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authorTejun Heo <tj@kernel.org>2013-04-01 19:08:06 -0700
committerTejun Heo <tj@kernel.org>2013-04-01 19:08:06 -0700
commit839a8e8660b6777e7fe4e80af1a048aebe2b5977 (patch)
tree80398cd4dd8ebc4c51be20725c0cc427bfe321b3 /include/linux/backing-dev.h
parent181387da2d64c3129e5b5186c4dd388bc5041d53 (diff)
writeback: replace custom worker pool implementation with unbound workqueue
Writeback implements its own worker pool - each bdi can be associated with a worker thread which is created and destroyed dynamically. The worker thread for the default bdi is always present and serves as the "forker" thread which forks off worker threads for other bdis. there's no reason for writeback to implement its own worker pool when using unbound workqueue instead is much simpler and more efficient. This patch replaces custom worker pool implementation in writeback with an unbound workqueue. The conversion isn't too complicated but the followings are worth mentioning. * bdi_writeback->last_active, task and wakeup_timer are removed. delayed_work ->dwork is added instead. Explicit timer handling is no longer necessary. Everything works by either queueing / modding / flushing / canceling the delayed_work item. * bdi_writeback_thread() becomes bdi_writeback_workfn() which runs off bdi_writeback->dwork. On each execution, it processes bdi->work_list and reschedules itself if there are more things to do. The function also handles low-mem condition, which used to be handled by the forker thread. If the function is running off a rescuer thread, it only writes out limited number of pages so that the rescuer can serve other bdis too. This preserves the flusher creation failure behavior of the forker thread. * INIT_LIST_HEAD(&bdi->bdi_list) is used to tell bdi_writeback_workfn() about on-going bdi unregistration so that it always drains work_list even if it's running off the rescuer. Note that the original code was broken in this regard. Under memory pressure, a bdi could finish unregistration with non-empty work_list. * The default bdi is no longer special. It now is treated the same as any other bdi and bdi_cap_flush_forker() is removed. * BDI_pending is no longer used. Removed. * Some tracepoints become non-applicable. The following TPs are removed - writeback_nothread, writeback_wake_thread, writeback_wake_forker_thread, writeback_thread_start, writeback_thread_stop. Everything, including devices coming and going away and rescuer operation under simulated memory pressure, seems to work fine in my test setup. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Jeff Moyer <jmoyer@redhat.com>
Diffstat (limited to 'include/linux/backing-dev.h')
-rw-r--r--include/linux/backing-dev.h15
1 files changed, 5 insertions, 10 deletions
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index a5ef27f5411..c3881553f7d 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -18,6 +18,7 @@
#include <linux/writeback.h>
#include <linux/atomic.h>
#include <linux/sysctl.h>
+#include <linux/workqueue.h>
struct page;
struct device;
@@ -27,7 +28,6 @@ struct dentry;
* Bits in backing_dev_info.state
*/
enum bdi_state {
- BDI_pending, /* On its way to being activated */
BDI_wb_alloc, /* Default embedded wb allocated */
BDI_async_congested, /* The async (write) queue is getting full */
BDI_sync_congested, /* The sync queue is getting full */
@@ -53,10 +53,8 @@ struct bdi_writeback {
unsigned int nr;
unsigned long last_old_flush; /* last old data flush */
- unsigned long last_active; /* last time bdi thread was active */
- struct task_struct *task; /* writeback thread */
- struct timer_list wakeup_timer; /* used for delayed bdi thread wakeup */
+ struct delayed_work dwork; /* work item used for writeback */
struct list_head b_dirty; /* dirty inodes */
struct list_head b_io; /* parked for writeback */
struct list_head b_more_io; /* parked for more writeback */
@@ -123,7 +121,7 @@ int bdi_setup_and_register(struct backing_dev_info *, char *, unsigned int);
void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
enum wb_reason reason);
void bdi_start_background_writeback(struct backing_dev_info *bdi);
-int bdi_writeback_thread(void *data);
+void bdi_writeback_workfn(struct work_struct *work);
int bdi_has_dirty_io(struct backing_dev_info *bdi);
void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi);
void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2);
@@ -131,6 +129,8 @@ void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2);
extern spinlock_t bdi_lock;
extern struct list_head bdi_list;
+extern struct workqueue_struct *bdi_wq;
+
static inline int wb_has_dirty_io(struct bdi_writeback *wb)
{
return !list_empty(&wb->b_dirty) ||
@@ -335,11 +335,6 @@ static inline bool bdi_cap_swap_backed(struct backing_dev_info *bdi)
return bdi->capabilities & BDI_CAP_SWAP_BACKED;
}
-static inline bool bdi_cap_flush_forker(struct backing_dev_info *bdi)
-{
- return bdi == &default_backing_dev_info;
-}
-
static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
{
return bdi_cap_writeback_dirty(mapping->backing_dev_info);