Fix snapshots with dirty inodes

Filesystems which are mounted read-only or are immutable because
they are snapshots must not be allowed to dirty and inode.  This
will result in a write which will correctly cause a kernel panic
because these filesystem are (and must be) immutable.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2812

diff --git a/module/zfs/zfs_vnops.c b/module/zfs/zfs_vnops.c
index 2f55e562eaaee9ce66b12e541d1f1f06087d6bd3..d05ccef39506e0bdd9d8f792c102e51b5c4d7a41 100644 (file)
--- a/module/zfs/zfs_vnops.c
+++ b/module/zfs/zfs_vnops.c
@@ -3975,6 +3975,9 @@ zfs_dirty_inode(struct inode *ip, int flags)
        int             error;
        int             cnt = 0;
 
+       if (zfs_is_readonly(zsb) || dmu_objset_is_snapshot(zsb->z_os))
+               return (0);
+
        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);