linux-ext4 - Re: [PATCH] ext4: fix off-by-one fsmap error on 1k block filesystems

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Message-ID: <20170623050131.2feyc7daq7adwtat@thunk.org>
Date:   Fri, 23 Jun 2017 01:01:31 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: fix off-by-one fsmap error on 1k block filesystems

On Wed, Jun 21, 2017 at 11:29:40AM -0700, Darrick J. Wong wrote:
> For 1k-block filesystems, the filesystem starts at block 1, not block 0.
> This fact is recorded in s_first_data_block, so use that to bump up the
> start_fsb before we start querying the filesystem for its space map.
> Without this, ext4/026 fails on 1k block ext4 because various functions
> (notably ext4_get_group_no_and_offset) don't know what to do with an
> fsblock that is "before" the start of the filesystem and return garbage
> results (blockgroup 2^32-1, etc.) that confuse fsmap.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>

Thanks, applied.

					- Ted