Commit cc395d7f authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe

writeback: implement bdi_wait_for_completion()

If the completion of a wb_writeback_work can be waited upon by setting
its ->done to a struct completion and waiting on it; however, for
cgroup writeback support, it's necessary to issue multiple work items
to multiple bdi_writebacks and wait for the completion of all.

This patch implements wb_completion which can wait for multiple work
items and replaces the struct completion with it.  It can be defined
using DEFINE_WB_COMPLETION_ONSTACK(), used for multiple work items and
waited for by wb_wait_for_completion().

Nobody currently issues multiple work items and this patch doesn't
introduce any behavior changes.
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent ac7b19a3
......@@ -34,6 +34,10 @@
*/
#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_CACHE_SHIFT - 10))
struct wb_completion {
atomic_t cnt;
};
/*
* Passed into wb_writeback(), essentially a subset of writeback_control
*/
......@@ -51,9 +55,22 @@ struct wb_writeback_work {
enum wb_reason reason; /* why was writeback initiated? */
struct list_head list; /* pending work list */
struct completion *done; /* set if the caller waits */
struct wb_completion *done; /* set if the caller waits */
};
/*
* If one wants to wait for one or more wb_writeback_works, each work's
* ->done should be set to a wb_completion defined using the following
* macro. Once all work items are issued with wb_queue_work(), the caller
* can wait for the completion of all using wb_wait_for_completion(). Work
* items which are waited upon aren't freed automatically on completion.
*/
#define DEFINE_WB_COMPLETION_ONSTACK(cmpl) \
struct wb_completion cmpl = { \
.cnt = ATOMIC_INIT(1), \
}
/*
* If an inode is constantly having its pages dirtied, but then the
* updates stop dirtytime_expire_interval seconds in the past, it's
......@@ -161,17 +178,34 @@ static void wb_queue_work(struct bdi_writeback *wb,
trace_writeback_queue(wb->bdi, work);
spin_lock_bh(&wb->work_lock);
if (!test_bit(WB_registered, &wb->state)) {
if (work->done)
complete(work->done);
if (!test_bit(WB_registered, &wb->state))
goto out_unlock;
}
if (work->done)
atomic_inc(&work->done->cnt);
list_add_tail(&work->list, &wb->work_list);
mod_delayed_work(bdi_wq, &wb->dwork, 0);
out_unlock:
spin_unlock_bh(&wb->work_lock);
}
/**
* wb_wait_for_completion - wait for completion of bdi_writeback_works
* @bdi: bdi work items were issued to
* @done: target wb_completion
*
* Wait for one or more work items issued to @bdi with their ->done field
* set to @done, which should have been defined with
* DEFINE_WB_COMPLETION_ONSTACK(). This function returns after all such
* work items are completed. Work items which are waited upon aren't freed
* automatically on completion.
*/
static void wb_wait_for_completion(struct backing_dev_info *bdi,
struct wb_completion *done)
{
atomic_dec(&done->cnt); /* put down the initial count */
wait_event(bdi->wb_waitq, !atomic_read(&done->cnt));
}
#ifdef CONFIG_CGROUP_WRITEBACK
/**
......@@ -1143,7 +1177,7 @@ static long wb_do_writeback(struct bdi_writeback *wb)
set_bit(WB_writeback_running, &wb->state);
while ((work = get_next_work_item(wb)) != NULL) {
struct completion *done = work->done;
struct wb_completion *done = work->done;
trace_writeback_exec(wb->bdi, work);
......@@ -1151,8 +1185,8 @@ static long wb_do_writeback(struct bdi_writeback *wb)
if (work->auto_free)
kfree(work);
if (done)
complete(done);
if (done && atomic_dec_and_test(&done->cnt))
wake_up_all(&wb->bdi->wb_waitq);
}
/*
......@@ -1518,7 +1552,7 @@ void writeback_inodes_sb_nr(struct super_block *sb,
unsigned long nr,
enum wb_reason reason)
{
DECLARE_COMPLETION_ONSTACK(done);
DEFINE_WB_COMPLETION_ONSTACK(done);
struct wb_writeback_work work = {
.sb = sb,
.sync_mode = WB_SYNC_NONE,
......@@ -1533,7 +1567,7 @@ void writeback_inodes_sb_nr(struct super_block *sb,
return;
WARN_ON(!rwsem_is_locked(&sb->s_umount));
wb_queue_work(&bdi->wb, &work);
wait_for_completion(&done);
wb_wait_for_completion(bdi, &done);
}
EXPORT_SYMBOL(writeback_inodes_sb_nr);
......@@ -1600,7 +1634,7 @@ EXPORT_SYMBOL(try_to_writeback_inodes_sb);
*/
void sync_inodes_sb(struct super_block *sb)
{
DECLARE_COMPLETION_ONSTACK(done);
DEFINE_WB_COMPLETION_ONSTACK(done);
struct wb_writeback_work work = {
.sb = sb,
.sync_mode = WB_SYNC_ALL,
......@@ -1618,7 +1652,7 @@ void sync_inodes_sb(struct super_block *sb)
WARN_ON(!rwsem_is_locked(&sb->s_umount));
wb_queue_work(&bdi->wb, &work);
wait_for_completion(&done);
wb_wait_for_completion(bdi, &done);
wait_sb_inodes(sb);
}
......
......@@ -155,6 +155,8 @@ struct backing_dev_info {
struct rb_root cgwb_congested_tree; /* their congested states */
atomic_t usage_cnt; /* counts both cgwbs and cgwb_contested's */
#endif
wait_queue_head_t wb_waitq;
struct device *dev;
struct timer_list laptop_mode_wb_timer;
......
......@@ -768,6 +768,7 @@ int bdi_init(struct backing_dev_info *bdi)
bdi->max_ratio = 100;
bdi->max_prop_frac = FPROP_FRAC_BASE;
INIT_LIST_HEAD(&bdi->bdi_list);
init_waitqueue_head(&bdi->wb_waitq);
err = wb_init(&bdi->wb, bdi, GFP_KERNEL);
if (err)
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment