Re: [PATCH] reiserfs: Expand i_mutex to enclose lookup_one_len

Al Viro
2009-05-03T10:06:45Z

On Sun, May 03, 2009 at 10:15:08AM +0100, Al Viro wrote:

> > I've applied your patch as-is, and unless you have objections to the
> > variant above I'll do that as incremental. Comments?
>
> BTW, what in the name of everything unholy is ->xattr_root? Never
> assigned a non-NULL value...

Looks like your xattr journalling is b0rken - the check in there should
be that for ->priv_root, AFAICS. Anyway, promised incremental follows (FWIW,
it's commit ff4559 in git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6.git/
on #untested).

[PATCH] Always lookup priv_root on reiserfs mount and keep it

... even if it's a negative dentry. That way we can set ->d_op on
root before anyone could race with us. Simplify d_compare(), while
we are at it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/reiserfs/super.c | 6 ++-
fs/reiserfs/xattr.c | 86 +++++++++++++++++-----------------------
include/linux/reiserfs_xattr.h | 1 +
3 files changed, 41 insertions(+), 52 deletions(-)

diff --git a/fs/reiserfs/super.c b/fs/reiserfs/super.c
index 5d0064d..f45cac9 100644
--- a/fs/reiserfs/super.c
+++ b/fs/reiserfs/super.c
@@ -1845,7 +1845,8 @@ static int reiserfs_fill_super(struct super_block *s, void *data, int silent)
goto error;
}

- if ((errval = reiserfs_xattr_init(s, s->s_flags))) {
+ if ((errval = reiserfs_lookup_privroot(s)) ||
+ (errval = reiserfs_xattr_init(s, s->s_flags))) {
dput(s->s_root);
s->s_root = NULL;
goto error;
@@ -1858,7 +1859,8 @@ static int reiserfs_fill_super(struct super_block *s, void *data, int silent)
reiserfs_info(s, "using 3.5.x disk format\n");
}

- if ((errval = reiserfs_xattr_init(s, s->s_flags))) {
+ if ((errval = reiserfs_lookup_privroot(s)) ||
+ (errval = reiserfs_xattr_init(s, s->s_flags))) {
dput(s->s_root);
s->s_root = NULL;
goto error;
diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c
index 31a3dbb..2891f78 100644
--- a/fs/reiserfs/xattr.c
+++ b/fs/reiserfs/xattr.c
@@ -903,16 +903,19 @@ static int create_privroot(struct dentry *dentry)
WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));

err = xattr_mkdir(inode, dentry, 0700);
- if (err) {
- dput(dentry);
- dentry = NULL;
+ 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;
}

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

- return err;
+ return 0;
}

static int xattr_mount_check(struct super_block *s)
@@ -944,11 +947,9 @@ 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)) {
+ if (container_of(q1, struct dentry, d_name) == priv_root)
return -ENOENT;
- } else if (q1->len == name->len &&
+ if (q1->len == name->len &&
!memcmp(q1->name, name->name, name->len))
return 0;
return 1;
@@ -958,6 +959,27 @@ static const struct dentry_operations xattr_lookup_poison_ops = {
.d_compare = xattr_lookup_poison,
};

+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 */
+ mutex_lock(&s->s_root->d_inode->i_mutex);
+ dentry = lookup_one_len(PRIVROOT_NAME, s->s_root,
+ strlen(PRIVROOT_NAME));
+ if (!IS_ERR(dentry)) {
+ REISERFS_SB(s)->priv_root = dentry;
+ s->s_root->d_op = &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 */
@@ -969,48 +991,12 @@ int reiserfs_xattr_init(struct super_block *s, int mount_flags)
err = xattr_mount_check(s);
if (err)
goto error;
-#endif

- /* If we don't have the privroot located yet - go find it */
- if (!REISERFS_SB(s)->priv_root) {
- struct dentry *dentry;
- mutex_lock_nested(&s->s_root->d_inode->i_mutex, I_MUTEX_CHILD);
- dentry = lookup_one_len(PRIVROOT_NAME, s->s_root,
- strlen(PRIVROOT_NAME));
- if (!IS_ERR(dentry)) {
-#ifdef CONFIG_REISERFS_FS_XATTR
- if (!(mount_flags & MS_RDONLY) && !dentry->d_inode)
- err = create_privroot(dentry);
-#endif
- if (!dentry->d_inode) {
- dput(dentry);
- dentry = NULL;
- }
- } else
- err = PTR_ERR(dentry);
+ if (!REISERFS_SB(s)->priv_root->d_inode && !(mount_flags & MS_RDONLY)) {
+ mutex_lock(&s->s_root->d_inode->i_mutex);
+ err = create_privroot(REISERFS_SB(s)->priv_root);
mutex_unlock(&s->s_root->d_inode->i_mutex);
-
- if (!err && dentry) {
- s->s_root->d_op = &xattr_lookup_poison_ops;
- dentry->d_inode->i_flags |= S_PRIVATE;
- REISERFS_SB(s)->priv_root = dentry;
-#ifdef CONFIG_REISERFS_FS_XATTR
- /* xattrs are unavailable */
- } else if (!(mount_flags & MS_RDONLY)) {
- /* 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, "jdm-20006",
- "xattrs/ACLs enabled and couldn't "
- "find/create .reiserfs_priv. "
- "Failing mount.");
- err = -EOPNOTSUPP;
-#endif
- }
}
-
-#ifdef CONFIG_REISERFS_FS_XATTR
if (!err)
s->s_xattr = reiserfs_xattr_handlers;

diff --git a/include/linux/reiserfs_xattr.h b/include/linux/reiserfs_xattr.h
index dcae01e..fea1a8e 100644
--- a/include/linux/reiserfs_xattr.h
+++ b/include/linux/reiserfs_xattr.h
@@ -38,6 +38,7 @@ struct nameidata;
int reiserfs_xattr_register_handlers(void) __init;
void reiserfs_xattr_unregister_handlers(void);
int reiserfs_xattr_init(struct super_block *sb, int mount_flags);
+int reiserfs_lookup_privroot(struct super_block *sb);
int reiserfs_delete_xattrs(struct inode *inode);
int reiserfs_chown_xattrs(struct inode *inode, struct iattr *attrs);

--
1.5.6.5