[PATCH v2] zram: do not forget to endio for partial discard requests

[PATCH v2] zram: do not forget to endio for partial discard requests

[Sergey Senozhatsky]

As reported by Qu Wenruo, the following

 getconf PAGESIZE
 65536
 blkdiscard -p 4k /dev/zram0

takes literally forever to complete.  zram doesn't support
partial discards and just returns immediately w/o doing any
discard work in such cases.  The problem is that we forget
to endio on our way out, so blkdiscard sleeps forever in
submit_bio_wait().  Fix this by adding a missing bio_endio()
call.

Fixes: 0120dd6e4e202 ("zram: make zram_bio_discard more self-contained")
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reported-by: Qu Wenruo <wqu@suse.com>
Closes: https://lore.kernel.org/linux-block/92361cd3-fb8b-482e-bc89-15ff1acb9a59@suse.com
Test-by: Qu Wenruo <wqu@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
---

v1->v2:
- use goto end_bio (Christoph)

 drivers/block/zram/zram_drv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index dcea703a6766..aca67d7144e4 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -2684,7 +2684,7 @@ static void zram_bio_discard(struct zram *zram, struct bio *bio)
 	 */
 	if (offset) {
 		if (n <= (PAGE_SIZE - offset))
-			return;
+			goto end_bio;
 
 		n -= (PAGE_SIZE - offset);
 		index++;
@@ -2699,6 +2699,7 @@ static void zram_bio_discard(struct zram *zram, struct bio *bio)
 		n -= PAGE_SIZE;
 	}
 
+end_bio:
 	bio_endio(bio);
 }
 
-- 
2.53.0.1018.g2bb0e51243-goog

Re: [PATCH v2] zram: do not forget to endio for partial discard requests

[Qu Wenruo]

在 2026/3/31 18:05, Sergey Senozhatsky 写道:
> As reported by Qu Wenruo, the following
> 
>   getconf PAGESIZE
>   65536
>   blkdiscard -p 4k /dev/zram0
> 
> takes literally forever to complete.  zram doesn't support
> partial discards and just returns immediately w/o doing any
> discard work in such cases.  The problem is that we forget
> to endio on our way out, so blkdiscard sleeps forever in
> submit_bio_wait().  Fix this by adding a missing bio_endio()
> call.
> 
> Fixes: 0120dd6e4e202 ("zram: make zram_bio_discard more self-contained")
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> Reported-by: Qu Wenruo <wqu@suse.com>
> Closes: https://lore.kernel.org/linux-block/92361cd3-fb8b-482e-bc89-15ff1acb9a59@suse.com
> Test-by: Qu Wenruo <wqu@suse.com>
> Cc: Christoph Hellwig <hch@lst.de>


And forgot to mention, I'm just a messenger who also did the triage.

The original reporter is Avinesh Kumar <avinesh.kumar@suse.com>, who 
noticed a test failure from LTP runs.

The detailed public bugzilla can be found here:

https://bugzilla.suse.com/show_bug.cgi?id=1256530

Thanks,
Qu

> ---
> 
> v1->v2:
> - use goto end_bio (Christoph)
> 
>   drivers/block/zram/zram_drv.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index dcea703a6766..aca67d7144e4 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -2684,7 +2684,7 @@ static void zram_bio_discard(struct zram *zram, struct bio *bio)
>   	 */
>   	if (offset) {
>   		if (n <= (PAGE_SIZE - offset))
> -			return;
> +			goto end_bio;
>   
>   		n -= (PAGE_SIZE - offset);
>   		index++;
> @@ -2699,6 +2699,7 @@ static void zram_bio_discard(struct zram *zram, struct bio *bio)
>   		n -= PAGE_SIZE;
>   	}
>   
> +end_bio:
>   	bio_endio(bio);
>   }
>   

Re: [PATCH v2] zram: do not forget to endio for partial discard requests

[Sergey Senozhatsky]

On (26/03/31 18:10), Qu Wenruo wrote:
> And forgot to mention, I'm just a messenger who also did the triage.
> 
> The original reporter is Avinesh Kumar <avinesh.kumar@suse.com>, who noticed
> a test failure from LTP runs.

Cc-ed Avinesh on the v3.

Re: [PATCH v2] zram: do not forget to endio for partial discard requests

[Sergey Senozhatsky]

On (26/03/31 16:35), Sergey Senozhatsky wrote:
> As reported by Qu Wenruo, the following
> 
>  getconf PAGESIZE
>  65536
>  blkdiscard -p 4k /dev/zram0
> 
> takes literally forever to complete.  zram doesn't support
> partial discards and just returns immediately w/o doing any
> discard work in such cases.  The problem is that we forget
> to endio on our way out, so blkdiscard sleeps forever in
> submit_bio_wait().  Fix this by adding a missing bio_endio()
> call.

The last sentence should be something like "Fix this by jumping to endio
label which calls bio_endio()"