NFS_INO_INVALID_CHANGE | NFS_INO_INVALID_SIZE);
        } else if (flags & NFS_INO_REVAL_PAGECACHE)
                flags |= NFS_INO_INVALID_CHANGE | NFS_INO_INVALID_SIZE;

        if (!nfs_has_xattr_cache(nfsi))
                flags &= ~NFS_INO_INVALID_XATTR;
        if (flags & NFS_INO_INVALID_DATA)
                nfs_fscache_invalidate(inode);
        if (inode->i_mapping->nrpages == 0)
                flags &= ~(NFS_INO_INVALID_DATA|NFS_INO_DATA_INVAL_DEFER);
        flags &= ~(NFS_INO_REVAL_PAGECACHE | NFS_INO_REVAL_FORCED);
        nfsi->cache_validity |= flags;
}
EXPORT_SYMBOL_GPL(nfs_set_cache_invalid);

/*
 * Invalidate the local caches
 */
static void nfs_zap_caches_locked(struct inode *inode)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        int mode = inode->i_mode;

        nfs_inc_stats(inode, NFSIOS_ATTRINVALIDATE);

        nfsi->attrtimeo = NFS_MINATTRTIMEO(inode);
        nfsi->attrtimeo_timestamp = jiffies;

        if (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)) {
                nfs_set_cache_invalid(inode, NFS_INO_INVALID_ATTR
                                        | NFS_INO_INVALID_DATA
                                        | NFS_INO_INVALID_ACCESS
                                        | NFS_INO_INVALID_ACL
                                        | NFS_INO_INVALID_XATTR
                                        | NFS_INO_REVAL_PAGECACHE);
        } else
                nfs_set_cache_invalid(inode, NFS_INO_INVALID_ATTR
                                        | NFS_INO_INVALID_ACCESS
                                        | NFS_INO_INVALID_ACL
                                        | NFS_INO_INVALID_XATTR
                                        | NFS_INO_REVAL_PAGECACHE);
        nfs_zap_label_cache_locked(nfsi);
}

void nfs_zap_caches(struct inode *inode)
{
        spin_lock(&inode->i_lock);
        nfs_zap_caches_locked(inode);
        spin_unlock(&inode->i_lock);
}

void nfs_zap_mapping(struct inode *inode, struct address_space *mapping)
{
        if (mapping->nrpages != 0) {
                spin_lock(&inode->i_lock);
                nfs_set_cache_invalid(inode, NFS_INO_INVALID_DATA);
                spin_unlock(&inode->i_lock);
        }
}

void nfs_zap_acl_cache(struct inode *inode)
{
        void (*clear_acl_cache)(struct inode *);

        clear_acl_cache = NFS_PROTO(inode)->clear_acl_cache;
        if (clear_acl_cache != NULL)
                clear_acl_cache(inode);
        spin_lock(&inode->i_lock);
        NFS_I(inode)->cache_validity &= ~NFS_INO_INVALID_ACL;
        spin_unlock(&inode->i_lock);
}
EXPORT_SYMBOL_GPL(nfs_zap_acl_cache);

void nfs_invalidate_atime(struct inode *inode)
{
        spin_lock(&inode->i_lock);
        nfs_set_cache_invalid(inode, NFS_INO_INVALID_ATIME);
        spin_unlock(&inode->i_lock);
}
EXPORT_SYMBOL_GPL(nfs_invalidate_atime);

/*
 * Invalidate, but do not unhash, the inode.
 * NB: must be called with inode->i_lock held!
 */
static void nfs_set_inode_stale_locked(struct inode *inode)
{
        set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
        nfs_zap_caches_locked(inode);
        trace_nfs_set_inode_stale(inode);
}

void nfs_set_inode_stale(struct inode *inode)
{
        spin_lock(&inode->i_lock);
        nfs_set_inode_stale_locked(inode);
        spin_unlock(&inode->i_lock);
}

struct nfs_find_desc {
        struct nfs_fh           *fh;
        struct nfs_fattr        *fattr;
};

/*
 * In NFSv3 we can have 64bit inode numbers. In order to support
 * this, and re-exported directories (also seen in NFSv2)
 * we are forced to allow 2 different inodes to have the same
 * i_ino.
 */
static int
nfs_find_actor(struct inode *inode, void *opaque)
{
        struct nfs_find_desc    *desc = (struct nfs_find_desc *)opaque;
        struct nfs_fh           *fh = desc->fh;
        struct nfs_fattr        *fattr = desc->fattr;

        if (NFS_FILEID(inode) != fattr->fileid)
                return 0;
        if (inode_wrong_type(inode, fattr->mode))
                return 0;
        if (nfs_compare_fh(NFS_FH(inode), fh))
                return 0;
        if (is_bad_inode(inode) || NFS_STALE(inode))
                return 0;
        return 1;
}

static int
nfs_init_locked(struct inode *inode, void *opaque)
{
        struct nfs_find_desc    *desc = (struct nfs_find_desc *)opaque;
        struct nfs_fattr        *fattr = desc->fattr;

        set_nfs_fileid(inode, fattr->fileid);
        inode->i_mode = fattr->mode;
        nfs_copy_fh(NFS_FH(inode), desc->fh);
        return 0;
}

#ifdef CONFIG_NFS_V4_SECURITY_LABEL
static void nfs_clear_label_invalid(struct inode *inode)
{
        spin_lock(&inode->i_lock);
        NFS_I(inode)->cache_validity &= ~NFS_INO_INVALID_LABEL;
        spin_unlock(&inode->i_lock);
}

void nfs_setsecurity(struct inode *inode, struct nfs_fattr *fattr,
                                        struct nfs4_label *label)
{
        int error;

        if (label == NULL)
                return;

        if ((fattr->valid & NFS_ATTR_FATTR_V4_SECURITY_LABEL) && inode->i_security) {
                error = security_inode_notifysecctx(inode, label->label,
                                label->len);
                if (error)
                        printk(KERN_ERR "%s() %s %d "
                                        "security_inode_notifysecctx() %d\n",
                                        __func__,
                                        (char *)label->label,
                                        label->len, error);
                nfs_clear_label_invalid(inode);
        }
}

struct nfs4_label *nfs4_label_alloc(struct nfs_server *server, gfp_t flags)
{
        struct nfs4_label *label = NULL;
        int minor_version = server->nfs_client->cl_minorversion;

        if (minor_version < 2)
                return label;

        if (!(server->caps & NFS_CAP_SECURITY_LABEL))
                return label;

        label = kzalloc(sizeof(struct nfs4_label), flags);
        if (label == NULL)
                return ERR_PTR(-ENOMEM);

        label->label = kzalloc(NFS4_MAXLABELLEN, flags);
        if (label->label == NULL) {
                kfree(label);
                return ERR_PTR(-ENOMEM);
        }
        label->len = NFS4_MAXLABELLEN;

        return label;
}
EXPORT_SYMBOL_GPL(nfs4_label_alloc);
#else
void nfs_setsecurity(struct inode *inode, struct nfs_fattr *fattr,
                                        struct nfs4_label *label)
{
}
#endif
EXPORT_SYMBOL_GPL(nfs_setsecurity);

/* Search for inode identified by fh, fileid and i_mode in inode cache. */
struct inode *
nfs_ilookup(struct super_block *sb, struct nfs_fattr *fattr, struct nfs_fh *fh)
{
        struct nfs_find_desc desc = {
                .fh     = fh,
                .fattr  = fattr,
        };
        struct inode *inode;
        unsigned long hash;

        if (!(fattr->valid & NFS_ATTR_FATTR_FILEID) ||
            !(fattr->valid & NFS_ATTR_FATTR_TYPE))
                return NULL;

        hash = nfs_fattr_to_ino_t(fattr);
        inode = ilookup5(sb, hash, nfs_find_actor, &desc);

        dprintk("%s: returning %p\n", __func__, inode);
        return inode;
}

/*
 * This is our front-end to iget that looks up inodes by file handle
 * instead of inode number.
 */
struct inode *
nfs_fhget(struct super_block *sb, struct nfs_fh *fh, struct nfs_fattr *fattr, struct nfs4_label *label)
{
        struct nfs_find_desc desc = {
                .fh     = fh,
                .fattr  = fattr
        };
        struct inode *inode = ERR_PTR(-ENOENT);
        u64 fattr_supported = NFS_SB(sb)->fattr_valid;
        unsigned long hash;

        nfs_attr_check_mountpoint(sb, fattr);

        if (nfs_attr_use_mounted_on_fileid(fattr))
                fattr->fileid = fattr->mounted_on_fileid;
        else if ((fattr->valid & NFS_ATTR_FATTR_FILEID) == 0)
                goto out_no_inode;
        if ((fattr->valid & NFS_ATTR_FATTR_TYPE) == 0)
                goto out_no_inode;

        hash = nfs_fattr_to_ino_t(fattr);

        inode = iget5_locked(sb, hash, nfs_find_actor, nfs_init_locked, &desc);
        if (inode == NULL) {
                inode = ERR_PTR(-ENOMEM);
                goto out_no_inode;
        }

        if (inode->i_state & I_NEW) {
                struct nfs_inode *nfsi = NFS_I(inode);
                unsigned long now = jiffies;

                /* We set i_ino for the few things that still rely on it,
                 * such as stat(2) */
                inode->i_ino = hash;

                /* We can't support update_atime(), since the server will reset it */
                inode->i_flags |= S_NOATIME|S_NOCMTIME;
                inode->i_mode = fattr->mode;
                nfsi->cache_validity = 0;
                if ((fattr->valid & NFS_ATTR_FATTR_MODE) == 0
                                && (fattr_supported & NFS_ATTR_FATTR_MODE))
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_MODE);
                /* Why so? Because we want revalidate for devices/FIFOs, and
                 * that's precisely what we have in nfs_file_inode_operations.
                 */
                inode->i_op = NFS_SB(sb)->nfs_client->rpc_ops->file_inode_ops;
                if (S_ISREG(inode->i_mode)) {
                        inode->i_fop = NFS_SB(sb)->nfs_client->rpc_ops->file_ops;
                        inode->i_data.a_ops = &nfs_file_aops;
                } else if (S_ISDIR(inode->i_mode)) {
                        inode->i_op = NFS_SB(sb)->nfs_client->rpc_ops->dir_inode_ops;
                        inode->i_fop = &nfs_dir_operations;
                        inode->i_data.a_ops = &nfs_dir_aops;
                        /* Deal with crossing mountpoints */
                        if (fattr->valid & NFS_ATTR_FATTR_MOUNTPOINT ||
                                        fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
                                if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
                                        inode->i_op = &nfs_referral_inode_operations;
                                else
                                        inode->i_op = &nfs_mountpoint_inode_operations;
                                inode->i_fop = NULL;
                                inode->i_flags |= S_AUTOMOUNT;
                        }
                } else if (S_ISLNK(inode->i_mode)) {
                        inode->i_op = &nfs_symlink_inode_operations;
                        inode_nohighmem(inode);
                } else
                        init_special_inode(inode, inode->i_mode, fattr->rdev);

                memset(&inode->i_atime, 0, sizeof(inode->i_atime));
                memset(&inode->i_mtime, 0, sizeof(inode->i_mtime));
                memset(&inode->i_ctime, 0, sizeof(inode->i_ctime));
                inode_set_iversion_raw(inode, 0);
                inode->i_size = 0;
                clear_nlink(inode);
                inode->i_uid = make_kuid(&init_user_ns, -2);
                inode->i_gid = make_kgid(&init_user_ns, -2);
                inode->i_blocks = 0;
                memset(nfsi->cookieverf, 0, sizeof(nfsi->cookieverf));
                nfsi->write_io = 0;
                nfsi->read_io = 0;

                nfsi->read_cache_jiffies = fattr->time_start;
                nfsi->attr_gencount = fattr->gencount;
                if (fattr->valid & NFS_ATTR_FATTR_ATIME)
                        inode->i_atime = fattr->atime;
                else if (fattr_supported & NFS_ATTR_FATTR_ATIME)
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_ATIME);
                if (fattr->valid & NFS_ATTR_FATTR_MTIME)
                        inode->i_mtime = fattr->mtime;
                else if (fattr_supported & NFS_ATTR_FATTR_MTIME)
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_MTIME);
                if (fattr->valid & NFS_ATTR_FATTR_CTIME)
                        inode->i_ctime = fattr->ctime;
                else if (fattr_supported & NFS_ATTR_FATTR_CTIME)
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_CTIME);
                if (fattr->valid & NFS_ATTR_FATTR_CHANGE)
                        inode_set_iversion_raw(inode, fattr->change_attr);
                else
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_CHANGE);
                if (fattr->valid & NFS_ATTR_FATTR_SIZE)
                        inode->i_size = nfs_size_to_loff_t(fattr->size);
                else
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_SIZE);
                if (fattr->valid & NFS_ATTR_FATTR_NLINK)
                        set_nlink(inode, fattr->nlink);
                else if (fattr_supported & NFS_ATTR_FATTR_NLINK)
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_NLINK);
                if (fattr->valid & NFS_ATTR_FATTR_OWNER)
                        inode->i_uid = fattr->uid;
                else if (fattr_supported & NFS_ATTR_FATTR_OWNER)
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_OTHER);
                if (fattr->valid & NFS_ATTR_FATTR_GROUP)
                        inode->i_gid = fattr->gid;
                else if (fattr_supported & NFS_ATTR_FATTR_GROUP)
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_OTHER);
                if (nfs_server_capable(inode, NFS_CAP_XATTR))
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_XATTR);
                if (fattr->valid & NFS_ATTR_FATTR_BLOCKS_USED)
                        inode->i_blocks = fattr->du.nfs2.blocks;
                else if (fattr_supported & NFS_ATTR_FATTR_BLOCKS_USED &&
                         fattr->size != 0)
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_BLOCKS);
                if (fattr->valid & NFS_ATTR_FATTR_SPACE_USED) {
                        /*
                         * report the blocks in 512byte units
                         */
                        inode->i_blocks = nfs_calc_block_size(fattr->du.nfs3.used);
                } else if (fattr_supported & NFS_ATTR_FATTR_SPACE_USED &&
                           fattr->size != 0)
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_BLOCKS);

                nfs_setsecurity(inode, fattr, label);

                nfsi->attrtimeo = NFS_MINATTRTIMEO(inode);
                nfsi->attrtimeo_timestamp = now;
                nfsi->access_cache = RB_ROOT;

                nfs_fscache_init_inode(inode);

                unlock_new_inode(inode);
        } else {
                int err = nfs_refresh_inode(inode, fattr);
                if (err < 0) {
                        iput(inode);
                        inode = ERR_PTR(err);
                        goto out_no_inode;
                }
        }
        dprintk("NFS: nfs_fhget(%s/%Lu fh_crc=0x%08x ct=%d)\n",
                inode->i_sb->s_id,
                (unsigned long long)NFS_FILEID(inode),
                nfs_display_fhandle_hash(fh),
                atomic_read(&inode->i_count));

out:
        return inode;

out_no_inode:
        dprintk("nfs_fhget: iget failed with error %ld\n", PTR_ERR(inode));
        goto out;
}
EXPORT_SYMBOL_GPL(nfs_fhget);

#define NFS_VALID_ATTRS (ATTR_MODE|ATTR_UID|ATTR_GID|ATTR_SIZE|ATTR_ATIME|ATTR_ATIME_SET|ATTR_MTIME|ATTR_MTIME_SET|ATTR_FILE|ATTR_OPEN)

int
nfs_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
            struct iattr *attr)
{
        struct inode *inode = d_inode(dentry);
        struct nfs_fattr *fattr;
        int error = 0;

        nfs_inc_stats(inode, NFSIOS_VFSSETATTR);

        /* skip mode change if it's just for clearing setuid/setgid */
        if (attr->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID))
                attr->ia_valid &= ~ATTR_MODE;

        if (attr->ia_valid & ATTR_SIZE) {
                BUG_ON(!S_ISREG(inode->i_mode));

                error = inode_newsize_ok(inode, attr->ia_size);
                if (error)
                        return error;

                if (attr->ia_size == i_size_read(inode))
                        attr->ia_valid &= ~ATTR_SIZE;
        }

        /* Optimization: if the end result is no change, don't RPC */
        if (((attr->ia_valid & NFS_VALID_ATTRS) & ~(ATTR_FILE|ATTR_OPEN)) == 0)
                return 0;

        trace_nfs_setattr_enter(inode);

        /* Write all dirty data */
        if (S_ISREG(inode->i_mode))
                nfs_sync_inode(inode);

        fattr = nfs_alloc_fattr();
        if (fattr == NULL) {
                error = -ENOMEM;
                goto out;
        }

        error = NFS_PROTO(inode)->setattr(dentry, fattr, attr);
        if (error == 0)
                error = nfs_refresh_inode(inode, fattr);
        nfs_free_fattr(fattr);
out:
        trace_nfs_setattr_exit(inode, error);
        return error;
}
EXPORT_SYMBOL_GPL(nfs_setattr);

/**
 * nfs_vmtruncate - unmap mappings "freed" by truncate() syscall
 * @inode: inode of the file used
 * @offset: file offset to start truncating
 *
 * This is a copy of the common vmtruncate, but with the locking
 * corrected to take into account the fact that NFS requires
 * inode->i_size to be updated under the inode->i_lock.
 * Note: must be called with inode->i_lock held!
 */
static int nfs_vmtruncate(struct inode * inode, loff_t offset)
{
        int err;

        err = inode_newsize_ok(inode, offset);
        if (err)
                goto out;

        i_size_write(inode, offset);
        /* Optimisation */
        if (offset == 0)
                NFS_I(inode)->cache_validity &= ~(NFS_INO_INVALID_DATA |
                                NFS_INO_DATA_INVAL_DEFER);
        NFS_I(inode)->cache_validity &= ~NFS_INO_INVALID_SIZE;

        spin_unlock(&inode->i_lock);
        truncate_pagecache(inode, offset);
        spin_lock(&inode->i_lock);
out:
        return err;
}

/**
 * nfs_setattr_update_inode - Update inode metadata after a setattr call.
 * @inode: pointer to struct inode
 * @attr: pointer to struct iattr
 * @fattr: pointer to struct nfs_fattr
 *
 * Note: we do this in the *proc.c in order to ensure that
 *       it works for things like exclusive creates too.
 */
void nfs_setattr_update_inode(struct inode *inode, struct iattr *attr,
                struct nfs_fattr *fattr)
{
        /* Barrier: bump the attribute generation count. */
        nfs_fattr_set_barrier(fattr);

        spin_lock(&inode->i_lock);
        NFS_I(inode)->attr_gencount = fattr->gencount;
        if ((attr->ia_valid & ATTR_SIZE) != 0) {
                nfs_set_cache_invalid(inode, NFS_INO_INVALID_MTIME |
                                                     NFS_INO_INVALID_BLOCKS);
                nfs_inc_stats(inode, NFSIOS_SETATTRTRUNC);
                nfs_vmtruncate(inode, attr->ia_size);
        }
        if ((attr->ia_valid & (ATTR_MODE|ATTR_UID|ATTR_GID)) != 0) {
                NFS_I(inode)->cache_validity &= ~NFS_INO_INVALID_CTIME;
                if ((attr->ia_valid & ATTR_KILL_SUID) != 0 &&
                    inode->i_mode & S_ISUID)
                        inode->i_mode &= ~S_ISUID;
                if ((attr->ia_valid & ATTR_KILL_SGID) != 0 &&
                    (inode->i_mode & (S_ISGID | S_IXGRP)) ==
                     (S_ISGID | S_IXGRP))
                        inode->i_mode &= ~S_ISGID;
                if ((attr->ia_valid & ATTR_MODE) != 0) {
                        int mode = attr->ia_mode & S_IALLUGO;
                        mode |= inode->i_mode & ~S_IALLUGO;
                        inode->i_mode = mode;
                }
                if ((attr->ia_valid & ATTR_UID) != 0)
                        inode->i_uid = attr->ia_uid;
                if ((attr->ia_valid & ATTR_GID) != 0)
                        inode->i_gid = attr->ia_gid;
                if (fattr->valid & NFS_ATTR_FATTR_CTIME)
                        inode->i_ctime = fattr->ctime;
                else
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_CHANGE
                                        | NFS_INO_INVALID_CTIME);
                nfs_set_cache_invalid(inode, NFS_INO_INVALID_ACCESS
                                | NFS_INO_INVALID_ACL);
        }
        if (attr->ia_valid & (ATTR_ATIME_SET|ATTR_ATIME)) {
                NFS_I(inode)->cache_validity &= ~(NFS_INO_INVALID_ATIME
                                | NFS_INO_INVALID_CTIME);
                if (fattr->valid & NFS_ATTR_FATTR_ATIME)
                        inode->i_atime = fattr->atime;
                else if (attr->ia_valid & ATTR_ATIME_SET)
                        inode->i_atime = attr->ia_atime;
                else
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_ATIME);

                if (fattr->valid & NFS_ATTR_FATTR_CTIME)
                        inode->i_ctime = fattr->ctime;
                else
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_CHANGE
                                        | NFS_INO_INVALID_CTIME);
        }
        if (attr->ia_valid & (ATTR_MTIME_SET|ATTR_MTIME)) {
                NFS_I(inode)->cache_validity &= ~(NFS_INO_INVALID_MTIME
                                | NFS_INO_INVALID_CTIME);
                if (fattr->valid & NFS_ATTR_FATTR_MTIME)
                        inode->i_mtime = fattr->mtime;
                else if (attr->ia_valid & ATTR_MTIME_SET)
                        inode->i_mtime = attr->ia_mtime;
                else
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_MTIME);

                if (fattr->valid & NFS_ATTR_FATTR_CTIME)
                        inode->i_ctime = fattr->ctime;
                else
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_CHANGE
                                        | NFS_INO_INVALID_CTIME);
        }
        if (fattr->valid)
                nfs_update_inode(inode, fattr);
        spin_unlock(&inode->i_lock);
}
EXPORT_SYMBOL_GPL(nfs_setattr_update_inode);

static void nfs_readdirplus_parent_cache_miss(struct dentry *dentry)
{
        struct dentry *parent;

        if (!nfs_server_capable(d_inode(dentry), NFS_CAP_READDIRPLUS))
                return;
        parent = dget_parent(dentry);
        nfs_force_use_readdirplus(d_inode(parent));
        dput(parent);
}

static void nfs_readdirplus_parent_cache_hit(struct dentry *dentry)
{
        struct dentry *parent;

        if (!nfs_server_capable(d_inode(dentry), NFS_CAP_READDIRPLUS))
                return;
        parent = dget_parent(dentry);
        nfs_advise_use_readdirplus(d_inode(parent));
        dput(parent);
}

static u32 nfs_get_valid_attrmask(struct inode *inode)
{
        unsigned long cache_validity = READ_ONCE(NFS_I(inode)->cache_validity);
        u32 reply_mask = STATX_INO | STATX_TYPE;

        if (!(cache_validity & NFS_INO_INVALID_ATIME))
                reply_mask |= STATX_ATIME;
        if (!(cache_validity & NFS_INO_INVALID_CTIME))
                reply_mask |= STATX_CTIME;
        if (!(cache_validity & NFS_INO_INVALID_MTIME))
                reply_mask |= STATX_MTIME;
        if (!(cache_validity & NFS_INO_INVALID_SIZE))
                reply_mask |= STATX_SIZE;
        if (!(cache_validity & NFS_INO_INVALID_NLINK))
                reply_mask |= STATX_NLINK;
        if (!(cache_validity & NFS_INO_INVALID_MODE))
                reply_mask |= STATX_MODE;
        if (!(cache_validity & NFS_INO_INVALID_OTHER))
                reply_mask |= STATX_UID | STATX_GID;
        if (!(cache_validity & NFS_INO_INVALID_BLOCKS))
                reply_mask |= STATX_BLOCKS;
        return reply_mask;
}

int nfs_getattr(struct user_namespace *mnt_userns, const struct path *path,
                struct kstat *stat, u32 request_mask, unsigned int query_flags)
{
        struct inode *inode = d_inode(path->dentry);
        struct nfs_server *server = NFS_SERVER(inode);
        unsigned long cache_validity;
        int err = 0;
        bool force_sync = query_flags & AT_STATX_FORCE_SYNC;
        bool do_update = false;

        trace_nfs_getattr_enter(inode);

        request_mask &= STATX_TYPE | STATX_MODE | STATX_NLINK | STATX_UID |
                        STATX_GID | STATX_ATIME | STATX_MTIME | STATX_CTIME |
                        STATX_INO | STATX_SIZE | STATX_BLOCKS;

        if ((query_flags & AT_STATX_DONT_SYNC) && !force_sync) {
                nfs_readdirplus_parent_cache_hit(path->dentry);
                goto out_no_revalidate;
        }

        /* Flush out writes to the server in order to update c/mtime.  */
        if ((request_mask & (STATX_CTIME|STATX_MTIME)) &&
                        S_ISREG(inode->i_mode)) {
                err = filemap_write_and_wait(inode->i_mapping);
                if (err)
                        goto out;
        }

        /*
         * We may force a getattr if the user cares about atime.
         *
         * Note that we only have to check the vfsmount flags here:
         *  - NFS always sets S_NOATIME by so checking it would give a
         *    bogus result
         *  - NFS never sets SB_NOATIME or SB_NODIRATIME so there is
         *    no point in checking those.
         */
        if ((path->mnt->mnt_flags & MNT_NOATIME) ||
            ((path->mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode)))
                request_mask &= ~STATX_ATIME;

        /* Is the user requesting attributes that might need revalidation? */
        if (!(request_mask & (STATX_MODE|STATX_NLINK|STATX_ATIME|STATX_CTIME|
                                        STATX_MTIME|STATX_UID|STATX_GID|
                                        STATX_SIZE|STATX_BLOCKS)))
                goto out_no_revalidate;

        /* Check whether the cached attributes are stale */
        do_update |= force_sync || nfs_attribute_cache_expired(inode);
        cache_validity = READ_ONCE(NFS_I(inode)->cache_validity);
        do_update |= cache_validity & NFS_INO_INVALID_CHANGE;
        if (request_mask & STATX_ATIME)
                do_update |= cache_validity & NFS_INO_INVALID_ATIME;
        if (request_mask & STATX_CTIME)
                do_update |= cache_validity & NFS_INO_INVALID_CTIME;
        if (request_mask & STATX_MTIME)
                do_update |= cache_validity & NFS_INO_INVALID_MTIME;
        if (request_mask & STATX_SIZE)
                do_update |= cache_validity & NFS_INO_INVALID_SIZE;
        if (request_mask & STATX_NLINK)
                do_update |= cache_validity & NFS_INO_INVALID_NLINK;
        if (request_mask & STATX_MODE)
                do_update |= cache_validity & NFS_INO_INVALID_MODE;
        if (request_mask & (STATX_UID | STATX_GID))
                do_update |= cache_validity & NFS_INO_INVALID_OTHER;
        if (request_mask & STATX_BLOCKS)
                do_update |= cache_validity & NFS_INO_INVALID_BLOCKS;

        if (do_update) {
                /* Update the attribute cache */
                if (!(server->flags & NFS_MOUNT_NOAC))
                        nfs_readdirplus_parent_cache_miss(path->dentry);
                else
                        nfs_readdirplus_parent_cache_hit(path->dentry);
                err = __nfs_revalidate_inode(server, inode);
                if (err)
                        goto out;
        } else
                nfs_readdirplus_parent_cache_hit(path->dentry);
out_no_revalidate:
        /* Only return attributes that were revalidated. */
        stat->result_mask = nfs_get_valid_attrmask(inode) | request_mask;

        generic_fillattr(&init_user_ns, inode, stat);
        stat->ino = nfs_compat_user_ino64(NFS_FILEID(inode));
        if (S_ISDIR(inode->i_mode))
                stat->blksize = NFS_SERVER(inode)->dtsize;
out:
        trace_nfs_getattr_exit(inode, err);
        return err;
}
EXPORT_SYMBOL_GPL(nfs_getattr);

static void nfs_init_lock_context(struct nfs_lock_context *l_ctx)
{
        refcount_set(&l_ctx->count, 1);
        l_ctx->lockowner = current->files;
        INIT_LIST_HEAD(&l_ctx->list);
        atomic_set(&l_ctx->io_count, 0);
}

static struct nfs_lock_context *__nfs_find_lock_context(struct nfs_open_context *ctx)
{
        struct nfs_lock_context *pos;

        list_for_each_entry_rcu(pos, &ctx->lock_context.list, list) {
                if (pos->lockowner != current->files)
                        continue;
                if (refcount_inc_not_zero(&pos->count))
                        return pos;
        }
        return NULL;
}

struct nfs_lock_context *nfs_get_lock_context(struct nfs_open_context *ctx)
{
        struct nfs_lock_context *res, *new = NULL;
        struct inode *inode = d_inode(ctx->dentry);

        rcu_read_lock();
        res = __nfs_find_lock_context(ctx);
        rcu_read_unlock();
        if (res == NULL) {
                new = kmalloc(sizeof(*new), GFP_KERNEL);
                if (new == NULL)
                        return ERR_PTR(-ENOMEM);
                nfs_init_lock_context(new);
                spin_lock(&inode->i_lock);
                res = __nfs_find_lock_context(ctx);
                if (res == NULL) {
                        new->open_context = get_nfs_open_context(ctx);
                        if (new->open_context) {
                                list_add_tail_rcu(&new->list,
                                                &ctx->lock_context.list);
                                res = new;
                                new = NULL;
                        } else
                                res = ERR_PTR(-EBADF);
                }
                spin_unlock(&inode->i_lock);
                kfree(new);
        }
        return res;
}
EXPORT_SYMBOL_GPL(nfs_get_lock_context);

void nfs_put_lock_context(struct nfs_lock_context *l_ctx)
{
        struct nfs_open_context *ctx = l_ctx->open_context;
        struct inode *inode = d_inode(ctx->dentry);

        if (!refcount_dec_and_lock(&l_ctx->count, &inode->i_lock))
                return;
        list_del_rcu(&l_ctx->list);
        spin_unlock(&inode->i_lock);
        put_nfs_open_context(ctx);
        kfree_rcu(l_ctx, rcu_head);
}
EXPORT_SYMBOL_GPL(nfs_put_lock_context);

/**
 * nfs_close_context - Common close_context() routine NFSv2/v3
 * @ctx: pointer to context
 * @is_sync: is this a synchronous close
 *
 * Ensure that the attributes are up to date if we're mounted
 * with close-to-open semantics and we have cached data that will
 * need to be revalidated on open.
 */
void nfs_close_context(struct nfs_open_context *ctx, int is_sync)
{
        struct nfs_inode *nfsi;
        struct inode *inode;

        if (!(ctx->mode & FMODE_WRITE))
                return;
        if (!is_sync)
                return;
        inode = d_inode(ctx->dentry);
        if (NFS_PROTO(inode)->have_delegation(inode, FMODE_READ))
                return;
        nfsi = NFS_I(inode);
        if (inode->i_mapping->nrpages == 0)
                return;

        if (nfsi->cache_validity & NFS_INO_INVALID_DATA)
                return;
        if (!list_empty(&nfsi->open_files))
                return;
        if (NFS_SERVER(inode)->flags & NFS_MOUNT_NOCTO)
                return;
        nfs_revalidate_inode(inode,
                             NFS_INO_INVALID_CHANGE | NFS_INO_INVALID_SIZE);
}
EXPORT_SYMBOL_GPL(nfs_close_context);

struct nfs_open_context *alloc_nfs_open_context(struct dentry *dentry,
                                                fmode_t f_mode,
                                                struct file *filp)
{
        struct nfs_open_context *ctx;

        ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
        if (!ctx)
                return ERR_PTR(-ENOMEM);
        nfs_sb_active(dentry->d_sb);
        ctx->dentry = dget(dentry);
        if (filp)
                ctx->cred = get_cred(filp->f_cred);
        else
                ctx->cred = get_current_cred();
        ctx->ll_cred = NULL;
        ctx->state = NULL;
        ctx->mode = f_mode;
        ctx->flags = 0;
        ctx->error = 0;
        ctx->flock_owner = (fl_owner_t)filp;
        nfs_init_lock_context(&ctx->lock_context);
        ctx->lock_context.open_context = ctx;
        INIT_LIST_HEAD(&ctx->list);
        ctx->mdsthreshold = NULL;
        return ctx;
}
EXPORT_SYMBOL_GPL(alloc_nfs_open_context);

struct nfs_open_context *get_nfs_open_context(struct nfs_open_context *ctx)
{
        if (ctx != NULL && refcount_inc_not_zero(&ctx->lock_context.count))
                return ctx;
        return NULL;
}
EXPORT_SYMBOL_GPL(get_nfs_open_context);

static void __put_nfs_open_context(struct nfs_open_context *ctx, int is_sync)
{
        struct inode *inode = d_inode(ctx->dentry);
        struct super_block *sb = ctx->dentry->d_sb;

        if (!refcount_dec_and_test(&ctx->lock_context.count))
                return;
        if (!list_empty(&ctx->list)) {
                spin_lock(&inode->i_lock);
                list_del_rcu(&ctx->list);
                spin_unlock(&inode->i_lock);
        }
        if (inode != NULL)
                NFS_PROTO(inode)->close_context(ctx, is_sync);
        put_cred(ctx->cred);
        dput(ctx->dentry);
        nfs_sb_deactive(sb);
        put_rpccred(ctx->ll_cred);
        kfree(ctx->mdsthreshold);
        kfree_rcu(ctx, rcu_head);
}

void put_nfs_open_context(struct nfs_open_context *ctx)
{
        __put_nfs_open_context(ctx, 0);
}
EXPORT_SYMBOL_GPL(put_nfs_open_context);

static void put_nfs_open_context_sync(struct nfs_open_context *ctx)
{
        __put_nfs_open_context(ctx, 1);
}

/*
 * Ensure that mmap has a recent RPC credential for use when writing out
 * shared pages
 */
void nfs_inode_attach_open_context(struct nfs_open_context *ctx)
{
        struct inode *inode = d_inode(ctx->dentry);
        struct nfs_inode *nfsi = NFS_I(inode);

        spin_lock(&inode->i_lock);
        if (list_empty(&nfsi->open_files) &&
            (nfsi->cache_validity & NFS_INO_DATA_INVAL_DEFER))
                nfs_set_cache_invalid(inode, NFS_INO_INVALID_DATA |
                                                     NFS_INO_REVAL_FORCED);
        list_add_tail_rcu(&ctx->list, &nfsi->open_files);
        spin_unlock(&inode->i_lock);
}
EXPORT_SYMBOL_GPL(nfs_inode_attach_open_context);

void nfs_file_set_open_context(struct file *filp, struct nfs_open_context *ctx)
{
        filp->private_data = get_nfs_open_context(ctx);
        set_bit(NFS_CONTEXT_FILE_OPEN, &ctx->flags);
        if (list_empty(&ctx->list))
                nfs_inode_attach_open_context(ctx);
}
EXPORT_SYMBOL_GPL(nfs_file_set_open_context);

/*
 * Given an inode, search for an open context with the desired characteristics
 */
struct nfs_open_context *nfs_find_open_context(struct inode *inode, const struct cred *cred, fmode_t mode)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_open_context *pos, *ctx = NULL;

        rcu_read_lock();
        list_for_each_entry_rcu(pos, &nfsi->open_files, list) {
                if (cred != NULL && cred_fscmp(pos->cred, cred) != 0)
                        continue;
                if ((pos->mode & (FMODE_READ|FMODE_WRITE)) != mode)
                        continue;
                if (!test_bit(NFS_CONTEXT_FILE_OPEN, &pos->flags))
                        continue;
                ctx = get_nfs_open_context(pos);
                if (ctx)
                        break;
        }
        rcu_read_unlock();
        return ctx;
}

void nfs_file_clear_open_context(struct file *filp)
{
        struct nfs_open_context *ctx = nfs_file_open_context(filp);

        if (ctx) {
                struct inode *inode = d_inode(ctx->dentry);

                clear_bit(NFS_CONTEXT_FILE_OPEN, &ctx->flags);
                /*
                 * We fatal error on write before. Try to writeback
                 * every page again.
                 */
                if (ctx->error < 0)
                        invalidate_inode_pages2(inode->i_mapping);
                filp->private_data = NULL;
                put_nfs_open_context_sync(ctx);
        }
}

/*
 * These allocate and release file read/write context information.
 */
int nfs_open(struct inode *inode, struct file *filp)
{
        struct nfs_open_context *ctx;

        ctx = alloc_nfs_open_context(file_dentry(filp), filp->f_mode, filp);
        if (IS_ERR(ctx))
                return PTR_ERR(ctx);
        nfs_file_set_open_context(filp, ctx);
        put_nfs_open_context(ctx);
        nfs_fscache_open_file(inode, filp);
        return 0;
}
EXPORT_SYMBOL_GPL(nfs_open);

/*
 * This function is called whenever some part of NFS notices that
 * the cached attributes have to be refreshed.
 */
int
__nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
{
        int              status = -ESTALE;
        struct nfs4_label *label = NULL;
        struct nfs_fattr *fattr = NULL;
        struct nfs_inode *nfsi = NFS_I(inode);

        dfprintk(PAGECACHE, "NFS: revalidating (%s/%Lu)\n",
                inode->i_sb->s_id, (unsigned long long)NFS_FILEID(inode));

        trace_nfs_revalidate_inode_enter(inode);

        if (is_bad_inode(inode))
                goto out;
        if (NFS_STALE(inode))
                goto out;

        /* pNFS: Attributes aren't updated until we layoutcommit */
        if (S_ISREG(inode->i_mode)) {
                status = pnfs_sync_inode(inode, false);
                if (status)
                        goto out;
        }

        status = -ENOMEM;
        fattr = nfs_alloc_fattr();
        if (fattr == NULL)
                goto out;

        nfs_inc_stats(inode, NFSIOS_INODEREVALIDATE);

        label = nfs4_label_alloc(NFS_SERVER(inode), GFP_KERNEL);
        if (IS_ERR(label)) {
                status = PTR_ERR(label);
                goto out;
        }

        status = NFS_PROTO(inode)->getattr(server, NFS_FH(inode), fattr,
                        label, inode);
        if (status != 0) {
                dfprintk(PAGECACHE, "nfs_revalidate_inode: (%s/%Lu) getattr failed, error=%d\n",
                         inode->i_sb->s_id,
                         (unsigned long long)NFS_FILEID(inode), status);
                switch (status) {
                case -ETIMEDOUT:
                        /* A soft timeout occurred. Use cached information? */
                        if (server->flags & NFS_MOUNT_SOFTREVAL)
                                status = 0;
                        break;
                case -ESTALE:
                        if (!S_ISDIR(inode->i_mode))
                                nfs_set_inode_stale(inode);
                        else
                                nfs_zap_caches(inode);
                }
                goto err_out;
        }

        status = nfs_refresh_inode(inode, fattr);
        if (status) {
                dfprintk(PAGECACHE, "nfs_revalidate_inode: (%s/%Lu) refresh failed, error=%d\n",
                         inode->i_sb->s_id,
                         (unsigned long long)NFS_FILEID(inode), status);
                goto err_out;
        }

        if (nfsi->cache_validity & NFS_INO_INVALID_ACL)
                nfs_zap_acl_cache(inode);

        nfs_setsecurity(inode, fattr, label);

        dfprintk(PAGECACHE, "NFS: (%s/%Lu) revalidation complete\n",
                inode->i_sb->s_id,
                (unsigned long long)NFS_FILEID(inode));

err_out:
        nfs4_label_free(label);
out:
        nfs_free_fattr(fattr);
        trace_nfs_revalidate_inode_exit(inode, status);
        return status;
}

int nfs_attribute_cache_expired(struct inode *inode)
{
        if (nfs_have_delegated_attributes(inode))
                return 0;
        return nfs_attribute_timeout(inode);
}

/**
 * nfs_revalidate_inode - Revalidate the inode attributes
 * @inode: pointer to inode struct
 * @flags: cache flags to check
 *
 * Updates inode attribute information by retrieving the data from the server.
 */
int nfs_revalidate_inode(struct inode *inode, unsigned long flags)
{
        if (!nfs_check_cache_invalid(inode, flags))
                return NFS_STALE(inode) ? -ESTALE : 0;
        return __nfs_revalidate_inode(NFS_SERVER(inode), inode);
}
EXPORT_SYMBOL_GPL(nfs_revalidate_inode);

static int nfs_invalidate_mapping(struct inode *inode, struct address_space *mapping)
{
        int ret;

        if (mapping->nrpages != 0) {
                if (S_ISREG(inode->i_mode)) {
                        ret = nfs_sync_mapping(mapping);
                        if (ret < 0)
                                return ret;
                }
                ret = invalidate_inode_pages2(mapping);
                if (ret < 0)
                        return ret;
        }
        nfs_inc_stats(inode, NFSIOS_DATAINVALIDATE);
        nfs_fscache_wait_on_invalidate(inode);

        dfprintk(PAGECACHE, "NFS: (%s/%Lu) data cache invalidated\n",
                        inode->i_sb->s_id,
                        (unsigned long long)NFS_FILEID(inode));
        return 0;
}

/**
 * nfs_clear_invalid_mapping - Conditionally clear a mapping
 * @mapping: pointer to mapping
 *
 * If the NFS_INO_INVALID_DATA inode flag is set, clear the mapping.
 */
int nfs_clear_invalid_mapping(struct address_space *mapping)
{
        struct inode *inode = mapping->host;
        struct nfs_inode *nfsi = NFS_I(inode);
        unsigned long *bitlock = &nfsi->flags;
        int ret = 0;

        /*
         * We must clear NFS_INO_INVALID_DATA first to ensure that
         * invalidations that come in while we're shooting down the mappings
         * are respected. But, that leaves a race window where one revalidator
         * can clear the flag, and then another checks it before the mapping
         * gets invalidated. Fix that by serializing access to this part of
         * the function.
         *
         * At the same time, we need to allow other tasks to see whether we
         * might be in the middle of invalidating the pages, so we only set
         * the bit lock here if it looks like we're going to be doing that.
         */
        for (;;) {
                ret = wait_on_bit_action(bitlock, NFS_INO_INVALIDATING,
                                         nfs_wait_bit_killable, TASK_KILLABLE);
                if (ret)
                        goto out;
                spin_lock(&inode->i_lock);
                if (test_bit(NFS_INO_INVALIDATING, bitlock)) {
                        spin_unlock(&inode->i_lock);
                        continue;
                }
                if (nfsi->cache_validity & NFS_INO_INVALID_DATA)
                        break;
                spin_unlock(&inode->i_lock);
                goto out;
        }

        set_bit(NFS_INO_INVALIDATING, bitlock);
        smp_wmb();
        nfsi->cache_validity &=
                ~(NFS_INO_INVALID_DATA | NFS_INO_DATA_INVAL_DEFER);
        spin_unlock(&inode->i_lock);
        trace_nfs_invalidate_mapping_enter(inode);
        ret = nfs_invalidate_mapping(inode, mapping);
        trace_nfs_invalidate_mapping_exit(inode, ret);

        clear_bit_unlock(NFS_INO_INVALIDATING, bitlock);
        smp_mb__after_atomic();
        wake_up_bit(bitlock, NFS_INO_INVALIDATING);
out:
        return ret;
}

bool nfs_mapping_need_revalidate_inode(struct inode *inode)
{
        return nfs_check_cache_invalid(inode, NFS_INO_INVALID_CHANGE) ||
                NFS_STALE(inode);
}

int nfs_revalidate_mapping_rcu(struct inode *inode)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        unsigned long *bitlock = &nfsi->flags;
        int ret = 0;

        if (IS_SWAPFILE(inode))
                goto out;
        if (nfs_mapping_need_revalidate_inode(inode)) {
                ret = -ECHILD;
                goto out;
        }
        spin_lock(&inode->i_lock);
        if (test_bit(NFS_INO_INVALIDATING, bitlock) ||
            (nfsi->cache_validity & NFS_INO_INVALID_DATA))
                ret = -ECHILD;
        spin_unlock(&inode->i_lock);
out:
        return ret;
}

/**
 * nfs_revalidate_mapping - Revalidate the pagecache
 * @inode: pointer to host inode
 * @mapping: pointer to mapping
 */
int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping)
{
        /* swapfiles are not supposed to be shared. */
        if (IS_SWAPFILE(inode))
                return 0;

        if (nfs_mapping_need_revalidate_inode(inode)) {
                int ret = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
                if (ret < 0)
                        return ret;
        }

        return nfs_clear_invalid_mapping(mapping);
}

static bool nfs_file_has_writers(struct nfs_inode *nfsi)
{
        struct inode *inode = &nfsi->vfs_inode;

        if (!S_ISREG(inode->i_mode))
                return false;
        if (list_empty(&nfsi->open_files))
                return false;
        return inode_is_open_for_write(inode);
}

static bool nfs_file_has_buffered_writers(struct nfs_inode *nfsi)
{
        return nfs_file_has_writers(nfsi) && nfs_file_io_is_buffered(nfsi);
}

static void nfs_wcc_update_inode(struct inode *inode, struct nfs_fattr *fattr)
{
        struct timespec64 ts;

        if ((fattr->valid & NFS_ATTR_FATTR_PRECHANGE)
                        && (fattr->valid & NFS_ATTR_FATTR_CHANGE)
                        && inode_eq_iversion_raw(inode, fattr->pre_change_attr)) {
                inode_set_iversion_raw(inode, fattr->change_attr);
                if (S_ISDIR(inode->i_mode))
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_DATA);
                else if (nfs_server_capable(inode, NFS_CAP_XATTR))
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_XATTR);
        }
        /* If we have atomic WCC data, we may update some attributes */
        ts = inode->i_ctime;
        if ((fattr->valid & NFS_ATTR_FATTR_PRECTIME)
                        && (fattr->valid & NFS_ATTR_FATTR_CTIME)
                        && timespec64_equal(&ts, &fattr->pre_ctime)) {
                inode->i_ctime = fattr->ctime;
        }

        ts = inode->i_mtime;
        if ((fattr->valid & NFS_ATTR_FATTR_PREMTIME)
                        && (fattr->valid & NFS_ATTR_FATTR_MTIME)
                        && timespec64_equal(&ts, &fattr->pre_mtime)) {
                inode->i_mtime = fattr->mtime;
                if (S_ISDIR(inode->i_mode))
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_DATA);
        }
        if ((fattr->valid & NFS_ATTR_FATTR_PRESIZE)
                        && (fattr->valid & NFS_ATTR_FATTR_SIZE)
                        && i_size_read(inode) == nfs_size_to_loff_t(fattr->pre_size)
                        && !nfs_have_writebacks(inode)) {
                i_size_write(inode, nfs_size_to_loff_t(fattr->size));
        }
}

/**
 * nfs_check_inode_attributes - verify consistency of the inode attribute cache
 * @inode: pointer to inode
 * @fattr: updated attributes
 *
 * Verifies the attribute cache. If we have just changed the attributes,
 * so that fattr carries weak cache consistency data, then it may
 * also update the ctime/mtime/change_attribute.
 */
static int nfs_check_inode_attributes(struct inode *inode, struct nfs_fattr *fattr)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        loff_t cur_size, new_isize;
        unsigned long invalid = 0;
        struct timespec64 ts;

        if (NFS_PROTO(inode)->have_delegation(inode, FMODE_READ))
                return 0;

        if (!(fattr->valid & NFS_ATTR_FATTR_FILEID)) {
                /* Only a mounted-on-fileid? Just exit */
                if (fattr->valid & NFS_ATTR_FATTR_MOUNTED_ON_FILEID)
                        return 0;
        /* Has the inode gone and changed behind our back? */
        } else if (nfsi->fileid != fattr->fileid) {
                /* Is this perhaps the mounted-on fileid? */
                if ((fattr->valid & NFS_ATTR_FATTR_MOUNTED_ON_FILEID) &&
                    nfsi->fileid == fattr->mounted_on_fileid)
                        return 0;
                return -ESTALE;
        }
        if ((fattr->valid & NFS_ATTR_FATTR_TYPE) && inode_wrong_type(inode, fattr->mode))
                return -ESTALE;


        if (!nfs_file_has_buffered_writers(nfsi)) {
                /* Verify a few of the more important attributes */
                if ((fattr->valid & NFS_ATTR_FATTR_CHANGE) != 0 && !inode_eq_iversion_raw(inode, fattr->change_attr))
                        invalid |= NFS_INO_INVALID_CHANGE;

                ts = inode->i_mtime;
                if ((fattr->valid & NFS_ATTR_FATTR_MTIME) && !timespec64_equal(&ts, &fattr->mtime))
                        invalid |= NFS_INO_INVALID_MTIME;

                ts = inode->i_ctime;
                if ((fattr->valid & NFS_ATTR_FATTR_CTIME) && !timespec64_equal(&ts, &fattr->ctime))
                        invalid |= NFS_INO_INVALID_CTIME;

                if (fattr->valid & NFS_ATTR_FATTR_SIZE) {
                        cur_size = i_size_read(inode);
                        new_isize = nfs_size_to_loff_t(fattr->size);
                        if (cur_size != new_isize)
                                invalid |= NFS_INO_INVALID_SIZE;
                }
        }

        /* Have any file permissions changed? */
        if ((fattr->valid & NFS_ATTR_FATTR_MODE) && (inode->i_mode & S_IALLUGO) != (fattr->mode & S_IALLUGO))
                invalid |= NFS_INO_INVALID_MODE;
        if ((fattr->valid & NFS_ATTR_FATTR_OWNER) && !uid_eq(inode->i_uid, fattr->uid))
                invalid |= NFS_INO_INVALID_OTHER;
        if ((fattr->valid & NFS_ATTR_FATTR_GROUP) && !gid_eq(inode->i_gid, fattr->gid))
                invalid |= NFS_INO_INVALID_OTHER;

        /* Has the link count changed? */
        if ((fattr->valid & NFS_ATTR_FATTR_NLINK) && inode->i_nlink != fattr->nlink)
                invalid |= NFS_INO_INVALID_NLINK;

        ts = inode->i_atime;
        if ((fattr->valid & NFS_ATTR_FATTR_ATIME) && !timespec64_equal(&ts, &fattr->atime))
                invalid |= NFS_INO_INVALID_ATIME;

        if (invalid != 0)
                nfs_set_cache_invalid(inode, invalid);

        nfsi->read_cache_jiffies = fattr->time_start;
        return 0;
}

static atomic_long_t nfs_attr_generation_counter;

static unsigned long nfs_read_attr_generation_counter(void)
{
        return atomic_long_read(&nfs_attr_generation_counter);
}

unsigned long nfs_inc_attr_generation_counter(void)
{
        return atomic_long_inc_return(&nfs_attr_generation_counter);
}
EXPORT_SYMBOL_GPL(nfs_inc_attr_generation_counter);

void nfs_fattr_init(struct nfs_fattr *fattr)
{
        fattr->valid = 0;
        fattr->time_start = jiffies;
        fattr->gencount = nfs_inc_attr_generation_counter();
        fattr->owner_name = NULL;
        fattr->group_name = NULL;
}
EXPORT_SYMBOL_GPL(nfs_fattr_init);

/**
 * nfs_fattr_set_barrier
 * @fattr: attributes
 *
 * Used to set a barrier after an attribute was updated. This
 * barrier ensures that older attributes from RPC calls that may
 * have raced with our update cannot clobber these new values.
 * Note that you are still responsible for ensuring that other
 * operations which change the attribute on the server do not
 * collide.
 */
void nfs_fattr_set_barrier(struct nfs_fattr *fattr)
{
        fattr->gencount = nfs_inc_attr_generation_counter();
}

struct nfs_fattr *nfs_alloc_fattr(void)
{
        struct nfs_fattr *fattr;

        fattr = kmalloc(sizeof(*fattr), GFP_NOFS);
        if (fattr != NULL)
                nfs_fattr_init(fattr);
        return fattr;
}
EXPORT_SYMBOL_GPL(nfs_alloc_fattr);

struct nfs_fh *nfs_alloc_fhandle(void)
{
        struct nfs_fh *fh;

        fh = kmalloc(sizeof(struct nfs_fh), GFP_NOFS);
        if (fh != NULL)
                fh->size = 0;
        return fh;
}
EXPORT_SYMBOL_GPL(nfs_alloc_fhandle);

#ifdef NFS_DEBUG
/*
 * _nfs_display_fhandle_hash - calculate the crc32 hash for the filehandle
 *                             in the same way that wireshark does
 *
 * @fh: file handle
 *
 * For debugging only.
 */
u32 _nfs_display_fhandle_hash(const struct nfs_fh *fh)
{
        /* wireshark uses 32-bit AUTODIN crc and does a bitwise
         * not on the result */
        return nfs_fhandle_hash(fh);
}
EXPORT_SYMBOL_GPL(_nfs_display_fhandle_hash);

/*
 * _nfs_display_fhandle - display an NFS file handle on the console
 *
 * @fh: file handle to display
 * @caption: display caption
 *
 * For debugging only.
 */
void _nfs_display_fhandle(const struct nfs_fh *fh, const char *caption)
{
        unsigned short i;

        if (fh == NULL || fh->size == 0) {
                printk(KERN_DEFAULT "%s at %p is empty\n", caption, fh);
                return;
        }

        printk(KERN_DEFAULT "%s at %p is %u bytes, crc: 0x%08x:\n",
               caption, fh, fh->size, _nfs_display_fhandle_hash(fh));
        for (i = 0; i < fh->size; i += 16) {
                __be32 *pos = (__be32 *)&fh->data[i];

                switch ((fh->size - i - 1) >> 2) {
                case 0:
                        printk(KERN_DEFAULT " %08x\n",
                                be32_to_cpup(pos));
                        break;
                case 1:
                        printk(KERN_DEFAULT " %08x %08x\n",
                                be32_to_cpup(pos), be32_to_cpup(pos + 1));
                        break;
                case 2:
                        printk(KERN_DEFAULT " %08x %08x %08x\n",
                                be32_to_cpup(pos), be32_to_cpup(pos + 1),
                                be32_to_cpup(pos + 2));
                        break;
                default:
                        printk(KERN_DEFAULT " %08x %08x %08x %08x\n",
                                be32_to_cpup(pos), be32_to_cpup(pos + 1),
                                be32_to_cpup(pos + 2), be32_to_cpup(pos + 3));
                }
        }
}
EXPORT_SYMBOL_GPL(_nfs_display_fhandle);
#endif

/**
 * nfs_inode_attrs_cmp_generic - compare attributes
 * @fattr: attributes
 * @inode: pointer to inode
 *
 * Attempt to divine whether or not an RPC call reply carrying stale
 * attributes got scheduled after another call carrying updated ones.
 * Note also the check for wraparound of 'attr_gencount'
 *
 * The function returns '1' if it thinks the attributes in @fattr are
 * more recent than the ones cached in @inode. Otherwise it returns
 * the value '0'.
 */
static int nfs_inode_attrs_cmp_generic(const struct nfs_fattr *fattr,
                                       const struct inode *inode)
{
        unsigned long attr_gencount = NFS_I(inode)->attr_gencount;

        return (long)(fattr->gencount - attr_gencount) > 0 ||
               (long)(attr_gencount - nfs_read_attr_generation_counter()) > 0;
}

/**
 * nfs_inode_attrs_cmp_monotonic - compare attributes
 * @fattr: attributes
 * @inode: pointer to inode
 *
 * Attempt to divine whether or not an RPC call reply carrying stale
 * attributes got scheduled after another call carrying updated ones.
 *
 * We assume that the server observes monotonic semantics for
 * the change attribute, so a larger value means that the attributes in
 * @fattr are more recent, in which case the function returns the
 * value '1'.
 * A return value of '0' indicates no measurable change
 * A return value of '-1' means that the attributes in @inode are
 * more recent.
 */
static int nfs_inode_attrs_cmp_monotonic(const struct nfs_fattr *fattr,
                                         const struct inode *inode)
{
        s64 diff = fattr->change_attr - inode_peek_iversion_raw(inode);
        if (diff > 0)
                return 1;
        return diff == 0 ? 0 : -1;
}

/**
 * nfs_inode_attrs_cmp_strict_monotonic - compare attributes
 * @fattr: attributes
 * @inode: pointer to inode
 *
 * Attempt to divine whether or not an RPC call reply carrying stale
 * attributes got scheduled after another call carrying updated ones.
 *
 * We assume that the server observes strictly monotonic semantics for
 * the change attribute, so a larger value means that the attributes in
 * @fattr are more recent, in which case the function returns the
 * value '1'.
 * A return value of '-1' means that the attributes in @inode are
 * more recent or unchanged.
 */
static int nfs_inode_attrs_cmp_strict_monotonic(const struct nfs_fattr *fattr,
                                                const struct inode *inode)
{
        return  nfs_inode_attrs_cmp_monotonic(fattr, inode) > 0 ? 1 : -1;
}

/**
 * nfs_inode_attrs_cmp - compare attributes
 * @fattr: attributes
 * @inode: pointer to inode
 *
 * This function returns '1' if it thinks the attributes in @fattr are
 * more recent than the ones cached in @inode. It returns '-1' if
 * the attributes in @inode are more recent than the ones in @fattr,
 * and it returns 0 if not sure.
 */
static int nfs_inode_attrs_cmp(const struct nfs_fattr *fattr,
                               const struct inode *inode)
{
        if (nfs_inode_attrs_cmp_generic(fattr, inode) > 0)
                return 1;
        switch (NFS_SERVER(inode)->change_attr_type) {
        case NFS4_CHANGE_TYPE_IS_UNDEFINED:
                break;
        case NFS4_CHANGE_TYPE_IS_TIME_METADATA:
                if (!(fattr->valid & NFS_ATTR_FATTR_CHANGE))
                        break;
                return nfs_inode_attrs_cmp_monotonic(fattr, inode);
        default:
                if (!(fattr->valid & NFS_ATTR_FATTR_CHANGE))
                        break;
                return nfs_inode_attrs_cmp_strict_monotonic(fattr, inode);
        }
        return 0;
}

/**
 * nfs_inode_finish_partial_attr_update - complete a previous inode update
 * @fattr: attributes
 * @inode: pointer to inode
 *
 * Returns '1' if the last attribute update left the inode cached
 * attributes in a partially unrevalidated state, and @fattr
 * matches the change attribute of that partial update.
 * Otherwise returns '0'.
 */
static int nfs_inode_finish_partial_attr_update(const struct nfs_fattr *fattr,
                                                const struct inode *inode)
{
        const unsigned long check_valid =
                NFS_INO_INVALID_ATIME | NFS_INO_INVALID_CTIME |
                NFS_INO_INVALID_MTIME | NFS_INO_INVALID_SIZE |
                NFS_INO_INVALID_BLOCKS | NFS_INO_INVALID_OTHER |
                NFS_INO_INVALID_NLINK;
        unsigned long cache_validity = NFS_I(inode)->cache_validity;

        if (!(cache_validity & NFS_INO_INVALID_CHANGE) &&
            (cache_validity & check_valid) != 0 &&
            (fattr->valid & NFS_ATTR_FATTR_CHANGE) != 0 &&
            nfs_inode_attrs_cmp_monotonic(fattr, inode) == 0)
                return 1;
        return 0;
}

static int nfs_refresh_inode_locked(struct inode *inode,
                                    struct nfs_fattr *fattr)
{
        int attr_cmp = nfs_inode_attrs_cmp(fattr, inode);
        int ret = 0;

        trace_nfs_refresh_inode_enter(inode);

        if (attr_cmp > 0 || nfs_inode_finish_partial_attr_update(fattr, inode))
                ret = nfs_update_inode(inode, fattr);
        else if (attr_cmp == 0)
                ret = nfs_check_inode_attributes(inode, fattr);

        trace_nfs_refresh_inode_exit(inode, ret);
        return ret;
}

/**
 * nfs_refresh_inode - try to update the inode attribute cache
 * @inode: pointer to inode
 * @fattr: updated attributes
 *
 * Check that an RPC call that returned attributes has not overlapped with
 * other recent updates of the inode metadata, then decide whether it is
 * safe to do a full update of the inode attributes, or whether just to
 * call nfs_check_inode_attributes.
 */
int nfs_refresh_inode(struct inode *inode, struct nfs_fattr *fattr)
{
        int status;

        if ((fattr->valid & NFS_ATTR_FATTR) == 0)
                return 0;
        spin_lock(&inode->i_lock);
        status = nfs_refresh_inode_locked(inode, fattr);
        spin_unlock(&inode->i_lock);

        return status;
}
EXPORT_SYMBOL_GPL(nfs_refresh_inode);

static int nfs_post_op_update_inode_locked(struct inode *inode,
                struct nfs_fattr *fattr, unsigned int invalid)
{
        if (S_ISDIR(inode->i_mode))
                invalid |= NFS_INO_INVALID_DATA;
        nfs_set_cache_invalid(inode, invalid);
        if ((fattr->valid & NFS_ATTR_FATTR) == 0)
                return 0;
        return nfs_refresh_inode_locked(inode, fattr);
}

/**
 * nfs_post_op_update_inode - try to update the inode attribute cache
 * @inode: pointer to inode
 * @fattr: updated attributes
 *
 * After an operation that has changed the inode metadata, mark the
 * attribute cache as being invalid, then try to update it.
 *
 * NB: if the server didn't return any post op attributes, this
 * function will force the retrieval of attributes before the next
 * NFS request.  Thus it should be used only for operations that
 * are expected to change one or more attributes, to avoid
 * unnecessary NFS requests and trips through nfs_update_inode().
 */
int nfs_post_op_update_inode(struct inode *inode, struct nfs_fattr *fattr)
{
        int status;

        spin_lock(&inode->i_lock);
        nfs_fattr_set_barrier(fattr);
        status = nfs_post_op_update_inode_locked(inode, fattr,
                        NFS_INO_INVALID_CHANGE
                        | NFS_INO_INVALID_CTIME
                        | NFS_INO_REVAL_FORCED);
        spin_unlock(&inode->i_lock);

        return status;
}
EXPORT_SYMBOL_GPL(nfs_post_op_update_inode);

/**
 * nfs_post_op_update_inode_force_wcc_locked - update the inode attribute cache
 * @inode: pointer to inode
 * @fattr: updated attributes
 *
 * After an operation that has changed the inode metadata, mark the
 * attribute cache as being invalid, then try to update it. Fake up
 * weak cache consistency data, if none exist.
 *
 * This function is mainly designed to be used by the ->write_done() functions.
 */
int nfs_post_op_update_inode_force_wcc_locked(struct inode *inode, struct nfs_fattr *fattr)
{
        int attr_cmp = nfs_inode_attrs_cmp(fattr, inode);
        int status;

        /* Don't do a WCC update if these attributes are already stale */
        if (attr_cmp < 0)
                return 0;
        if ((fattr->valid & NFS_ATTR_FATTR) == 0 || !attr_cmp) {
                fattr->valid &= ~(NFS_ATTR_FATTR_PRECHANGE
                                | NFS_ATTR_FATTR_PRESIZE
                                | NFS_ATTR_FATTR_PREMTIME
                                | NFS_ATTR_FATTR_PRECTIME);
                goto out_noforce;
        }
        if ((fattr->valid & NFS_ATTR_FATTR_CHANGE) != 0 &&
                        (fattr->valid & NFS_ATTR_FATTR_PRECHANGE) == 0) {
                fattr->pre_change_attr = inode_peek_iversion_raw(inode);
                fattr->valid |= NFS_ATTR_FATTR_PRECHANGE;
        }
        if ((fattr->valid & NFS_ATTR_FATTR_CTIME) != 0 &&
                        (fattr->valid & NFS_ATTR_FATTR_PRECTIME) == 0) {
                fattr->pre_ctime = inode->i_ctime;
                fattr->valid |= NFS_ATTR_FATTR_PRECTIME;
        }
        if ((fattr->valid & NFS_ATTR_FATTR_MTIME) != 0 &&
                        (fattr->valid & NFS_ATTR_FATTR_PREMTIME) == 0) {
                fattr->pre_mtime = inode->i_mtime;
                fattr->valid |= NFS_ATTR_FATTR_PREMTIME;
        }
        if ((fattr->valid & NFS_ATTR_FATTR_SIZE) != 0 &&
                        (fattr->valid & NFS_ATTR_FATTR_PRESIZE) == 0) {
                fattr->pre_size = i_size_read(inode);
                fattr->valid |= NFS_ATTR_FATTR_PRESIZE;
        }
out_noforce:
        status = nfs_post_op_update_inode_locked(inode, fattr,
                        NFS_INO_INVALID_CHANGE
                        | NFS_INO_INVALID_CTIME
                        | NFS_INO_INVALID_MTIME
                        | NFS_INO_INVALID_BLOCKS);
        return status;
}

/**
 * nfs_post_op_update_inode_force_wcc - try to update the inode attribute cache
 * @inode: pointer to inode
 * @fattr: updated attributes
 *
 * After an operation that has changed the inode metadata, mark the
 * attribute cache as being invalid, then try to update it. Fake up
 * weak cache consistency data, if none exist.
 *
 * This function is mainly designed to be used by the ->write_done() functions.
 */
int nfs_post_op_update_inode_force_wcc(struct inode *inode, struct nfs_fattr *fattr)
{
        int status;

        spin_lock(&inode->i_lock);
        nfs_fattr_set_barrier(fattr);
        status = nfs_post_op_update_inode_force_wcc_locked(inode, fattr);
        spin_unlock(&inode->i_lock);
        return status;
}
EXPORT_SYMBOL_GPL(nfs_post_op_update_inode_force_wcc);


/*
 * Many nfs protocol calls return the new file attributes after
 * an operation.  Here we update the inode to reflect the state
 * of the server's inode.
 *
 * This is a bit tricky because we have to make sure all dirty pages
 * have been sent off to the server before calling invalidate_inode_pages.
 * To make sure no other process adds more write requests while we try
 * our best to flush them, we make them sleep during the attribute refresh.
 *
 * A very similar scenario holds for the dir cache.
 */
static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
{
        struct nfs_server *server = NFS_SERVER(inode);
        struct nfs_inode *nfsi = NFS_I(inode);
        loff_t cur_isize, new_isize;
        u64 fattr_supported = server->fattr_valid;
        unsigned long invalid = 0;
        unsigned long now = jiffies;
        unsigned long save_cache_validity;
        bool have_writers = nfs_file_has_buffered_writers(nfsi);
        bool cache_revalidated = true;
        bool attr_changed = false;
        bool have_delegation;

        dfprintk(VFS, "NFS: %s(%s/%lu fh_crc=0x%08x ct=%d info=0x%x)\n",
                        __func__, inode->i_sb->s_id, inode->i_ino,
                        nfs_display_fhandle_hash(NFS_FH(inode)),
                        atomic_read(&inode->i_count), fattr->valid);

        if (!(fattr->valid & NFS_ATTR_FATTR_FILEID)) {
                /* Only a mounted-on-fileid? Just exit */
                if (fattr->valid & NFS_ATTR_FATTR_MOUNTED_ON_FILEID)
                        return 0;
        /* Has the inode gone and changed behind our back? */
        } else if (nfsi->fileid != fattr->fileid) {
                /* Is this perhaps the mounted-on fileid? */
                if ((fattr->valid & NFS_ATTR_FATTR_MOUNTED_ON_FILEID) &&
                    nfsi->fileid == fattr->mounted_on_fileid)
                        return 0;
                printk(KERN_ERR "NFS: server %s error: fileid changed\n"
                        "fsid %s: expected fileid 0x%Lx, got 0x%Lx\n",
                        NFS_SERVER(inode)->nfs_client->cl_hostname,
                        inode->i_sb->s_id, (long long)nfsi->fileid,
                        (long long)fattr->fileid);
                goto out_err;
        }

        /*
         * Make sure the inode's type hasn't changed.

         */
        if ((fattr->valid & NFS_ATTR_FATTR_TYPE) && inode_wrong_type(inode, fattr->mode)) {
                /*
                * Big trouble! The inode has become a different object.
                */
                printk(KERN_DEBUG "NFS: %s: inode %lu mode changed, %07o to %07o\n",
                                __func__, inode->i_ino, inode->i_mode, fattr->mode);
                goto out_err;
        }

        /* Update the fsid? */
        if (S_ISDIR(inode->i_mode) && (fattr->valid & NFS_ATTR_FATTR_FSID) &&
                        !nfs_fsid_equal(&server->fsid, &fattr->fsid) &&
                        !IS_AUTOMOUNT(inode))
                server->fsid = fattr->fsid;

        /* Save the delegation state before clearing cache_validity */
        have_delegation = nfs_have_delegated_attributes(inode);

        /*
         * Update the read time so we don't revalidate too often.
         */
        nfsi->read_cache_jiffies = fattr->time_start;

        save_cache_validity = nfsi->cache_validity;
        nfsi->cache_validity &= ~(NFS_INO_INVALID_ATTR
                        | NFS_INO_INVALID_ATIME
                        | NFS_INO_REVAL_FORCED
                        | NFS_INO_INVALID_BLOCKS);

        /* Do atomic weak cache consistency updates */
        nfs_wcc_update_inode(inode, fattr);

        if (pnfs_layoutcommit_outstanding(inode)) {
                nfsi->cache_validity |=
                        save_cache_validity &
                        (NFS_INO_INVALID_CHANGE | NFS_INO_INVALID_CTIME |
                         NFS_INO_INVALID_MTIME | NFS_INO_INVALID_SIZE |
                         NFS_INO_INVALID_BLOCKS);
                cache_revalidated = false;
        }

        /* More cache consistency checks */
        if (fattr->valid & NFS_ATTR_FATTR_CHANGE) {
                if (!inode_eq_iversion_raw(inode, fattr->change_attr)) {
                        /* Could it be a race with writeback? */
                        if (!(have_writers || have_delegation)) {
                                invalid |= NFS_INO_INVALID_DATA
                                        | NFS_INO_INVALID_ACCESS
                                        | NFS_INO_INVALID_ACL
                                        | NFS_INO_INVALID_XATTR;
                                /* Force revalidate of all attributes */
                                save_cache_validity |= NFS_INO_INVALID_CTIME
                                        | NFS_INO_INVALID_MTIME
                                        | NFS_INO_INVALID_SIZE
                                        | NFS_INO_INVALID_BLOCKS
                                        | NFS_INO_INVALID_NLINK
                                        | NFS_INO_INVALID_MODE
                                        | NFS_INO_INVALID_OTHER;
                                if (S_ISDIR(inode->i_mode))
                                        nfs_force_lookup_revalidate(inode);
                                attr_changed = true;
                                dprintk("NFS: change_attr change on server for file %s/%ld\n",
                                                inode->i_sb->s_id,
                                                inode->i_ino);
                        } else if (!have_delegation)
                                nfsi->cache_validity |= NFS_INO_DATA_INVAL_DEFER;
                        inode_set_iversion_raw(inode, fattr->change_attr);
                }
        } else {
                nfsi->cache_validity |=
                        save_cache_validity & NFS_INO_INVALID_CHANGE;
                if (!have_delegation ||
                    (nfsi->cache_validity & NFS_INO_INVALID_CHANGE) != 0)
                        cache_revalidated = false;
        }

        if (fattr->valid & NFS_ATTR_FATTR_MTIME)
                inode->i_mtime = fattr->mtime;
        else if (fattr_supported & NFS_ATTR_FATTR_MTIME)
                nfsi->cache_validity |=
                        save_cache_validity & NFS_INO_INVALID_MTIME;

        if (fattr->valid & NFS_ATTR_FATTR_CTIME)
                inode->i_ctime = fattr->ctime;
        else if (fattr_supported & NFS_ATTR_FATTR_CTIME)
                nfsi->cache_validity |=
                        save_cache_validity & NFS_INO_INVALID_CTIME;

        /* Check if our cached file size is stale */
        if (fattr->valid & NFS_ATTR_FATTR_SIZE) {
                new_isize = nfs_size_to_loff_t(fattr->size);
                cur_isize = i_size_read(inode);
                if (new_isize != cur_isize && !have_delegation) {
                        /* Do we perhaps have any outstanding writes, or has
                         * the file grown beyond our last write? */
                        if (!nfs_have_writebacks(inode) || new_isize > cur_isize) {
                                i_size_write(inode, new_isize);
                                if (!have_writers)
                                        invalid |= NFS_INO_INVALID_DATA;
                        }
                        dprintk("NFS: isize change on server for file %s/%ld "
                                        "(%Ld to %Ld)\n",
                                        inode->i_sb->s_id,
                                        inode->i_ino,
                                        (long long)cur_isize,
                                        (long long)new_isize);
                }
                if (new_isize == 0 &&
                    !(fattr->valid & (NFS_ATTR_FATTR_SPACE_USED |
                                      NFS_ATTR_FATTR_BLOCKS_USED))) {
                        fattr->du.nfs3.used = 0;
                        fattr->valid |= NFS_ATTR_FATTR_SPACE_USED;
                }
        } else
                nfsi->cache_validity |=
                        save_cache_validity & NFS_INO_INVALID_SIZE;

        if (fattr->valid & NFS_ATTR_FATTR_ATIME)
                inode->i_atime = fattr->atime;
        else if (fattr_supported & NFS_ATTR_FATTR_ATIME)
                nfsi->cache_validity |=
                        save_cache_validity & NFS_INO_INVALID_ATIME;

        if (fattr->valid & NFS_ATTR_FATTR_MODE) {
                if ((inode->i_mode & S_IALLUGO) != (fattr->mode & S_IALLUGO)) {
                        umode_t newmode = inode->i_mode & S_IFMT;
                        newmode |= fattr->mode & S_IALLUGO;
                        inode->i_mode = newmode;
                        invalid |= NFS_INO_INVALID_ACCESS
                                | NFS_INO_INVALID_ACL;
                }
        } else if (fattr_supported & NFS_ATTR_FATTR_MODE)
                nfsi->cache_validity |=
                        save_cache_validity & NFS_INO_INVALID_MODE;

        if (fattr->valid & NFS_ATTR_FATTR_OWNER) {
                if (!uid_eq(inode->i_uid, fattr->uid)) {
                        invalid |= NFS_INO_INVALID_ACCESS
                                | NFS_INO_INVALID_ACL;
                        inode->i_uid = fattr->uid;
                }
        } else if (fattr_supported & NFS_ATTR_FATTR_OWNER)
                nfsi->cache_validity |=
                        save_cache_validity & NFS_INO_INVALID_OTHER;

        if (fattr->valid & NFS_ATTR_FATTR_GROUP) {
                if (!gid_eq(inode->i_gid, fattr->gid)) {
                        invalid |= NFS_INO_INVALID_ACCESS
                                | NFS_INO_INVALID_ACL;
                        inode->i_gid = fattr->gid;
                }
        } else if (fattr_supported & NFS_ATTR_FATTR_GROUP)
                nfsi->cache_validity |=
                        save_cache_validity & NFS_INO_INVALID_OTHER;

        if (fattr->valid & NFS_ATTR_FATTR_NLINK) {
                if (inode->i_nlink != fattr->nlink) {
                        if (S_ISDIR(inode->i_mode))
                                invalid |= NFS_INO_INVALID_DATA;
                        set_nlink(inode, fattr->nlink);
                }
        } else if (fattr_supported & NFS_ATTR_FATTR_NLINK)
                nfsi->cache_validity |=
                        save_cache_validity & NFS_INO_INVALID_NLINK;

        if (fattr->valid & NFS_ATTR_FATTR_SPACE_USED) {
                /*
                 * report the blocks in 512byte units
                 */
                inode->i_blocks = nfs_calc_block_size(fattr->du.nfs3.used);
        } else if (fattr_supported & NFS_ATTR_FATTR_SPACE_USED)
                nfsi->cache_validity |=
                        save_cache_validity & NFS_INO_INVALID_BLOCKS;

        if (fattr->valid & NFS_ATTR_FATTR_BLOCKS_USED)
                inode->i_blocks = fattr->du.nfs2.blocks;
        else if (fattr_supported & NFS_ATTR_FATTR_BLOCKS_USED)
                nfsi->cache_validity |=
                        save_cache_validity & NFS_INO_INVALID_BLOCKS;

        /* Update attrtimeo value if we're out of the unstable period */
        if (attr_changed) {
                nfs_inc_stats(inode, NFSIOS_ATTRINVALIDATE);
                nfsi->attrtimeo = NFS_MINATTRTIMEO(inode);
                nfsi->attrtimeo_timestamp = now;
                /* Set barrier to be more recent than all outstanding updates */
                nfsi->attr_gencount = nfs_inc_attr_generation_counter();
        } else {
                if (cache_revalidated) {
                        if (!time_in_range_open(now, nfsi->attrtimeo_timestamp,
                                nfsi->attrtimeo_timestamp + nfsi->attrtimeo)) {
                                nfsi->attrtimeo <<= 1;
                                if (nfsi->attrtimeo > NFS_MAXATTRTIMEO(inode))
                                        nfsi->attrtimeo = NFS_MAXATTRTIMEO(inode);
                        }
                        nfsi->attrtimeo_timestamp = now;
                }
                /* Set the barrier to be more recent than this fattr */
                if ((long)(fattr->gencount - nfsi->attr_gencount) > 0)
                        nfsi->attr_gencount = fattr->gencount;
        }

        /* Don't invalidate the data if we were to blame */
        if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)
                                || S_ISLNK(inode->i_mode)))
                invalid &= ~NFS_INO_INVALID_DATA;
        nfs_set_cache_invalid(inode, invalid);

        return 0;
 out_err:
        /*
         * No need to worry about unhashing the dentry, as the
         * lookup validation will know that the inode is bad.
         * (But we fall through to invalidate the caches.)
         */
        nfs_set_inode_stale_locked(inode);
        return -ESTALE;
}

struct inode *nfs_alloc_inode(struct super_block *sb)
{
        struct nfs_inode *nfsi;
        nfsi = kmem_cache_alloc(nfs_inode_cachep, GFP_KERNEL);
        if (!nfsi)
                return NULL;
        nfsi->flags = 0UL;
        nfsi->cache_validity = 0UL;
#if IS_ENABLED(CONFIG_NFS_V4)
        nfsi->nfs4_acl = NULL;
#endif /* CONFIG_NFS_V4 */
#ifdef CONFIG_NFS_V4_2
        nfsi->xattr_cache = NULL;
#endif
        return &nfsi->vfs_inode;
}
EXPORT_SYMBOL_GPL(nfs_alloc_inode);

void nfs_free_inode(struct inode *inode)
{
        kmem_cache_free(nfs_inode_cachep, NFS_I(inode));
}
EXPORT_SYMBOL_GPL(nfs_free_inode);

static inline void nfs4_init_once(struct nfs_inode *nfsi)
{
#if IS_ENABLED(CONFIG_NFS_V4)
        INIT_LIST_HEAD(&nfsi->open_states);
        nfsi->delegation = NULL;
        init_rwsem(&nfsi->rwsem);
        nfsi->layout = NULL;
#endif
}

static void init_once(void *foo)
{
        struct nfs_inode *nfsi = (struct nfs_inode *) foo;

        inode_init_once(&nfsi->vfs_inode);
        INIT_LIST_HEAD(&nfsi->open_files);
        INIT_LIST_HEAD(&nfsi->access_cache_entry_lru);
        INIT_LIST_HEAD(&nfsi->access_cache_inode_lru);
        INIT_LIST_HEAD(&nfsi->commit_info.list);
        atomic_long_set(&nfsi->nrequests, 0);
        atomic_long_set(&nfsi->commit_info.ncommit, 0);
        atomic_set(&nfsi->commit_info.rpcs_out, 0);
        init_rwsem(&nfsi->rmdir_sem);
        mutex_init(&nfsi->commit_mutex);
        nfs4_init_once(nfsi);
        nfsi->cache_change_attribute = 0;
}

static int __init nfs_init_inodecache(void)
{
        nfs_inode_cachep = kmem_cache_create("nfs_inode_cache",
                                             sizeof(struct nfs_inode),
                                             0, (SLAB_RECLAIM_ACCOUNT|
                                                SLAB_MEM_SPREAD|SLAB_ACCOUNT),
                                             init_once);
        if (nfs_inode_cachep == NULL)
                return -ENOMEM;

        return 0;
}

static void nfs_destroy_inodecache(void)
{
        /*
         * Make sure all delayed rcu free inodes are flushed before we
         * destroy cache.
         */
        rcu_barrier();
        kmem_cache_destroy(nfs_inode_cachep);
}

struct workqueue_struct *nfsiod_workqueue;
EXPORT_SYMBOL_GPL(nfsiod_workqueue);

/*
 * start up the nfsiod workqueue
 */
static int nfsiod_start(void)
{
        struct workqueue_struct *wq;
        dprintk("RPC:       creating workqueue nfsiod\n");
        wq = alloc_workqueue("nfsiod", WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
        if (wq == NULL)
                return -ENOMEM;
        nfsiod_workqueue = wq;
        return 0;
}

/*
 * Destroy the nfsiod workqueue
 */
static void nfsiod_stop(void)
{
        struct workqueue_struct *wq;

        wq = nfsiod_workqueue;
        if (wq == NULL)
                return;
        nfsiod_workqueue = NULL;
        destroy_workqueue(wq);
}

unsigned int nfs_net_id;
EXPORT_SYMBOL_GPL(nfs_net_id);

static int nfs_net_init(struct net *net)
{
        nfs_clients_init(net);
        return nfs_fs_proc_net_init(net);
}

static void nfs_net_exit(struct net *net)
{
        nfs_fs_proc_net_exit(net);
        nfs_clients_exit(net);
}

static struct pernet_operations nfs_net_ops = {
        .init = nfs_net_init,
        .exit = nfs_net_exit,
        .id   = &nfs_net_id,
        .size = sizeof(struct nfs_net),
};

/*
 * Initialize NFS
 */
static int __init init_nfs_fs(void)
{
        int err;

        err = nfs_sysfs_init();
        if (err < 0)
                goto out10;

        err = register_pernet_subsys(&nfs_net_ops);
        if (err < 0)
                goto out9;

        err = nfs_fscache_register();
        if (err < 0)
                goto out8;

        err = nfsiod_start();
        if (err)
                goto out7;

        err = nfs_fs_proc_init();
        if (err)
                goto out6;

        err = nfs_init_nfspagecache();
        if (err)
                goto out5;

        err = nfs_init_inodecache();
        if (err)
                goto out4;

        err = nfs_init_readpagecache();
        if (err)
                goto out3;

        err = nfs_init_writepagecache();
        if (err)
                goto out2;

        err = nfs_init_directcache();
        if (err)
                goto out1;

        rpc_proc_register(&init_net, &nfs_rpcstat);

        err = register_nfs_fs();
        if (err)
                goto out0;

        return 0;
out0:
        rpc_proc_unregister(&init_net, "nfs");
        nfs_destroy_directcache();
out1:
        nfs_destroy_writepagecache();
out2:
        nfs_destroy_readpagecache();
out3:
        nfs_destroy_inodecache();
out4:
        nfs_destroy_nfspagecache();
out5:
        nfs_fs_proc_exit();
out6:
        nfsiod_stop();
out7:
        nfs_fscache_unregister();
out8:
        unregister_pernet_subsys(&nfs_net_ops);
out9:
        nfs_sysfs_exit();
out10:
        return err;
}

static void __exit exit_nfs_fs(void)
{
        nfs_destroy_directcache();
        nfs_destroy_writepagecache();
        nfs_destroy_readpagecache();
        nfs_destroy_inodecache();
        nfs_destroy_nfspagecache();
        nfs_fscache_unregister();
        unregister_pernet_subsys(&nfs_net_ops);
        rpc_proc_unregister(&init_net, "nfs");
        unregister_nfs_fs();
        nfs_fs_proc_exit();
        nfsiod_stop();
        nfs_sysfs_exit();
}

/* Not quite true; I just maintain it */
MODULE_AUTHOR("Olaf Kirch <okir@monad.swb.de>");
MODULE_LICENSE("GPL");
module_param(enable_ino64, bool, 0644);

module_init(init_nfs_fs)
module_exit(exit_nfs_fs)