linux-ext4 - Re: [PATCH V2] ext4: avoid deadlock on sync-mounted FS w/o journal

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Date:	Mon, 20 Feb 2012 23:08:31 -0500
From:	Ted Ts'o <tytso@....edu>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>,
	Martin.Wilck@...fujitsu.com
Subject: Re: [PATCH V2] ext4: avoid deadlock on sync-mounted FS w/o journal

On Thu, Feb 16, 2012 at 03:41:45PM -0800, Eric Sandeen wrote:
> From: Martin.Wilck@...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@...fujitsu.com
> [sandeen@...hat.com: move mb_cache_entry_release before unlock, edit commit msg]
> Signed-off-by: Eric Sandeen <sandeen@...hat.com>

Thanks, applied.

						- Ted
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