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Re: [PATCH] block/gluster: correctly set max_pdiscard which is int64_t
From: |
Fabian Ebner |
Subject: |
Re: [PATCH] block/gluster: correctly set max_pdiscard which is int64_t |
Date: |
Mon, 9 May 2022 08:49:56 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 |
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@nongnu.org
>> Signed-off-by: Fabian Ebner <f.ebner@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
>>
>>
>>
>