[PATCH] block: clear zone write plugging flag before failing rejected BIOs

[PATCH] block: clear zone write plugging flag before failing rejected BIOs

[Jackie Liu]

From: Jackie Liu <liuyun01@kylinos.cn>

Commit fe0418eb9bd6 ("block: Prevent potential deadlocks in zone write plug
error recovery") changed blk_zone_wplug_handle_write() to fail BIOs
directly when blk_zone_wplug_prepare_bio() rejects them, for example
because the write is not aligned to the cached write pointer or the plug
needs a write pointer update. However, the BIO is already marked with
BIO_ZONE_WRITE_PLUGGING at that point even though it is not issued.

Completing such a BIO with bio_io_error() makes bio_endio() call
blk_zone_write_plug_bio_endio(), which treats the completion as a failed
device write and may poison the cached zone write pointer state by setting
BLK_ZONE_WPLUG_NEED_WP_UPDATE.

Clear BIO_ZONE_WRITE_PLUGGING and drop the zone write plug reference before
failing the rejected BIO.

Fixes: fe0418eb9bd6 ("block: Prevent potential deadlocks in zone write plug error recovery")
Cc: stable@vger.kernel.org # 6.13+
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
---
 block/blk-zoned.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 6a221c180889..855767d8bfc1 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -1502,7 +1502,9 @@ static bool blk_zone_wplug_handle_write(struct bio *bio, unsigned int nr_segs)
 		goto queue_bio;
 
 	if (!blk_zone_wplug_prepare_bio(zwplug, bio)) {
+		bio_clear_flag(bio, BIO_ZONE_WRITE_PLUGGING);
 		spin_unlock_irqrestore(&zwplug->lock, flags);
+		disk_put_zone_wplug(zwplug);
 		bio_io_error(bio);
 		return true;
 	}
-- 
2.54.0

Re: [PATCH] block: clear zone write plugging flag before failing rejected BIOs

[Damien Le Moal]

On 2026/06/07 11:18, Jackie Liu wrote:
> From: Jackie Liu <liuyun01@kylinos.cn>
> 
> Commit fe0418eb9bd6 ("block: Prevent potential deadlocks in zone write plug
> error recovery") changed blk_zone_wplug_handle_write() to fail BIOs
> directly when blk_zone_wplug_prepare_bio() rejects them, for example
> because the write is not aligned to the cached write pointer or the plug
> needs a write pointer update. However, the BIO is already marked with
> BIO_ZONE_WRITE_PLUGGING at that point even though it is not issued.
> 
> Completing such a BIO with bio_io_error() makes bio_endio() call
> blk_zone_write_plug_bio_endio(), which treats the completion as a failed
> device write and may poison the cached zone write pointer state by setting
> BLK_ZONE_WPLUG_NEED_WP_UPDATE.

Yes, true. But you did not explain clearly why that is a problem. After all, if
we hit this case, the user issued an unaligned BIO, and so forcing it to do a
report zones to get everything in sync and the correct write pointer is not a
bad thing.

If fe0418eb9bd6 change is actually causing you problems, please describe that
problem clearly. But ideally, I do not want to special case some error
completions over others and prefer to have a single error path that result in
the same state for the zone write plugs, regardless of a write error root cause.

> 
> Clear BIO_ZONE_WRITE_PLUGGING and drop the zone write plug reference before
> failing the rejected BIO.
> 
> Fixes: fe0418eb9bd6 ("block: Prevent potential deadlocks in zone write plug error recovery")
> Cc: stable@vger.kernel.org # 6.13+
> Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
> ---
>  block/blk-zoned.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 6a221c180889..855767d8bfc1 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -1502,7 +1502,9 @@ static bool blk_zone_wplug_handle_write(struct bio *bio, unsigned int nr_segs)
>  		goto queue_bio;
>  
>  	if (!blk_zone_wplug_prepare_bio(zwplug, bio)) {
> +		bio_clear_flag(bio, BIO_ZONE_WRITE_PLUGGING);
>  		spin_unlock_irqrestore(&zwplug->lock, flags);
> +		disk_put_zone_wplug(zwplug);
>  		bio_io_error(bio);
>  		return true;
>  	}


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH] block: clear zone write plugging flag before failing rejected BIOs

[Jackie Liu]

2026年6月8日 19:42, "Damien Le Moal" <dlemoal@kernel.org mailto:dlemoal@kernel.org?to=%22Damien%20Le%20Moal%22%20%3Cdlemoal%40kernel.org%3E > 写到:


> 
> On 2026/06/07 11:18, Jackie Liu wrote:
> 
> > 
> > From: Jackie Liu <liuyun01@kylinos.cn>
> >  
> >  Commit fe0418eb9bd6 ("block: Prevent potential deadlocks in zone write plug
> >  error recovery") changed blk_zone_wplug_handle_write() to fail BIOs
> >  directly when blk_zone_wplug_prepare_bio() rejects them, for example
> >  because the write is not aligned to the cached write pointer or the plug
> >  needs a write pointer update. However, the BIO is already marked with
> >  BIO_ZONE_WRITE_PLUGGING at that point even though it is not issued.
> >  
> >  Completing such a BIO with bio_io_error() makes bio_endio() call
> >  blk_zone_write_plug_bio_endio(), which treats the completion as a failed
> >  device write and may poison the cached zone write pointer state by setting
> >  BLK_ZONE_WPLUG_NEED_WP_UPDATE.
> > 
> Yes, true. But you did not explain clearly why that is a problem. After all, if
> we hit this case, the user issued an unaligned BIO, and so forcing it to do a
> report zones to get everything in sync and the correct write pointer is not a
> bad thing.
> 
> If fe0418eb9bd6 change is actually causing you problems, please describe that
> problem clearly. But ideally, I do not want to special case some error
> completions over others and prefer to have a single error path that result in
> the same state for the zone write plugs, regardless of a write error root cause.

Thanks for the review. I agree that the changelog did not describe a
concrete user-visible problem clearly enough.

I was treating NEED_WP_UPDATE on a BIO rejected before submission as stale
state poisoning, because no device write was actually issued. But as you
pointed out, for an invalid/non-sequential write, forcing the user to
resynchronize the write pointer through report zones is consistent with the
current conservative recovery model.

I do not have a concrete regression from fe0418eb9bd6 beyond that extra
recovery requirement, so please drop this patch for now.

Thanks.

Jackie

> 
> > 
> > Clear BIO_ZONE_WRITE_PLUGGING and drop the zone write plug reference before
> >  failing the rejected BIO.
> >  
> >  Fixes: fe0418eb9bd6 ("block: Prevent potential deadlocks in zone write plug error recovery")
> >  Cc: stable@vger.kernel.org # 6.13+
> >  Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
> >  ---
> >  block/blk-zoned.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >  
> >  diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> >  index 6a221c180889..855767d8bfc1 100644
> >  --- a/block/blk-zoned.c
> >  +++ b/block/blk-zoned.c
> >  @@ -1502,7 +1502,9 @@ static bool blk_zone_wplug_handle_write(struct bio *bio, unsigned int nr_segs)
> >  goto queue_bio;
> >  
> >  if (!blk_zone_wplug_prepare_bio(zwplug, bio)) {
> >  + bio_clear_flag(bio, BIO_ZONE_WRITE_PLUGGING);
> >  spin_unlock_irqrestore(&zwplug->lock, flags);
> >  + disk_put_zone_wplug(zwplug);
> >  bio_io_error(bio);
> >  return true;
> >  }
> > 
> -- 
> Damien Le Moal
> Western Digital Research
>