[v3,0/2] btrfs: zoned: skip reporting zone for new block group

Message

Naohiro Aota March 19, 2025, 1:49 a.m. UTC

Newly created block group should reside on empty zones, whose write pointer
should always be 0. Also, we can load the zone capacity from the block
layer. So, we don't need to REPORT_ZONE to load the info.

The reporting zone on a new block group is not only unnecessary, but also
can cause a deadlock. When one process do a report zones and another
process freezes the block device, the report zones side cannot allocate
a tag because the freeze is already started. This can thus result in new
block group creation to hang forever, blocking the write path.

v1: https://patch.msgid.link/[e-mail]
v2: https://patch.msgid.link/[e-mail]
  - Move other zone related functions into the same #ifdef block.
v3:
  - Rename argument variable and fix the kerneldoc.

Naohiro Aota (2):
  block: introduce zone capacity helper
  btrfs: zoned: skip reporting zone for new block group

 fs/btrfs/zoned.c       | 18 ++++++++++--
 include/linux/blkdev.h | 67 ++++++++++++++++++++++++++++--------------
 2 files changed, 61 insertions(+), 24 deletions(-)

Comments

David Sterba April 3, 2025, 8:03 p.m. UTC | #1

On Wed, Mar 19, 2025 at 10:49:15AM +0900, Naohiro Aota wrote:
> Newly created block group should reside on empty zones, whose write pointer
> should always be 0. Also, we can load the zone capacity from the block
> layer. So, we don't need to REPORT_ZONE to load the info.
> 
> The reporting zone on a new block group is not only unnecessary, but also
> can cause a deadlock. When one process do a report zones and another
> process freezes the block device, the report zones side cannot allocate
> a tag because the freeze is already started. This can thus result in new
> block group creation to hang forever, blocking the write path.
> 
> v1: https://patch.msgid.link/[e-mail]
> v2: https://patch.msgid.link/[e-mail]
>   - Move other zone related functions into the same #ifdef block.
> v3:
>   - Rename argument variable and fix the kerneldoc.
> 
> Naohiro Aota (2):
>   block: introduce zone capacity helper
>   btrfs: zoned: skip reporting zone for new block group

There seem to be no further comments. I'll add the patches to for-next
and queue it for merge in 6.15-rc2. Thanks.