Am 12.05.22 um 18:05 schrieb Stefano Garzarella: > On Thu, May 12, 2022 at 05:44:13PM +0200, Stefano Garzarella wrote: >> On Thu, May 12, 2022 at 12:30:48PM +0200, Fabian Ebner wrote: >>> On 64-bit platforms, SIZE_MAX is too large for max_pdiscard, which is >> >> The main problem is that SIZE_MAX for an int64_t is a negative value. >>
Yes, I should've stated that directly. >>> int64_t, and the following assertion would be triggered: >>> 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-sta...@nongnu.org >>> Signed-off-by: Fabian Ebner <f.eb...@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..f711bf0bd6 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 = MIN(SIZE_MAX, INT64_MAX); >> >> What would be the problem if we use INT64_MAX? > > Okay, I just saw Eric's answer to v1 and I think this is right. > Sorry for not mentioning the changes from v1. > Please explain it in the commit message and also the initial problem > that is SIZE_MAX on a 64-bit platform is a negative number for int64_t, > so the assert fails. > I'll try and improve the commit message for v3. > Thanks, > Stefano > >> (I guess the intention of the original patch was to set the maximum >> value in drivers that do not have a specific maximum). >> >> Or we can set to 0, since in block/io.c we have this code: >> >> max_pdiscard = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_pdiscard, >> INT64_MAX), >> align); >> assert(max_pdiscard >= bs->bl.request_alignment); >> >> Where `max_pdiscard` is set to INT64_MAX (and aligned) if >> bs->bl.max_pdiscard is 0. >> >>> } >>> >>> 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 <= MIN(SIZE_MAX, INT64_MAX)); /* rely on >>> max_pdiscard */ >> >> Can we use bs->bl.max_pdiscard directly here? >> Now I'm thinking that the assert is actually for checking that the value can be passed to glfs_discard_async(), which takes a size_t for the argument in question. So maybe it's best to keep assert(bytes <= SIZE_MAX) as is? >> Thanks, >> Stefano > > >