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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: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
This commit is contained in:
Christoph Hellwig 2015-10-05 09:31:09 +02:00 committed by NeilBrown
parent d8858f4321
commit 56fef7c6e0
1 changed files with 29 additions and 4 deletions
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33
drivers/md/raid5-cache.c
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@ -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;
@ -219,11 +237,15 @@ 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);
r5l_move_io_unit_list(&log->running_ios, &log->io_end_ios,
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);
md_wakeup_thread(log->rdev->mddev->thread);
if (log->need_cache_flush)
md_wakeup_thread(log->rdev->mddev->thread);
}
static void r5l_submit_current_io(struct r5l_log *log)
@ -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));