[GEDI] [PATCH] block/gluster: correctly set max_pdiscard which is int64_t

[Fabian Ebner]

Am 06.05.22 um 17:39 schrieb Eric Blake:
> On Thu, May 05, 2022 at 10:31:24AM +0200, Fabian Ebner wrote:
>> Previously, max_pdiscard would be zero in the following assertion:
>> qemu-system-x86_64: ../block/io.c:3166: bdrv_co_pdiscard: Assertion
>> `max_pdiscard >= bs->bl.request_alignment' failed.
>>
>> Fixes: 0c8022876f ("block: use int64_t instead of int in driver discard handlers")
>> Cc: qemu-stable at nongnu.org
>> Signed-off-by: Fabian Ebner <f.ebner at proxmox.com>
>> ---
>>  block/gluster.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/block/gluster.c b/block/gluster.c
>> index 398976bc66..592e71b22a 100644
>> --- a/block/gluster.c
>> +++ b/block/gluster.c
>> @@ -891,7 +891,7 @@ out:
>>  static void qemu_gluster_refresh_limits(BlockDriverState *bs, Error **errp)
>>  {
>>      bs->bl.max_transfer = GLUSTER_MAX_TRANSFER;
>> -    bs->bl.max_pdiscard = SIZE_MAX;
>> +    bs->bl.max_pdiscard = INT64_MAX;
> 
> SIZE_MAX is unsigned, but can differ between 32- and 64-bit platforms.
> Blindly setting max_pdiscard to a signed 64-bit value seems wrong if
> glfs_discard_async() takes a size_t and you are on a 32-bit platform.
> 

Sorry, I did not consider this.

> Is the real issue that SIZE_MAX on a 64-bit platform is too large,

Yes, there it's too big for max_pdiscard which is int64_t.

> where we want min(SIZE_MAX,INT_MAX) as our real cap?
> 

Why not min(SIZE_MAX,INT64_MAX)? Since the constraint is to fit in both
size_t and int64_t. That would also preserve the current value on 32-bit
platforms.

>>  }
>>  
>>  static int qemu_gluster_reopen_prepare(BDRVReopenState *state,
>> @@ -1304,7 +1304,7 @@ static coroutine_fn int qemu_gluster_co_pdiscard(BlockDriverState *bs,
>>      GlusterAIOCB acb;
>>      BDRVGlusterState *s = bs->opaque;
>>  
>> -    assert(bytes <= SIZE_MAX); /* rely on max_pdiscard */
>> +    assert(bytes <= INT64_MAX); /* rely on max_pdiscard */
>>  
>>      acb.size = 0;
>>      acb.ret = 0;
>> -- 
>> 2.30.2
>>
>>
>>
>