From 6f6071745bd0366221f5a0160ed7d18d0e38b9f7 Mon Sep 17 00:00:00 2001
From: Fam Zheng <famz@redhat.com>
Date: Fri, 3 Jun 2016 10:07:02 +0800
Subject: [PATCH] raw-posix: Fetch max sectors for host block device

This is sometimes a useful value we should count in.

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@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 ce1cf14f66..ce2e20f203 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;