/*
 * Copyright 2012 Xyratex Technology Limited
 *
 * Copyright (c) 2013, 2015, Intel Corporation.
 *
 * Author: Andrew Perepechko <Andrew_Perepechko@xyratex.com>
 *
 */

#define DEBUG_SUBSYSTEM S_LLITE

#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include "../include/obd_support.h"
#include "../include/lustre_dlm.h"
#include "../include/lustre_ver.h"
#include "llite_internal.h"

/* If we ever have hundreds of extended attributes, we might want to consider
 * using a hash or a tree structure instead of list for faster lookups.
 */
struct ll_xattr_entry {
        struct list_head        xe_list;    /* protected with
                                             * lli_xattrs_list_rwsem
                                             */
        char                    *xe_name;   /* xattr name, \0-terminated */
        char                    *xe_value;  /* xattr value */
        unsigned                xe_namelen; /* strlen(xe_name) + 1 */
        unsigned                xe_vallen;  /* xattr value length */
};

static struct kmem_cache *xattr_kmem;
static struct lu_kmem_descr xattr_caches[] = {
        {
                .ckd_cache = &xattr_kmem,
                .ckd_name  = "xattr_kmem",
                .ckd_size  = sizeof(struct ll_xattr_entry)
        },
        {
                .ckd_cache = NULL
        }
};

int ll_xattr_init(void)
{
        return lu_kmem_init(xattr_caches);
}

void ll_xattr_fini(void)
{
        lu_kmem_fini(xattr_caches);
}

/**
 * Initializes xattr cache for an inode.
 *
 * This initializes the xattr list and marks cache presence.
 */
static void ll_xattr_cache_init(struct ll_inode_info *lli)
{
        INIT_LIST_HEAD(&lli->lli_xattrs);
        lli->lli_flags |= LLIF_XATTR_CACHE;
}

/**
 *  This looks for a specific extended attribute.
 *
 *  Find in @cache and return @xattr_name attribute in @xattr,
 *  for the NULL @xattr_name return the first cached @xattr.
 *
 *  \retval 0        success
 *  \retval -ENODATA if not found
 */
static int ll_xattr_cache_find(struct list_head *cache,
                               const char *xattr_name,
                               struct ll_xattr_entry **xattr)
{
        struct ll_xattr_entry *entry;

        list_for_each_entry(entry, cache, xe_list) {
                /* xattr_name == NULL means look for any entry */
                if (!xattr_name || strcmp(xattr_name, entry->xe_name) == 0) {
                        *xattr = entry;
                        CDEBUG(D_CACHE, "find: [%s]=%.*s\n",
                               entry->xe_name, entry->xe_vallen,
                               entry->xe_value);
                        return 0;
                }
        }

        return -ENODATA;
}

/**
 * This adds an xattr.
 *
 * Add @xattr_name attr with @xattr_val value and @xattr_val_len length,
 *
 * \retval 0       success
 * \retval -ENOMEM if no memory could be allocated for the cached attr
 * \retval -EPROTO if duplicate xattr is being added
 */
static int ll_xattr_cache_add(struct list_head *cache,
                              const char *xattr_name,
                              const char *xattr_val,
                              unsigned xattr_val_len)
{
        struct ll_xattr_entry *xattr;

        if (ll_xattr_cache_find(cache, xattr_name, &xattr) == 0) {
                CDEBUG(D_CACHE, "duplicate xattr: [%s]\n", xattr_name);
                return -EPROTO;
        }

        xattr = kmem_cache_zalloc(xattr_kmem, GFP_NOFS);
        if (!xattr) {
                CDEBUG(D_CACHE, "failed to allocate xattr\n");
                return -ENOMEM;
        }

        xattr->xe_name = kstrdup(xattr_name, GFP_NOFS);
        if (!xattr->xe_name) {
                CDEBUG(D_CACHE, "failed to alloc xattr name %u\n",
                       xattr->xe_namelen);
                goto err_name;
        }
        xattr->xe_value = kmemdup(xattr_val, xattr_val_len, GFP_NOFS);
        if (!xattr->xe_value)
                goto err_value;

        xattr->xe_vallen = xattr_val_len;
        list_add(&xattr->xe_list, cache);

        CDEBUG(D_CACHE, "set: [%s]=%.*s\n", xattr_name, xattr_val_len,
               xattr_val);

        return 0;
err_value:
        kfree(xattr->xe_name);
err_name:
        kmem_cache_free(xattr_kmem, xattr);

        return -ENOMEM;
}

/**
 * This removes an extended attribute from cache.
 *
 * Remove @xattr_name attribute from @cache.
 *
 * \retval 0        success
 * \retval -ENODATA if @xattr_name is not cached
 */
static int ll_xattr_cache_del(struct list_head *cache,
                              const char *xattr_name)
{
        struct ll_xattr_entry *xattr;

        CDEBUG(D_CACHE, "del xattr: %s\n", xattr_name);

        if (ll_xattr_cache_find(cache, xattr_name, &xattr) == 0) {
                list_del(&xattr->xe_list);
                kfree(xattr->xe_name);
                kfree(xattr->xe_value);
                kmem_cache_free(xattr_kmem, xattr);

                return 0;
        }

        return -ENODATA;
}

/**
 * This iterates cached extended attributes.
 *
 * Walk over cached attributes in @cache and
 * fill in @xld_buffer or only calculate buffer
 * size if @xld_buffer is NULL.
 *
 * \retval >= 0     buffer list size
 * \retval -ENODATA if the list cannot fit @xld_size buffer
 */
static int ll_xattr_cache_list(struct list_head *cache,
                               char *xld_buffer,
                               int xld_size)
{
        struct ll_xattr_entry *xattr, *tmp;
        int xld_tail = 0;

        list_for_each_entry_safe(xattr, tmp, cache, xe_list) {
                CDEBUG(D_CACHE, "list: buffer=%p[%d] name=%s\n",
                       xld_buffer, xld_tail, xattr->xe_name);

                if (xld_buffer) {
                        xld_size -= xattr->xe_namelen;
                        if (xld_size < 0)
                                break;
                        memcpy(&xld_buffer[xld_tail],
                               xattr->xe_name, xattr->xe_namelen);
                }
                xld_tail += xattr->xe_namelen;
        }

        if (xld_size < 0)
                return -ERANGE;

        return xld_tail;
}

/**
 * Check if the xattr cache is initialized (filled).
 *
 * \retval 0 @cache is not initialized
 * \retval 1 @cache is initialized
 */
static int ll_xattr_cache_valid(struct ll_inode_info *lli)
{
        return !!(lli->lli_flags & LLIF_XATTR_CACHE);
}

/**
 * This finalizes the xattr cache.
 *
 * Free all xattr memory. @lli is the inode info pointer.
 *
 * \retval 0 no error occurred
 */
static int ll_xattr_cache_destroy_locked(struct ll_inode_info *lli)
{
        if (!ll_xattr_cache_valid(lli))
                return 0;

        while (ll_xattr_cache_del(&lli->lli_xattrs, NULL) == 0)
                ; /* empty loop */
        lli->lli_flags &= ~LLIF_XATTR_CACHE;

        return 0;
}

int ll_xattr_cache_destroy(struct inode *inode)
{
        struct ll_inode_info *lli = ll_i2info(inode);
        int rc;

        down_write(&lli->lli_xattrs_list_rwsem);
        rc = ll_xattr_cache_destroy_locked(lli);
        up_write(&lli->lli_xattrs_list_rwsem);

        return rc;
}

/**
 * Match or enqueue a PR lock.
 *
 * Find or request an LDLM lock with xattr data.
 * Since LDLM does not provide API for atomic match_or_enqueue,
 * the function handles it with a separate enq lock.
 * If successful, the function exits with the list lock held.
 *
 * \retval 0       no error occurred
 * \retval -ENOMEM not enough memory
 */
static int ll_xattr_find_get_lock(struct inode *inode,
                                  struct lookup_intent *oit,
                                  struct ptlrpc_request **req)
{
        enum ldlm_mode mode;
        struct lustre_handle lockh = { 0 };
        struct md_op_data *op_data;
        struct ll_inode_info *lli = ll_i2info(inode);
        struct ldlm_enqueue_info einfo = {
                .ei_type = LDLM_IBITS,
                .ei_mode = it_to_lock_mode(oit),
                .ei_cb_bl = &ll_md_blocking_ast,
                .ei_cb_cp = &ldlm_completion_ast,
        };
        struct ll_sb_info *sbi = ll_i2sbi(inode);
        struct obd_export *exp = sbi->ll_md_exp;
        int rc;

        mutex_lock(&lli->lli_xattrs_enq_lock);
        /* inode may have been shrunk and recreated, so data is gone, match lock
         * only when data exists.
         */
        if (ll_xattr_cache_valid(lli)) {
                /* Try matching first. */
                mode = ll_take_md_lock(inode, MDS_INODELOCK_XATTR, &lockh, 0,
                                       LCK_PR);
                if (mode != 0) {
                        /* fake oit in mdc_revalidate_lock() manner */
                        oit->it_lock_handle = lockh.cookie;
                        oit->it_lock_mode = mode;
                        goto out;
                }
        }

        /* Enqueue if the lock isn't cached locally. */
        op_data = ll_prep_md_op_data(NULL, inode, NULL, NULL, 0, 0,
                                     LUSTRE_OPC_ANY, NULL);
        if (IS_ERR(op_data)) {
                mutex_unlock(&lli->lli_xattrs_enq_lock);
                return PTR_ERR(op_data);
        }

        op_data->op_valid = OBD_MD_FLXATTR | OBD_MD_FLXATTRLS;

        rc = md_enqueue(exp, &einfo, NULL, oit, op_data, &lockh, 0);
        ll_finish_md_op_data(op_data);

        if (rc < 0) {
                CDEBUG(D_CACHE,
                       "md_intent_lock failed with %d for fid "DFID"\n",
                       rc, PFID(ll_inode2fid(inode)));
                mutex_unlock(&lli->lli_xattrs_enq_lock);
                return rc;
        }

        *req = oit->it_request;
out:
        down_write(&lli->lli_xattrs_list_rwsem);
        mutex_unlock(&lli->lli_xattrs_enq_lock);

        return 0;
}

/**
 * Refill the xattr cache.
 *
 * Fetch and cache the whole of xattrs for @inode, acquiring
 * a read or a write xattr lock depending on operation in @oit.
 * Intent is dropped on exit unless the operation is setxattr.
 *
 * \retval 0       no error occurred
 * \retval -EPROTO network protocol error
 * \retval -ENOMEM not enough memory for the cache
 */
static int ll_xattr_cache_refill(struct inode *inode, struct lookup_intent *oit)
{
        struct ll_sb_info *sbi = ll_i2sbi(inode);
        struct ptlrpc_request *req = NULL;
        const char *xdata, *xval, *xtail, *xvtail;
        struct ll_inode_info *lli = ll_i2info(inode);
        struct mdt_body *body;
        __u32 *xsizes;
        int rc, i;

        rc = ll_xattr_find_get_lock(inode, oit, &req);
        if (rc)
                goto out_no_unlock;

        /* Do we have the data at this point? */
        if (ll_xattr_cache_valid(lli)) {
                ll_stats_ops_tally(sbi, LPROC_LL_GETXATTR_HITS, 1);
                rc = 0;
                goto out_maybe_drop;
        }

        /* Matched but no cache? Cancelled on error by a parallel refill. */
        if (unlikely(!req)) {
                CDEBUG(D_CACHE, "cancelled by a parallel getxattr\n");
                rc = -EIO;
                goto out_maybe_drop;
        }

        if (oit->it_status < 0) {
                CDEBUG(D_CACHE, "getxattr intent returned %d for fid "DFID"\n",
                       oit->it_status, PFID(ll_inode2fid(inode)));
                rc = oit->it_status;
                /* xattr data is so large that we don't want to cache it */
                if (rc == -ERANGE)
                        rc = -EAGAIN;
                goto out_destroy;
        }

        body = req_capsule_server_get(&req->rq_pill, &RMF_MDT_BODY);
        if (!body) {
                CERROR("no MDT BODY in the refill xattr reply\n");
                rc = -EPROTO;
                goto out_destroy;
        }
        /* do not need swab xattr data */
        xdata = req_capsule_server_sized_get(&req->rq_pill, &RMF_EADATA,
                                             body->mbo_eadatasize);
        xval = req_capsule_server_sized_get(&req->rq_pill, &RMF_EAVALS,
                                            body->mbo_aclsize);
        xsizes = req_capsule_server_sized_get(&req->rq_pill, &RMF_EAVALS_LENS,
                                              body->mbo_max_mdsize * sizeof(__u32));
        if (!xdata || !xval || !xsizes) {
                CERROR("wrong setxattr reply\n");
                rc = -EPROTO;
                goto out_destroy;
        }

        xtail = xdata + body->mbo_eadatasize;
        xvtail = xval + body->mbo_aclsize;

        CDEBUG(D_CACHE, "caching: xdata=%p xtail=%p\n", xdata, xtail);

        ll_xattr_cache_init(lli);

        for (i = 0; i < body->mbo_max_mdsize; i++) {
                CDEBUG(D_CACHE, "caching [%s]=%.*s\n", xdata, *xsizes, xval);
                /* Perform consistency checks: attr names and vals in pill */
                if (!memchr(xdata, 0, xtail - xdata)) {
                        CERROR("xattr protocol violation (names are broken)\n");
                        rc = -EPROTO;
                } else if (xval + *xsizes > xvtail) {
                        CERROR("xattr protocol violation (vals are broken)\n");
                        rc = -EPROTO;
                } else if (OBD_FAIL_CHECK(OBD_FAIL_LLITE_XATTR_ENOMEM)) {
                        rc = -ENOMEM;
                } else if (!strcmp(xdata, XATTR_NAME_ACL_ACCESS)) {
                        /* Filter out ACL ACCESS since it's cached separately */
                        CDEBUG(D_CACHE, "not caching %s\n",
                               XATTR_NAME_ACL_ACCESS);
                        rc = 0;
                } else {
                        rc = ll_xattr_cache_add(&lli->lli_xattrs, xdata, xval,
                                                *xsizes);
                }
                if (rc < 0) {
                        ll_xattr_cache_destroy_locked(lli);
                        goto out_destroy;
                }
                xdata += strlen(xdata) + 1;
                xval  += *xsizes;
                xsizes++;
        }

        if (xdata != xtail || xval != xvtail)
                CERROR("a hole in xattr data\n");

        ll_set_lock_data(sbi->ll_md_exp, inode, oit, NULL);

        goto out_maybe_drop;
out_maybe_drop:

                ll_intent_drop_lock(oit);

        if (rc != 0)
                up_write(&lli->lli_xattrs_list_rwsem);
out_no_unlock:
        ptlrpc_req_finished(req);

        return rc;

out_destroy:
        up_write(&lli->lli_xattrs_list_rwsem);

        ldlm_lock_decref_and_cancel((struct lustre_handle *)
                                        &oit->it_lock_handle,
                                        oit->it_lock_mode);

        goto out_no_unlock;
}

/**
 * Get an xattr value or list xattrs using the write-through cache.
 *
 * Get the xattr value (@valid has OBD_MD_FLXATTR set) of @name or
 * list xattr names (@valid has OBD_MD_FLXATTRLS set) for @inode.
 * The resulting value/list is stored in @buffer if the former
 * is not larger than @size.
 *
 * \retval 0        no error occurred
 * \retval -EPROTO  network protocol error
 * \retval -ENOMEM  not enough memory for the cache
 * \retval -ERANGE  the buffer is not large enough
 * \retval -ENODATA no such attr or the list is empty
 */
int ll_xattr_cache_get(struct inode *inode, const char *name, char *buffer,
                       size_t size, __u64 valid)
{
        struct lookup_intent oit = { .it_op = IT_GETXATTR };
        struct ll_inode_info *lli = ll_i2info(inode);
        int rc = 0;

        LASSERT(!!(valid & OBD_MD_FLXATTR) ^ !!(valid & OBD_MD_FLXATTRLS));

        down_read(&lli->lli_xattrs_list_rwsem);
        if (!ll_xattr_cache_valid(lli)) {
                up_read(&lli->lli_xattrs_list_rwsem);
                rc = ll_xattr_cache_refill(inode, &oit);
                if (rc)
                        return rc;
                downgrade_write(&lli->lli_xattrs_list_rwsem);
        } else {
                ll_stats_ops_tally(ll_i2sbi(inode), LPROC_LL_GETXATTR_HITS, 1);
        }

        if (valid & OBD_MD_FLXATTR) {
                struct ll_xattr_entry *xattr;

                rc = ll_xattr_cache_find(&lli->lli_xattrs, name, &xattr);
                if (rc == 0) {
                        rc = xattr->xe_vallen;
                        /* zero size means we are only requested size in rc */
                        if (size != 0) {
                                if (size >= xattr->xe_vallen)
                                        memcpy(buffer, xattr->xe_value,
                                               xattr->xe_vallen);
                                else
                                        rc = -ERANGE;
                        }
                }
        } else if (valid & OBD_MD_FLXATTRLS) {
                rc = ll_xattr_cache_list(&lli->lli_xattrs,
                                         size ? buffer : NULL, size);
        }

        goto out;
out:
        up_read(&lli->lli_xattrs_list_rwsem);

        return rc;
}