On Wed 09-10-13 14:21:25, Andrew Morton wrote:
> On Wed, 9 Oct 2013 17:03:25 +0200 Jan Kara <jack@xxxxxxx> wrote:
>
> > From: Jan Kara <jack@xxxxxxx>
> > Date: Wed, 9 Oct 2013 15:41:50 +0200
> > Subject: [PATCH] writeback: Use older_than_this_is_set instead of magic
> > older_than_this == 0
> >
> > Currently we use 0 as a special value of work->older_than_this to
> > indicate that wb_writeback() should set work->older_that_this to current
> > time. This works but it is a bit magic. So use a special flag in
> > work_struct for that.
>
> OK.
>
> > - if (!work->older_than_this)
> > + if (!work->older_than_this_is_set)
> > work->older_than_this = jiffies;
>
> It would be logical although presumably unneeded to set
> older_than_this_is_set here?
Yes. Updated.
> > Also fixup writeback from workqueue rescuer to include all inodes.
>
> There's nothing in the patch which matches this sentence?
The sentence is about the hunk below. writeback_inodes_wb() is special in
that it directly calls queue_io() (everything else goes through
wb_writeback()) and my previous patch thus resulted in using 0 as an
older_than_this value => likely we wouldn't queue any inodes for writeback.
I've added WARN_ON_ONCE into move_expired_inodes() to increase a chance of
catching such mistakes in future (although in this particular case it
wouldn't really help because writeback_inodes_wb() gets hardly ever
called).
> @@ -732,6 +737,8 @@ static long writeback_inodes_wb(struct b
> .sync_mode = WB_SYNC_NONE,
> .range_cyclic = 1,
> .reason = reason,
> + .older_than_this = jiffies,
> + .older_than_this_is_set = 1,
> };
>
> spin_lock(&wb->list_lock);
Updated version of the patch attached.
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
>From a872d2374364ac1d8f0a9a6fa529afdc06f9d1a1 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Wed, 9 Oct 2013 15:41:50 +0200
Subject: [PATCH] writeback: Use older_than_this_is_set instead of magic
older_than_this == 0
Currently we use 0 as a special value of work->older_than_this to
indicate that wb_writeback() should set work->older_that_this to current
time. This works but it is a bit magic. So use a special flag in
work_struct for that.
Also fixup writeback from workqueue rescuer (writeback_inodes_wb()) to
include all inodes. Currently it would use 0 as an older_than_this value
thus queue_io() would likely not queue any inodes for writeback.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/fs-writeback.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 70837dadad72..ba332d2c596a 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -39,6 +39,10 @@
struct wb_writeback_work {
long nr_pages;
struct super_block *sb;
+ /*
+ * Write only inodes dirtied before this time. Don't forget to set
+ * older_than_this_is_set when you set this.
+ */
unsigned long older_than_this;
enum writeback_sync_modes sync_mode;
unsigned int tagged_writepages:1;
@@ -46,6 +50,7 @@ struct wb_writeback_work {
unsigned int range_cyclic:1;
unsigned int for_background:1;
unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
+ unsigned int older_than_this_is_set:1;
enum wb_reason reason; /* why was writeback initiated? */
struct list_head list; /* pending work list */
@@ -246,6 +251,7 @@ static int move_expired_inodes(struct list_head *delaying_queue,
int do_sb_sort = 0;
int moved = 0;
+ WARN_ON_ONCE(!work->older_than_this_is_set);
while (!list_empty(delaying_queue)) {
inode = wb_inode(delaying_queue->prev);
if (inode_dirtied_after(inode, work->older_than_this))
@@ -732,6 +738,8 @@ static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
.sync_mode = WB_SYNC_NONE,
.range_cyclic = 1,
.reason = reason,
+ .older_than_this = jiffies,
+ .older_than_this_is_set = 1,
};
spin_lock(&wb->list_lock);
@@ -793,8 +801,10 @@ static long wb_writeback(struct bdi_writeback *wb,
struct inode *inode;
long progress;
- if (!work->older_than_this)
+ if (!work->older_than_this_is_set) {
work->older_than_this = jiffies;
+ work->older_than_this_is_set = 1;
+ }
spin_lock(&wb->list_lock);
for (;;) {
@@ -1356,6 +1366,7 @@ void sync_inodes_sb(struct super_block *sb, unsigned long older_than_this)
.sync_mode = WB_SYNC_ALL,
.nr_pages = LONG_MAX,
.older_than_this = older_than_this,
+ .older_than_this_is_set = 1,
.range_cyclic = 0,
.done = &done,
.reason = WB_REASON_SYNC,
--
1.8.1.4
