linux-ext4 - Re: [PATCH 1/2] ext4: Fix stripe-unaligned allocations

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Message-ID: <20170210055335.dnujxjtv4ew3sprb@thunk.org>
Date:   Fri, 10 Feb 2017 00:53:35 -0500
From:   Theodore Ts'o <tytso@....edu>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-ext4@...r.kernel.org,
        Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [PATCH 1/2] ext4: Fix stripe-unaligned allocations

On Thu, Feb 09, 2017 at 04:30:49PM +0100, Jan Kara wrote:
> When a filesystem is created using:
> 
> mkfs.ext4 -b 4096 -E stride=512 <dev>
> 
> and we try to allocate 64MB extent, we will end up directly in
> ext4_mb_complex_scan_group(). This is because the request is detected as
> power-of-two allocation (so we start in ext4_mb_regular_allocator()
> with ac_criteria == 0) however the check before
> ext4_mb_simple_scan_group() refuses the direct buddy scan because the
> allocation request is too large. Since cr == 0, the check whether we
> should use ext4_mb_scan_aligned() fails as well and we fall back to
> ext4_mb_complex_scan_group().
> 
> Fix the problem by checking for upper limit on power-of-two requests
> directly when detecting them.
> 
> Reported-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
> Signed-off-by: Jan Kara <jack@...e.cz>

Thanks, applied.

						- Ted