xattr.c

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/*
 * linux/fs/reiserfs/xattr.c
 *
 * Copyright (c) 2002 by Jeff Mahoney, <[email protected]>
 *
 */

/*
 * In order to implement EA/ACLs in a clean, backwards compatible manner,
 * they are implemented as files in a "private" directory.
 * Each EA is in it's own file, with the directory layout like so (/ is assumed
 * to be relative to fs root). Inside the /.reiserfs_priv/xattrs directory,
 * directories named using the capital-hex form of the objectid and
 * generation number are used. Inside each directory are individual files
 * named with the name of the extended attribute.
 *
 * So, for objectid 12648430, we could have:
 * /.reiserfs_priv/xattrs/C0FFEE.0/system.posix_acl_access
 * /.reiserfs_priv/xattrs/C0FFEE.0/system.posix_acl_default
 * /.reiserfs_priv/xattrs/C0FFEE.0/user.Content-Type
 * .. or similar.
 *
 * The file contents are the text of the EA. The size is known based on the
 * stat data describing the file.
 *
 * In the case of system.posix_acl_access and system.posix_acl_default, since
 * these are special cases for filesystem ACLs, they are interpreted by the
 * kernel, in addition, they are negatively and positively cached and attached
 * to the inode so that unnecessary lookups are avoided.
 *
 * Locking works like so:
 * Directory components (xattr root, xattr dir) are protectd by their i_mutex.
 * The xattrs themselves are protected by the xattr_sem.
 */

#include "reiserfs.h"
#include <linux/capability.h>
#include <linux/dcache.h>
#include <linux/namei.h>
#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/xattr.h>
#include "xattr.h"
#include "acl.h"
#include <asm/uaccess.h>
#include <net/checksum.h>
#include <linux/stat.h>
#include <linux/quotaops.h>
#include <linux/security.h>

#define PRIVROOT_NAME ".reiserfs_priv"
#define XAROOT_NAME   "xattrs"


/* Helpers for inode ops. We do this so that we don't have all the VFS
 * overhead and also for proper i_mutex annotation.
 * dir->i_mutex must be held for all of them. */
#ifdef CONFIG_REISERFS_FS_XATTR
static int xattr_create(struct inode *dir, struct dentry *dentry, int mode)
{
    BUG_ON(!mutex_is_locked(&dir->i_mutex));
    return dir->i_op->create(dir, dentry, mode, true);
}
#endif

static int xattr_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
    BUG_ON(!mutex_is_locked(&dir->i_mutex));
    return dir->i_op->mkdir(dir, dentry, mode);
}

/* We use I_MUTEX_CHILD here to silence lockdep. It's safe because xattr
 * mutation ops aren't called during rename or splace, which are the
 * only other users of I_MUTEX_CHILD. It violates the ordering, but that's
 * better than allocating another subclass just for this code. */
static int xattr_unlink(struct inode *dir, struct dentry *dentry)
{
    int error;
    BUG_ON(!mutex_is_locked(&dir->i_mutex));

    reiserfs_mutex_lock_nested_safe(&dentry->d_inode->i_mutex,
                    I_MUTEX_CHILD, dir->i_sb);
    error = dir->i_op->unlink(dir, dentry);
    mutex_unlock(&dentry->d_inode->i_mutex);

    if (!error)
        d_delete(dentry);
    return error;
}

static int xattr_rmdir(struct inode *dir, struct dentry *dentry)
{
    int error;
    BUG_ON(!mutex_is_locked(&dir->i_mutex));

    reiserfs_mutex_lock_nested_safe(&dentry->d_inode->i_mutex,
                    I_MUTEX_CHILD, dir->i_sb);
    error = dir->i_op->rmdir(dir, dentry);
    if (!error)
        dentry->d_inode->i_flags |= S_DEAD;
    mutex_unlock(&dentry->d_inode->i_mutex);
    if (!error)
        d_delete(dentry);

    return error;
}

#define xattr_may_create(flags) (!flags || flags & XATTR_CREATE)

static struct dentry *open_xa_root(struct super_block *sb, int flags)
{
    struct dentry *privroot = REISERFS_SB(sb)->priv_root;
    struct dentry *xaroot;
    if (!privroot->d_inode)
        return ERR_PTR(-ENODATA);

    mutex_lock_nested(&privroot->d_inode->i_mutex, I_MUTEX_XATTR);

    xaroot = dget(REISERFS_SB(sb)->xattr_root);
    if (!xaroot)
        xaroot = ERR_PTR(-ENODATA);
    else if (!xaroot->d_inode) {
        int err = -ENODATA;
        if (xattr_may_create(flags))
            err = xattr_mkdir(privroot->d_inode, xaroot, 0700);
        if (err) {
            dput(xaroot);
            xaroot = ERR_PTR(err);
        }
    }

    mutex_unlock(&privroot->d_inode->i_mutex);
    return xaroot;
}

static struct dentry *open_xa_dir(const struct inode *inode, int flags)
{
    struct dentry *xaroot, *xadir;
    char namebuf[17];

    xaroot = open_xa_root(inode->i_sb, flags);
    if (IS_ERR(xaroot))
        return xaroot;

    snprintf(namebuf, sizeof(namebuf), "%X.%X",
         le32_to_cpu(INODE_PKEY(inode)->k_objectid),
         inode->i_generation);

    mutex_lock_nested(&xaroot->d_inode->i_mutex, I_MUTEX_XATTR);

    xadir = lookup_one_len(namebuf, xaroot, strlen(namebuf));
    if (!IS_ERR(xadir) && !xadir->d_inode) {
        int err = -ENODATA;
        if (xattr_may_create(flags))
            err = xattr_mkdir(xaroot->d_inode, xadir, 0700);
        if (err) {
            dput(xadir);
            xadir = ERR_PTR(err);
        }
    }

    mutex_unlock(&xaroot->d_inode->i_mutex);
    dput(xaroot);
    return xadir;
}

/* The following are side effects of other operations that aren't explicitly
 * modifying extended attributes. This includes operations such as permissions
 * or ownership changes, object deletions, etc. */
struct reiserfs_dentry_buf {
    struct dentry *xadir;
    int count;
    struct dentry *dentries[8];
};

static int
fill_with_dentries(void *buf, const char *name, int namelen, loff_t offset,
            u64 ino, unsigned int d_type)
{
    struct reiserfs_dentry_buf *dbuf = buf;
    struct dentry *dentry;
    WARN_ON_ONCE(!mutex_is_locked(&dbuf->xadir->d_inode->i_mutex));

    if (dbuf->count == ARRAY_SIZE(dbuf->dentries))
        return -ENOSPC;

    if (name[0] == '.' && (name[1] == '\0' ||
                   (name[1] == '.' && name[2] == '\0')))
        return 0;

    dentry = lookup_one_len(name, dbuf->xadir, namelen);
    if (IS_ERR(dentry)) {
        return PTR_ERR(dentry);
    } else if (!dentry->d_inode) {
        /* A directory entry exists, but no file? */
        reiserfs_error(dentry->d_sb, "xattr-20003",
                   "Corrupted directory: xattr %s listed but "
                   "not found for file %s.\n",
                   dentry->d_name.name, dbuf->xadir->d_name.name);
        dput(dentry);
        return -EIO;
    }

    dbuf->dentries[dbuf->count++] = dentry;
    return 0;
}

static void
cleanup_dentry_buf(struct reiserfs_dentry_buf *buf)
{
    int i;
    for (i = 0; i < buf->count; i++)
        if (buf->dentries[i])
            dput(buf->dentries[i]);
}

static int reiserfs_for_each_xattr(struct inode *inode,
                   int (*action)(struct dentry *, void *),
                   void *data)
{
    struct dentry *dir;
    int i, err = 0;
    loff_t pos = 0;
    struct reiserfs_dentry_buf buf = {
        .count = 0,
    };

    /* Skip out, an xattr has no xattrs associated with it */
    if (IS_PRIVATE(inode) || get_inode_sd_version(inode) == STAT_DATA_V1)
        return 0;

    reiserfs_write_unlock(inode->i_sb);
    dir = open_xa_dir(inode, XATTR_REPLACE);
    if (IS_ERR(dir)) {
        err = PTR_ERR(dir);
        reiserfs_write_lock(inode->i_sb);
        goto out;
    } else if (!dir->d_inode) {
        err = 0;
        reiserfs_write_lock(inode->i_sb);
        goto out_dir;
    }

    mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_XATTR);

    reiserfs_write_lock(inode->i_sb);

    buf.xadir = dir;
    err = reiserfs_readdir_dentry(dir, &buf, fill_with_dentries, &pos);
    while ((err == 0 || err == -ENOSPC) && buf.count) {
        err = 0;

        for (i = 0; i < buf.count && buf.dentries[i]; i++) {
            int lerr = 0;
            struct dentry *dentry = buf.dentries[i];

            if (err == 0 && !S_ISDIR(dentry->d_inode->i_mode))
                lerr = action(dentry, data);

            dput(dentry);
            buf.dentries[i] = NULL;
            err = lerr ?: err;
        }
        buf.count = 0;
        if (!err)
            err = reiserfs_readdir_dentry(dir, &buf,
                              fill_with_dentries, &pos);
    }
    mutex_unlock(&dir->d_inode->i_mutex);

    /* Clean up after a failed readdir */
    cleanup_dentry_buf(&buf);

    if (!err) {
        /* We start a transaction here to avoid a ABBA situation
         * between the xattr root's i_mutex and the journal lock.
         * This doesn't incur much additional overhead since the
         * new transaction will just nest inside the
         * outer transaction. */
        int blocks = JOURNAL_PER_BALANCE_CNT * 2 + 2 +
                 4 * REISERFS_QUOTA_TRANS_BLOCKS(inode->i_sb);
        struct reiserfs_transaction_handle th;
        err = journal_begin(&th, inode->i_sb, blocks);
        if (!err) {
            int jerror;
            reiserfs_mutex_lock_nested_safe(
                      &dir->d_parent->d_inode->i_mutex,
                      I_MUTEX_XATTR, inode->i_sb);
            err = action(dir, data);
            jerror = journal_end(&th, inode->i_sb, blocks);
            mutex_unlock(&dir->d_parent->d_inode->i_mutex);
            err = jerror ?: err;
        }
    }
out_dir:
    dput(dir);
out:
    /* -ENODATA isn't an error */
    if (err == -ENODATA)
        err = 0;
    return err;
}

static int delete_one_xattr(struct dentry *dentry, void *data)
{
    struct inode *dir = dentry->d_parent->d_inode;

    /* This is the xattr dir, handle specially. */
    if (S_ISDIR(dentry->d_inode->i_mode))
        return xattr_rmdir(dir, dentry);

    return xattr_unlink(dir, dentry);
}

static int chown_one_xattr(struct dentry *dentry, void *data)
{
    struct iattr *attrs = data;
    return reiserfs_setattr(dentry, attrs);
}

/* No i_mutex, but the inode is unconnected. */
int reiserfs_delete_xattrs(struct inode *inode)
{
    int err = reiserfs_for_each_xattr(inode, delete_one_xattr, NULL);
    if (err)
        reiserfs_warning(inode->i_sb, "jdm-20004",
                 "Couldn't delete all xattrs (%d)\n", err);
    return err;
}

/* inode->i_mutex: down */
int reiserfs_chown_xattrs(struct inode *inode, struct iattr *attrs)
{
    int err = reiserfs_for_each_xattr(inode, chown_one_xattr, attrs);
    if (err)
        reiserfs_warning(inode->i_sb, "jdm-20007",
                 "Couldn't chown all xattrs (%d)\n", err);
    return err;
}

#ifdef CONFIG_REISERFS_FS_XATTR
/* Returns a dentry corresponding to a specific extended attribute file
 * for the inode. If flags allow, the file is created. Otherwise, a
 * valid or negative dentry, or an error is returned. */
static struct dentry *xattr_lookup(struct inode *inode, const char *name,
                    int flags)
{
    struct dentry *xadir, *xafile;
    int err = 0;

    xadir = open_xa_dir(inode, flags);
    if (IS_ERR(xadir))
        return ERR_CAST(xadir);

    mutex_lock_nested(&xadir->d_inode->i_mutex, I_MUTEX_XATTR);
    xafile = lookup_one_len(name, xadir, strlen(name));
    if (IS_ERR(xafile)) {
        err = PTR_ERR(xafile);
        goto out;
    }

    if (xafile->d_inode && (flags & XATTR_CREATE))
        err = -EEXIST;

    if (!xafile->d_inode) {
        err = -ENODATA;
        if (xattr_may_create(flags))
            err = xattr_create(xadir->d_inode, xafile,
                          0700|S_IFREG);
    }

    if (err)
        dput(xafile);
out:
    mutex_unlock(&xadir->d_inode->i_mutex);
    dput(xadir);
    if (err)
        return ERR_PTR(err);
    return xafile;
}

/* Internal operations on file data */
static inline void reiserfs_put_page(struct page *page)
{
    kunmap(page);
    page_cache_release(page);
}

static struct page *reiserfs_get_page(struct inode *dir, size_t n)
{
    struct address_space *mapping = dir->i_mapping;
    struct page *page;
    /* We can deadlock if we try to free dentries,
       and an unlink/rmdir has just occurred - GFP_NOFS avoids this */
    mapping_set_gfp_mask(mapping, GFP_NOFS);
    page = read_mapping_page(mapping, n >> PAGE_CACHE_SHIFT, NULL);
    if (!IS_ERR(page)) {
        kmap(page);
        if (PageError(page))
            goto fail;
    }
    return page;

      fail:
    reiserfs_put_page(page);
    return ERR_PTR(-EIO);
}

static inline __u32 xattr_hash(const char *msg, int len)
{
    return csum_partial(msg, len, 0);
}

int reiserfs_commit_write(struct file *f, struct page *page,
              unsigned from, unsigned to);

static void update_ctime(struct inode *inode)
{
    struct timespec now = current_fs_time(inode->i_sb);
    if (inode_unhashed(inode) || !inode->i_nlink ||
        timespec_equal(&inode->i_ctime, &now))
        return;

    inode->i_ctime = CURRENT_TIME_SEC;
    mark_inode_dirty(inode);
}

static int lookup_and_delete_xattr(struct inode *inode, const char *name)
{
    int err = 0;
    struct dentry *dentry, *xadir;

    xadir = open_xa_dir(inode, XATTR_REPLACE);
    if (IS_ERR(xadir))
        return PTR_ERR(xadir);

    mutex_lock_nested(&xadir->d_inode->i_mutex, I_MUTEX_XATTR);
    dentry = lookup_one_len(name, xadir, strlen(name));
    if (IS_ERR(dentry)) {
        err = PTR_ERR(dentry);
        goto out_dput;
    }

    if (dentry->d_inode) {
        reiserfs_write_lock(inode->i_sb);
        err = xattr_unlink(xadir->d_inode, dentry);
        reiserfs_write_unlock(inode->i_sb);
        update_ctime(inode);
    }

    dput(dentry);
out_dput:
    mutex_unlock(&xadir->d_inode->i_mutex);
    dput(xadir);
    return err;
}


/* Generic extended attribute operations that can be used by xa plugins */

/*
 * inode->i_mutex: down
 */
int
reiserfs_xattr_set_handle(struct reiserfs_transaction_handle *th,
              struct inode *inode, const char *name,
              const void *buffer, size_t buffer_size, int flags)
{
    int err = 0;
    struct dentry *dentry;
    struct page *page;
    char *data;
    size_t file_pos = 0;
    size_t buffer_pos = 0;
    size_t new_size;
    __u32 xahash = 0;

    if (get_inode_sd_version(inode) == STAT_DATA_V1)
        return -EOPNOTSUPP;

    reiserfs_write_unlock(inode->i_sb);

    if (!buffer) {
        err = lookup_and_delete_xattr(inode, name);
        reiserfs_write_lock(inode->i_sb);
        return err;
    }

    dentry = xattr_lookup(inode, name, flags);
    if (IS_ERR(dentry)) {
        reiserfs_write_lock(inode->i_sb);
        return PTR_ERR(dentry);
    }

    down_write(&REISERFS_I(inode)->i_xattr_sem);

    reiserfs_write_lock(inode->i_sb);

    xahash = xattr_hash(buffer, buffer_size);
    while (buffer_pos < buffer_size || buffer_pos == 0) {
        size_t chunk;
        size_t skip = 0;
        size_t page_offset = (file_pos & (PAGE_CACHE_SIZE - 1));
        if (buffer_size - buffer_pos > PAGE_CACHE_SIZE)
            chunk = PAGE_CACHE_SIZE;
        else
            chunk = buffer_size - buffer_pos;

        page = reiserfs_get_page(dentry->d_inode, file_pos);
        if (IS_ERR(page)) {
            err = PTR_ERR(page);
            goto out_unlock;
        }

        lock_page(page);
        data = page_address(page);

        if (file_pos == 0) {
            struct reiserfs_xattr_header *rxh;
            skip = file_pos = sizeof(struct reiserfs_xattr_header);
            if (chunk + skip > PAGE_CACHE_SIZE)
                chunk = PAGE_CACHE_SIZE - skip;
            rxh = (struct reiserfs_xattr_header *)data;
            rxh->h_magic = cpu_to_le32(REISERFS_XATTR_MAGIC);
            rxh->h_hash = cpu_to_le32(xahash);
        }

        err = __reiserfs_write_begin(page, page_offset, chunk + skip);
        if (!err) {
            if (buffer)
                memcpy(data + skip, buffer + buffer_pos, chunk);
            err = reiserfs_commit_write(NULL, page, page_offset,
                            page_offset + chunk +
                            skip);
        }
        unlock_page(page);
        reiserfs_put_page(page);
        buffer_pos += chunk;
        file_pos += chunk;
        skip = 0;
        if (err || buffer_size == 0 || !buffer)
            break;
    }

    new_size = buffer_size + sizeof(struct reiserfs_xattr_header);
    if (!err && new_size < i_size_read(dentry->d_inode)) {
        struct iattr newattrs = {
            .ia_ctime = current_fs_time(inode->i_sb),
            .ia_size = new_size,
            .ia_valid = ATTR_SIZE | ATTR_CTIME,
        };

        reiserfs_write_unlock(inode->i_sb);
        mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_XATTR);
        inode_dio_wait(dentry->d_inode);
        reiserfs_write_lock(inode->i_sb);

        err = reiserfs_setattr(dentry, &newattrs);
        mutex_unlock(&dentry->d_inode->i_mutex);
    } else
        update_ctime(inode);
out_unlock:
    up_write(&REISERFS_I(inode)->i_xattr_sem);
    dput(dentry);
    return err;
}

/* We need to start a transaction to maintain lock ordering */
int reiserfs_xattr_set(struct inode *inode, const char *name,
               const void *buffer, size_t buffer_size, int flags)
{

    struct reiserfs_transaction_handle th;
    int error, error2;
    size_t jbegin_count = reiserfs_xattr_nblocks(inode, buffer_size);

    if (!(flags & XATTR_REPLACE))
        jbegin_count += reiserfs_xattr_jcreate_nblocks(inode);

    reiserfs_write_lock(inode->i_sb);
    error = journal_begin(&th, inode->i_sb, jbegin_count);
    if (error) {
        reiserfs_write_unlock(inode->i_sb);
        return error;
    }

    error = reiserfs_xattr_set_handle(&th, inode, name,
                      buffer, buffer_size, flags);

    error2 = journal_end(&th, inode->i_sb, jbegin_count);
    if (error == 0)
        error = error2;
    reiserfs_write_unlock(inode->i_sb);

    return error;
}

/*
 * inode->i_mutex: down
 */
int
reiserfs_xattr_get(struct inode *inode, const char *name, void *buffer,
           size_t buffer_size)
{
    ssize_t err = 0;
    struct dentry *dentry;
    size_t isize;
    size_t file_pos = 0;
    size_t buffer_pos = 0;
    struct page *page;
    __u32 hash = 0;

    if (name == NULL)
        return -EINVAL;

    /* We can't have xattrs attached to v1 items since they don't have
     * generation numbers */
    if (get_inode_sd_version(inode) == STAT_DATA_V1)
        return -EOPNOTSUPP;

    dentry = xattr_lookup(inode, name, XATTR_REPLACE);
    if (IS_ERR(dentry)) {
        err = PTR_ERR(dentry);
        goto out;
    }

    down_read(&REISERFS_I(inode)->i_xattr_sem);

    isize = i_size_read(dentry->d_inode);

    /* Just return the size needed */
    if (buffer == NULL) {
        err = isize - sizeof(struct reiserfs_xattr_header);
        goto out_unlock;
    }

    if (buffer_size < isize - sizeof(struct reiserfs_xattr_header)) {
        err = -ERANGE;
        goto out_unlock;
    }

    while (file_pos < isize) {
        size_t chunk;
        char *data;
        size_t skip = 0;
        if (isize - file_pos > PAGE_CACHE_SIZE)
            chunk = PAGE_CACHE_SIZE;
        else
            chunk = isize - file_pos;

        page = reiserfs_get_page(dentry->d_inode, file_pos);
        if (IS_ERR(page)) {
            err = PTR_ERR(page);
            goto out_unlock;
        }

        lock_page(page);
        data = page_address(page);
        if (file_pos == 0) {
            struct reiserfs_xattr_header *rxh =
                (struct reiserfs_xattr_header *)data;
            skip = file_pos = sizeof(struct reiserfs_xattr_header);
            chunk -= skip;
            /* Magic doesn't match up.. */
            if (rxh->h_magic != cpu_to_le32(REISERFS_XATTR_MAGIC)) {
                unlock_page(page);
                reiserfs_put_page(page);
                reiserfs_warning(inode->i_sb, "jdm-20001",
                         "Invalid magic for xattr (%s) "
                         "associated with %k", name,
                         INODE_PKEY(inode));
                err = -EIO;
                goto out_unlock;
            }
            hash = le32_to_cpu(rxh->h_hash);
        }
        memcpy(buffer + buffer_pos, data + skip, chunk);
        unlock_page(page);
        reiserfs_put_page(page);
        file_pos += chunk;
        buffer_pos += chunk;
        skip = 0;
    }
    err = isize - sizeof(struct reiserfs_xattr_header);

    if (xattr_hash(buffer, isize - sizeof(struct reiserfs_xattr_header)) !=
        hash) {
        reiserfs_warning(inode->i_sb, "jdm-20002",
                 "Invalid hash for xattr (%s) associated "
                 "with %k", name, INODE_PKEY(inode));
        err = -EIO;
    }

out_unlock:
    up_read(&REISERFS_I(inode)->i_xattr_sem);
    dput(dentry);

out:
    return err;
}

/*
 * In order to implement different sets of xattr operations for each xattr
 * prefix with the generic xattr API, a filesystem should create a
 * null-terminated array of struct xattr_handler (one for each prefix) and
 * hang a pointer to it off of the s_xattr field of the superblock.
 *
 * The generic_fooxattr() functions will use this list to dispatch xattr
 * operations to the correct xattr_handler.
 */
#define for_each_xattr_handler(handlers, handler)       \
        for ((handler) = *(handlers)++;         \
            (handler) != NULL;          \
            (handler) = *(handlers)++)

/* This is the implementation for the xattr plugin infrastructure */
static inline const struct xattr_handler *
find_xattr_handler_prefix(const struct xattr_handler **handlers,
               const char *name)
{
    const struct xattr_handler *xah;

    if (!handlers)
        return NULL;

    for_each_xattr_handler(handlers, xah) {
        if (strncmp(xah->prefix, name, strlen(xah->prefix)) == 0)
            break;
    }

    return xah;
}


/*
 * Inode operation getxattr()
 */
ssize_t
reiserfs_getxattr(struct dentry * dentry, const char *name, void *buffer,
          size_t size)
{
    const struct xattr_handler *handler;

    handler = find_xattr_handler_prefix(dentry->d_sb->s_xattr, name);

    if (!handler || get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
        return -EOPNOTSUPP;

    return handler->get(dentry, name, buffer, size, handler->flags);
}

/*
 * Inode operation setxattr()
 *
 * dentry->d_inode->i_mutex down
 */
int
reiserfs_setxattr(struct dentry *dentry, const char *name, const void *value,
          size_t size, int flags)
{
    const struct xattr_handler *handler;

    handler = find_xattr_handler_prefix(dentry->d_sb->s_xattr, name);

    if (!handler || get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
        return -EOPNOTSUPP;

    return handler->set(dentry, name, value, size, flags, handler->flags);
}

/*
 * Inode operation removexattr()
 *
 * dentry->d_inode->i_mutex down
 */
int reiserfs_removexattr(struct dentry *dentry, const char *name)
{
    const struct xattr_handler *handler;
    handler = find_xattr_handler_prefix(dentry->d_sb->s_xattr, name);

    if (!handler || get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
        return -EOPNOTSUPP;

    return handler->set(dentry, name, NULL, 0, XATTR_REPLACE, handler->flags);
}

struct listxattr_buf {
    size_t size;
    size_t pos;
    char *buf;
    struct dentry *dentry;
};

static int listxattr_filler(void *buf, const char *name, int namelen,
                loff_t offset, u64 ino, unsigned int d_type)
{
    struct listxattr_buf *b = (struct listxattr_buf *)buf;
    size_t size;
    if (name[0] != '.' ||
        (namelen != 1 && (name[1] != '.' || namelen != 2))) {
        const struct xattr_handler *handler;
        handler = find_xattr_handler_prefix(b->dentry->d_sb->s_xattr,
                            name);
        if (!handler)   /* Unsupported xattr name */
            return 0;
        if (b->buf) {
            size = handler->list(b->dentry, b->buf + b->pos,
                     b->size, name, namelen,
                     handler->flags);
            if (size > b->size)
                return -ERANGE;
        } else {
            size = handler->list(b->dentry, NULL, 0, name,
                         namelen, handler->flags);
        }

        b->pos += size;
    }
    return 0;
}

/*
 * Inode operation listxattr()
 *
 * We totally ignore the generic listxattr here because it would be stupid
 * not to. Since the xattrs are organized in a directory, we can just
 * readdir to find them.
 */
ssize_t reiserfs_listxattr(struct dentry * dentry, char *buffer, size_t size)
{
    struct dentry *dir;
    int err = 0;
    loff_t pos = 0;
    struct listxattr_buf buf = {
        .dentry = dentry,
        .buf = buffer,
        .size = buffer ? size : 0,
    };

    if (!dentry->d_inode)
        return -EINVAL;

    if (!dentry->d_sb->s_xattr ||
        get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
        return -EOPNOTSUPP;

    dir = open_xa_dir(dentry->d_inode, XATTR_REPLACE);
    if (IS_ERR(dir)) {
        err = PTR_ERR(dir);
        if (err == -ENODATA)
            err = 0;  /* Not an error if there aren't any xattrs */
        goto out;
    }

    mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_XATTR);
    err = reiserfs_readdir_dentry(dir, &buf, listxattr_filler, &pos);
    mutex_unlock(&dir->d_inode->i_mutex);

    if (!err)
        err = buf.pos;

    dput(dir);
out:
    return err;
}

static int create_privroot(struct dentry *dentry)
{
    int err;
    struct inode *inode = dentry->d_parent->d_inode;
    WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));

    err = xattr_mkdir(inode, dentry, 0700);
    if (err || !dentry->d_inode) {
        reiserfs_warning(dentry->d_sb, "jdm-20006",
                 "xattrs/ACLs enabled and couldn't "
                 "find/create .reiserfs_priv. "
                 "Failing mount.");
        return -EOPNOTSUPP;
    }

    dentry->d_inode->i_flags |= S_PRIVATE;
    reiserfs_info(dentry->d_sb, "Created %s - reserved for xattr "
              "storage.\n", PRIVROOT_NAME);

    return 0;
}

#else
int __init reiserfs_xattr_register_handlers(void) { return 0; }
void reiserfs_xattr_unregister_handlers(void) {}
static int create_privroot(struct dentry *dentry) { return 0; }
#endif

/* Actual operations that are exported to VFS-land */
static const struct xattr_handler *reiserfs_xattr_handlers[] = {
#ifdef CONFIG_REISERFS_FS_XATTR
    &reiserfs_xattr_user_handler,
    &reiserfs_xattr_trusted_handler,
#endif
#ifdef CONFIG_REISERFS_FS_SECURITY
    &reiserfs_xattr_security_handler,
#endif
#ifdef CONFIG_REISERFS_FS_POSIX_ACL
    &reiserfs_posix_acl_access_handler,
    &reiserfs_posix_acl_default_handler,
#endif
    NULL
};

static int xattr_mount_check(struct super_block *s)
{
    /* We need generation numbers to ensure that the oid mapping is correct
     * v3.5 filesystems don't have them. */
    if (old_format_only(s)) {
        if (reiserfs_xattrs_optional(s)) {
            /* Old format filesystem, but optional xattrs have
             * been enabled. Error out. */
            reiserfs_warning(s, "jdm-2005",
                     "xattrs/ACLs not supported "
                     "on pre-v3.6 format filesystems. "
                     "Failing mount.");
            return -EOPNOTSUPP;
        }
    }

    return 0;
}

int reiserfs_permission(struct inode *inode, int mask)
{
    /*
     * We don't do permission checks on the internal objects.
     * Permissions are determined by the "owning" object.
     */
    if (IS_PRIVATE(inode))
        return 0;

    return generic_permission(inode, mask);
}

static int xattr_hide_revalidate(struct dentry *dentry, unsigned int flags)
{
    return -EPERM;
}

static const struct dentry_operations xattr_lookup_poison_ops = {
    .d_revalidate = xattr_hide_revalidate,
};

int reiserfs_lookup_privroot(struct super_block *s)
{
    struct dentry *dentry;
    int err = 0;

    /* If we don't have the privroot located yet - go find it */
    reiserfs_mutex_lock_safe(&s->s_root->d_inode->i_mutex, s);
    dentry = lookup_one_len(PRIVROOT_NAME, s->s_root,
                strlen(PRIVROOT_NAME));
    if (!IS_ERR(dentry)) {
        REISERFS_SB(s)->priv_root = dentry;
        d_set_d_op(dentry, &xattr_lookup_poison_ops);
        if (dentry->d_inode)
            dentry->d_inode->i_flags |= S_PRIVATE;
    } else
        err = PTR_ERR(dentry);
    mutex_unlock(&s->s_root->d_inode->i_mutex);

    return err;
}

/* We need to take a copy of the mount flags since things like
 * MS_RDONLY don't get set until *after* we're called.
 * mount_flags != mount_options */
int reiserfs_xattr_init(struct super_block *s, int mount_flags)
{
    int err = 0;
    struct dentry *privroot = REISERFS_SB(s)->priv_root;

    err = xattr_mount_check(s);
    if (err)
        goto error;

    if (!privroot->d_inode && !(mount_flags & MS_RDONLY)) {
        reiserfs_mutex_lock_safe(&s->s_root->d_inode->i_mutex, s);
        err = create_privroot(REISERFS_SB(s)->priv_root);
        mutex_unlock(&s->s_root->d_inode->i_mutex);
    }

    if (privroot->d_inode) {
        s->s_xattr = reiserfs_xattr_handlers;
        reiserfs_mutex_lock_safe(&privroot->d_inode->i_mutex, s);
        if (!REISERFS_SB(s)->xattr_root) {
            struct dentry *dentry;
            dentry = lookup_one_len(XAROOT_NAME, privroot,
                        strlen(XAROOT_NAME));
            if (!IS_ERR(dentry))
                REISERFS_SB(s)->xattr_root = dentry;
            else
                err = PTR_ERR(dentry);
        }
        mutex_unlock(&privroot->d_inode->i_mutex);
    }

error:
    if (err) {
        clear_bit(REISERFS_XATTRS_USER, &(REISERFS_SB(s)->s_mount_opt));
        clear_bit(REISERFS_POSIXACL, &(REISERFS_SB(s)->s_mount_opt));
    }

    /* The super_block MS_POSIXACL must mirror the (no)acl mount option. */
    if (reiserfs_posixacl(s))
        s->s_flags |= MS_POSIXACL;
    else
        s->s_flags &= ~MS_POSIXACL;

    return err;
}