writeback: fix time ordering of the per superblock dirty inode lists 7

This one fixes four bugs.

There are a few situation in there where writeback decides it is going to skip
over a blockdev inode on the kernel-internal blockdev superblock.  It
presently does this by moving the blockdev inode onto the tail of the blockdev
superblock's s_dirty.  But

a) this screws up s_dirty's reverse-time-orderedness and

b) refiling the blockdev for writeback in another 30 second is rude.  We
   should try again sooner than that.

Fix all this up by using redirty_head(): move the blockdev inode onto the head
of the blockdev superblock's s_dirty list for prompt writeback.

Cc: Mike Waychison <mikew@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 30d9383c87c376614bbff496668cb4fa7bae1a23..39fadfad86f7cf0f2991a0d7f8f612ec84eb453a 100644 (file)
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -410,14 +410,14 @@ sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
                        wbc->encountered_congestion = 1;
                        if (!sb_is_blkdev_sb(sb))
                                break;          /* Skip a congested fs */
-                       list_move(&inode->i_list, &sb->s_dirty);
+                       redirty_head(inode);
                        continue;               /* Skip a congested blockdev */
                }
 
                if (wbc->bdi && bdi != wbc->bdi) {
                        if (!sb_is_blkdev_sb(sb))
                                break;          /* fs has the wrong queue */
-                       list_move(&inode->i_list, &sb->s_dirty);
+                       redirty_head(inode);
                        continue;               /* blockdev has wrong queue */
                }