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[Qemu-devel] [PATCH v2 07/17] block: Give nonzero result to blk_get_max_
From: |
Eric Blake |
Subject: |
[Qemu-devel] [PATCH v2 07/17] block: Give nonzero result to blk_get_max_transfer_length() |
Date: |
Tue, 14 Jun 2016 15:30:29 -0600 |
Making all callers special-case 0 as unlimited is awkward,
and we DO have a hard maximum of BDRV_REQUEST_MAX_SECTORS given
our current block layer API limits.
In the case of scsi, this means that we now always advertise a
limit to the guest, even in cases where the underlying layers
previously use 0 for no inherent limit beyond the block layer.
Signed-off-by: Eric Blake <address@hidden>
---
v2: new patch
---
block/block-backend.c | 7 ++++---
hw/block/virtio-blk.c | 3 +--
hw/scsi/scsi-generic.c | 12 ++++++------
3 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/block/block-backend.c b/block/block-backend.c
index 34500e6..1fb070b 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1303,15 +1303,16 @@ int blk_get_flags(BlockBackend *blk)
}
}
+/* Returns the maximum transfer length, in sectors; guaranteed nonzero */
int blk_get_max_transfer_length(BlockBackend *blk)
{
BlockDriverState *bs = blk_bs(blk);
+ int max = 0;
if (bs) {
- return bs->bl.max_transfer_length;
- } else {
- return 0;
+ max = bs->bl.max_transfer_length;
}
+ return MIN_NON_ZERO(max, BDRV_REQUEST_MAX_SECTORS);
}
int blk_get_max_iov(BlockBackend *blk)
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 284e646..1d2792e 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -382,7 +382,7 @@ static int multireq_compare(const void *a, const void *b)
void virtio_blk_submit_multireq(BlockBackend *blk, MultiReqBuffer *mrb)
{
int i = 0, start = 0, num_reqs = 0, niov = 0, nb_sectors = 0;
- int max_xfer_len = 0;
+ int max_xfer_len;
int64_t sector_num = 0;
if (mrb->num_reqs == 1) {
@@ -392,7 +392,6 @@ void virtio_blk_submit_multireq(BlockBackend *blk,
MultiReqBuffer *mrb)
}
max_xfer_len = blk_get_max_transfer_length(mrb->reqs[0]->dev->blk);
- max_xfer_len = MIN_NON_ZERO(max_xfer_len, BDRV_REQUEST_MAX_SECTORS);
qsort(mrb->reqs, mrb->num_reqs, sizeof(*mrb->reqs),
&multireq_compare);
diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
index 71372a8..db04a76 100644
--- a/hw/scsi/scsi-generic.c
+++ b/hw/scsi/scsi-generic.c
@@ -226,12 +226,12 @@ static void scsi_read_complete(void * opaque, int ret)
r->req.cmd.buf[0] == INQUIRY &&
r->req.cmd.buf[2] == 0xb0) {
uint32_t max_xfer_len = blk_get_max_transfer_length(s->conf.blk);
- if (max_xfer_len) {
- stl_be_p(&r->buf[8], max_xfer_len);
- /* Also take care of the opt xfer len. */
- if (ldl_be_p(&r->buf[12]) > max_xfer_len) {
- stl_be_p(&r->buf[12], max_xfer_len);
- }
+
+ assert(max_xfer_len);
+ stl_be_p(&r->buf[8], max_xfer_len);
+ /* Also take care of the opt xfer len. */
+ if (ldl_be_p(&r->buf[12]) > max_xfer_len) {
+ stl_be_p(&r->buf[12], max_xfer_len);
}
}
scsi_req_data(&r->req, len);
--
2.5.5
- Re: [Qemu-devel] [PATCH v2 05/17] nbd: Advertise realistic limits to block layer, (continued)
- [Qemu-devel] [PATCH v2 03/17] block: Fix harmless off-by-one in bdrv_aligned_preadv(), Eric Blake, 2016/06/14
- [Qemu-devel] [PATCH v2 13/17] block: Set default request_alignment during bdrv_refresh_limits(), Eric Blake, 2016/06/14
- [Qemu-devel] [PATCH v2 11/17] raw-win32: Set request_alignment during .bdrv_refresh_limits(), Eric Blake, 2016/06/14
- [Qemu-devel] [PATCH v2 07/17] block: Give nonzero result to blk_get_max_transfer_length(),
Eric Blake <=
- [Qemu-devel] [PATCH v2 10/17] qcow2: Set request_alignment during .bdrv_refresh_limits(), Eric Blake, 2016/06/14
- [Qemu-devel] [PATCH v2 12/17] block: Set request_alignment during .bdrv_refresh_limits(), Eric Blake, 2016/06/14
- [Qemu-devel] [PATCH v2 06/17] iscsi: Advertise realistic limits to block layer, Eric Blake, 2016/06/14
- [Qemu-devel] [PATCH v2 15/17] block: Switch discard length bounds to byte-based, Eric Blake, 2016/06/14