On Sun, Sep 06, 2009 at 08:43:59PM +0200, Jens Axboe wrote:
> On Fri, Sep 04 2009, Christoph Hellwig wrote:
> > On Fri, Sep 04, 2009 at 08:53:57AM +0200, Jens Axboe wrote:
> > > > + if (wbc->sync_mode == WB_SYNC_ALL)
> > > > + bdi_wait_on_work_clear(&work);
> > > > }
> > >
> > > That doesn't work, you have to wait for on-stack work. So either we just
> > > punt and not do anything for WB_SYNC_NONE if the allocation fails, or we
> > > punt to stack and do the wait. Since it's a cleaning action and
> > > allocation fails, falling back to the stack and waiting seems like the
> > > most appropriate choice.
> >
> > True, the wait needs to be unconditional. Updated version below.
>
> (did you forget that patch? it's not there).
Here we go, sorry:
Index: linux-2.6/fs/fs-writeback.c
===================================================================
--- linux-2.6.orig/fs/fs-writeback.c 2009-09-04 12:37:27.022522276 -0300
+++ linux-2.6/fs/fs-writeback.c 2009-09-04 12:37:50.618022253 -0300
@@ -70,13 +70,6 @@ static inline void bdi_work_init(struct
work->state = WS_USED;
}
-static inline void bdi_work_init_on_stack(struct bdi_work *work,
- struct writeback_control *wbc)
-{
- bdi_work_init(work, wbc);
- work->state |= WS_ONSTACK;
-}
-
/**
* writeback_in_progress - determine whether there is writeback in progress
* @bdi: the device's backing_dev_info structure.
@@ -207,35 +200,21 @@ static struct bdi_work *bdi_alloc_work(s
void bdi_start_writeback(struct writeback_control *wbc)
{
- const bool must_wait = wbc->sync_mode == WB_SYNC_ALL;
- struct bdi_work work_stack, *work = NULL;
-
- if (!must_wait)
- work = bdi_alloc_work(wbc);
+ struct bdi_work work;
- if (!work) {
- work = &work_stack;
- bdi_work_init_on_stack(work, wbc);
+ if (wbc->sync_mode != WB_SYNC_ALL) {
+ struct bdi_work *w = bdi_alloc_work(wbc);
+ if (w) {
+ bdi_queue_work(wbc->bdi, w);
+ return;
+ }
}
- bdi_queue_work(wbc->bdi, work);
+ bdi_work_init(&work, wbc);
+ work.state |= WS_ONSTACK;
- /*
- * If the sync mode is WB_SYNC_ALL, block waiting for the work to
- * complete. If not, we only need to wait for the work to be started,
- * if we allocated it on-stack. We use the same mechanism, if the
- * wait bit is set in the bdi_work struct, then threads will not
- * clear pending until after they are done.
- *
- * Note that work == &work_stack if must_wait is true, so we don't
- * need to do call_rcu() here ever, since the completion path will
- * have done that for us.
- */
- if (must_wait || work == &work_stack) {
- bdi_wait_on_work_clear(work);
- if (work != &work_stack)
- call_rcu(&work->rcu_head, bdi_work_free);
- }
+ bdi_queue_work(wbc->bdi, &work);
+ bdi_wait_on_work_clear(&work);
}
/*
--
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