[PATCH v3 0/2] btrfs: Fix lost-data-profile caused by auto removing bg and balance bg

[PATCH v3 0/2] btrfs: Fix lost-data-profile caused by auto removing bg and balance bg

[Zhao Lei]

Sorry for sending v3 late for I'm in my holiday(until 10/7).

But it is necessary to send out in time because I wish to
end this bug in v4.3 release.

Changelog v2->v3:
1: Use list_is_singular() instead of
   block_group->list.next == block_group->list.prev
   Suggested-by: Jeff Mahoney <jeffm@suse.com>
2: Add Reviewed-by: Filipe Manana <fdmanana@suse.com>

Zhao Lei (2):
  btrfs: Fix lost-data-profile caused by auto removing bg
  btrfs: Fix lost-data-profile caused by balance bg

 fs/btrfs/extent-tree.c | 12 +++++++++++-
 fs/btrfs/volumes.c     | 24 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

-- 
1.8.5.1

[PATCH v3 1/2] btrfs: Fix lost-data-profile caused by auto removing bg

[Zhao Lei]

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.

Changelog v2->v3:
1: Use list_is_singular() instead of
   block_group->list.next == block_group->list.prev
   Suggested-by: Jeff Mahoney <jeffm@suse.com>

Changelog v1->v2:
1: Put code of checking block_group->list into
   semaphore of space_info->groups_sem.
Noticed-by: Filipe Manana <fdmanana@gmail.com>

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
---
 fs/btrfs/extent-tree.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 79a5bd9..c05b975 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10010,8 +10010,18 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 		block_group = list_first_entry(&fs_info->unused_bgs,
 					       struct btrfs_block_group_cache,
 					       bg_list);
-		space_info = block_group->space_info;
 		list_del_init(&block_group->bg_list);
+
+		space_info = block_group->space_info;
+
+		down_read(&space_info->groups_sem);
+		if (list_is_singular(&block_group->list)) {
+			up_read(&space_info->groups_sem);
+			btrfs_put_block_group(block_group);
+			continue;
+		}
+		up_read(&space_info->groups_sem);
+
 		if (ret || btrfs_mixed_space_info(space_info)) {
 			btrfs_put_block_group(block_group);
 			continue;
-- 
1.8.5.1

Re: [PATCH v3 1/2] btrfs: Fix lost-data-profile caused by auto removing bg

[Chris Mason]

Hi,

On Sun, Oct 04, 2015 at 12:28:39AM +0800, Zhao Lei wrote:
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 79a5bd9..c05b975 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -10010,8 +10010,18 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
>  		block_group = list_first_entry(&fs_info->unused_bgs,
>  					       struct btrfs_block_group_cache,
>  					       bg_list);
> -		space_info = block_group->space_info;
>  		list_del_init(&block_group->bg_list);
> +
> +		space_info = block_group->space_info;
> +
> +		down_read(&space_info->groups_sem);

Thanks for reworking this, are there other patches that I'm missing that
are meant to go in before this one?

The down_read() this patch adds is inside a spinlock().

-chris

[PATCH v3 2/2] btrfs: Fix lost-data-profile caused by balance bg

[Zhao Lei]

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"
 btrfs balance start -dusage=0 $TEST_DIR
 btrfs filesystem usage $TEST_DIR

 dd if=/dev/zero of="$TEST_DIR"/file count=100
 btrfs filesystem usage $TEST_DIR

Result:
 We can see "no data chunk" in first "btrfs filesystem usage":
 # btrfs filesystem usage $TEST_DIR
 Overall:
    ...
 Metadata,single: Size:8.00MiB, Used:0.00B
    /dev/vdg        8.00MiB
 Metadata,RAID1: Size:122.88MiB, Used:112.00KiB
    /dev/vdg      122.88MiB
    /dev/vdh      122.88MiB
 System,single: Size:4.00MiB, Used:0.00B
    /dev/vdg        4.00MiB
 System,RAID1: Size:8.00MiB, Used:16.00KiB
    /dev/vdg        8.00MiB
    /dev/vdh        8.00MiB
 Unallocated:
    /dev/vdg        1.06GiB
    /dev/vdh        1.07GiB

 And "data chunks changed from raid1 to single" in second
 "btrfs filesystem usage":
 # btrfs filesystem usage $TEST_DIR
 Overall:
    ...
 Data,single: Size:256.00MiB, Used:0.00B
    /dev/vdh      256.00MiB
 Metadata,single: Size:8.00MiB, Used:0.00B
    /dev/vdg        8.00MiB
 Metadata,RAID1: Size:122.88MiB, Used:112.00KiB
    /dev/vdg      122.88MiB
    /dev/vdh      122.88MiB
 System,single: Size:4.00MiB, Used:0.00B
    /dev/vdg        4.00MiB
 System,RAID1: Size:8.00MiB, Used:16.00KiB
    /dev/vdg        8.00MiB
    /dev/vdh        8.00MiB
 Unallocated:
    /dev/vdg        1.06GiB
    /dev/vdh      841.92MiB

Reason:
 btrfs balance delete last data chunk in case of no data in
 the filesystem, then we can see "no data chunk" by "fi usage"
 command.

 And when we do write operation to fs, the only available data
 profile is 0x0, result is all new chunks are allocated single type.

Fix:
 Allocate a data chunk explicitly to ensure we don't lose the
 raid profile for data.

Test:
 Test by above script, and confirmed the logic by debug output.

Changelog v1->v2:
1: Update patch description of "Fix" field
2: Use BTRFS_BLOCK_GROUP_DATA for btrfs_force_chunk_alloc instead
   of 1
3: Only reserve chunk if balance data chunk.
All suggested-by: Filipe Manana <fdmanana@gmail.com>

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
---
 fs/btrfs/volumes.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 6fc73586..cd9e5bd 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3277,6 +3277,7 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
 	u64 limit_data = bctl->data.limit;
 	u64 limit_meta = bctl->meta.limit;
 	u64 limit_sys = bctl->sys.limit;
+	int chunk_reserved = 0;
 
 	/* step one make some room on all the devices */
 	devices = &fs_info->fs_devices->devices;
@@ -3326,6 +3327,8 @@ again:
 	key.type = BTRFS_CHUNK_ITEM_KEY;
 
 	while (1) {
+		u64 chunk_type;
+
 		if ((!counting && atomic_read(&fs_info->balance_pause_req)) ||
 		    atomic_read(&fs_info->balance_cancel_req)) {
 			ret = -ECANCELED;
@@ -3371,8 +3374,10 @@ again:
 			spin_unlock(&fs_info->balance_lock);
 		}
 
+		chunk_type = btrfs_chunk_type(leaf, chunk);
 		ret = should_balance_chunk(chunk_root, leaf, chunk,
 					   found_key.offset);
+
 		btrfs_release_path(path);
 		if (!ret) {
 			mutex_unlock(&fs_info->delete_unused_bgs_mutex);
@@ -3387,6 +3392,25 @@ again:
 			goto loop;
 		}
 
+		if ((chunk_type & BTRFS_BLOCK_GROUP_DATA) && !chunk_reserved) {
+			trans = btrfs_start_transaction(chunk_root, 0);
+			if (IS_ERR(trans)) {
+				mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+				ret = PTR_ERR(trans);
+				goto error;
+			}
+
+			ret = btrfs_force_chunk_alloc(trans, chunk_root,
+						      BTRFS_BLOCK_GROUP_DATA);
+			if (ret < 0) {
+				mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+				goto error;
+			}
+
+			btrfs_end_transaction(trans, chunk_root);
+			chunk_reserved = 1;
+		}
+
 		ret = btrfs_relocate_chunk(chunk_root,
 					   found_key.offset);
 		mutex_unlock(&fs_info->delete_unused_bgs_mutex);
-- 
1.8.5.1