sg_get_max_transfer_length() and sg_get_max_segments() have nothing
to do with the sg driver or SG_IO at all. They can be and should be
used on all host devices / cdroms (on Linux).
Also use MIN_NON_ZERO instead when we clamp max_sectors against
max_segments.
Signed-off-by: Tom Yan <tom.ty89@gmail.com>
---
block/file-posix.c | 39 ++++++++++++++++++++++-----------------
1 file changed, 22 insertions(+), 17 deletions(-)
diff --git a/block/file-posix.c b/block/file-posix.c
index 9a00d4190a..a38f43af4f 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1163,7 +1163,7 @@ static void raw_reopen_abort(BDRVReopenState *state)
s->reopen_state = NULL;
}
-static int sg_get_max_transfer_length(int fd)
+static int get_max_transfer_length(int fd)
{
#ifdef BLKSECTGET
int max_bytes = 0;
@@ -1178,7 +1178,7 @@ static int sg_get_max_transfer_length(int fd)
#endif
}
-static int sg_get_max_segments(int fd)
+static int get_max_segments(int fd)
{
#ifdef CONFIG_LINUX
char buf[32];
@@ -1233,23 +1233,28 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
{
BDRVRawState *s = bs->opaque;
- if (bs->sg) {
- int ret = sg_get_max_transfer_length(s->fd);
+ raw_probe_alignment(bs, s->fd, errp);
+ bs->bl.min_mem_alignment = s->buf_align;
+ bs->bl.opt_mem_alignment = MAX(s->buf_align, qemu_real_host_page_size);
+}
- if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) {
- bs->bl.max_transfer = pow2floor(ret);
- }
+static void hdev_refresh_limits(BlockDriverState *bs, Error **errp)
+{
+ BDRVRawState *s = bs->opaque;
- ret = sg_get_max_segments(s->fd);
- if (ret > 0) {
- bs->bl.max_transfer = MIN(bs->bl.max_transfer,
- ret * qemu_real_host_page_size);
- }
+ int ret = get_max_transfer_length(s->fd);
+
+ if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) {
+ bs->bl.max_transfer = pow2floor(ret);
}
- raw_probe_alignment(bs, s->fd, errp);
- bs->bl.min_mem_alignment = s->buf_align;
- bs->bl.opt_mem_alignment = MAX(s->buf_align, qemu_real_host_page_size);
+ ret = get_max_segments(s->fd);
+ if (ret > 0) {
+ bs->bl.max_transfer = MIN_NON_ZERO(bs->bl.max_transfer,
+ ret * qemu_real_host_page_size);
+ }
+
+ raw_refresh_limits(bs, errp);
}
static int check_for_dasd(int fd)
@@ -3604,7 +3609,7 @@ static BlockDriver bdrv_host_device = {
.bdrv_co_pdiscard = hdev_co_pdiscard,
.bdrv_co_copy_range_from = raw_co_copy_range_from,
.bdrv_co_copy_range_to = raw_co_copy_range_to,
- .bdrv_refresh_limits = raw_refresh_limits,
+ .bdrv_refresh_limits = hdev_refresh_limits,
.bdrv_io_plug = raw_aio_plug,
.bdrv_io_unplug = raw_aio_unplug,
.bdrv_attach_aio_context = raw_aio_attach_aio_context,
@@ -3728,7 +3733,7 @@ static BlockDriver bdrv_host_cdrom = {
.bdrv_co_preadv = raw_co_preadv,
.bdrv_co_pwritev = raw_co_pwritev,
.bdrv_co_flush_to_disk = raw_co_flush_to_disk,
- .bdrv_refresh_limits = raw_refresh_limits,
+ .bdrv_refresh_limits = hdev_refresh_limits,
.bdrv_io_plug = raw_aio_plug,
.bdrv_io_unplug = raw_aio_unplug,
.bdrv_attach_aio_context = raw_aio_attach_aio_context,
--
2.28.0
Oops I forgot max_transfer needs to be in bytes (and BLKSECTGET in sg has always been implemented wrongly). Will send a new version. On Fri, 4 Sep 2020 at 06:37, Tom Yan <tom.ty89@gmail.com> wrote: > > sg_get_max_transfer_length() and sg_get_max_segments() have nothing > to do with the sg driver or SG_IO at all. They can be and should be > used on all host devices / cdroms (on Linux). > > Also use MIN_NON_ZERO instead when we clamp max_sectors against > max_segments. > > Signed-off-by: Tom Yan <tom.ty89@gmail.com> > --- > block/file-posix.c | 39 ++++++++++++++++++++++----------------- > 1 file changed, 22 insertions(+), 17 deletions(-) > > diff --git a/block/file-posix.c b/block/file-posix.c > index 9a00d4190a..a38f43af4f 100644 > --- a/block/file-posix.c > +++ b/block/file-posix.c > @@ -1163,7 +1163,7 @@ static void raw_reopen_abort(BDRVReopenState *state) > s->reopen_state = NULL; > } > > -static int sg_get_max_transfer_length(int fd) > +static int get_max_transfer_length(int fd) > { > #ifdef BLKSECTGET > int max_bytes = 0; > @@ -1178,7 +1178,7 @@ static int sg_get_max_transfer_length(int fd) > #endif > } > > -static int sg_get_max_segments(int fd) > +static int get_max_segments(int fd) > { > #ifdef CONFIG_LINUX > char buf[32]; > @@ -1233,23 +1233,28 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp) > { > BDRVRawState *s = bs->opaque; > > - if (bs->sg) { > - int ret = sg_get_max_transfer_length(s->fd); > + raw_probe_alignment(bs, s->fd, errp); > + bs->bl.min_mem_alignment = s->buf_align; > + bs->bl.opt_mem_alignment = MAX(s->buf_align, qemu_real_host_page_size); > +} > > - if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) { > - bs->bl.max_transfer = pow2floor(ret); > - } > +static void hdev_refresh_limits(BlockDriverState *bs, Error **errp) > +{ > + BDRVRawState *s = bs->opaque; > > - ret = sg_get_max_segments(s->fd); > - if (ret > 0) { > - bs->bl.max_transfer = MIN(bs->bl.max_transfer, > - ret * qemu_real_host_page_size); > - } > + int ret = get_max_transfer_length(s->fd); > + > + if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) { > + bs->bl.max_transfer = pow2floor(ret); > } > > - raw_probe_alignment(bs, s->fd, errp); > - bs->bl.min_mem_alignment = s->buf_align; > - bs->bl.opt_mem_alignment = MAX(s->buf_align, qemu_real_host_page_size); > + ret = get_max_segments(s->fd); > + if (ret > 0) { > + bs->bl.max_transfer = MIN_NON_ZERO(bs->bl.max_transfer, > + ret * qemu_real_host_page_size); > + } > + > + raw_refresh_limits(bs, errp); > } > > static int check_for_dasd(int fd) > @@ -3604,7 +3609,7 @@ static BlockDriver bdrv_host_device = { > .bdrv_co_pdiscard = hdev_co_pdiscard, > .bdrv_co_copy_range_from = raw_co_copy_range_from, > .bdrv_co_copy_range_to = raw_co_copy_range_to, > - .bdrv_refresh_limits = raw_refresh_limits, > + .bdrv_refresh_limits = hdev_refresh_limits, > .bdrv_io_plug = raw_aio_plug, > .bdrv_io_unplug = raw_aio_unplug, > .bdrv_attach_aio_context = raw_aio_attach_aio_context, > @@ -3728,7 +3733,7 @@ static BlockDriver bdrv_host_cdrom = { > .bdrv_co_preadv = raw_co_preadv, > .bdrv_co_pwritev = raw_co_pwritev, > .bdrv_co_flush_to_disk = raw_co_flush_to_disk, > - .bdrv_refresh_limits = raw_refresh_limits, > + .bdrv_refresh_limits = hdev_refresh_limits, > .bdrv_io_plug = raw_aio_plug, > .bdrv_io_unplug = raw_aio_unplug, > .bdrv_attach_aio_context = raw_aio_attach_aio_context, > -- > 2.28.0 >
We can and should get max transfer length and max segments for all host
devices / cdroms (on Linux).
Also use MIN_NON_ZERO instead when we clamp max transfer length against
max segments.
Signed-off-by: Tom Yan <tom.ty89@gmail.com>
---
v2: fix get_max_transfer_length for non-sg devices; also add/fix
sg_get_max_segments for sg devices
block/file-posix.c | 56 +++++++++++++++++++++++++++++++++-------------
1 file changed, 40 insertions(+), 16 deletions(-)
diff --git a/block/file-posix.c b/block/file-posix.c
index 9a00d4190a..0c9124c8aa 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1178,7 +1178,23 @@ static int sg_get_max_transfer_length(int fd)
#endif
}
-static int sg_get_max_segments(int fd)
+static int get_max_transfer_length(int fd)
+{
+#if defined(BLKSECTGET) && defined(BLKSSZGET)
+ int sect = 0;
+ int ssz = 0;
+
+ if (ioctl(fd, BLKSECTGET, §) == 0 && ioctl(fd, BLKSSZGET, &ssz)) {
+ return sect * ssz;
+ } else {
+ return -errno;
+ }
+#else
+ return -ENOSYS;
+#endif
+}
+
+static int get_max_segments(int fd)
{
#ifdef CONFIG_LINUX
char buf[32];
@@ -1233,23 +1249,31 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
{
BDRVRawState *s = bs->opaque;
- if (bs->sg) {
- int ret = sg_get_max_transfer_length(s->fd);
+ raw_probe_alignment(bs, s->fd, errp);
+ bs->bl.min_mem_alignment = s->buf_align;
+ bs->bl.opt_mem_alignment = MAX(s->buf_align, qemu_real_host_page_size);
+}
+
+static void hdev_refresh_limits(BlockDriverState *bs, Error **errp)
+{
+ BDRVRawState *s = bs->opaque;
+
+ /* BLKSECTGET has always been implemented wrongly in the sg driver
+ and BLKSSZGET has never been supported by it*/
+ int ret = bs->sg ? sg_get_max_transfer_length(s->fd) :
+ get_max_transfer_length(s->fd);
- if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) {
- bs->bl.max_transfer = pow2floor(ret);
- }
+ if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) {
+ bs->bl.max_transfer = pow2floor(ret);
+ }
- ret = sg_get_max_segments(s->fd);
- if (ret > 0) {
- bs->bl.max_transfer = MIN(bs->bl.max_transfer,
- ret * qemu_real_host_page_size);
- }
+ ret = get_max_segments(s->fd);
+ if (ret > 0) {
+ bs->bl.max_transfer = MIN_NON_ZERO(bs->bl.max_transfer,
+ ret * qemu_real_host_page_size);
}
- raw_probe_alignment(bs, s->fd, errp);
- bs->bl.min_mem_alignment = s->buf_align;
- bs->bl.opt_mem_alignment = MAX(s->buf_align, qemu_real_host_page_size);
+ raw_refresh_limits(bs, errp);
}
static int check_for_dasd(int fd)
@@ -3604,7 +3628,7 @@ static BlockDriver bdrv_host_device = {
.bdrv_co_pdiscard = hdev_co_pdiscard,
.bdrv_co_copy_range_from = raw_co_copy_range_from,
.bdrv_co_copy_range_to = raw_co_copy_range_to,
- .bdrv_refresh_limits = raw_refresh_limits,
+ .bdrv_refresh_limits = hdev_refresh_limits,
.bdrv_io_plug = raw_aio_plug,
.bdrv_io_unplug = raw_aio_unplug,
.bdrv_attach_aio_context = raw_aio_attach_aio_context,
@@ -3728,7 +3752,7 @@ static BlockDriver bdrv_host_cdrom = {
.bdrv_co_preadv = raw_co_preadv,
.bdrv_co_pwritev = raw_co_pwritev,
.bdrv_co_flush_to_disk = raw_co_flush_to_disk,
- .bdrv_refresh_limits = raw_refresh_limits,
+ .bdrv_refresh_limits = hdev_refresh_limits,
.bdrv_io_plug = raw_aio_plug,
.bdrv_io_unplug = raw_aio_unplug,
.bdrv_attach_aio_context = raw_aio_attach_aio_context,
--
2.28.0
sg devices have different major/minor than their corresponding
block devices. Using sysfs to get max segments never really worked
for them.
Fortunately the sg driver provides an ioctl to get sg_tablesize,
which is apparently equivalent to max segments.
Signed-off-by: Tom Yan <tom.ty89@gmail.com>
---
block/file-posix.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/block/file-posix.c b/block/file-posix.c
index 0c9124c8aa..d2cd9a3362 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1178,6 +1178,21 @@ static int sg_get_max_transfer_length(int fd)
#endif
}
+static int sg_get_max_segments(int fd)
+{
+#ifdef SG_GET_SG_TABLESIZE
+ long max_segments = 0;
+
+ if (ioctl(fd, SG_GET_SG_TABLESIZE, &max_segments) == 0) {
+ return max_segments;
+ } else {
+ return -errno;
+ }
+#else
+ return -ENOSYS;
+#endif
+}
+
static int get_max_transfer_length(int fd)
{
#if defined(BLKSECTGET) && defined(BLKSSZGET)
@@ -1267,7 +1282,7 @@ static void hdev_refresh_limits(BlockDriverState *bs, Error **errp)
bs->bl.max_transfer = pow2floor(ret);
}
- ret = get_max_segments(s->fd);
+ ret = bs->sg ? sg_get_max_segments(s->fd) : get_max_segments(s->fd);
if (ret > 0) {
bs->bl.max_transfer = MIN_NON_ZERO(bs->bl.max_transfer,
ret * qemu_real_host_page_size);
--
2.28.0
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