From f9e95af0a6be281f56ecc8413ea4a3ac3545ce17 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 23 Jun 2016 16:37:10 -0600 Subject: [PATCH] iscsi: Advertise realistic limits to block layer The function sector_limits_lun2qemu() returns a value in units of the block layer's 512-byte sector, and can be as large as 0x40000000, which is much larger than the block layer's inherent limit of BDRV_REQUEST_MAX_SECTORS. The block layer already handles '0' as a synonym to the inherent limit, and it is nicer to return this value than it is to calculate an arbitrary maximum, for two reasons: we want to ensure that the block layer continues to special-case '0' as 'no limit beyond the inherent limits'; and we want to be able to someday expand the block layer to allow 64-bit limits, where auditing for uses of BDRV_REQUEST_MAX_SECTORS will help us make sure we aren't artificially constraining iscsi to old block layer limits. Signed-off-by: Eric Blake Reviewed-by: Kevin Wolf Reviewed-by: Fam Zheng Reviewed-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/iscsi.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/block/iscsi.c b/block/iscsi.c index 9bb5ff6216..c5dedb3407 100644 --- a/block/iscsi.c +++ b/block/iscsi.c @@ -1698,7 +1698,9 @@ static void iscsi_close(BlockDriverState *bs) static int sector_limits_lun2qemu(int64_t sector, IscsiLun *iscsilun) { - return MIN(sector_lun2qemu(sector, iscsilun), INT_MAX / 2 + 1); + int limit = MIN(sector_lun2qemu(sector, iscsilun), INT_MAX / 2 + 1); + + return limit < BDRV_REQUEST_MAX_SECTORS ? limit : 0; } static void iscsi_refresh_limits(BlockDriverState *bs, Error **errp)