writeback: fix comment, use helper function

There's a comment in there which claims that the inode is left on s_io
if nfs chickened out of writing some data.

But that's not been true for three years.
9290280ced13c85689adeffa587e9a53bd3a5873 fixed a livelock by moving these
inodes back onto s_dirty.  Fix the comment.

In the second leg of the `if', use redirty_tail() rather than open-coding it.

Add weaselly comment indicating lack of confidence in the code and lack of the
fortitude which would be needed to fiddle with it.

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

1 files changed, 11 insertions, 4 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index eb8dc1f22775..a3d7a829137d 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -201,7 +201,6 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
 {
         unsigned dirty;
         struct address_space *mapping = inode->i_mapping;
-        struct super_block *sb = inode->i_sb;
         int wait = wbc->sync_mode == WB_SYNC_ALL;
         int ret;
 
@@ -237,7 +236,16 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
                         /*
                          * We didn't write back all the pages.  nfs_writepages()
                          * sometimes bales out without doing anything. Redirty
-                         * the inode.  It is still on sb->s_io.
+                         * the inode.  It is moved from s_io onto s_dirty.
+                         */
+                        /*
+                         * akpm: if the caller was the kupdate function we put
+                         * this inode at the head of s_dirty so it gets first
+                         * consideration.  Otherwise, move it to the tail, for
+                         * the reasons described there.  I'm not really sure
+                         * how much sense this makes.  Presumably I had a good
+                         * reasons for doing it this way, and I'd rather not
+                         * muck with it at present.
                          */
                         if (wbc->for_kupdate) {
                                 /*
@@ -257,8 +265,7 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
                                  * all the other files.
                                  */
                                 inode->i_state |= I_DIRTY_PAGES;
-                                inode->dirtied_when = jiffies;
-                                list_move(&inode->i_list, &sb->s_dirty);
+                                redirty_tail(inode);
                         }
                 } else if (inode->i_state & I_DIRTY) {
                         /*