* [PATCH V2] ext4: avoid deadlock on sync-mounted FS w/o journal
@ 2012-02-16 23:41 Eric Sandeen
2012-02-21 4:08 ` Ted Ts'o
0 siblings, 1 reply; 2+ messages in thread
From: Eric Sandeen @ 2012-02-16 23:41 UTC (permalink / raw)
To: ext4 development; +Cc: Martin.Wilck
From: Martin.Wilck@ts.fujitsu.com
Processes hang forever on a sync-mounted ext2 file system that
is mounted with the ext4 module (default in Fedora 16).
I can reproduce this reliably by mounting an ext2 partition with
"-o sync" and opening a new file an that partition with vim. vim
will hang in "D" state forever. The same happens on ext4 without
a journal.
I am attaching a small patch here that solves this issue for me.
In the sync mounted case without a journal,
ext4_handle_dirty_metadata() may call sync_dirty_buffer(), which
can't be called with buffer lock held.
Also move mb_cache_entry_release inside lock to avoid race
fixed previously by 8a2bfdcb ext[34]: EA block reference count racing fix
Nonte too that ext2 fixed this same problem in 2006 with
b2f49033 [PATCH] fix deadlock in ext2
Signed-off-by: Martin.Wilck@ts.fujitsu.com
[sandeen@redhat.com: move mb_cache_entry_release before unlock, edit commit msg]
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 93a00d8..4410ae7 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -487,18 +487,19 @@ ext4_xattr_release_block(handle_t *handle, struct inode *inode,
ext4_free_blocks(handle, inode, bh, 0, 1,
EXT4_FREE_BLOCKS_METADATA |
EXT4_FREE_BLOCKS_FORGET);
+ unlock_buffer(bh);
} else {
le32_add_cpu(&BHDR(bh)->h_refcount, -1);
+ if (ce)
+ mb_cache_entry_release(ce);
+ unlock_buffer(bh);
error = ext4_handle_dirty_metadata(handle, inode, bh);
if (IS_SYNC(inode))
ext4_handle_sync(handle);
dquot_free_block(inode, 1);
ea_bdebug(bh, "refcount now=%d; releasing",
le32_to_cpu(BHDR(bh)->h_refcount));
- if (ce)
- mb_cache_entry_release(ce);
}
- unlock_buffer(bh);
out:
ext4_std_error(inode->i_sb, error);
return;
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH V2] ext4: avoid deadlock on sync-mounted FS w/o journal
2012-02-16 23:41 [PATCH V2] ext4: avoid deadlock on sync-mounted FS w/o journal Eric Sandeen
@ 2012-02-21 4:08 ` Ted Ts'o
0 siblings, 0 replies; 2+ messages in thread
From: Ted Ts'o @ 2012-02-21 4:08 UTC (permalink / raw)
To: Eric Sandeen; +Cc: ext4 development, Martin.Wilck
On Thu, Feb 16, 2012 at 03:41:45PM -0800, Eric Sandeen wrote:
> From: Martin.Wilck@ts.fujitsu.com
>
> Processes hang forever on a sync-mounted ext2 file system that
> is mounted with the ext4 module (default in Fedora 16).
>
> I can reproduce this reliably by mounting an ext2 partition with
> "-o sync" and opening a new file an that partition with vim. vim
> will hang in "D" state forever. The same happens on ext4 without
> a journal.
>
> I am attaching a small patch here that solves this issue for me.
> In the sync mounted case without a journal,
> ext4_handle_dirty_metadata() may call sync_dirty_buffer(), which
> can't be called with buffer lock held.
>
> Also move mb_cache_entry_release inside lock to avoid race
> fixed previously by 8a2bfdcb ext[34]: EA block reference count racing fix
> Nonte too that ext2 fixed this same problem in 2006 with
> b2f49033 [PATCH] fix deadlock in ext2
>
> Signed-off-by: Martin.Wilck@ts.fujitsu.com
> [sandeen@redhat.com: move mb_cache_entry_release before unlock, edit commit msg]
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Thanks, applied.
- Ted
^ permalink raw reply [flat|nested] 2+ messages in thread
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2012-02-21 4:08 ` Ted Ts'o
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