linux-ext4 - Re: [PATCH 2/2] ext4: Fix deadlock in ext4

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Message-ID: <20110503151819.GD6462@thunk.org>
Date:	Tue, 3 May 2011 11:18:19 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/2] ext4: Fix deadlock in ext4_symlink() in ENOSPC
 conditions

On Fri, Apr 29, 2011 at 11:24:45PM +0200, Jan Kara wrote:
> ext4_symlink() cannot call __page_symlink() with transaction open.
> __page_symlink() calls ext4_write_begin() which can wait for
> transaction commit if we are running out of space thus causing a
> deadlock. Also error recovery in ext4_truncate_failed_write() does
> not count with the transaction being already started (although I'm
> not aware of any particular deadlock here).
> 
> Fix the problem by stopping a transaction before calling __page_symlink()
> (we have to be careful and put inode to orphan list so that it gets deleted
> in case of crash) and starting another one after __page_symlink() returns
> for addition of symlink into a directory.
> 
> Signed-off-by: Jan Kara <jack@...e.cz>

Thanks, added to the ext4 tree.

					- Ted
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