linux-ext4 - Re: [PATCH] ext4: fix reservation overflow in ext4_da_write

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Date:	Sat, 11 Oct 2014 19:52:00 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Andreas Dilger <adilger@...ger.ca>
Cc:	Eric Sandeen <sandeen@...hat.com>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: fix reservation overflow in ext4_da_write_begin

On Thu, Oct 02, 2014 at 03:00:23PM -0600, Andreas Dilger wrote:
> On Oct 2, 2014, at 9:28 AM, Eric Sandeen <sandeen@...hat.com> wrote:
> > Delalloc write journal reservations only reserve 1 credit,
> > to update the inode if necessary.  However, it may happen
> > once in a filesystem's lifetime that a file will cross
> > the 2G threshold, and require the LARGE_FILE feature to
> > be set in the superblock as well, if it was not set already.
> > 
> > This overruns the transaction reservation, and can be
> > demonstrated simply on any ext4 filesystem without the LARGE_FILE
> > feature already set:
> > 
> > dd if=/dev/zero of=testfile bs=1 seek=2147483646 count=1 \
> > 	conv=notrunc of=testfile
> > sync
> > dd if=/dev/zero of=testfile bs=1 seek=2147483647 count=1 \
> > 	conv=notrunc of=testfile
> > 
> > leads to:
> > 
> > EXT4-fs: ext4_do_update_inode:4296: aborting transaction: error 28 in __ext4_handle_dirty_super
> > EXT4-fs error (device loop0) in ext4_do_update_inode:4301: error 28
> > EXT4-fs error (device loop0) in ext4_reserve_inode_write:4757: Readonly filesystem
> > EXT4-fs error (device loop0) in ext4_dirty_inode:4876: error 28
> > EXT4-fs error (device loop0) in ext4_da_write_end:2685: error 28
> > 
> > Adjust the number of credits based on whether the flag is
> > already set, and whether the current write may extend past the
> > LARGE_FILE limit.
> > 
> > Signed-off-by: Eric Sandeen <sandeen@...hat.com>
> 
> Reviewed-by: Andreas Dilger <adilger@...ger.ca>

Applied, thanks.  I added the likely() qualifer per Andreas'
suggestion.

						- Ted
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