lkml.org 
[lkml]   [2007]   [Aug]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 1/6] writeback: fix time ordering of the per superblock inode lists 8
Streamline the management of dirty inode lists and fix time ordering bugs.

The writeback logic used to moving 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.

The new scheme is:
- s_dirty acts as a time ordered io delaying queue;
- s_io/s_more_io together acts as an io dispatching queue.

On kupdate writeback, we pull some inodes from s_dirty to s_io at the start of
every full scan of s_io. Otherwise(i.e. for sync/throttle/background
writeback), we always pull from s_dirty on each run(a partial scan).

Note that the line
list_splice_init(&sb->s_more_io, &sb->s_io);
is moved to queue_io() to leave s_io empty. Otherwise a big dirtied file will
sit in s_io for a long time, 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 | 60 +++++++++++++++++++++++++++-----------------
1 file changed, 38 insertions(+), 22 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 +172,33 @@ 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)
+{
+ list_splice_init(&sb->s_more_io, sb->s_io.prev);
+ 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 +248,7 @@ __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 +261,9 @@ __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 +321,10 @@ __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);

@@ -365,7 +391,7 @@ sync_sb_inodes(struct super_block *sb, s
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,
@@ -410,13 +436,6 @@ sync_sb_inodes(struct super_block *sb, s
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 +465,6 @@ 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 +474,7 @@ 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.
*
--
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-08-19 09:19    [from the cache]
©2003-2011 Jasper Spaans