On Tue, Sep 29, 2015 at 2:51 PM, Zhao Lei <[email protected]> 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 <[email protected]> > --- > 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 [email protected] > 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 [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
