[PATCH stable 3.3 thru 3.8] ext3: fix data=journal fast mount/umount hang

[PATCH stable 3.3 thru 3.8] ext3: fix data=journal fast mount/umount hang

[Benjamin LaHaise]

This patch appears to have been missed for ext3, while the ext4 version was 
merged back in March -- see 1363783057-3874-1-git-send-email-tytso@mit.edu.  
A customer of mine has been running into this bug on their production 
servers on 3.4-stable.  It applies cleanly to the 3.3 through 3.8 trees.

		-ben

commit e643692138cfa33528f054b071ba2583509bb217
Author: Jan Kara <jack@suse.cz>
Date:   Wed Mar 20 14:39:05 2013 +0100

ext3: fix data=journal fast mount/umount hang
    
In data=journal mode, if we unmount the file system before a
transaction has a chance to complete, when the journal inode is being
evicted, we can end up calling into log_wait_commit() for the
last transaction, after the journalling machinery has been shut down.
That triggers the WARN_ONCE in __log_start_commit().
    
Arguably we should adjust ext3_should_journal_data() to return FALSE
for the journal inode, but the only place it matters is
ext3_evict_inode(), and so it's to save a bit of CPU time, and to make
the patch much more obviously correct by inspection(tm), we'll fix it
by explicitly not trying to waiting for a journal commit when we are
evicting the journal inode, since it's guaranteed to never succeed in
this case.
    
This can be easily replicated via:
    
         mount -t ext3 -o data=journal /dev/vdb /vdb ; umount /vdb
    
This is a port of ext4 fix from Ted Ts'o.
    
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>

diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index d512c4b..d706dbf 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -218,7 +218,8 @@ void ext3_evict_inode (struct inode *inode)
 	 */
 	if (inode->i_nlink && ext3_should_journal_data(inode) &&
 	    EXT3_SB(inode->i_sb)->s_journal &&
-	    (S_ISLNK(inode->i_mode) || S_ISREG(inode->i_mode))) {
+	    (S_ISLNK(inode->i_mode) || S_ISREG(inode->i_mode)) &&
+	    inode->i_ino != EXT3_JOURNAL_INO) {
 		tid_t commit_tid = atomic_read(&ei->i_datasync_tid);
 		journal_t *journal = EXT3_SB(inode->i_sb)->s_journal;
 

Re: [PATCH stable 3.3 thru 3.8] ext3: fix data=journal fast mount/umount hang

[Luis Henriques]

Benjamin LaHaise <bcrl@kvack.org> writes:

> This patch appears to have been missed for ext3, while the ext4 version was 
> merged back in March -- see 1363783057-3874-1-git-send-email-tytso@mit.edu.  
> A customer of mine has been running into this bug on their production 
> servers on 3.4-stable.  It applies cleanly to the 3.3 through 3.8 trees.
>
> 		-ben

Thanks Ben, I'm queuing it for the 3.5 kernel.

Cheers,
-- 
Luis


>
> commit e643692138cfa33528f054b071ba2583509bb217
> Author: Jan Kara <jack@suse.cz>
> Date:   Wed Mar 20 14:39:05 2013 +0100
>
> ext3: fix data=journal fast mount/umount hang
>     
> In data=journal mode, if we unmount the file system before a
> transaction has a chance to complete, when the journal inode is being
> evicted, we can end up calling into log_wait_commit() for the
> last transaction, after the journalling machinery has been shut down.
> That triggers the WARN_ONCE in __log_start_commit().
>     
> Arguably we should adjust ext3_should_journal_data() to return FALSE
> for the journal inode, but the only place it matters is
> ext3_evict_inode(), and so it's to save a bit of CPU time, and to make
> the patch much more obviously correct by inspection(tm), we'll fix it
> by explicitly not trying to waiting for a journal commit when we are
> evicting the journal inode, since it's guaranteed to never succeed in
> this case.
>     
> This can be easily replicated via:
>     
>          mount -t ext3 -o data=journal /dev/vdb /vdb ; umount /vdb
>     
> This is a port of ext4 fix from Ted Ts'o.
>     
> Signed-off-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
>
> diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
> index d512c4b..d706dbf 100644
> --- a/fs/ext3/inode.c
> +++ b/fs/ext3/inode.c
> @@ -218,7 +218,8 @@ void ext3_evict_inode (struct inode *inode)
>  	 */
>  	if (inode->i_nlink && ext3_should_journal_data(inode) &&
>  	    EXT3_SB(inode->i_sb)->s_journal &&
> -	    (S_ISLNK(inode->i_mode) || S_ISREG(inode->i_mode))) {
> +	    (S_ISLNK(inode->i_mode) || S_ISREG(inode->i_mode)) &&
> +	    inode->i_ino != EXT3_JOURNAL_INO) {
>  		tid_t commit_tid = atomic_read(&ei->i_datasync_tid);
>  		journal_t *journal = EXT3_SB(inode->i_sb)->s_journal;
>  
> --
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