[PATCH] btrfs: reset RO counter on block group if we fail to relocate

[PATCH] btrfs: reset RO counter on block group if we fail to relocate

[Josef Bacik]

With the automatic block group reclaim code we will preemptively try to
mark the block group RO before we start the relocation.  We do this to
make sure we should actually try to relocate the block group.

However if we hit an error during the actual relocation we won't clean
up our RO counter and the block group will remain RO.  This was observed
internally with file systems reporting less space available from df when
we had failed background relocations.

Fix this by doing the dec_ro in the error case.

Fixes: 18bb8bbf13c1 ("btrfs: zoned: automatically reclaim zones")
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/block-group.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index c3aecfb0a71d..993aca2f1e18 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1640,9 +1640,11 @@ void btrfs_reclaim_bgs_work(struct work_struct *work)
 				div64_u64(zone_unusable * 100, bg->length));
 		trace_btrfs_reclaim_block_group(bg);
 		ret = btrfs_relocate_chunk(fs_info, bg->start);
-		if (ret)
+		if (ret) {
+			btrfs_dec_block_group_ro(bg);
 			btrfs_err(fs_info, "error relocating chunk %llu",
 				  bg->start);
+		}
 
 next:
 		btrfs_put_block_group(bg);
-- 
2.26.3

Re: [PATCH] btrfs: reset RO counter on block group if we fail to relocate

[Boris Burkov]

On Mon, Jul 25, 2022 at 01:05:05PM -0400, Josef Bacik wrote:
> With the automatic block group reclaim code we will preemptively try to
> mark the block group RO before we start the relocation.  We do this to
> make sure we should actually try to relocate the block group.
> 
> However if we hit an error during the actual relocation we won't clean
> up our RO counter and the block group will remain RO.  This was observed
> internally with file systems reporting less space available from df when
> we had failed background relocations.
> 
> Fix this by doing the dec_ro in the error case.
> 
> Fixes: 18bb8bbf13c1 ("btrfs: zoned: automatically reclaim zones")
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Boris Burkov <boris@bur.io>
> ---
>  fs/btrfs/block-group.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
> index c3aecfb0a71d..993aca2f1e18 100644
> --- a/fs/btrfs/block-group.c
> +++ b/fs/btrfs/block-group.c
> @@ -1640,9 +1640,11 @@ void btrfs_reclaim_bgs_work(struct work_struct *work)
>  				div64_u64(zone_unusable * 100, bg->length));
>  		trace_btrfs_reclaim_block_group(bg);
>  		ret = btrfs_relocate_chunk(fs_info, bg->start);
> -		if (ret)
> +		if (ret) {
> +			btrfs_dec_block_group_ro(bg);
>  			btrfs_err(fs_info, "error relocating chunk %llu",
>  				  bg->start);
> +		}
>  
>  next:
>  		btrfs_put_block_group(bg);
> -- 
> 2.26.3
> 

Re: [PATCH] btrfs: reset RO counter on block group if we fail to relocate

[David Sterba]

On Mon, Jul 25, 2022 at 01:05:05PM -0400, Josef Bacik wrote:
> With the automatic block group reclaim code we will preemptively try to
> mark the block group RO before we start the relocation.  We do this to
> make sure we should actually try to relocate the block group.
> 
> However if we hit an error during the actual relocation we won't clean
> up our RO counter and the block group will remain RO.  This was observed
> internally with file systems reporting less space available from df when
> we had failed background relocations.
> 
> Fix this by doing the dec_ro in the error case.
> 
> Fixes: 18bb8bbf13c1 ("btrfs: zoned: automatically reclaim zones")
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Added to misc-next, thanks.