Commit 56fef7c6 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by NeilBrown
Browse files

raid5-cache: simplify state machine when caches flushes are not needed 



For devices without a volatile write cache we don't need to send a FLUSH
command to ensure writes are stable on disk, and thus can avoid the whole
step of batching up bios for processing by the MD thread.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarShaohua Li <shli@fb.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.com>
parent d8858f43

drivers/md/raid5-cache.c

+29 −4
Original line number Diff line number Diff line
@@ -83,6 +83,8 @@ struct r5l_log { 


	struct list_head no_space_stripes; /* pending stripes, log has no space */

	spinlock_t no_space_stripes_lock;



	bool need_cache_flush;

};



/*
@@ -206,6 +208,22 @@ static void r5l_io_run_stripes(struct r5l_io_unit *io) 
}



/* XXX: totally ignores I/O errors */

static void r5l_log_run_stripes(struct r5l_log *log)

{

	struct r5l_io_unit *io, *next;



	assert_spin_locked(&log->io_list_lock);



	list_for_each_entry_safe(io, next, &log->running_ios, log_sibling) {

		/* don't change list order */

		if (io->state < IO_UNIT_IO_END)

			break;



		list_move_tail(&io->log_sibling, &log->finished_ios);

		r5l_io_run_stripes(io);

	}

}



static void r5l_log_endio(struct bio *bio)

{

	struct r5l_io_unit *io = bio->bi_private;
@@ -219,10 +237,14 @@ static void r5l_log_endio(struct bio *bio) 


	spin_lock_irqsave(&log->io_list_lock, flags);

	__r5l_set_io_unit_state(io, IO_UNIT_IO_END);

	if (log->need_cache_flush)

		r5l_move_io_unit_list(&log->running_ios, &log->io_end_ios,

				      IO_UNIT_IO_END);

	else

		r5l_log_run_stripes(log);

	spin_unlock_irqrestore(&log->io_list_lock, flags);



	if (log->need_cache_flush)

		md_wakeup_thread(log->rdev->mddev->thread);

}
@@ -620,7 +642,8 @@ static void r5l_log_flush_endio(struct bio *bio) 
void r5l_flush_stripe_to_raid(struct r5l_log *log)

{

	bool do_flush;

	if (!log)



	if (!log || !log->need_cache_flush)

		return;



	spin_lock_irq(&log->io_list_lock);
@@ -1065,6 +1088,8 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev) 
		return -ENOMEM;

	log->rdev = rdev;



	log->need_cache_flush = (rdev->bdev->bd_disk->queue->flush_flags != 0);



	log->uuid_checksum = crc32c_le(~0, rdev->mddev->uuid,

				       sizeof(rdev->mddev->uuid));

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