libmount: fix auto-loopdev

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/libmount/src/context_loopdev.c b/libmount/src/context_loopdev.c
index d32e7096620ec2c4467236fd8f5f50fb2e754ced..226b562c4650615c6027decaa9e03dabffc08f65 100644 (file)
--- a/libmount/src/context_loopdev.c
+++ b/libmount/src/context_loopdev.c
@@ -22,6 +22,7 @@ int mnt_context_is_loopdev(struct libmnt_context *cxt)
        const char *type, *src;
 
        assert(cxt);
+
        /* The mount flags have to be merged, otherwise we have to use
         * expensive mnt_context_get_user_mflags() instead of cxt->user_mountflags. */
        assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
@@ -35,15 +36,20 @@ int mnt_context_is_loopdev(struct libmnt_context *cxt)
        if (cxt->user_mountflags & (MNT_MS_LOOP |
                                    MNT_MS_OFFSET |
                                    MNT_MS_SIZELIMIT |
-                                   MNT_MS_ENCRYPTION))
+                                   MNT_MS_ENCRYPTION)) {
+
+               DBG(CXT, mnt_debug_h(cxt, "loopdev specific options detected"));
                return 1;
+       }
 
        if (cxt->mountflags & (MS_BIND | MS_MOVE | MS_PROPAGATION))
                return 0;
 
-       /* Automatically create a loop device from a regular file if a filesystem
-        * is not specified or the filesystem is known for libblkid (these
-        * filesystems work with block devices only).
+       /* Automatically create a loop device from a regular file if a
+        * filesystem is not specified or the filesystem is known for libblkid
+        * (these filesystems work with block devices only). The file size
+        * should be at least 1KiB otherwise we will create empty loopdev where
+        * is no mountable filesystem...
         *
         * Note that there is not a restriction (on kernel side) that prevents regular
         * file as a mount(2) source argument. A filesystem that is able to mount
@@ -55,11 +61,12 @@ int mnt_context_is_loopdev(struct libmnt_context *cxt)
            (!type || strcmp(type, "auto") == 0 || blkid_known_fstype(type))) {
                struct stat st;
 
-               if (stat(src, &st) || !S_ISREG(st.st_mode))
-                       return 0;
+               if (stat(src, &st) == 0 && S_ISREG(st.st_mode) &&
+                   st.st_size > 1024)
+                       return 1;
        }
 
-       return 1;
+       return 0;
 }
 
 int mnt_context_setup_loopdev(struct libmnt_context *cxt)