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Commit f0fad8a5 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

writeback: merely wakeup flusher thread if work allocation fails for WB_SYNC_NONE 



Since it's an opportunistic writeback and not a data integrity action,
don't punt to blocking writeback. Just wakeup the thread and it will
flush old data.

Acked-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarChristoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 1fe06ad8

fs/fs-writeback.c

+14 −32
Original line number Diff line number Diff line
@@ -75,13 +75,6 @@ static inline void bdi_work_init(struct bdi_work *work, 
	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.
@@ -207,34 +200,23 @@ static struct bdi_work *bdi_alloc_work(struct writeback_control *wbc) 


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);

	/*

	 * WB_SYNC_NONE is opportunistic writeback. If this allocation fails,

	 * bdi_queue_work() will wake up the thread and flush old data. This

	 * should ensure some amount of progress in freeing memory.

	 */

	if (wbc->sync_mode != WB_SYNC_ALL) {

		struct bdi_work *w = bdi_alloc_work(wbc);



	if (!work) {

		work = &work_stack;

		bdi_work_init_on_stack(work, wbc);

	}

		bdi_queue_work(wbc->bdi, w);

	} else {

		struct bdi_work work;



	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);

	}

}