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[Qemu-block] [PATCH 3/5] block: Switch transfer length bounds to byte-ba
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From: |
Eric Blake |
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Subject: |
[Qemu-block] [PATCH 3/5] block: Switch transfer length bounds to byte-based |
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Date: |
Fri, 3 Jun 2016 11:03:06 -0600 |
Sector-based limits are awkward to think about; in our on-going
quest to move to byte-based interfaces, convert max_transfer_length
and opt_transfer_length. Rename them (dropping the _length suffix)
so that the compiler will help us catch the change in semantics
across any rebased code. Improve the documentation, and guarantee
that blk_get_max_transfer() returns a non-zero value. Use unsigned
values, so that we don't have to worry about negative values and
so that bit-twiddling is easier; however, we are still constrained
by 2^31 of signed int in most APIs.
Of note: the iscsi calculations use a 64-bit number internally,
but the final result is guaranteed to fit in 32 bits. NBD is
fixed to advertise the maximum length of 32M that the qemu and
kernel servers enforce, rather than a number of sectors that
would overflow int when converted back to bytes. scsi-generic
now advertises a maximum always, rather than just when the
underlying device advertised a maximum.
Signed-off-by: Eric Blake <address@hidden>
---
include/block/block_int.h | 10 ++++++----
include/sysemu/block-backend.h | 2 +-
block/block-backend.c | 9 +++++----
block/io.c | 23 +++++++++++------------
block/iscsi.c | 18 ++++++++++--------
block/nbd.c | 2 +-
block/raw-posix.c | 2 +-
hw/block/virtio-blk.c | 12 +++++++-----
hw/scsi/scsi-generic.c | 14 +++++++-------
qemu-img.c | 8 ++++----
10 files changed, 53 insertions(+), 47 deletions(-)
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 8a4963c..96e8476 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -336,11 +336,13 @@ typedef struct BlockLimits {
* power of 2, and less than max_pwrite_zeroes if that is set */
uint32_t pwrite_zeroes_alignment;
- /* optimal transfer length in sectors */
- int opt_transfer_length;
+ /* optimal transfer length in bytes (must be power of 2, and
+ * multiple of bs->request_alignment), or 0 if no preferred size */
+ uint32_t opt_transfer;
- /* maximal transfer length in sectors */
- int max_transfer_length;
+ /* maximal transfer length in bytes (need not be power of 2, but
+ * should be multiple of opt_transfer), or 0 for no 32-bit limit */
+ uint32_t max_transfer;
/* memory alignment so that no bounce buffer is needed */
size_t min_mem_alignment;
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index c04af8e..2469a1c 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -170,7 +170,7 @@ bool blk_is_available(BlockBackend *blk);
void blk_lock_medium(BlockBackend *blk, bool locked);
void blk_eject(BlockBackend *blk, bool eject_flag);
int blk_get_flags(BlockBackend *blk);
-int blk_get_max_transfer_length(BlockBackend *blk);
+uint32_t blk_get_max_transfer(BlockBackend *blk);
int blk_get_max_iov(BlockBackend *blk);
void blk_set_guest_block_size(BlockBackend *blk, int align);
void *blk_try_blockalign(BlockBackend *blk, size_t size);
diff --git a/block/block-backend.c b/block/block-backend.c
index 34500e6..19c1f7f 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1303,15 +1303,16 @@ int blk_get_flags(BlockBackend *blk)
}
}
-int blk_get_max_transfer_length(BlockBackend *blk)
+/* Returns the maximum transfer length, in bytes; guaranteed nonzero */
+uint32_t blk_get_max_transfer(BlockBackend *blk)
{
BlockDriverState *bs = blk_bs(blk);
+ uint32_t max = 0;
if (bs) {
- return bs->bl.max_transfer_length;
- } else {
- return 0;
+ max = bs->bl.max_transfer;
}
+ return MIN_NON_ZERO(max, BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS);
}
int blk_get_max_iov(BlockBackend *blk)
diff --git a/block/io.c b/block/io.c
index 3c7b233..a2bc254 100644
--- a/block/io.c
+++ b/block/io.c
@@ -85,8 +85,8 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
error_propagate(errp, local_err);
return;
}
- bs->bl.opt_transfer_length = bs->file->bs->bl.opt_transfer_length;
- bs->bl.max_transfer_length = bs->file->bs->bl.max_transfer_length;
+ bs->bl.opt_transfer = bs->file->bs->bl.opt_transfer;
+ bs->bl.max_transfer = bs->file->bs->bl.max_transfer;
bs->bl.min_mem_alignment = bs->file->bs->bl.min_mem_alignment;
bs->bl.opt_mem_alignment = bs->file->bs->bl.opt_mem_alignment;
bs->bl.max_iov = bs->file->bs->bl.max_iov;
@@ -104,12 +104,10 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error
**errp)
error_propagate(errp, local_err);
return;
}
- bs->bl.opt_transfer_length =
- MAX(bs->bl.opt_transfer_length,
- bs->backing->bs->bl.opt_transfer_length);
- bs->bl.max_transfer_length =
- MIN_NON_ZERO(bs->bl.max_transfer_length,
- bs->backing->bs->bl.max_transfer_length);
+ bs->bl.opt_transfer = MAX(bs->bl.opt_transfer,
+ bs->backing->bs->bl.opt_transfer);
+ bs->bl.max_transfer = MIN_NON_ZERO(bs->bl.max_transfer,
+ bs->backing->bs->bl.max_transfer);
bs->bl.opt_mem_alignment =
MAX(bs->bl.opt_mem_alignment,
bs->backing->bs->bl.opt_mem_alignment);
@@ -1119,7 +1117,8 @@ int coroutine_fn bdrv_co_readv(BlockDriverState *bs,
int64_t sector_num,
return bdrv_co_do_readv(bs, sector_num, nb_sectors, qiov, 0);
}
-#define MAX_WRITE_ZEROES_BOUNCE_BUFFER 32768
+/* Maximum buffer for write zeroes fallback, in bytes */
+#define MAX_WRITE_ZEROES_BOUNCE_BUFFER (32768 << BDRV_SECTOR_BITS)
static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
int64_t offset, int count, BdrvRequestFlags flags)
@@ -1177,7 +1176,7 @@ static int coroutine_fn
bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
if (ret == -ENOTSUP) {
/* Fall back to bounce buffer if write zeroes is unsupported */
- int max_xfer_len = MIN_NON_ZERO(bs->bl.max_transfer_length,
+ int max_xfer_len = MIN_NON_ZERO(bs->bl.max_transfer,
MAX_WRITE_ZEROES_BOUNCE_BUFFER);
BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE;
@@ -1188,7 +1187,7 @@ static int coroutine_fn
bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
write_flags &= ~BDRV_REQ_FUA;
need_flush = true;
}
- num = MIN(num, max_xfer_len << BDRV_SECTOR_BITS);
+ num = MIN(num, max_xfer_len);
iov.iov_len = num;
if (iov.iov_base == NULL) {
iov.iov_base = qemu_try_blockalign(bs, num);
@@ -1205,7 +1204,7 @@ static int coroutine_fn
bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
/* Keep bounce buffer around if it is big enough for all
* all future requests.
*/
- if (num < max_xfer_len << BDRV_SECTOR_BITS) {
+ if (num < max_xfer_len) {
qemu_vfree(iov.iov_base);
iov.iov_base = NULL;
}
diff --git a/block/iscsi.c b/block/iscsi.c
index 7e78ade..c5855be 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -473,9 +473,10 @@ iscsi_co_writev_flags(BlockDriverState *bs, int64_t
sector_num, int nb_sectors,
return -EINVAL;
}
- if (bs->bl.max_transfer_length && nb_sectors > bs->bl.max_transfer_length)
{
+ if (bs->bl.max_transfer &&
+ nb_sectors << BDRV_SECTOR_BITS > bs->bl.max_transfer) {
error_report("iSCSI Error: Write of %d sectors exceeds max_xfer_len "
- "of %d sectors", nb_sectors, bs->bl.max_transfer_length);
+ "of %" PRIu32 " bytes", nb_sectors, bs->bl.max_transfer);
return -EINVAL;
}
@@ -650,9 +651,10 @@ static int coroutine_fn iscsi_co_readv(BlockDriverState
*bs,
return -EINVAL;
}
- if (bs->bl.max_transfer_length && nb_sectors > bs->bl.max_transfer_length)
{
+ if (bs->bl.max_transfer &&
+ nb_sectors << BDRV_SECTOR_BITS > bs->bl.max_transfer) {
error_report("iSCSI Error: Read of %d sectors exceeds max_xfer_len "
- "of %d sectors", nb_sectors, bs->bl.max_transfer_length);
+ "of %" PRIu32 " bytes", nb_sectors, bs->bl.max_transfer);
return -EINVAL;
}
@@ -1706,13 +1708,14 @@ static void iscsi_refresh_limits(BlockDriverState *bs,
Error **errp)
* iscsi_open(): iscsi targets don't change their limits. */
IscsiLun *iscsilun = bs->opaque;
- uint32_t max_xfer_len = iscsilun->use_16_for_rw ? 0xffffffff : 0xffff;
+ uint64_t max_xfer_len = iscsilun->use_16_for_rw ? 0xffffffff : 0xffff;
if (iscsilun->bl.max_xfer_len) {
max_xfer_len = MIN(max_xfer_len, iscsilun->bl.max_xfer_len);
}
- bs->bl.max_transfer_length = sector_limits_lun2qemu(max_xfer_len,
iscsilun);
+ bs->bl.max_transfer = MIN(BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS,
+ max_xfer_len * iscsilun->block_size);
if (iscsilun->lbp.lbpu) {
if (iscsilun->bl.max_unmap < 0xffffffff) {
@@ -1735,8 +1738,7 @@ static void iscsi_refresh_limits(BlockDriverState *bs,
Error **errp)
} else {
bs->bl.pwrite_zeroes_alignment = iscsilun->block_size;
}
- bs->bl.opt_transfer_length =
- sector_limits_lun2qemu(iscsilun->bl.opt_xfer_len, iscsilun);
+ bs->bl.opt_transfer = iscsilun->bl.opt_xfer_len * iscsilun->block_size;
}
/* Note that this will not re-establish a connection with an iSCSI target - it
diff --git a/block/nbd.c b/block/nbd.c
index 6015e8b..2ce7b4d 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -363,7 +363,7 @@ static int nbd_co_flush(BlockDriverState *bs)
static void nbd_refresh_limits(BlockDriverState *bs, Error **errp)
{
bs->bl.max_discard = UINT32_MAX >> BDRV_SECTOR_BITS;
- bs->bl.max_transfer_length = UINT32_MAX >> BDRV_SECTOR_BITS;
+ bs->bl.max_transfer = NBD_MAX_BUFFER_SIZE;
}
static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num,
diff --git a/block/raw-posix.c b/block/raw-posix.c
index ce2e20f..f3bd5ef 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -752,7 +752,7 @@ static void raw_refresh_limits(BlockDriverState *bs, Error
**errp)
if (S_ISBLK(st.st_mode)) {
int ret = hdev_get_max_transfer_length(s->fd);
if (ret >= 0) {
- bs->bl.max_transfer_length = ret;
+ bs->bl.max_transfer = ret << BDRV_SECTOR_BITS;
}
}
}
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 284e646..fbaf8f5 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;
+ uint32_t max_xfer_len = 0;
int64_t sector_num = 0;
if (mrb->num_reqs == 1) {
@@ -391,8 +391,9 @@ void virtio_blk_submit_multireq(BlockBackend *blk,
MultiReqBuffer *mrb)
return;
}
- 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);
+ max_xfer_len = blk_get_max_transfer(mrb->reqs[0]->dev->blk);
+ assert(max_xfer_len &&
+ max_xfer_len >> BDRV_SECTOR_BITS <= BDRV_REQUEST_MAX_SECTORS);
qsort(mrb->reqs, mrb->num_reqs, sizeof(*mrb->reqs),
&multireq_compare);
@@ -408,8 +409,9 @@ void virtio_blk_submit_multireq(BlockBackend *blk,
MultiReqBuffer *mrb)
*/
if (sector_num + nb_sectors != req->sector_num ||
niov > blk_get_max_iov(blk) - req->qiov.niov ||
- req->qiov.size / BDRV_SECTOR_SIZE > max_xfer_len ||
- nb_sectors > max_xfer_len - req->qiov.size / BDRV_SECTOR_SIZE)
{
+ req->qiov.size > max_xfer_len ||
+ nb_sectors > (max_xfer_len -
+ req->qiov.size) / BDRV_SECTOR_SIZE) {
submit_requests(blk, mrb, start, num_reqs, niov);
num_reqs = 0;
}
diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
index 71372a8..c6fef32 100644
--- a/hw/scsi/scsi-generic.c
+++ b/hw/scsi/scsi-generic.c
@@ -225,13 +225,13 @@ static void scsi_read_complete(void * opaque, int ret)
if (s->type == TYPE_DISK &&
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);
- }
+ uint32_t max_xfer_len =
+ blk_get_max_transfer(s->conf.blk) >> BDRV_SECTOR_BITS;
+
+ 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);
diff --git a/qemu-img.c b/qemu-img.c
index 4b56ad3..577df0d 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2074,13 +2074,13 @@ static int img_convert(int argc, char **argv)
}
out_bs = blk_bs(out_blk);
- /* increase bufsectors from the default 4096 (2M) if opt_transfer_length
+ /* increase bufsectors from the default 4096 (2M) if opt_transfer
* or discard_alignment of the out_bs is greater. Limit to 32768 (16MB)
* as maximum. */
bufsectors = MIN(32768,
- MAX(bufsectors, MAX(out_bs->bl.opt_transfer_length,
- out_bs->bl.discard_alignment))
- );
+ MAX(bufsectors,
+ MAX(out_bs->bl.opt_transfer >> BDRV_SECTOR_BITS,
+ out_bs->bl.discard_alignment)));
if (skip_create) {
int64_t output_sectors = blk_nb_sectors(out_blk);
--
2.5.5