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writeback: move backing_dev_info->wb_lock and ->worklist into bdi_writeback

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Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
and the role of the separation is unclear.  For cgroup support for
writeback IOs, a bdi will be updated to host multiple wb's where each
wb serves writeback IOs of a different cgroup on the bdi.  To achieve
that, a wb should carry all states necessary for servicing writeback
IOs for a cgroup independently.

This patch moves bdi->wb_lock and ->worklist into wb.

* The lock protects bdi->worklist and bdi->wb.dwork scheduling.  While
  moving, rename it to wb->work_lock as wb->wb_lock is confusing.
  Also, move wb->dwork downwards so that it's colocated with the new
  ->work_lock and ->work_list fields.

* bdi_writeback_workfn()		-> wb_workfn()
  bdi_wakeup_thread_delayed(bdi)	-> wb_wakeup_delayed(wb)
  bdi_wakeup_thread(bdi)		-> wb_wakeup(wb)
  bdi_queue_work(bdi, ...)		-> wb_queue_work(wb, ...)
  __bdi_start_writeback(bdi, ...)	-> __wb_start_writeback(wb, ...)
  get_next_work_item(bdi)		-> get_next_work_item(wb)

* bdi_wb_shutdown() is renamed to wb_shutdown() and now takes @wb.
  The function contained parts which belong to the containing bdi
  rather than the wb itself - testing cap_writeback_dirty and
  bdi_remove_from_list() invocation.  Those are moved to
  bdi_unregister().

* bdi_wb_{init|exit}() are renamed to wb_{init|exit}().
  Initializations of the moved bdi->wb_lock and ->work_list are
  relocated from bdi_init() to wb_init().

* As there's still only one bdi_writeback per backing_dev_info, all
  uses of bdi->state are mechanically replaced with bdi->wb.state
  introducing no behavior changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Tejun Heo
2015-05-22 17:13:30 -04:00
committed by Jens Axboe
parent de1fff37b2
commit f0054bb1e1
3 changed files with 75 additions and 82 deletions
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59
mm/backing-dev.c
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@@ -261,7 +261,7 @@ int bdi_has_dirty_io(struct backing_dev_info *bdi)
}
/*
* This function is used when the first inode for this bdi is marked dirty. It
* This function is used when the first inode for this wb is marked dirty. It
* wakes-up the corresponding bdi thread which should then take care of the
* periodic background write-out of dirty inodes. Since the write-out would
* starts only 'dirty_writeback_interval' centisecs from now anyway, we just
@@ -274,15 +274,15 @@ int bdi_has_dirty_io(struct backing_dev_info *bdi)
* We have to be careful not to postpone flush work if it is scheduled for
* earlier. Thus we use queue_delayed_work().
*/
void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
void wb_wakeup_delayed(struct bdi_writeback *wb)
{
unsigned long timeout;
timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
spin_lock_bh(&bdi->wb_lock);
if (test_bit(WB_registered, &bdi->wb.state))
queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
spin_unlock_bh(&bdi->wb_lock);
spin_lock_bh(&wb->work_lock);
if (test_bit(WB_registered, &wb->state))
queue_delayed_work(bdi_wq, &wb->dwork, timeout);
spin_unlock_bh(&wb->work_lock);
}
/*
@@ -335,28 +335,24 @@ EXPORT_SYMBOL(bdi_register_dev);
/*
* Remove bdi from the global list and shutdown any threads we have running
*/
static void bdi_wb_shutdown(struct backing_dev_info *bdi)
static void wb_shutdown(struct bdi_writeback *wb)
{
/* Make sure nobody queues further work */
spin_lock_bh(&bdi->wb_lock);
if (!test_and_clear_bit(WB_registered, &bdi->wb.state)) {
spin_unlock_bh(&bdi->wb_lock);
spin_lock_bh(&wb->work_lock);
if (!test_and_clear_bit(WB_registered, &wb->state)) {
spin_unlock_bh(&wb->work_lock);
return;
}
spin_unlock_bh(&bdi->wb_lock);
spin_unlock_bh(&wb->work_lock);
/*
* Make sure nobody finds us on the bdi_list anymore
* Drain work list and shutdown the delayed_work. !WB_registered
* tells wb_workfn() that @wb is dying and its work_list needs to
* be drained no matter what.
*/
bdi_remove_from_list(bdi);
/*
* Drain work list and shutdown the delayed_work. At this point,
* @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi
* is dying and its work_list needs to be drained no matter what.
*/
mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
flush_delayed_work(&bdi->wb.dwork);
mod_delayed_work(bdi_wq, &wb->dwork, 0);
flush_delayed_work(&wb->dwork);
WARN_ON(!list_empty(&wb->work_list));
}
/*
@@ -381,7 +377,7 @@ EXPORT_SYMBOL(bdi_unregister);
*/
#define INIT_BW (100 << (20 - PAGE_SHIFT))
static int bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
{
int i, err;
@@ -394,7 +390,6 @@ static int bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
INIT_LIST_HEAD(&wb->b_more_io);
INIT_LIST_HEAD(&wb->b_dirty_time);
spin_lock_init(&wb->list_lock);
INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);
wb->bw_time_stamp = jiffies;
wb->balanced_dirty_ratelimit = INIT_BW;
@@ -402,6 +397,10 @@ static int bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
wb->write_bandwidth = INIT_BW;
wb->avg_write_bandwidth = INIT_BW;
spin_lock_init(&wb->work_lock);
INIT_LIST_HEAD(&wb->work_list);
INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
err = fprop_local_init_percpu(&wb->completions, GFP_KERNEL);
if (err)
return err;
@@ -419,7 +418,7 @@ static int bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
return 0;
}
static void bdi_wb_exit(struct bdi_writeback *wb)
static void wb_exit(struct bdi_writeback *wb)
{
int i;
@@ -440,11 +439,9 @@ int bdi_init(struct backing_dev_info *bdi)
bdi->min_ratio = 0;
bdi->max_ratio = 100;
bdi->max_prop_frac = FPROP_FRAC_BASE;
spin_lock_init(&bdi->wb_lock);
INIT_LIST_HEAD(&bdi->bdi_list);
INIT_LIST_HEAD(&bdi->work_list);
err = bdi_wb_init(&bdi->wb, bdi);
err = wb_init(&bdi->wb, bdi);
if (err)
return err;
@@ -454,9 +451,9 @@ EXPORT_SYMBOL(bdi_init);
void bdi_destroy(struct backing_dev_info *bdi)
{
bdi_wb_shutdown(bdi);
WARN_ON(!list_empty(&bdi->work_list));
/* make sure nobody finds us on the bdi_list anymore */
bdi_remove_from_list(bdi);
wb_shutdown(&bdi->wb);
if (bdi->dev) {
bdi_debug_unregister(bdi);
@@ -464,7 +461,7 @@ void bdi_destroy(struct backing_dev_info *bdi)
bdi->dev = NULL;
}
bdi_wb_exit(&bdi->wb);
wb_exit(&bdi->wb);
}
EXPORT_SYMBOL(bdi_destroy);