Merge pull request #6943 from poettering/dissect-ro

Automatically recognize that "squashfs" and "iso9660" area always read-only

src/basic/mount-util.c

@@ -564,6 +564,7 @@ bool fstype_is_api_vfs(const char *fstype) {
                 "devpts\0"
                 "devtmpfs\0"
                 "efivarfs\0"
+                "fusectl\0"
                 "hugetlbfs\0"
                 "mqueue\0"
                 "proc\0"
@@ -578,6 +579,31 @@ bool fstype_is_api_vfs(const char *fstype) {
         return nulstr_contains(table, fstype);
 }
 
+bool fstype_is_ro(const char *fstype) {
+
+        /* All Linux file systems that are necessarily read-only */
+
+        static const char table[] =
+                "DM_verity_hash\0"
+                "iso9660\0"
+                "squashfs\0"
+                ;
+
+        return nulstr_contains(table, fstype);
+}
+
+bool fstype_can_discard(const char *fstype) {
+
+        static const char table[] =
+                "btrfs\0"
+                "ext4\0"
+                "vfat\0"
+                "xfs\0"
+                ;
+
+        return nulstr_contains(table, fstype);
+}
+
 int repeat_unmount(const char *path, int flags) {
         bool done = false;
 

src/basic/mount-util.h

@@ -45,6 +45,8 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(FILE*, endmntent);
 
 bool fstype_is_network(const char *fstype);
 bool fstype_is_api_vfs(const char *fstype);
+bool fstype_is_ro(const char *fsype);
+bool fstype_can_discard(const char *fstype);
 
 union file_handle_union {
         struct file_handle handle;

src/shared/dissect-image.c

@@ -591,6 +591,9 @@ int dissect_image(int fd, const void *root_hash, size_t root_hash_size, DissectI
 
                 if (streq_ptr(p->fstype, "crypto_LUKS"))
                         m->encrypted = true;
+
+                if (p->fstype && fstype_is_ro(p->fstype))
+                        p->rw = false;
         }
 
         *ret = m;
@@ -681,7 +684,7 @@ static int mount_partition(
                 p = where;
 
         /* If requested, turn on discard support. */
-        if (STR_IN_SET(fstype, "btrfs", "ext4", "vfat", "xfs") &&
+        if (fstype_can_discard(fstype) &&
             ((flags & DISSECT_IMAGE_DISCARD) ||
              ((flags & DISSECT_IMAGE_DISCARD_ON_LOOP) && is_loop_device(m->node))))
                 options = "discard";