[PATCH] scsi: sd_zbc: ensure buffer size is aligned to SECTOR_SIZE

[PATCH] scsi: sd_zbc: ensure buffer size is aligned to SECTOR_SIZE

[Naohiro Aota]

Reporting zones on a SCSI device sometimes fail with the following error.

[76248.516390] ata16.00: invalid transfer count 131328
[76248.523618] sd 15:0:0:0: [sda] REPORT ZONES start lba 536870912 failed

The error (from drivers/ata/libata-scsi.c ata_scsi_zbc_in_xlat())
indicates that buffer size is not aligned to SECTOR_SIZE.

This happens when the __vmalloc() failed. Consider we are reporting 4096
zones, then we will have "bufsize = roundup((4096 + 1) * 64,
SECTOR_SIZE)" = (513 * 512) = 262656. Then, __vmalloc() failure halven
the bufsize to 131328, which is no longer aligned to SECTOR_SIZE.

Use rounddown() to ensure the size is always aligned to SECTOR_SIZE and
fix the comment as well.

Fixes: 23a50861adda ("scsi: sd_zbc: Cleanup sd_zbc_alloc_report_buffer()")
Cc: stable@vger.kernel.org # 5.5+
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 drivers/scsi/sd_zbc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
index 186b5ff52c3a..ea8b3f6ee5cd 100644
--- a/drivers/scsi/sd_zbc.c
+++ b/drivers/scsi/sd_zbc.c
@@ -154,8 +154,8 @@ static void *sd_zbc_alloc_report_buffer(struct scsi_disk *sdkp,
 
 	/*
 	 * Report zone buffer size should be at most 64B times the number of
-	 * zones requested plus the 64B reply header, but should be at least
-	 * SECTOR_SIZE for ATA devices.
+	 * zones requested plus the 64B reply header, but should be aligned
+	 * to SECTOR_SIZE for ATA devices.
 	 * Make sure that this size does not exceed the hardware capabilities.
 	 * Furthermore, since the report zone command cannot be split, make
 	 * sure that the allocated buffer can always be mapped by limiting the
@@ -174,7 +174,7 @@ static void *sd_zbc_alloc_report_buffer(struct scsi_disk *sdkp,
 			*buflen = bufsize;
 			return buf;
 		}
-		bufsize >>= 1;
+		bufsize = rounddown(bufsize >> 1, SECTOR_SIZE);
 	}
 
 	return NULL;
-- 
2.33.0

Re: [PATCH] scsi: sd_zbc: ensure buffer size is aligned to SECTOR_SIZE

[Johannes Thumshirn]

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

Re: [PATCH] scsi: sd_zbc: ensure buffer size is aligned to SECTOR_SIZE

[Damien Le Moal]

On 2021/09/06 23:06, Naohiro Aota wrote:
> Reporting zones on a SCSI device sometimes fail with the following error.
> 
> [76248.516390] ata16.00: invalid transfer count 131328
> [76248.523618] sd 15:0:0:0: [sda] REPORT ZONES start lba 536870912 failed
> 
> The error (from drivers/ata/libata-scsi.c ata_scsi_zbc_in_xlat())
> indicates that buffer size is not aligned to SECTOR_SIZE.
> 
> This happens when the __vmalloc() failed. Consider we are reporting 4096
> zones, then we will have "bufsize = roundup((4096 + 1) * 64,
> SECTOR_SIZE)" = (513 * 512) = 262656. Then, __vmalloc() failure halven
> the bufsize to 131328, which is no longer aligned to SECTOR_SIZE.
> 
> Use rounddown() to ensure the size is always aligned to SECTOR_SIZE and
> fix the comment as well.
> 
> Fixes: 23a50861adda ("scsi: sd_zbc: Cleanup sd_zbc_alloc_report_buffer()")
> Cc: stable@vger.kernel.org # 5.5+
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> ---
>  drivers/scsi/sd_zbc.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
> index 186b5ff52c3a..ea8b3f6ee5cd 100644
> --- a/drivers/scsi/sd_zbc.c
> +++ b/drivers/scsi/sd_zbc.c
> @@ -154,8 +154,8 @@ static void *sd_zbc_alloc_report_buffer(struct scsi_disk *sdkp,
>  
>  	/*
>  	 * Report zone buffer size should be at most 64B times the number of
> -	 * zones requested plus the 64B reply header, but should be at least
> -	 * SECTOR_SIZE for ATA devices.
> +	 * zones requested plus the 64B reply header, but should be aligned
> +	 * to SECTOR_SIZE for ATA devices.
>  	 * Make sure that this size does not exceed the hardware capabilities.
>  	 * Furthermore, since the report zone command cannot be split, make
>  	 * sure that the allocated buffer can always be mapped by limiting the
> @@ -174,7 +174,7 @@ static void *sd_zbc_alloc_report_buffer(struct scsi_disk *sdkp,
>  			*buflen = bufsize;
>  			return buf;
>  		}
> -		bufsize >>= 1;
> +		bufsize = rounddown(bufsize >> 1, SECTOR_SIZE);
>  	}
>  
>  	return NULL;
> 

Good catch ! My bad :)

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>

-- 
Damien Le Moal
Western Digital Research

Re: [PATCH] scsi: sd_zbc: ensure buffer size is aligned to SECTOR_SIZE

[Himanshu Madhani]

> On Sep 6, 2021, at 9:06 AM, Naohiro Aota <naohiro.aota@wdc.com> wrote:
> 
> Reporting zones on a SCSI device sometimes fail with the following error.
> 
> [76248.516390] ata16.00: invalid transfer count 131328
> [76248.523618] sd 15:0:0:0: [sda] REPORT ZONES start lba 536870912 failed
> 
> The error (from drivers/ata/libata-scsi.c ata_scsi_zbc_in_xlat())
> indicates that buffer size is not aligned to SECTOR_SIZE.
> 
> This happens when the __vmalloc() failed. Consider we are reporting 4096
> zones, then we will have "bufsize = roundup((4096 + 1) * 64,
> SECTOR_SIZE)" = (513 * 512) = 262656. Then, __vmalloc() failure halven
> the bufsize to 131328, which is no longer aligned to SECTOR_SIZE.
> 
> Use rounddown() to ensure the size is always aligned to SECTOR_SIZE and
> fix the comment as well.
> 
> Fixes: 23a50861adda ("scsi: sd_zbc: Cleanup sd_zbc_alloc_report_buffer()")
> Cc: stable@vger.kernel.org # 5.5+
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> ---
> drivers/scsi/sd_zbc.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
> index 186b5ff52c3a..ea8b3f6ee5cd 100644
> --- a/drivers/scsi/sd_zbc.c
> +++ b/drivers/scsi/sd_zbc.c
> @@ -154,8 +154,8 @@ static void *sd_zbc_alloc_report_buffer(struct scsi_disk *sdkp,
> 
> 	/*
> 	 * Report zone buffer size should be at most 64B times the number of
> -	 * zones requested plus the 64B reply header, but should be at least
> -	 * SECTOR_SIZE for ATA devices.
> +	 * zones requested plus the 64B reply header, but should be aligned
> +	 * to SECTOR_SIZE for ATA devices.
> 	 * Make sure that this size does not exceed the hardware capabilities.
> 	 * Furthermore, since the report zone command cannot be split, make
> 	 * sure that the allocated buffer can always be mapped by limiting the
> @@ -174,7 +174,7 @@ static void *sd_zbc_alloc_report_buffer(struct scsi_disk *sdkp,
> 			*buflen = bufsize;
> 			return buf;
> 		}
> -		bufsize >>= 1;
> +		bufsize = rounddown(bufsize >> 1, SECTOR_SIZE);
> 	}
> 
> 	return NULL;
> -- 
> 2.33.0
> 

Makes sense. 

Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>

--
Himanshu Madhani	 Oracle Linux Engineering

Re: [PATCH] scsi: sd_zbc: ensure buffer size is aligned to SECTOR_SIZE

[Martin K. Petersen]

On Mon, 6 Sep 2021 23:06:42 +0900, Naohiro Aota wrote:

> Reporting zones on a SCSI device sometimes fail with the following error.
> 
> [76248.516390] ata16.00: invalid transfer count 131328
> [76248.523618] sd 15:0:0:0: [sda] REPORT ZONES start lba 536870912 failed
> 
> The error (from drivers/ata/libata-scsi.c ata_scsi_zbc_in_xlat())
> indicates that buffer size is not aligned to SECTOR_SIZE.
> 
> [...]

Applied to 5.15/scsi-fixes, thanks!

[1/1] scsi: sd_zbc: ensure buffer size is aligned to SECTOR_SIZE
      https://git.kernel.org/mkp/scsi/c/7215e909814f

-- 
Martin K. Petersen	Oracle Linux Engineering