aboutsummaryrefslogtreecommitdiff
path: root/mm/backing-dev.c
diff options
context:
space:
mode:
authorArtem Bityutskiy <Artem.Bityutskiy@nokia.com>2010-07-25 14:29:19 +0300
committerJens Axboe <jaxboe@fusionio.com>2010-08-07 18:53:56 +0200
commitadf392407076b85816d48714fb8eeaedb2157884 (patch)
treee926a18b55e67724e0267fe359caf51d530d5b09 /mm/backing-dev.c
parentecd584030da67ede1bf17955746a6ce834d9fc6b (diff)
downloadlinux-adf392407076b85816d48714fb8eeaedb2157884.tar.gz
writeback: restructure bdi forker loop a little
This patch re-structures the bdi forker a little: 1. Add 'bdi_cap_flush_forker(bdi)' condition check to the bdi loop. The reason for this is that the forker thread can start _before_ the 'BDI_registered' flag is set (see 'bdi_register()'), so the WARN() statement will fire for the default bdi. I observed this warning at boot-up. 2. Introduce an enum 'action' and use "switch" statement in the outer loop. This is a preparation to the further patch which will teach the forker thread killing bdi threads, so we'll have another case in the "switch" statement. This change was suggested by Christoph Hellwig. This patch is just a small step towards the coming change where the forker thread will kill the bdi threads. It should simplify reviewing the following changes, which would otherwise be larger. This patch also amends comments a little. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'mm/backing-dev.c')
-rw-r--r--mm/backing-dev.c69
1 files changed, 39 insertions, 30 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 672c17bb32d..e104e32c2ee 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -329,9 +329,12 @@ static int bdi_forker_thread(void *ptr)
set_user_nice(current, 0);
for (;;) {
- bool fork = false;
struct task_struct *task;
struct backing_dev_info *bdi;
+ enum {
+ NO_ACTION, /* Nothing to do */
+ FORK_THREAD, /* Fork bdi thread */
+ } action = NO_ACTION;
/*
* Temporary measure, we want to make sure we don't see
@@ -348,25 +351,31 @@ static int bdi_forker_thread(void *ptr)
* a thread registered. If so, set that up.
*/
list_for_each_entry(bdi, &bdi_list, bdi_list) {
- if (!bdi_cap_writeback_dirty(bdi))
- continue;
- if (bdi->wb.task)
- continue;
- if (list_empty(&bdi->work_list) &&
- !bdi_has_dirty_io(bdi))
+ bool have_dirty_io;
+
+ if (!bdi_cap_writeback_dirty(bdi) ||
+ bdi_cap_flush_forker(bdi))
continue;
WARN(!test_bit(BDI_registered, &bdi->state),
"bdi %p/%s is not registered!\n", bdi, bdi->name);
- fork = true;
+ have_dirty_io = !list_empty(&bdi->work_list) ||
+ wb_has_dirty_io(&bdi->wb);
/*
- * Set the pending bit - if someone will try to
- * unregister this bdi - it'll wait on this bit.
+ * If the bdi has work to do, but the thread does not
+ * exist - create it.
*/
- set_bit(BDI_pending, &bdi->state);
- break;
+ if (!bdi->wb.task && have_dirty_io) {
+ /*
+ * Set the pending bit - if someone will try to
+ * unregister this bdi - it'll wait on this bit.
+ */
+ set_bit(BDI_pending, &bdi->state);
+ action = FORK_THREAD;
+ break;
+ }
}
spin_unlock_bh(&bdi_lock);
@@ -374,30 +383,30 @@ static int bdi_forker_thread(void *ptr)
if (!list_empty(&me->bdi->work_list))
__set_current_state(TASK_RUNNING);
- if (!fork) {
- unsigned long wait;
+ switch (action) {
+ case FORK_THREAD:
+ __set_current_state(TASK_RUNNING);
+ task = kthread_run(bdi_writeback_thread, &bdi->wb, "flush-%s",
+ dev_name(bdi->dev));
+ if (IS_ERR(task)) {
+ /*
+ * If thread creation fails, force writeout of
+ * the bdi from the thread.
+ */
+ bdi_flush_io(bdi);
+ } else
+ bdi->wb.task = task;
+ break;
- wait = msecs_to_jiffies(dirty_writeback_interval * 10);
- if (wait)
- schedule_timeout(wait);
+ case NO_ACTION:
+ if (dirty_writeback_interval)
+ schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
else
schedule();
try_to_freeze();
+ /* Back to the main loop */
continue;
}
-
- __set_current_state(TASK_RUNNING);
-
- task = kthread_run(bdi_writeback_thread, &bdi->wb, "flush-%s",
- dev_name(bdi->dev));
- if (IS_ERR(task)) {
- /*
- * If thread creation fails, force writeout of the bdi
- * from the thread.
- */
- bdi_flush_io(bdi);
- } else
- bdi->wb.task = task;
}
return 0;