linux-ext4 - Re: [2/2] libext2fs: Skip start_blk adjustment when stride and flex

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Date:   Sat, 14 Oct 2017 10:50:57 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Lukas Czerner <lczerner@...hat.com>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [2/2] libext2fs: Skip start_blk adjustment when stride and
 flex_bg is set

On Thu, Aug 24, 2017 at 03:35:39PM +0200, Lukas Czerner wrote:
> Currently some stride optimization is done in
> ext2fs_allocate_group_table() by adjusting start_blk block where we
> start allocating block, or inode bitmaps.
> 
> However in flex_bg case this is currently useless since the values are
> going to be overridden anyway. Moreover in flex_bg case the group might
> already be full and the stride optimization will fail. As a result file
> system resize might fail needlessly in some situations.
> 
> It can be shown by this example:
> 
> mke2fs -b 1024 -i 1024 -E stride=8192 -t ext4 /dev/loop0 1024000
> resize2fs /dev/loop0 102400000
> resize2fs 1.43.5 (04-Aug-2017)
> Resizing the filesystem on /dev/loop0 to 102400000 (1k) blocks.
> ./resize/resize2fs: Could not allocate block in ext2 filesystem while trying to resize /dev/loop0
> Please run 'e2fsck -fy /dev/loop0' to fix the filesystem
> after the aborted resize operation.
> 
> Fix this by not doing the stride adjustment in case of flex_bg.
> 
> Signed-off-by: Lukas Czerner <lczerner@...hat.com>

Thanks, applied.

					- Ted