From: David Sterba <dsterba@suse.cz>
To: Marcos Paulo de Souza <marcos@mpdesouza.com>
Cc: linux-kernel@vger.kernel.org, dsterba@suse.com,
linux-btrfs@vger.kernel.org,
Marcos Paulo de Souza <mpdesouza@suse.com>,
stable@vger.kernel.org, Qu Wenruo <wqu@suse.com>,
Filipe Manana <fdmanana@suse.com>
Subject: Re: [PATCH v3] btrfs: block-group: Fix free-space bitmap threshould
Date: Mon, 24 Aug 2020 17:28:29 +0200 [thread overview]
Message-ID: <20200824152829.GK2026@twin.jikos.cz> (raw)
In-Reply-To: <20200821145444.25791-1-marcos@mpdesouza.com>
On Fri, Aug 21, 2020 at 11:54:44AM -0300, Marcos Paulo de Souza wrote:
> From: Marcos Paulo de Souza <mpdesouza@suse.com>
>
> [BUG]
> After commit 9afc66498a0b ("btrfs: block-group: refactor how we read one
> block group item"), cache->length is being assigned after calling
> btrfs_create_block_group_cache. This causes a problem since
> set_free_space_tree_thresholds is calculate the free-space threshould to
> decide is the free-space tree should convert from extents to bitmaps.
>
> The current code calls set_free_space_tree_thresholds with cache->length
> being 0, which then makes cache->bitmap_high_thresh being zero. This
> implies the system will always use bitmap instead of extents, which is
> not desired if the block group is not fragmented.
>
> This behavior can be seen by a test that expects to repair systems
> with FREE_SPACE_EXTENT and FREE_SPACE_BITMAP, but the current code only
> created FREE_SPACE_BITMAP.
>
> [FIX]
> Call set_free_space_tree_thresholds after setting cache->length. There
> is now a WARN_ON in set_free_space_tree_thresholds to help preventing
> the same mistake to happen again in the future.
>
> Link: https://github.com/kdave/btrfs-progs/issues/251
> Fixes: 9afc66498a0b ("btrfs: block-group: refactor how we read one block group item")
> CC: stable@vger.kernel.org # 5.8+
> Reviewed-by: Qu Wenruo <wqu@suse.com>
> Reviewed-by: Filipe Manana <fdmanana@suse.com>
> Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Added to misc-next, thanks.
prev parent reply other threads:[~2020-08-24 15:30 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 14:54 [PATCH v3] btrfs: block-group: Fix free-space bitmap threshould Marcos Paulo de Souza
2020-08-24 15:28 ` David Sterba [this message]
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