[PATCH v2] reiserfs: fix race in readdir

[PATCH v2] reiserfs: fix race in readdir

[Jeff Mahoney]

jdm-20004 reiserfs_delete_xattrs: Couldn't delete all xattrs (-2)

The -ENOENT is due to readdir calling dir_emit on the same entry twice.

If the dir_emit callback sleeps and the tree is changed underneath us,
we won't be able to trust deh_offset(deh) anymore. We need to save
next_pos before we might sleep so we can find the next entry.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
---
 fs/reiserfs/dir.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/reiserfs/dir.c
+++ b/fs/reiserfs/dir.c
@@ -125,6 +125,7 @@ int reiserfs_readdir_inode(struct inode
 				int d_reclen;
 				char *d_name;
 				ino_t d_ino;
+				loff_t cur_pos = deh_offset(deh);
 
 				if (!de_visible(deh))
 					/* it is hidden entry */
@@ -196,8 +197,9 @@ int reiserfs_readdir_inode(struct inode
 				if (local_buf != small_buf) {
 					kfree(local_buf);
 				}
-				// next entry should be looked for with such offset
-				next_pos = deh_offset(deh) + 1;
+
+				/* deh_offset(deh) may be invalid now. */
+				next_pos = cur_pos + 1;
 
 				if (item_moved(&tmp_ih, &path_to_entry)) {
 					set_cpu_key_k_offset(&pos_key,

-- 
Jeff Mahoney
SUSE Labs

Re: [PATCH v2] reiserfs: fix race in readdir

[Jan Kara]

On Wed 02-04-14 14:40:26, Jeff Mahoney wrote:
> jdm-20004 reiserfs_delete_xattrs: Couldn't delete all xattrs (-2)
> 
> The -ENOENT is due to readdir calling dir_emit on the same entry twice.
> 
> If the dir_emit callback sleeps and the tree is changed underneath us,
> we won't be able to trust deh_offset(deh) anymore. We need to save
> next_pos before we might sleep so we can find the next entry.
> 
> Signed-off-by: Jeff Mahoney <jeffm@suse.com>
  Thanks for a quick fix. I've merged the patch to my tree.

								Honza

> ---
>  fs/reiserfs/dir.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> --- a/fs/reiserfs/dir.c
> +++ b/fs/reiserfs/dir.c
> @@ -125,6 +125,7 @@ int reiserfs_readdir_inode(struct inode
>  				int d_reclen;
>  				char *d_name;
>  				ino_t d_ino;
> +				loff_t cur_pos = deh_offset(deh);
>  
>  				if (!de_visible(deh))
>  					/* it is hidden entry */
> @@ -196,8 +197,9 @@ int reiserfs_readdir_inode(struct inode
>  				if (local_buf != small_buf) {
>  					kfree(local_buf);
>  				}
> -				// next entry should be looked for with such offset
> -				next_pos = deh_offset(deh) + 1;
> +
> +				/* deh_offset(deh) may be invalid now. */
> +				next_pos = cur_pos + 1;
>  
>  				if (item_moved(&tmp_ih, &path_to_entry)) {
>  					set_cpu_key_k_offset(&pos_key,
> 
> -- 
> Jeff Mahoney
> SUSE Labs
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR