/*
 * linux/fs/reiserfs/xattr.c
 *
 * Copyright (c) 2002 by Jeff Mahoney, <jeffm@suse.com>
 *
 */

/*
 * 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.
 */

#include <linux/reiserfs_fs.h>
#include <linux/capability.h>
#include <linux/dcache.h>
#include <linux/namei.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/xattr.h>
#include <linux/reiserfs_xattr.h>
#include <linux/reiserfs_acl.h>
#include <asm/uaccess.h>
#include <net/checksum.h>
#include <linux/smp_lock.h>
#include <linux/stat.h>
#include <asm/semaphore.h>

#define FL_READONLY 128
#define FL_DIR_SEM_HELD 256
#define PRIVROOT_NAME ".reiserfs_priv"
#define XAROOT_NAME   "xattrs"

static struct reiserfs_xattr_handler *find_xattr_handler_prefix(const char
                                                                *prefix);

/* Returns the dentry referring to the root of the extended attribute
 * directory tree. If it has already been retrieved, it is used. If it
 * hasn't been created and the flags indicate creation is allowed, we
 * attempt to create it. On error, we return a pointer-encoded error.
 */
static struct dentry *get_xa_root(struct super_block *sb, int flags)
{
        struct dentry *privroot = dget(REISERFS_SB(sb)->priv_root);
        struct dentry *xaroot;

        /* This needs to be created at mount-time */
        if (!privroot)
                return ERR_PTR(-ENODATA);

        mutex_lock_nested(&privroot->d_inode->i_mutex, I_MUTEX_XATTR);
        if (REISERFS_SB(sb)->xattr_root) {
                xaroot = dget(REISERFS_SB(sb)->xattr_root);
                goto out;
        }

        xaroot = lookup_one_len(XAROOT_NAME, privroot, strlen(XAROOT_NAME));
        if (IS_ERR(xaroot)) {
                goto out;
        } else if (!xaroot->d_inode) {
                int err = -ENODATA;
                if (flags == 0 || flags & XATTR_CREATE)
                        err = privroot->d_inode->i_op->mkdir(privroot->d_inode,
                                                             xaroot, 0700);
                if (err) {
                        dput(xaroot);
                        xaroot = ERR_PTR(err);
                        goto out;
                }
        }
        REISERFS_SB(sb)->xattr_root = dget(xaroot);

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

/* Opens the directory corresponding to the inode's extended attribute store.
 * If flags allow, the tree to the directory may be created. If creation is
 * prohibited, -ENODATA is returned. */
static struct dentry *open_xa_dir(const struct inode *inode, int flags)
{
        struct dentry *xaroot, *xadir;
        char namebuf[17];

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

        /* ok, we have xaroot open */
        snprintf(namebuf, sizeof(namebuf), "%X.%X",
                 le32_to_cpu(INODE_PKEY(inode)->k_objectid),
                 inode->i_generation);
        xadir = lookup_one_len(namebuf, xaroot, strlen(namebuf));
        if (IS_ERR(xadir)) {
                dput(xaroot);
                return xadir;
        }

        if (!xadir->d_inode) {
                int err;
                if (flags == 0 || flags & XATTR_CREATE) {
                        /* Although there is nothing else trying to create this directory,
                         * another directory with the same hash may be created, so we need
                         * to protect against that */
                        err =
                            xaroot->d_inode->i_op->mkdir(xaroot->d_inode, xadir,
                                                         0700);
                        if (err) {
                                dput(xaroot);
                                dput(xadir);
                                return ERR_PTR(err);
                        }
                }
                if (!xadir->d_inode) {
                        dput(xaroot);
                        dput(xadir);
                        return ERR_PTR(-ENODATA);
                }
        }

        dput(xaroot);
        return xadir;
}

/* 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 *get_xa_file_dentry(const 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_PTR(PTR_ERR(xadir));
        } else if (xadir && !xadir->d_inode) {
                dput(xadir);
                return ERR_PTR(-ENODATA);
        }

        xafile = lookup_one_len(name, xadir, strlen(name));
        if (IS_ERR(xafile)) {
                dput(xadir);
                return ERR_PTR(PTR_ERR(xafile));
        }

        if (xafile->d_inode) {  /* file exists */
                if (flags & XATTR_CREATE) {
                        err = -EEXIST;
                        dput(xafile);
                        goto out;
                }
        } else if (flags & XATTR_REPLACE || flags & FL_READONLY) {
                goto out;
        } else {
                /* inode->i_mutex is down, so nothing else can try to create
                 * the same xattr */
                err = xadir->d_inode->i_op->create(xadir->d_inode, xafile,
                                                   0700 | S_IFREG, NULL);

                if (err) {
                        dput(xafile);
                        goto out;
                }
        }

      out:
        dput(xadir);
        if (err)
                xafile = ERR_PTR(err);
        return xafile;
}

/* Opens a file pointer to the attribute associated with inode */
static struct file *open_xa_file(const struct inode *inode, const char *name,
                                 int flags)
{
        struct dentry *xafile;
        struct file *fp;

        xafile = get_xa_file_dentry(inode, name, flags);
        if (IS_ERR(xafile))
                return ERR_PTR(PTR_ERR(xafile));
        else if (!xafile->d_inode) {
                dput(xafile);
                return ERR_PTR(-ENODATA);
        }

        fp = dentry_open(xafile, NULL, O_RDWR);
        /* dentry_open dputs the dentry if it fails */

        return fp;
}

/*
 * this is very similar to fs/reiserfs/dir.c:reiserfs_readdir, but
 * we need to drop the path before calling the filldir struct.  That
 * would be a big performance hit to the non-xattr case, so I've copied
 * the whole thing for now. --clm
 *
 * the big difference is that I go backwards through the directory,
 * and don't mess with f->f_pos, but the idea is the same.  Do some
 * action on each and every entry in the directory.
 *
 * we're called with i_mutex held, so there are no worries about the directory
 * changing underneath us.
 */
static int __xattr_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
        struct inode *inode = filp->f_path.dentry->d_inode;
        struct cpu_key pos_key; /* key of current position in the directory (key of directory entry) */
        INITIALIZE_PATH(path_to_entry);
        struct buffer_head *bh;
        int entry_num;
        struct item_head *ih, tmp_ih;
        int search_res;
        char *local_buf;
        loff_t next_pos;
        char small_buf[32];     /* avoid kmalloc if we can */
        struct reiserfs_de_head *deh;
        int d_reclen;
        char *d_name;
        off_t d_off;
        ino_t d_ino;
        struct reiserfs_dir_entry de;

        /* form key for search the next directory entry using f_pos field of
           file structure */
        next_pos = max_reiserfs_offset(inode);

        while (1) {
              research:
                if (next_pos <= DOT_DOT_OFFSET)
                        break;
                make_cpu_key(&pos_key, inode, next_pos, TYPE_DIRENTRY, 3);

                search_res =
                    search_by_entry_key(inode->i_sb, &pos_key, &path_to_entry,
                                        &de);
                if (search_res == IO_ERROR) {
                        // FIXME: we could just skip part of directory which could
                        // not be read
                        pathrelse(&path_to_entry);
                        return -EIO;
                }

                if (search_res == NAME_NOT_FOUND)
                        de.de_entry_num--;

                set_de_name_and_namelen(&de);
                entry_num = de.de_entry_num;
                deh = &(de.de_deh[entry_num]);

                bh = de.de_bh;
                ih = de.de_ih;

                if (!is_direntry_le_ih(ih)) {
                        reiserfs_warning(inode->i_sb, "not direntry %h", ih);
                        break;
                }
                copy_item_head(&tmp_ih, ih);

                /* we must have found item, that is item of this directory, */
                RFALSE(COMP_SHORT_KEYS(&(ih->ih_key), &pos_key),
                       "vs-9000: found item %h does not match to dir we readdir %K",
                       ih, &pos_key);

                if (deh_offset(deh) <= DOT_DOT_OFFSET) {
                        break;
                }

                /* look for the previous entry in the directory */
                next_pos = deh_offset(deh) - 1;

                if (!de_visible(deh))
                        /* it is hidden entry */
                        continue;

                d_reclen = entry_length(bh, ih, entry_num);
                d_name = B_I_DEH_ENTRY_FILE_NAME(bh, ih, deh);
                d_off = deh_offset(deh);
                d_ino = deh_objectid(deh);

                if (!d_name[d_reclen - 1])
                        d_reclen = strlen(d_name);

                if (d_reclen > REISERFS_MAX_NAME(inode->i_sb->s_blocksize)) {
                        /* too big to send back to VFS */
                        continue;
                }

                /* Ignore the .reiserfs_priv entry */
                if (reiserfs_xattrs(inode->i_sb) &&
                    !old_format_only(inode->i_sb) &&
                    deh_objectid(deh) ==
                    le32_to_cpu(INODE_PKEY
                                (REISERFS_SB(inode->i_sb)->priv_root->d_inode)->
                                k_objectid))
                        continue;

                if (d_reclen <= 32) {
                        local_buf = small_buf;
                } else {
                        local_buf = kmalloc(d_reclen, GFP_NOFS);
                        if (!local_buf) {
                                pathrelse(&path_to_entry);
                                return -ENOMEM;
                        }
                        if (item_moved(&tmp_ih, &path_to_entry)) {
                                kfree(local_buf);

                                /* sigh, must retry.  Do this same offset again */
                                next_pos = d_off;
                                goto research;
                        }
                }

                // Note, that we copy name to user space via temporary
                // buffer (local_buf) because filldir will block if
                // user space buffer is swapped out. At that time
                // entry can move to somewhere else
                memcpy(local_buf, d_name, d_reclen);

                /* the filldir function might need to start transactions,
                 * or do who knows what.  Release the path now that we've
                 * copied all the important stuff out of the deh
                 */
                pathrelse(&path_to_entry);

                if (filldir(dirent, local_buf, d_reclen, d_off, d_ino,
                            DT_UNKNOWN) < 0) {
                        if (local_buf != small_buf) {
                                kfree(local_buf);
                        }
                        goto end;
                }
                if (local_buf != small_buf) {
                        kfree(local_buf);
                }
        }                       /* while */

      end:
        pathrelse(&path_to_entry);
        return 0;
}

/*
 * this could be done with dedicated readdir ops for the xattr files,
 * but I want to get something working asap
 * this is stolen from vfs_readdir
 *
 */
static
int xattr_readdir(struct file *file, filldir_t filler, void *buf)
{
        struct inode *inode = file->f_path.dentry->d_inode;
        int res = -ENOTDIR;
        if (!file->f_op || !file->f_op->readdir)
                goto out;
        mutex_lock_nested(&inode->i_mutex, I_MUTEX_XATTR);
//        down(&inode->i_zombie);
        res = -ENOENT;
        if (!IS_DEADDIR(inode)) {
                lock_kernel();
                res = __xattr_readdir(file, buf, filler);
                unlock_kernel();
        }
//        up(&inode->i_zombie);
        mutex_unlock(&inode->i_mutex);
      out:
        return res;
}

/* 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, unsigned long 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 occured - GFP_NOFS avoids this */
        mapping_set_gfp_mask(mapping, GFP_NOFS);
        page = read_mapping_page(mapping, n, 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);
int reiserfs_prepare_write(struct file *f, struct page *page,
                           unsigned from, unsigned to);


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

/*
 * inode->i_mutex: down
 */
int
reiserfs_xattr_set(struct inode *inode, const char *name, const void *buffer,
                   size_t buffer_size, int flags)
{
        int err = 0;
        struct file *fp;
        struct page *page;
        char *data;
        struct address_space *mapping;
        size_t file_pos = 0;
        size_t buffer_pos = 0;
        struct inode *xinode;
        struct iattr newattrs;
        __u32 xahash = 0;

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

        /* Empty xattrs are ok, they're just empty files, no hash */
        if (buffer && buffer_size)
                xahash = xattr_hash(buffer, buffer_size);

      open_file:
        fp = open_xa_file(inode, name, flags);
        if (IS_ERR(fp)) {
                err = PTR_ERR(fp);
                goto out;
        }

        xinode = fp->f_path.dentry->d_inode;
        REISERFS_I(inode)->i_flags |= i_has_xattr_dir;

        /* we need to copy it off.. */
        if (xinode->i_nlink > 1) {
                fput(fp);
                err = reiserfs_xattr_del(inode, name);
                if (err < 0)
                        goto out;
                /* We just killed the old one, we're not replacing anymore */
                if (flags & XATTR_REPLACE)
                        flags &= ~XATTR_REPLACE;
                goto open_file;
        }

        /* Resize it so we're ok to write there */
        newattrs.ia_size = buffer_size;
        newattrs.ia_valid = ATTR_SIZE | ATTR_CTIME;
        mutex_lock_nested(&xinode->i_mutex, I_MUTEX_XATTR);
        err = notify_change(fp->f_path.dentry, &newattrs);
        if (err)
                goto out_filp;

        mapping = xinode->i_mapping;
        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(xinode, file_pos >> PAGE_CACHE_SHIFT);
                if (IS_ERR(page)) {
                        err = PTR_ERR(page);
                        goto out_filp;
                }

                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_prepare_write(fp, page, page_offset,
                                            page_offset + chunk + skip);
                if (!err) {
                        if (buffer)
                                memcpy(data + skip, buffer + buffer_pos, chunk);
                        err =
                            reiserfs_commit_write(fp, 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;
        }

        /* We can't mark the inode dirty if it's not hashed. This is the case
         * when we're inheriting the default ACL. If we dirty it, the inode
         * gets marked dirty, but won't (ever) make it onto the dirty list until
         * it's synced explicitly to clear I_DIRTY. This is bad. */
        if (!hlist_unhashed(&inode->i_hash)) {
                inode->i_ctime = CURRENT_TIME_SEC;
                mark_inode_dirty(inode);
        }

      out_filp:
        mutex_unlock(&xinode->i_mutex);
        fput(fp);

      out:
        return err;
}

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

        fp = open_xa_file(inode, name, FL_READONLY);
        if (IS_ERR(fp)) {
                err = PTR_ERR(fp);
                goto out;
        }

        xinode = fp->f_path.dentry->d_inode;
        isize = xinode->i_size;
        REISERFS_I(inode)->i_flags |= i_has_xattr_dir;

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

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

        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(xinode, file_pos >> PAGE_CACHE_SHIFT);
                if (IS_ERR(page)) {
                        err = PTR_ERR(page);
                        goto out_dput;
                }

                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,
                                                 "Invalid magic for xattr (%s) "
                                                 "associated with %k", name,
                                                 INODE_PKEY(inode));
                                err = -EIO;
                                goto out_dput;
                        }
                        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,
                                 "Invalid hash for xattr (%s) associated "
                                 "with %k", name, INODE_PKEY(inode));
                err = -EIO;
        }

      out_dput:
        fput(fp);

      out:
        return err;
}

static int
__reiserfs_xattr_del(struct dentry *xadir, const char *name, int namelen)
{
        struct dentry *dentry;
        struct inode *dir = xadir->d_inode;
        int err = 0;

        dentry = lookup_one_len(name, xadir, namelen);
        if (IS_ERR(dentry)) {
                err = PTR_ERR(dentry);
                goto out;
        } else if (!dentry->d_inode) {
                err = -ENODATA;
                goto out_file;
        }

        /* Skip directories.. */
        if (S_ISDIR(dentry->d_inode->i_mode))
                goto out_file;

        if (!is_reiserfs_priv_object(dentry->d_inode)) {
                reiserfs_warning(dir->i_sb, "OID %08x [%.*s/%.*s] doesn't have "
                                 "priv flag set [parent is %sset].",
                                 le32_to_cpu(INODE_PKEY(dentry->d_inode)->
                                             k_objectid), xadir->d_name.len,
                                 xadir->d_name.name, namelen, name,
                                 is_reiserfs_priv_object(xadir->
                                                         d_inode) ? "" :
                                 "not ");
                dput(dentry);
                return -EIO;
        }

        err = dir->i_op->unlink(dir, dentry);
        if (!err)
                d_delete(dentry);

      out_file:
        dput(dentry);

      out:
        return err;
}

int reiserfs_xattr_del(struct inode *inode, const char *name)
{
        struct dentry *dir;
        int err;

        dir = open_xa_dir(inode, FL_READONLY);
        if (IS_ERR(dir)) {
                err = PTR_ERR(dir);
                goto out;
        }

        err = __reiserfs_xattr_del(dir, name, strlen(name));
        dput(dir);

        if (!err) {
                inode->i_ctime = CURRENT_TIME_SEC;
                mark_inode_dirty(inode);
        }

      out:
        return err;
}

/* 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. */

static int
reiserfs_delete_xattrs_filler(void *buf, const char *name, int namelen,
                              loff_t offset, u64 ino, unsigned int d_type)
{
        struct dentry *xadir = (struct dentry *)buf;

        return __reiserfs_xattr_del(xadir, name, namelen);

}

/* This is called w/ inode->i_mutex downed */
int reiserfs_delete_xattrs(struct inode *inode)
{
        struct file *fp;
        struct dentry *dir, *root;
        int err = 0;

        /* Skip out, an xattr has no xattrs associated with it */
        if (is_reiserfs_priv_object(inode) ||
            get_inode_sd_version(inode) == STAT_DATA_V1 ||
            !reiserfs_xattrs(inode->i_sb)) {
                return 0;
        }
        reiserfs_read_lock_xattrs(inode->i_sb);
        dir = open_xa_dir(inode, FL_READONLY);
        reiserfs_read_unlock_xattrs(inode->i_sb);
        if (IS_ERR(dir)) {
                err = PTR_ERR(dir);
                goto out;
        } else if (!dir->d_inode) {
                dput(dir);
                return 0;
        }

        fp = dentry_open(dir, NULL, O_RDWR);
        if (IS_ERR(fp)) {
                err = PTR_ERR(fp);
                /* dentry_open dputs the dentry if it fails */
                goto out;
        }

        lock_kernel();
        err = xattr_readdir(fp, reiserfs_delete_xattrs_filler, dir);
        if (err) {
                unlock_kernel();
                goto out_dir;
        }

        /* Leftovers besides . and .. -- that's not good. */
        if (dir->d_inode->i_nlink <= 2) {
                root = get_xa_root(inode->i_sb, XATTR_REPLACE);
                reiserfs_write_lock_xattrs(inode->i_sb);
                err = vfs_rmdir(root->d_inode, dir);
                reiserfs_write_unlock_xattrs(inode->i_sb);
                dput(root);
        } else {
                reiserfs_warning(inode->i_sb,
                                 "Couldn't remove all entries in directory");
        }
        unlock_kernel();

      out_dir:
        fput(fp);

      out:
        if (!err)
                REISERFS_I(inode)->i_flags =
                    REISERFS_I(inode)->i_flags & ~i_has_xattr_dir;
        return err;
}

struct reiserfs_chown_buf {
        struct inode *inode;
        struct dentry *xadir;
        struct iattr *attrs;
};

/* XXX: If there is a better way to do this, I'd love to hear about it */
static int
reiserfs_chown_xattrs_filler(void *buf, const char *name, int namelen,
                             loff_t offset, u64 ino, unsigned int d_type)
{
        struct reiserfs_chown_buf *chown_buf = (struct reiserfs_chown_buf *)buf;
        struct dentry *xafile, *xadir = chown_buf->xadir;
        struct iattr *attrs = chown_buf->attrs;
        int err = 0;

        xafile = lookup_one_len(name, xadir, namelen);
        if (IS_ERR(xafile))
                return PTR_ERR(xafile);
        else if (!xafile->d_inode) {
                dput(xafile);
                return -ENODATA;
        }

        if (!S_ISDIR(xafile->d_inode->i_mode))
                err = notify_change(xafile, attrs);
        dput(xafile);

        return err;
}

int reiserfs_chown_xattrs(struct inode *inode, struct iattr *attrs)
{
        struct file *fp;
        struct dentry *dir;
        int err = 0;
        struct reiserfs_chown_buf buf;
        unsigned int ia_valid = attrs->ia_valid;

        /* Skip out, an xattr has no xattrs associated with it */
        if (is_reiserfs_priv_object(inode) ||
            get_inode_sd_version(inode) == STAT_DATA_V1 ||
            !reiserfs_xattrs(inode->i_sb)) {
                return 0;
        }
        reiserfs_read_lock_xattrs(inode->i_sb);
        dir = open_xa_dir(inode, FL_READONLY);
        reiserfs_read_unlock_xattrs(inode->i_sb);
        if (IS_ERR(dir)) {
                if (PTR_ERR(dir) != -ENODATA)
                        err = PTR_ERR(dir);
                goto out;
        } else if (!dir->d_inode) {
                dput(dir);
                goto out;
        }

        fp = dentry_open(dir, NULL, O_RDWR);
        if (IS_ERR(fp)) {
                err = PTR_ERR(fp);
                /* dentry_open dputs the dentry if it fails */
                goto out;
        }

        lock_kernel();

        attrs->ia_valid &= (ATTR_UID | ATTR_GID | ATTR_CTIME);
        buf.xadir = dir;
        buf.attrs = attrs;
        buf.inode = inode;

        err = xattr_readdir(fp, reiserfs_chown_xattrs_filler, &buf);
        if (err) {
                unlock_kernel();
                goto out_dir;
        }

        err = notify_change(dir, attrs);
        unlock_kernel();

      out_dir:
        fput(fp);

      out:
        attrs->ia_valid = ia_valid;
        return err;
}

/* Actual operations that are exported to VFS-land */

/*
 * Inode operation getxattr()
 * Preliminary locking: we down dentry->d_inode->i_mutex
 */
ssize_t
reiserfs_getxattr(struct dentry * dentry, const char *name, void *buffer,
                  size_t size)
{
        struct reiserfs_xattr_handler *xah = find_xattr_handler_prefix(name);
        int err;

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

        reiserfs_read_lock_xattr_i(dentry->d_inode);
        reiserfs_read_lock_xattrs(dentry->d_sb);
        err = xah->get(dentry->d_inode, name, buffer, size);
        reiserfs_read_unlock_xattrs(dentry->d_sb);
        reiserfs_read_unlock_xattr_i(dentry->d_inode);
        return err;
}

/*
 * 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)
{
        struct reiserfs_xattr_handler *xah = find_xattr_handler_prefix(name);
        int err;
        int lock;

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

        reiserfs_write_lock_xattr_i(dentry->d_inode);
        lock = !has_xattr_dir(dentry->d_inode);
        if (lock)
                reiserfs_write_lock_xattrs(dentry->d_sb);
        else
                reiserfs_read_lock_xattrs(dentry->d_sb);
        err = xah->set(dentry->d_inode, name, value, size, flags);
        if (lock)
                reiserfs_write_unlock_xattrs(dentry->d_sb);
        else
                reiserfs_read_unlock_xattrs(dentry->d_sb);
        reiserfs_write_unlock_xattr_i(dentry->d_inode);
        return err;
}

/*
 * Inode operation removexattr()
 *
 * dentry->d_inode->i_mutex down
 */
int reiserfs_removexattr(struct dentry *dentry, const char *name)
{
        int err;
        struct reiserfs_xattr_handler *xah = find_xattr_handler_prefix(name);

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

        reiserfs_write_lock_xattr_i(dentry->d_inode);
        reiserfs_read_lock_xattrs(dentry->d_sb);

        /* Deletion pre-operation */
        if (xah->del) {
                err = xah->del(dentry->d_inode, name);
                if (err)
                        goto out;
        }

        err = reiserfs_xattr_del(dentry->d_inode, name);

        dentry->d_inode->i_ctime = CURRENT_TIME_SEC;
        mark_inode_dirty(dentry->d_inode);

      out:
        reiserfs_read_unlock_xattrs(dentry->d_sb);
        reiserfs_write_unlock_xattr_i(dentry->d_inode);
        return err;
}

/* This is what filldir will use:
 * r_pos will always contain the amount of space required for the entire
 * list. If r_pos becomes larger than r_size, we need more space and we
 * return an error indicating this. If r_pos is less than r_size, then we've
 * filled the buffer successfully and we return success */
struct reiserfs_listxattr_buf {
        int r_pos;
        int r_size;
        char *r_buf;
        struct inode *r_inode;
};

static int
reiserfs_listxattr_filler(void *buf, const char *name, int namelen,
                          loff_t offset, u64 ino, unsigned int d_type)
{
        struct reiserfs_listxattr_buf *b = (struct reiserfs_listxattr_buf *)buf;
        int len = 0;

        if (name[0] != '.'
            || (namelen != 1 && (name[1] != '.' || namelen != 2))) {
                struct reiserfs_xattr_handler *xah =
                    find_xattr_handler_prefix(name);
                if (!xah)
                        return 0;       /* Unsupported xattr name, skip it */

                /* We call ->list() twice because the operation isn't required to just
                 * return the name back - we want to make sure we have enough space */
                len += xah->list(b->r_inode, name, namelen, NULL);

                if (len) {
                        if (b->r_pos + len + 1 <= b->r_size) {
                                char *p = b->r_buf + b->r_pos;
                                p += xah->list(b->r_inode, name, namelen, p);
                                *p++ = '\0';
                        }
                        b->r_pos += len + 1;
                }
        }

        return 0;
}

/*
 * Inode operation listxattr()
 *
 * Preliminary locking: we down dentry->d_inode->i_mutex
 */
ssize_t reiserfs_listxattr(struct dentry * dentry, char *buffer, size_t size)
{
        struct file *fp;
        struct dentry *dir;
        int err = 0;
        struct reiserfs_listxattr_buf buf;

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

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

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

        fp = dentry_open(dir, NULL, O_RDWR);
        if (IS_ERR(fp)) {
                err = PTR_ERR(fp);
                /* dentry_open dputs the dentry if it fails */
                goto out;
        }

        buf.r_buf = buffer;
        buf.r_size = buffer ? size : 0;
        buf.r_pos = 0;
        buf.r_inode = dentry->d_inode;

        REISERFS_I(dentry->d_inode)->i_flags |= i_has_xattr_dir;

        err = xattr_readdir(fp, reiserfs_listxattr_filler, &buf);
        if (err)
                goto out_dir;

        if (buf.r_pos > buf.r_size && buffer != NULL)
                err = -ERANGE;
        else
                err = buf.r_pos;

      out_dir:
        fput(fp);

      out:
        reiserfs_read_unlock_xattr_i(dentry->d_inode);
        return err;
}

/* This is the implementation for the xattr plugin infrastructure */
static struct list_head xattr_handlers = LIST_HEAD_INIT(xattr_handlers);
static DEFINE_RWLOCK(handler_lock);

static struct reiserfs_xattr_handler *find_xattr_handler_prefix(const char
                                                                *prefix)
{
        struct reiserfs_xattr_handler *xah = NULL;
        struct list_head *p;

        read_lock(&handler_lock);
        list_for_each(p, &xattr_handlers) {
                xah = list_entry(p, struct reiserfs_xattr_handler, handlers);
                if (strncmp(xah->prefix, prefix, strlen(xah->prefix)) == 0)
                        break;
                xah = NULL;
        }

        read_unlock(&handler_lock);
        return xah;
}

static void __unregister_handlers(void)
{
        struct reiserfs_xattr_handler *xah;
        struct list_head *p, *tmp;

        list_for_each_safe(p, tmp, &xattr_handlers) {
                xah = list_entry(p, struct reiserfs_xattr_handler, handlers);
                if (xah->exit)
                        xah->exit();

                list_del_init(p);
        }
        INIT_LIST_HEAD(&xattr_handlers);
}

int __init reiserfs_xattr_register_handlers(void)
{
        int err = 0;
        struct reiserfs_xattr_handler *xah;
        struct list_head *p;

        write_lock(&handler_lock);

        /* If we're already initialized, nothing to do */
        if (!list_empty(&xattr_handlers)) {
                write_unlock(&handler_lock);
                return 0;
        }

        /* Add the handlers */
        list_add_tail(&user_handler.handlers, &xattr_handlers);
        list_add_tail(&trusted_handler.handlers, &xattr_handlers);
#ifdef CONFIG_REISERFS_FS_SECURITY
        list_add_tail(&security_handler.handlers, &xattr_handlers);
#endif
#ifdef CONFIG_REISERFS_FS_POSIX_ACL
        list_add_tail(&posix_acl_access_handler.handlers, &xattr_handlers);
        list_add_tail(&posix_acl_default_handler.handlers, &xattr_handlers);
#endif

        /* Run initializers, if available */
        list_for_each(p, &xattr_handlers) {
                xah = list_entry(p, struct reiserfs_xattr_handler, handlers);
                if (xah->init) {
                        err = xah->init();
                        if (err) {
                                list_del_init(p);
                                break;
                        }
                }
        }

        /* Clean up other handlers, if any failed */
        if (err)
                __unregister_handlers();

        write_unlock(&handler_lock);
        return err;
}

void reiserfs_xattr_unregister_handlers(void)
{
        write_lock(&handler_lock);
        __unregister_handlers();
        write_unlock(&handler_lock);
}

/* This will catch lookups from the fs root to .reiserfs_priv */
static int
xattr_lookup_poison(struct dentry *dentry, struct qstr *q1, struct qstr *name)
{
        struct dentry *priv_root = REISERFS_SB(dentry->d_sb)->priv_root;
        if (name->len == priv_root->d_name.len &&
            name->hash == priv_root->d_name.hash &&
            !memcmp(name->name, priv_root->d_name.name, name->len)) {
                return -ENOENT;
        } else if (q1->len == name->len &&
                   !memcmp(q1->name, name->name, name->len))
                return 0;
        return 1;
}

static struct dentry_operations xattr_lookup_poison_ops = {
        .d_compare = xattr_lookup_poison,
};

/* 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;

        /* We need generation numbers to ensure that the oid mapping is correct
         * v3.5 filesystems don't have them. */
        if (!old_format_only(s)) {
                set_bit(REISERFS_XATTRS, &(REISERFS_SB(s)->s_mount_opt));
        } else if (reiserfs_xattrs_optional(s)) {
                /* Old format filesystem, but optional xattrs have been enabled
                 * at mount time. Error out. */
                reiserfs_warning(s, "xattrs/ACLs not supported on pre v3.6 "
                                 "format filesystem. Failing mount.");
                err = -EOPNOTSUPP;
                goto error;
        } else {
                /* Old format filesystem, but no optional xattrs have been enabled. This
                 * means we silently disable xattrs on the filesystem. */
                clear_bit(REISERFS_XATTRS, &(REISERFS_SB(s)->s_mount_opt));
        }

        /* If we don't have the privroot located yet - go find it */
        if (reiserfs_xattrs(s) && !REISERFS_SB(s)->priv_root) {
                struct dentry *dentry;
                dentry = lookup_one_len(PRIVROOT_NAME, s->s_root,
                                        strlen(PRIVROOT_NAME));
                if (!IS_ERR(dentry)) {
                        if (!(mount_flags & MS_RDONLY) && !dentry->d_inode) {
                                struct inode *inode = dentry->d_parent->d_inode;
                                mutex_lock_nested(&inode->i_mutex,
                                                  I_MUTEX_XATTR);
                                err = inode->i_op->mkdir(inode, dentry, 0700);
                                mutex_unlock(&inode->i_mutex);
                                if (err) {
                                        dput(dentry);
                                        dentry = NULL;
                                }

                                if (dentry && dentry->d_inode)
                                        reiserfs_warning(s,
                                                         "Created %s on %s - reserved for "
                                                         "xattr storage.",
                                                         PRIVROOT_NAME,
                                                         reiserfs_bdevname
                                                         (inode->i_sb));
                        } else if (!dentry->d_inode) {
                                dput(dentry);
                                dentry = NULL;
                        }
                } else
                        err = PTR_ERR(dentry);

                if (!err && dentry) {
                        s->s_root->d_op = &xattr_lookup_poison_ops;
                        reiserfs_mark_inode_private(dentry->d_inode);
                        REISERFS_SB(s)->priv_root = dentry;
                } else if (!(mount_flags & MS_RDONLY)) {        /* xattrs are unavailable */
                        /* If we're read-only it just means that the dir hasn't been
                         * created. Not an error -- just no xattrs on the fs. We'll
                         * check again if we go read-write */
                        reiserfs_warning(s, "xattrs/ACLs enabled and couldn't "
                                         "find/create .reiserfs_priv. Failing mount.");
                        err = -EOPNOTSUPP;
                }
        }

      error:
        /* This is only nonzero if there was an error initializing the xattr
         * directory or if there is a condition where we don't support them. */
        if (err) {
                clear_bit(REISERFS_XATTRS, &(REISERFS_SB(s)->s_mount_opt));
                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. */
        s->s_flags = s->s_flags & ~MS_POSIXACL;
        if (reiserfs_posixacl(s))
                s->s_flags |= MS_POSIXACL;

        return err;
}

static int reiserfs_check_acl(struct inode *inode, int mask)
{
        struct posix_acl *acl;
        int error = -EAGAIN; /* do regular unix permission checks by default */

        reiserfs_read_lock_xattr_i(inode);
        reiserfs_read_lock_xattrs(inode->i_sb);

        acl = reiserfs_get_acl(inode, ACL_TYPE_ACCESS);

        reiserfs_read_unlock_xattrs(inode->i_sb);
        reiserfs_read_unlock_xattr_i(inode);

        if (acl) {
                if (!IS_ERR(acl)) {
                        error = posix_acl_permission(inode, acl, mask);
                        posix_acl_release(acl);
                } else if (PTR_ERR(acl) != -ENODATA)
                        error = PTR_ERR(acl);
        }

        return error;
}

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

        /*
         * Stat data v1 doesn't support ACLs.
         */
        if (get_inode_sd_version(inode) == STAT_DATA_V1)
                return generic_permission(inode, mask, NULL);
        else
                return generic_permission(inode, mask, reiserfs_check_acl);
}