Subject: patch ext4: fix data exposure after a crash still work ?

Hi Kara

Since we move to kernel 3.18 stable branch. i found the patch " ext4: fix data exposure after a crash " not available but I found below commit which mentioned that patch.
I want to check with you whether " ext4: fix data exposure after a crash " still needed currently ?
I guess yes but I want to confirm with you.
Thanks
Huang weller

ext4: fix deadlock during page writeback
[ Upstream commit 646caa9c8e196880b41cd3e3d33a2ebc752bdb85 ]

Commit 06bd3c36a733 (ext4: fix data exposure after a crash) uncovered a
deadlock in ext4_writepages() which was previously much harder to hit.
After this commit xfstest generic/130 reproduces the deadlock on small
filesystems.

The problem happens when ext4_do_update_inode() sets LARGE_FILE feature
and marks current inode handle as synchronous. That subsequently results
in ext4_journal_stop() called from ext4_writepages() to block waiting for
transaction commit while still holding page locks, reference to io_end,
and some prepared bio in mpd structure each of which can possibly block
transaction commit from completing and thus results in deadlock.

Fix the problem by releasing page locks, io_end reference, and
submitting prepared bio before calling ext4_journal_stop().

[ Changed to defer the call to ext4_journal_stop() only if the handle
is synchronous. --tytso ]


Best regards

Weller HUANG

Base SW (CM/ESW12-CN)
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2016-12-07 11:47:35

by Jan Kara

[permalink] [raw]
Subject: Re: patch ext4: fix data exposure after a crash still work ?

Hi!

On Tue 06-12-16 09:52:01, HUANG Weller (CM/ESW12-CN) wrote:
> Since we move to kernel 3.18 stable branch. i found the patch " ext4: fix data exposure after a crash " not available but I found below commit which mentioned that patch.
> I want to check with you whether " ext4: fix data exposure after a crash " still needed currently ?
> I guess yes but I want to confirm with you.

Yes, it is still needed. Actually, I've already backported the fix to
3.12-based kernel we use for our distribution kernel. Probably I should
push it to official 3.12-stable kernel as well.

Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR