[PATCH] ext3/4: don't do orphan processing on readonly devices

If you do something like:

  # touch foo
  # tail -f foo &
  # rm foo
  # <take snapshot>
  # <mount snapshot>

you'll panic, because ext3/4 tries to do orphan list processing on the
readonly snapshot device, and:

  kernel: journal commit I/O error
  kernel: Assertion failure in journal_flush_Rsmp_e2f189ce() at journal.c:1356: "!journal->j_checkpoint_transactions"
  kernel: Kernel panic: Fatal exception

for a truly readonly underlying device, it's reasonable and necessary
to just skip orphan list processing.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 2ede7e2c7019..486a641ca71b 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1321,6 +1321,12 @@ static void ext4_orphan_cleanup (struct super_block * sb,
                 return;
         }
 
+        if (bdev_read_only(sb->s_bdev)) {
+                printk(KERN_ERR "EXT4-fs: write access "
+                        "unavailable, skipping orphan cleanup.\n");
+                return;
+        }
+
         if (EXT4_SB(sb)->s_mount_state & EXT4_ERROR_FS) {
                 if (es->s_last_orphan)
                         jbd_debug(1, "Errors on filesystem, "