[Qemu-devel] [PATCH v2] raw-posix: Fetch max sectors for host block device

[Qemu-devel] [PATCH v2] raw-posix: Fetch max sectors for host block device

[Fam Zheng]

This is sometimes a useful value we should count in.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block/raw-posix.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index a4f5a1b..32f9596 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -729,9 +729,33 @@ static void raw_reopen_abort(BDRVReopenState *state)
     state->opaque = NULL;
 }
 
+static int hdev_get_max_transfer_length(int fd)
+{
+#ifdef BLKSECTGET
+    int max_sectors = 0;
+    if (ioctl(fd, BLKSECTGET, &max_sectors) == 0) {
+        return max_sectors;
+    } else {
+        return -errno;
+    }
+#else
+    return -ENOSYS;
+#endif
+}
+
 static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
 {
     BDRVRawState *s = bs->opaque;
+    struct stat st;
+
+    if (!fstat(s->fd, &st)) {
+        if (S_ISBLK(st.st_mode)) {
+            int ret = hdev_get_max_transfer_length(s->fd);
+            if (ret >= 0) {
+                bs->bl.max_transfer_length = ret;
+            }
+        }
+    }
 
     raw_probe_alignment(bs, s->fd, errp);
     bs->bl.min_mem_alignment = s->buf_align;
-- 
2.8.2

Re: [Qemu-devel] [PATCH v2] raw-posix: Fetch max sectors for host block device

[Eric Blake]

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On 06/02/2016 08:07 PM, Fam Zheng wrote:
> This is sometimes a useful value we should count in.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  block/raw-posix.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 

Will conflict with patches I'm about to post to rework BlockLimits to be
byte-based, rather than a mix of byte- and sector values.  First one in
gets to watch the other rebase :)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH v2] raw-posix: Fetch max sectors for host block device

[Fam Zheng]

On Thu, 06/02 20:42, Eric Blake wrote:
> On 06/02/2016 08:07 PM, Fam Zheng wrote:
> > This is sometimes a useful value we should count in.
> > 
> > Signed-off-by: Fam Zheng <famz@redhat.com>
> > ---
> >  block/raw-posix.c | 24 ++++++++++++++++++++++++
> >  1 file changed, 24 insertions(+)
> > 
> 
> Will conflict with patches I'm about to post to rework BlockLimits to be
> byte-based, rather than a mix of byte- and sector values.  First one in
> gets to watch the other rebase :)

Thanks!  I'm looking forward to a byte based BlockLimits!

Fam

Re: [Qemu-devel] [PATCH v2] raw-posix: Fetch max sectors for host block device

[Kevin Wolf]

Am 03.06.2016 um 04:07 hat Fam Zheng geschrieben:
> This is sometimes a useful value we should count in.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>

Thanks, applied to the block branch.

Kevin