[PATCH V2] oslib: Fix blkzoned_get_max_open_zones()

[PATCH V2] oslib: Fix blkzoned_get_max_open_zones()

[Damien Le Moal]

When the kernel does not have the sysfs atttribute file
queue/max_open_zones, blkzoned_get_max_open_zones() returns success
without initializing the max_open_zones value to 0 to indicate to the
caller (zbd_get_max_open_zones() in zbd.c) that the device limit is
unknown. If the max_open_zones variable in zbd_get_max_open_zones() is
not already 0 (depending on the memory status), the missing
initialization in blkzoned_get_max_open_zones() can cause errors or
misbehavior as an incorrect, random, limit may be used.

Fix this by always initializing max_open_zones to 0 when the
max_open_zones sysfs attribute file does not exist.

Reported-by: Bao-Hua Li <baohua.li@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---

Changes from v1:
* Added missing reported-by tag

 oslib/linux-blkzoned.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/oslib/linux-blkzoned.c b/oslib/linux-blkzoned.c
index 4e441d29..185bd501 100644
--- a/oslib/linux-blkzoned.c
+++ b/oslib/linux-blkzoned.c
@@ -169,8 +169,10 @@ int blkzoned_get_max_open_zones(struct thread_data *td, struct fio_file *f,
 		return -EIO;
 
 	max_open_str = blkzoned_get_sysfs_attr(f->file_name, "queue/max_open_zones");
-	if (!max_open_str)
+	if (!max_open_str) {
+		*max_open_zones = 0;
 		return 0;
+	}
 
 	dprint(FD_ZBD, "%s: max open zones supported by device: %s\n",
 	       f->file_name, max_open_str);
-- 
2.31.1

Re: [PATCH V2] oslib: Fix blkzoned_get_max_open_zones()

[Damien Le Moal]

On 2021/09/01 15:42, Damien Le Moal wrote:
> When the kernel does not have the sysfs atttribute file
> queue/max_open_zones, blkzoned_get_max_open_zones() returns success
> without initializing the max_open_zones value to 0 to indicate to the
> caller (zbd_get_max_open_zones() in zbd.c) that the device limit is
> unknown. If the max_open_zones variable in zbd_get_max_open_zones() is
> not already 0 (depending on the memory status), the missing
> initialization in blkzoned_get_max_open_zones() can cause errors or
> misbehavior as an incorrect, random, limit may be used.
> 
> Fix this by always initializing max_open_zones to 0 when the
> max_open_zones sysfs attribute file does not exist.

Hi Jens,

We are getting problem reports from the field due to this bug. Could you apply
this patch please ?

Thanks !

> 
> Reported-by: Bao-Hua Li <baohua.li@wdc.com>
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> ---
> 
> Changes from v1:
> * Added missing reported-by tag
> 
>  oslib/linux-blkzoned.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/oslib/linux-blkzoned.c b/oslib/linux-blkzoned.c
> index 4e441d29..185bd501 100644
> --- a/oslib/linux-blkzoned.c
> +++ b/oslib/linux-blkzoned.c
> @@ -169,8 +169,10 @@ int blkzoned_get_max_open_zones(struct thread_data *td, struct fio_file *f,
>  		return -EIO;
>  
>  	max_open_str = blkzoned_get_sysfs_attr(f->file_name, "queue/max_open_zones");
> -	if (!max_open_str)
> +	if (!max_open_str) {
> +		*max_open_zones = 0;
>  		return 0;
> +	}
>  
>  	dprint(FD_ZBD, "%s: max open zones supported by device: %s\n",
>  	       f->file_name, max_open_str);
> 


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH V2] oslib: Fix blkzoned_get_max_open_zones()

[Jens Axboe]

On 9/1/21 12:41 AM, Damien Le Moal wrote:
> When the kernel does not have the sysfs atttribute file
> queue/max_open_zones, blkzoned_get_max_open_zones() returns success
> without initializing the max_open_zones value to 0 to indicate to the
> caller (zbd_get_max_open_zones() in zbd.c) that the device limit is
> unknown. If the max_open_zones variable in zbd_get_max_open_zones() is
> not already 0 (depending on the memory status), the missing
> initialization in blkzoned_get_max_open_zones() can cause errors or
> misbehavior as an incorrect, random, limit may be used.
> 
> Fix this by always initializing max_open_zones to 0 when the
> max_open_zones sysfs attribute file does not exist.

Applied, thanks.

-- 
Jens Axboe