1 files changed, 15 insertions, 3 deletions

diff --git a/fs/super.c b/fs/super.c
index aff046b0fe78..903896ec7c73 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -568,7 +568,7 @@ out:
 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 {
         int retval;
-        int remount_rw;
+        int remount_rw, remount_ro;
 
         if (sb->s_frozen != SB_UNFROZEN)
                 return -EBUSY;
@@ -583,9 +583,12 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
         shrink_dcache_sb(sb);
         sync_filesystem(sb);
 
+        remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
+        remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
+
         /* If we are remounting RDONLY and current sb is read/write,
            make sure there are no rw files opened */
-        if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
+        if (remount_ro) {
                 if (force)
                         mark_files_ro(sb);
                 else if (!fs_may_remount_ro(sb))
@@ -594,7 +597,6 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
                 if (retval < 0 && retval != -ENOSYS)
                         return -EBUSY;
         }
-        remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
 
         if (sb->s_op->remount_fs) {
                 retval = sb->s_op->remount_fs(sb, &flags, data);
@@ -604,6 +606,16 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
         sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
         if (remount_rw)
                 vfs_dq_quota_on_remount(sb);
+        /*
+         * Some filesystems modify their metadata via some other path than the
+         * bdev buffer cache (eg. use a private mapping, or directories in
+         * pagecache, etc). Also file data modifications go via their own
+         * mappings. So If we try to mount readonly then copy the filesystem
+         * from bdev, we could get stale data, so invalidate it to give a best
+         * effort at coherency.
+         */
+        if (remount_ro && sb->s_bdev)
+                invalidate_bdev(sb->s_bdev);
         return 0;
 }