[PATCH 1/6] writeback: fix time ordering of the per superblock inode lists 8

Fengguang Wu
2007-08-12T09:23:34Z

[-- Attachment #1: inode-dirty-time-ordering-fix.patch --]
[-- Type: text/plain, Size: 5386 bytes --]

Fix the time ordering bug re-introduced by
writeback-fix-periodic-superblock-dirty-inode-flushing.patch.

The old logic moves not-yet-expired dirty inodes from s_dirty to s_io,
*only to* move them back. The move-inodes-back-and-forth thing is a mess,
which is eliminated by this patch.

Note that the line
list_splice_init(&sb->s_more_io, &sb->s_io);
is also moved to queue_io(). Otherwise when there are big dirtied files,
s_io never becomes empty, preventing new expired inodes to get in.

Cc: Ken Chen <kenchen@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
---
fs/fs-writeback.c | 67 +++++++++++++++++++++++++-------------------
1 file changed, 39 insertions(+), 28 deletions(-)

--- linux-2.6.23-rc2-mm2.orig/fs/fs-writeback.c
+++ linux-2.6.23-rc2-mm2/fs/fs-writeback.c
@@ -118,7 +118,7 @@ void __mark_inode_dirty(struct inode *in
goto out;

/*
- * If the inode was already on s_dirty or s_io, don't
+ * If the inode was already on s_dirty/s_io/s_more_io, don't
* reposition it (that would break s_dirty time-ordering).
*/
if (!was_dirty) {
@@ -172,6 +172,34 @@ static void requeue_io(struct inode *ino
}

/*
+ * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
+ */
+static void move_expired_inodes(struct list_head *delaying_queue,
+ struct list_head *dispatch_queue,
+ unsigned long *older_than_this)
+{
+ while (!list_empty(delaying_queue)) {
+ struct inode *inode = list_entry(delaying_queue->prev,
+ struct inode, i_list);
+ if (older_than_this &&
+ time_after(inode->dirtied_when, *older_than_this))
+ break;
+ list_move(&inode->i_list, dispatch_queue);
+ }
+}
+
+/*
+ * Queue all expired dirty inodes for io, eldest first.
+ */
+static void queue_io(struct super_block *sb,
+ unsigned long *older_than_this)
+{
+ if (list_empty(&sb->s_io))
+ list_splice_init(&sb->s_more_io, &sb->s_io);
+ move_expired_inodes(&sb->s_dirty, &sb->s_io, older_than_this);
+}
+
+/*
* Write a single inode's dirty pages and inode data out to disk.
* If `wait' is set, wait on the writeout.
*
@@ -221,7 +249,7 @@ __sync_single_inode(struct inode *inode,
/*
* We didn't write back all the pages. nfs_writepages()
* sometimes bales out without doing anything. Redirty
- * the inode. It is moved from s_io onto s_dirty.
+ * the inode; Move it from s_io onto s_more_io/s_dirty.
*/
/*
* akpm: if the caller was the kupdate function we put
@@ -234,10 +262,9 @@ __sync_single_inode(struct inode *inode,
*/
if (wbc->for_kupdate) {
/*
- * For the kupdate function we leave the inode
- * at the head of sb_dirty so it will get more
- * writeout as soon as the queue becomes
- * uncongested.
+ * For the kupdate function we move the inode
+ * to s_more_io so it will get more writeout as
+ * soon as the queue becomes uncongested.
*/
inode->i_state |= I_DIRTY_PAGES;
requeue_io(inode);
@@ -295,10 +322,10 @@ __writeback_single_inode(struct inode *i

/*
* We're skipping this inode because it's locked, and we're not
- * doing writeback-for-data-integrity. Move it to the head of
- * s_dirty so that writeback can proceed with the other inodes
- * on s_io. We'll have another go at writing back this inode
- * when the s_dirty iodes get moved back onto s_io.
+ * doing writeback-for-data-integrity. Move it to s_more_io so
+ * that writeback can proceed with the other inodes on s_io.
+ * We'll have another go at writing back this inode when we
+ * completed a full scan of s_io.
*/
requeue_io(inode);

@@ -362,10 +389,8 @@ __writeback_single_inode(struct inode *i
static void
sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
{
- const unsigned long start = jiffies; /* livelock avoidance */
-
if (!wbc->for_kupdate || list_empty(&sb->s_io))
- list_splice_init(&sb->s_dirty, &sb->s_io);
+ queue_io(sb, wbc->older_than_this);

while (!list_empty(&sb->s_io)) {
struct inode *inode = list_entry(sb->s_io.prev,
@@ -406,17 +431,6 @@ sync_sb_inodes(struct super_block *sb, s
continue; /* blockdev has wrong queue */
}

- /* Was this inode dirtied after sync_sb_inodes was called? */
- if (time_after(inode->dirtied_when, start))
- break;
-
- /* Was this inode dirtied too recently? */
- if (wbc->older_than_this && time_after(inode->dirtied_when,
- *wbc->older_than_this)) {
- list_splice_init(&sb->s_io, sb->s_dirty.prev);
- break;
- }
-
/* Is another pdflush already flushing this queue? */
if (current_is_pdflush() && !writeback_acquire(bdi))
break;
@@ -446,9 +460,6 @@ sync_sb_inodes(struct super_block *sb, s
break;
}

- if (list_empty(&sb->s_io))
- list_splice_init(&sb->s_more_io, &sb->s_io);
-
return; /* Leave any unwritten inodes on s_io */
}

@@ -458,7 +469,7 @@ sync_sb_inodes(struct super_block *sb, s
* Note:
* We don't need to grab a reference to superblock here. If it has non-empty
* ->s_dirty it's hadn't been killed yet and kill_super() won't proceed
- * past sync_inodes_sb() until both the ->s_dirty and ->s_io lists are
+ * past sync_inodes_sb() until the ->s_dirty/s_io/s_more_io lists are all
* empty. Since __sync_single_inode() regains inode_lock before it finally moves
* inode from superblock lists we are OK.
*

--