| Message ID | 1465939839-30097-7-git-send-email-eblake@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, 06/14 15:30, Eric Blake wrote: > 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 <eblake@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com>
On Tue, Jun 14, 2016 at 03:30:28PM -0600, Eric Blake wrote: > 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 <eblake@redhat.com> > > --- > v2: new patch > --- > block/iscsi.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/block/iscsi.c b/block/iscsi.c index 7e78ade..4290e41 100644 --- a/block/iscsi.c +++ b/block/iscsi.c @@ -1697,7 +1697,9 @@ 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)
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 <eblake@redhat.com> --- v2: new patch --- block/iscsi.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)