| Message ID | 20210603133722.218465-3-pbonzini@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: file-posix queue | expand |
On 03.06.21 15:37, Paolo Bonzini wrote: > I/O to a disk via read/write is not limited by the number of segments allowed > by the host adapter; the kernel can split requests if needed, and the limit > imposed by the host adapter can be very low (256k or so) to avoid that SG_IO > returns EINVAL if memory is heavily fragmented. > > Since this value is only interesting for SG_IO-based I/O, do not include > it in the max_transfer and only take it into account when patching the > block limits VPD page in the scsi-generic device. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > block/file-posix.c | 3 +-- > hw/scsi/scsi-generic.c | 6 ++++-- > 2 files changed, 5 insertions(+), 4 deletions(-) Reviewed-by: Max Reitz <mreitz@redhat.com>
On 03.06.21 15:37, Paolo Bonzini wrote: > I/O to a disk via read/write is not limited by the number of segments allowed > by the host adapter; the kernel can split requests if needed, and the limit > imposed by the host adapter can be very low (256k or so) to avoid that SG_IO > returns EINVAL if memory is heavily fragmented. > > Since this value is only interesting for SG_IO-based I/O, do not include > it in the max_transfer and only take it into account when patching the > block limits VPD page in the scsi-generic device. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > block/file-posix.c | 3 +-- > hw/scsi/scsi-generic.c | 6 ++++-- > 2 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/block/file-posix.c b/block/file-posix.c > index 58db526cc2..e3241a0dd3 100644 > --- a/block/file-posix.c > +++ b/block/file-posix.c > @@ -1239,8 +1239,7 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp) > > 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); > + bs->bl.max_iov = ret; > } > } > > diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c > index 98c30c5d5c..82e1e2ee79 100644 > --- a/hw/scsi/scsi-generic.c > +++ b/hw/scsi/scsi-generic.c > @@ -179,10 +179,12 @@ static void scsi_handle_inquiry_reply(SCSIGenericReq *r, SCSIDevice *s) > (r->req.cmd.buf[1] & 0x01)) { > page = r->req.cmd.buf[2]; > if (page == 0xb0) { > - uint32_t max_transfer = > - blk_get_max_transfer(s->conf.blk) / s->blocksize; > + uint32_t max_transfer = blk_get_max_transfer(s->conf.blk); > + uint32_t max_iov = blk_get_max_iov(s->conf.blk); > > assert(max_transfer); > + max_transfer = MIN_NON_ZERO(max_transfer, max_iov * qemu_real_host_page_size) > + / s->blocksize; Now that I ran checkpatch for patch 3, I saw that it complains about this line being longer than 80 characters. I think it could be split so it doesn’t exceed that limit. It looks a bit like you intentionally exceeded the warning limit, but didn’t exceed the error limit (of 90). Is that so? Max
Yes, I try to avoid the 90 character limit (though sometimes that's hard too, hello QOM) but I don't think much of the lower one. Paolo Il mar 15 giu 2021, 18:20 Max Reitz <mreitz@redhat.com> ha scritto: > On 03.06.21 15:37, Paolo Bonzini wrote: > > I/O to a disk via read/write is not limited by the number of segments > allowed > > by the host adapter; the kernel can split requests if needed, and the > limit > > imposed by the host adapter can be very low (256k or so) to avoid that > SG_IO > > returns EINVAL if memory is heavily fragmented. > > > > Since this value is only interesting for SG_IO-based I/O, do not include > > it in the max_transfer and only take it into account when patching the > > block limits VPD page in the scsi-generic device. > > > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > > --- > > block/file-posix.c | 3 +-- > > hw/scsi/scsi-generic.c | 6 ++++-- > > 2 files changed, 5 insertions(+), 4 deletions(-) > > > > diff --git a/block/file-posix.c b/block/file-posix.c > > index 58db526cc2..e3241a0dd3 100644 > > --- a/block/file-posix.c > > +++ b/block/file-posix.c > > @@ -1239,8 +1239,7 @@ static void raw_refresh_limits(BlockDriverState > *bs, Error **errp) > > > > 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); > > + bs->bl.max_iov = ret; > > } > > } > > > > diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c > > index 98c30c5d5c..82e1e2ee79 100644 > > --- a/hw/scsi/scsi-generic.c > > +++ b/hw/scsi/scsi-generic.c > > @@ -179,10 +179,12 @@ static void > scsi_handle_inquiry_reply(SCSIGenericReq *r, SCSIDevice *s) > > (r->req.cmd.buf[1] & 0x01)) { > > page = r->req.cmd.buf[2]; > > if (page == 0xb0) { > > - uint32_t max_transfer = > > - blk_get_max_transfer(s->conf.blk) / s->blocksize; > > + uint32_t max_transfer = blk_get_max_transfer(s->conf.blk); > > + uint32_t max_iov = blk_get_max_iov(s->conf.blk); > > > > assert(max_transfer); > > + max_transfer = MIN_NON_ZERO(max_transfer, max_iov * > qemu_real_host_page_size) > > + / s->blocksize; > > Now that I ran checkpatch for patch 3, I saw that it complains about > this line being longer than 80 characters. I think it could be split so > it doesn’t exceed that limit. It looks a bit like you intentionally > exceeded the warning limit, but didn’t exceed the error limit (of 90). > Is that so? > > Max > >
diff --git a/block/file-posix.c b/block/file-posix.c index 58db526cc2..e3241a0dd3 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1239,8 +1239,7 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp) 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); + bs->bl.max_iov = ret; } } diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c index 98c30c5d5c..82e1e2ee79 100644 --- a/hw/scsi/scsi-generic.c +++ b/hw/scsi/scsi-generic.c @@ -179,10 +179,12 @@ static void scsi_handle_inquiry_reply(SCSIGenericReq *r, SCSIDevice *s) (r->req.cmd.buf[1] & 0x01)) { page = r->req.cmd.buf[2]; if (page == 0xb0) { - uint32_t max_transfer = - blk_get_max_transfer(s->conf.blk) / s->blocksize; + uint32_t max_transfer = blk_get_max_transfer(s->conf.blk); + uint32_t max_iov = blk_get_max_iov(s->conf.blk); assert(max_transfer); + max_transfer = MIN_NON_ZERO(max_transfer, max_iov * qemu_real_host_page_size) + / s->blocksize; stl_be_p(&r->buf[8], max_transfer); /* Also take care of the opt xfer len. */ stl_be_p(&r->buf[12],
I/O to a disk via read/write is not limited by the number of segments allowed by the host adapter; the kernel can split requests if needed, and the limit imposed by the host adapter can be very low (256k or so) to avoid that SG_IO returns EINVAL if memory is heavily fragmented. Since this value is only interesting for SG_IO-based I/O, do not include it in the max_transfer and only take it into account when patching the block limits VPD page in the scsi-generic device. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- block/file-posix.c | 3 +-- hw/scsi/scsi-generic.c | 6 ++++-- 2 files changed, 5 insertions(+), 4 deletions(-)