Signed-off-by: Dexuan Cui <de...@microsoft.com>
Reviewed-by: K. Y. Srinivasan <k...@microsoft.com>
---
 tools/hv/hv_vss_daemon.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tools/hv/hv_vss_daemon.c b/tools/hv/hv_vss_daemon.c
index 6a213b8..19567c5 100644
--- a/tools/hv/hv_vss_daemon.c
+++ b/tools/hv/hv_vss_daemon.c
@@ -51,6 +51,27 @@ static int vss_do_freeze(char *dir, unsigned int cmd, char 
*fs_op)
        if (fd < 0)
                return 1;
        ret = ioctl(fd, cmd, 0);
+
+       /*
+        * If a partition is mounted more than once, only the first
+        * FREEZE/THAW can succeed and the later ones will get
+        * EBUSY/EINVAL respectively: there could be 2 cases:
+        * 1) a user may mount the same partition to differnt directories
+        *  by mistake or on purpose;
+        * 2) The subvolume of btrfs appears to have the same partition
+        * mounted more than once.
+        */
+       if (ret) {
+               if ((cmd == FIFREEZE && errno == EBUSY) ||
+                   (cmd == FITHAW && errno == EINVAL)) {
+                       syslog(LOG_INFO, "VSS: %s of %s: %s: ignored\n",
+                               fs_op, dir,
+                               errno == EBUSY ? "EBUSY" : "EINVAL");
+                       close(fd);
+                       return 0;
+               }
+       }
+
        syslog(LOG_INFO, "VSS: %s of %s: %s\n", fs_op, dir, strerror(errno));
        close(fd);
        return !!ret;
-- 
1.9.1

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