// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/nfs/unlink.c
 *
 * nfs sillydelete handling
 *
 */

#include <linux/slab.h>
#include <linux/string.h>
#include <linux/dcache.h>
#include <linux/sunrpc/sched.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs_fs.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/namei.h>
#include <linux/fsnotify.h>

#include "internal.h"
#include "nfs4_fs.h"
#include "iostat.h"
#include "delegation.h"

#include "nfstrace.h"

/**
 * nfs_free_unlinkdata - release data from a sillydelete operation.
 * @data: pointer to unlink structure.
 */
static void
nfs_free_unlinkdata(struct nfs_unlinkdata *data)
{
        put_cred(data->cred);
        kfree(data->args.name.name);
        kfree(data);
}

/**
 * nfs_async_unlink_done - Sillydelete post-processing
 * @task: rpc_task of the sillydelete
 * @calldata: pointer to nfs_unlinkdata
 *
 * Do the directory attribute update.
 */
static void nfs_async_unlink_done(struct rpc_task *task, void *calldata)
{
        struct nfs_unlinkdata *data = calldata;
        struct inode *dir = d_inode(data->dentry->d_parent);

        trace_nfs_sillyrename_unlink(data, task->tk_status);
        if (!NFS_PROTO(dir)->unlink_done(task, dir))
                rpc_restart_call_prepare(task);
}

/**
 * nfs_async_unlink_release - Release the sillydelete data.
 * @calldata: struct nfs_unlinkdata to release
 *
 * We need to call nfs_put_unlinkdata as a 'tk_release' task since the
 * rpc_task would be freed too.
 */
static void nfs_async_unlink_release(void *calldata)
{
        struct nfs_unlinkdata   *data = calldata;
        struct dentry *dentry = data->dentry;
        struct super_block *sb = dentry->d_sb;

        up_read_non_owner(&NFS_I(d_inode(dentry->d_parent))->rmdir_sem);
        d_lookup_done(dentry);
        nfs_free_unlinkdata(data);
        dput(dentry);
        nfs_sb_deactive(sb);
}

static void nfs_unlink_prepare(struct rpc_task *task, void *calldata)
{
        struct nfs_unlinkdata *data = calldata;
        struct inode *dir = d_inode(data->dentry->d_parent);
        NFS_PROTO(dir)->unlink_rpc_prepare(task, data);
}

static const struct rpc_call_ops nfs_unlink_ops = {
        .rpc_call_done = nfs_async_unlink_done,
        .rpc_release = nfs_async_unlink_release,
        .rpc_call_prepare = nfs_unlink_prepare,
};

static void nfs_do_call_unlink(struct inode *inode, struct nfs_unlinkdata *data)
{
        struct rpc_message msg = {
                .rpc_argp = &data->args,
                .rpc_resp = &data->res,
                .rpc_cred = data->cred,
        };
        struct rpc_task_setup task_setup_data = {
                .rpc_message = &msg,
                .callback_ops = &nfs_unlink_ops,
                .callback_data = data,
                .workqueue = nfsiod_workqueue,
                .flags = RPC_TASK_ASYNC | RPC_TASK_CRED_NOREF,
        };
        struct rpc_task *task;
        struct inode *dir = d_inode(data->dentry->d_parent);
        nfs_sb_active(dir->i_sb);
        data->args.fh = NFS_FH(dir);
        nfs_fattr_init(data->res.dir_attr);

        NFS_PROTO(dir)->unlink_setup(&msg, data->dentry, inode);

        task_setup_data.rpc_client = NFS_CLIENT(dir);
        task = rpc_run_task(&task_setup_data);
        if (!IS_ERR(task))
                rpc_put_task_async(task);
}

static int nfs_call_unlink(struct dentry *dentry, struct inode *inode, struct nfs_unlinkdata *data)
{
        struct inode *dir = d_inode(dentry->d_parent);
        struct dentry *alias;

        down_read_non_owner(&NFS_I(dir)->rmdir_sem);
        alias = d_alloc_parallel(dentry->d_parent, &data->args.name, &data->wq);
        if (IS_ERR(alias)) {
                up_read_non_owner(&NFS_I(dir)->rmdir_sem);
                return 0;
        }
        if (!d_in_lookup(alias)) {
                int ret;
                void *devname_garbage = NULL;

                /*
                 * Hey, we raced with lookup... See if we need to transfer
                 * the sillyrename information to the aliased dentry.
                 */
                spin_lock(&alias->d_lock);
                if (d_really_is_positive(alias) &&
                    !(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
                        devname_garbage = alias->d_fsdata;
                        alias->d_fsdata = data;
                        alias->d_flags |= DCACHE_NFSFS_RENAMED;
                        ret = 1;
                } else
                        ret = 0;
                spin_unlock(&alias->d_lock);
                dput(alias);
                up_read_non_owner(&NFS_I(dir)->rmdir_sem);
                /*
                 * If we'd displaced old cached devname, free it.  At that
                 * point dentry is definitely not a root, so we won't need
                 * that anymore.
                 */
                kfree(devname_garbage);
                return ret;
        }
        data->dentry = alias;
        nfs_do_call_unlink(inode, data);
        return 1;
}

/**
 * nfs_async_unlink - asynchronous unlinking of a file
 * @dentry: parent directory of dentry
 * @name: name of dentry to unlink
 */
static int
nfs_async_unlink(struct dentry *dentry, const struct qstr *name)
{
        struct nfs_unlinkdata *data;
        int status = -ENOMEM;
        void *devname_garbage = NULL;

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (data == NULL)
                goto out;
        data->args.name.name = kstrdup(name->name, GFP_KERNEL);
        if (!data->args.name.name)
                goto out_free;
        data->args.name.len = name->len;

        data->cred = get_current_cred();
        data->res.dir_attr = &data->dir_attr;
        init_waitqueue_head(&data->wq);

        status = -EBUSY;
        spin_lock(&dentry->d_lock);
        if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
                goto out_unlock;
        dentry->d_flags |= DCACHE_NFSFS_RENAMED;
        devname_garbage = dentry->d_fsdata;
        dentry->d_fsdata = data;
        spin_unlock(&dentry->d_lock);
        /*
         * If we'd displaced old cached devname, free it.  At that
         * point dentry is definitely not a root, so we won't need
         * that anymore.
         */
        kfree(devname_garbage);
        return 0;
out_unlock:
        spin_unlock(&dentry->d_lock);
        put_cred(data->cred);
        kfree(data->args.name.name);
out_free:
        kfree(data);
out:
        return status;
}

/**
 * nfs_complete_unlink - Initialize completion of the sillydelete
 * @dentry: dentry to delete
 * @inode: inode
 *
 * Since we're most likely to be called by dentry_iput(), we
 * only use the dentry to find the sillydelete. We then copy the name
 * into the qstr.
 */
void
nfs_complete_unlink(struct dentry *dentry, struct inode *inode)
{
        struct nfs_unlinkdata   *data;

        spin_lock(&dentry->d_lock);
        dentry->d_flags &= ~DCACHE_NFSFS_RENAMED;
        data = dentry->d_fsdata;
        dentry->d_fsdata = NULL;
        spin_unlock(&dentry->d_lock);

        if (NFS_STALE(inode) || !nfs_call_unlink(dentry, inode, data))
                nfs_free_unlinkdata(data);
}

/* Cancel a queued async unlink. Called when a sillyrename run fails. */
static void
nfs_cancel_async_unlink(struct dentry *dentry)
{
        spin_lock(&dentry->d_lock);
        if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
                struct nfs_unlinkdata *data = dentry->d_fsdata;

                dentry->d_flags &= ~DCACHE_NFSFS_RENAMED;
                dentry->d_fsdata = NULL;
                spin_unlock(&dentry->d_lock);
                nfs_free_unlinkdata(data);
                return;
        }
        spin_unlock(&dentry->d_lock);
}

/**
 * nfs_async_rename_done - Sillyrename post-processing
 * @task: rpc_task of the sillyrename
 * @calldata: nfs_renamedata for the sillyrename
 *
 * Do the directory attribute updates and the d_move
 */
static void nfs_async_rename_done(struct rpc_task *task, void *calldata)
{
        struct nfs_renamedata *data = calldata;
        struct inode *old_dir = data->old_dir;
        struct inode *new_dir = data->new_dir;
        struct dentry *old_dentry = data->old_dentry;

        trace_nfs_sillyrename_rename(old_dir, old_dentry,
                        new_dir, data->new_dentry, task->tk_status);
        if (!NFS_PROTO(old_dir)->rename_done(task, old_dir, new_dir)) {
                rpc_restart_call_prepare(task);
                return;
        }

        if (data->complete)
                data->complete(task, data);
}

/**
 * nfs_async_rename_release - Release the sillyrename data.
 * @calldata: the struct nfs_renamedata to be released
 */
static void nfs_async_rename_release(void *calldata)
{
        struct nfs_renamedata   *data = calldata;
        struct super_block *sb = data->old_dir->i_sb;

        if (d_really_is_positive(data->old_dentry))
                nfs_mark_for_revalidate(d_inode(data->old_dentry));

        /* The result of the rename is unknown. Play it safe by
         * forcing a new lookup */
        if (data->cancelled) {
                spin_lock(&data->old_dir->i_lock);
                nfs_force_lookup_revalidate(data->old_dir);
                spin_unlock(&data->old_dir->i_lock);
                if (data->new_dir != data->old_dir) {
                        spin_lock(&data->new_dir->i_lock);
                        nfs_force_lookup_revalidate(data->new_dir);
                        spin_unlock(&data->new_dir->i_lock);
                }
        }

        dput(data->old_dentry);
        dput(data->new_dentry);
        iput(data->old_dir);
        iput(data->new_dir);
        nfs_sb_deactive(sb);
        put_cred(data->cred);
        kfree(data);
}

static void nfs_rename_prepare(struct rpc_task *task, void *calldata)
{
        struct nfs_renamedata *data = calldata;
        NFS_PROTO(data->old_dir)->rename_rpc_prepare(task, data);
}

static const struct rpc_call_ops nfs_rename_ops = {
        .rpc_call_done = nfs_async_rename_done,
        .rpc_release = nfs_async_rename_release,
        .rpc_call_prepare = nfs_rename_prepare,
};

/**
 * nfs_async_rename - perform an asynchronous rename operation
 * @old_dir: directory that currently holds the dentry to be renamed
 * @new_dir: target directory for the rename
 * @old_dentry: original dentry to be renamed
 * @new_dentry: dentry to which the old_dentry should be renamed
 * @complete: Function to run on successful completion
 *
 * It's expected that valid references to the dentries and inodes are held
 */
struct rpc_task *
nfs_async_rename(struct inode *old_dir, struct inode *new_dir,
                 struct dentry *old_dentry, struct dentry *new_dentry,
                 void (*complete)(struct rpc_task *, struct nfs_renamedata *))
{
        struct nfs_renamedata *data;
        struct rpc_message msg = { };
        struct rpc_task_setup task_setup_data = {
                .rpc_message = &msg,
                .callback_ops = &nfs_rename_ops,
                .workqueue = nfsiod_workqueue,
                .rpc_client = NFS_CLIENT(old_dir),
                .flags = RPC_TASK_ASYNC | RPC_TASK_CRED_NOREF,
        };

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (data == NULL)
                return ERR_PTR(-ENOMEM);
        task_setup_data.callback_data = data;

        data->cred = get_current_cred();

        msg.rpc_argp = &data->args;
        msg.rpc_resp = &data->res;
        msg.rpc_cred = data->cred;

        /* set up nfs_renamedata */
        data->old_dir = old_dir;
        ihold(old_dir);
        data->new_dir = new_dir;
        ihold(new_dir);
        data->old_dentry = dget(old_dentry);
        data->new_dentry = dget(new_dentry);
        nfs_fattr_init(&data->old_fattr);
        nfs_fattr_init(&data->new_fattr);
        data->complete = complete;

        /* set up nfs_renameargs */
        data->args.old_dir = NFS_FH(old_dir);
        data->args.old_name = &old_dentry->d_name;
        data->args.new_dir = NFS_FH(new_dir);
        data->args.new_name = &new_dentry->d_name;

        /* set up nfs_renameres */
        data->res.old_fattr = &data->old_fattr;
        data->res.new_fattr = &data->new_fattr;

        nfs_sb_active(old_dir->i_sb);

        NFS_PROTO(data->old_dir)->rename_setup(&msg, old_dentry, new_dentry);

        return rpc_run_task(&task_setup_data);
}

/*
 * Perform tasks needed when a sillyrename is done such as cancelling the
 * queued async unlink if it failed.
 */
static void
nfs_complete_sillyrename(struct rpc_task *task, struct nfs_renamedata *data)
{
        struct dentry *dentry = data->old_dentry;

        if (task->tk_status != 0) {
                nfs_cancel_async_unlink(dentry);
                return;
        }
}

#define SILLYNAME_PREFIX ".nfs"
#define SILLYNAME_PREFIX_LEN ((unsigned)sizeof(SILLYNAME_PREFIX) - 1)
#define SILLYNAME_FILEID_LEN ((unsigned)sizeof(u64) << 1)
#define SILLYNAME_COUNTER_LEN ((unsigned)sizeof(unsigned int) << 1)
#define SILLYNAME_LEN (SILLYNAME_PREFIX_LEN + \
                SILLYNAME_FILEID_LEN + \
                SILLYNAME_COUNTER_LEN)

/**
 * nfs_sillyrename - Perform a silly-rename of a dentry
 * @dir: inode of directory that contains dentry
 * @dentry: dentry to be sillyrenamed
 *
 * NFSv2/3 is stateless and the server doesn't know when the client is
 * holding a file open. To prevent application problems when a file is
 * unlinked while it's still open, the client performs a "silly-rename".
 * That is, it renames the file to a hidden file in the same directory,
 * and only performs the unlink once the last reference to it is put.
 *
 * The final cleanup is done during dentry_iput.
 *
 * (Note: NFSv4 is stateful, and has opens, so in theory an NFSv4 server
 * could take responsibility for keeping open files referenced.  The server
 * would also need to ensure that opened-but-deleted files were kept over
 * reboots.  However, we may not assume a server does so.  (RFC 5661
 * does provide an OPEN4_RESULT_PRESERVE_UNLINKED flag that a server can
 * use to advertise that it does this; some day we may take advantage of
 * it.))
 */
int
nfs_sillyrename(struct inode *dir, struct dentry *dentry)
{
        static unsigned int sillycounter;
        unsigned char silly[SILLYNAME_LEN + 1];
        unsigned long long fileid;
        struct dentry *sdentry;
        struct inode *inode = d_inode(dentry);
        struct rpc_task *task;
        int            error = -EBUSY;

        dfprintk(VFS, "NFS: silly-rename(%pd2, ct=%d)\n",
                dentry, d_count(dentry));
        nfs_inc_stats(dir, NFSIOS_SILLYRENAME);

        /*
         * We don't allow a dentry to be silly-renamed twice.
         */
        if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
                goto out;

        fileid = NFS_FILEID(d_inode(dentry));

        sdentry = NULL;
        do {
                int slen;
                dput(sdentry);
                sillycounter++;
                slen = scnprintf(silly, sizeof(silly),
                                SILLYNAME_PREFIX "%0*llx%0*x",
                                SILLYNAME_FILEID_LEN, fileid,
                                SILLYNAME_COUNTER_LEN, sillycounter);

                dfprintk(VFS, "NFS: trying to rename %pd to %s\n",
                                dentry, silly);

                sdentry = lookup_one_len(silly, dentry->d_parent, slen);
                /*
                 * N.B. Better to return EBUSY here ... it could be
                 * dangerous to delete the file while it's in use.
                 */
                if (IS_ERR(sdentry))
                        goto out;
        } while (d_inode(sdentry) != NULL); /* need negative lookup */

        ihold(inode);

        /* queue unlink first. Can't do this from rpc_release as it
         * has to allocate memory
         */
        error = nfs_async_unlink(dentry, &sdentry->d_name);
        if (error)
                goto out_dput;

        /* run the rename task, undo unlink if it fails */
        task = nfs_async_rename(dir, dir, dentry, sdentry,
                                        nfs_complete_sillyrename);
        if (IS_ERR(task)) {
                error = -EBUSY;
                nfs_cancel_async_unlink(dentry);
                goto out_dput;
        }

        /* wait for the RPC task to complete, unless a SIGKILL intervenes */
        error = rpc_wait_for_completion_task(task);
        if (error == 0)
                error = task->tk_status;
        switch (error) {
        case 0:
                /* The rename succeeded */
                nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
                spin_lock(&inode->i_lock);
                NFS_I(inode)->attr_gencount = nfs_inc_attr_generation_counter();
                nfs_set_cache_invalid(inode, NFS_INO_INVALID_CHANGE |
                                                     NFS_INO_INVALID_CTIME |
                                                     NFS_INO_REVAL_FORCED);
                spin_unlock(&inode->i_lock);
                d_move(dentry, sdentry);
                break;
        case -ERESTARTSYS:
                /* The result of the rename is unknown. Play it safe by
                 * forcing a new lookup */
                d_drop(dentry);
                d_drop(sdentry);
        }
        rpc_put_task(task);
out_dput:
        iput(inode);
        dput(sdentry);
out:
        return error;
}