Tools: hv: vss: Skip freezing filesystems backed by loop

Since a loop device is backed by a file, a backup will already result in
its parent filesystem being frozen. It's sufficient to just freeze the
parent filesystem, so we can skip the loop device.

This avoids a situation where a loop device and its parent filesystem are
both frozen and then thawed out of order. For example, if the loop device
is enumerated first, we would thaw it while its parent filesystem is still
frozen. The thaw operation fails and the loop device remains frozen.

Signed-off-by: Alex Ng <alexng@messages.microsoft.com>
Signed-off-by: Vyronas Tsingaras <vyronas@vtsingaras.me>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/tools/hv/hv_vss_daemon.c b/tools/hv/hv_vss_daemon.c
index 7ba54195934c9aba4083b28b2ea02ce2b2c456db..b2b4ebffab8ca491cb31f47c52c2e8406a546328 100644 (file)
--- a/tools/hv/hv_vss_daemon.c
+++ b/tools/hv/hv_vss_daemon.c
@@ -21,6 +21,7 @@
 #include <sys/types.h>
 #include <sys/poll.h>
 #include <sys/ioctl.h>
+#include <sys/stat.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <mntent.h>
@@ -30,6 +31,7 @@
 #include <ctype.h>
 #include <errno.h>
 #include <linux/fs.h>
+#include <linux/major.h>
 #include <linux/hyperv.h>
 #include <syslog.h>
 #include <getopt.h>
@@ -70,6 +72,7 @@ static int vss_operate(int operation)
        char match[] = "/dev/";
        FILE *mounts;
        struct mntent *ent;
+       struct stat sb;
        char errdir[1024] = {0};
        unsigned int cmd;
        int error = 0, root_seen = 0, save_errno = 0;
@@ -92,6 +95,10 @@ static int vss_operate(int operation)
        while ((ent = getmntent(mounts))) {
                if (strncmp(ent->mnt_fsname, match, strlen(match)))
                        continue;
+               if (stat(ent->mnt_fsname, &sb) == -1)
+                       continue;
+               if (S_ISBLK(sb.st_mode) && major(sb.st_rdev) == LOOP_MAJOR)
+                       continue;
                if (hasmntopt(ent, MNTOPT_RO) != NULL)
                        continue;
                if (strcmp(ent->mnt_type, "vfat") == 0)