On Tue, Sep 29, 2015 at 2:51 PM, Zhao Lei <zhaolei@xxxxxxxxxxxxxx> wrote:
> Reproduce:
> (In integration-4.3 branch)
>
> TEST_DEV=(/dev/vdg /dev/vdh)
> TEST_DIR=/mnt/tmp
>
> umount "$TEST_DEV" >/dev/null
> mkfs.btrfs -f -d raid1 "${TEST_DEV[@]}"
>
> mount -o nospace_cache "$TEST_DEV" "$TEST_DIR"
> umount "$TEST_DEV"
>
> mount -o nospace_cache "$TEST_DEV" "$TEST_DIR"
> btrfs filesystem usage $TEST_DIR
>
> We can see the data chunk changed from raid1 to single:
> # btrfs filesystem usage $TEST_DIR
> Data,single: Size:8.00MiB, Used:0.00B
> /dev/vdg 8.00MiB
> #
>
> Reason:
> When a empty filesystem mount with -o nospace_cache, the last
> data blockgroup will be auto-removed in umount.
>
> Then if we mount it again, there is no data chunk in the
> filesystem, so the only available data profile is 0x0, result
> is all new chunks are created as single type.
>
> Fix:
> Don't auto-delete last blockgroup for a raid type.
>
> Test:
> Test by above script, and confirmed the logic by debug output.
>
> Signed-off-by: Zhao Lei <zhaolei@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/extent-tree.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 79a5bd9..3505649 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -10012,7 +10012,8 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
> bg_list);
> space_info = block_group->space_info;
> list_del_init(&block_group->bg_list);
> - if (ret || btrfs_mixed_space_info(space_info)) {
> + if (ret || btrfs_mixed_space_info(space_info) ||
> + block_group->list.next == block_group->list.prev) {
This isn't race free. The list block_group->list is protected by the
groups_sem semaphore. Need to take before doing this check.
You can do that in the "if" statement below this one, where we're
holding &space_info->groups_sem [1]
thanks
[1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/btrfs/extent-tree.c?id=refs/tags/v4.3-rc3#n10021
> btrfs_put_block_group(block_group);
> continue;
> }
> --
> 1.8.5.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Filipe David Manana,
"Reasonable men adapt themselves to the world.
Unreasonable men adapt the world to themselves.
That's why all progress depends on unreasonable men."
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
