two small raid5 cache updates

two small raid5 cache updates

[Christoph Hellwig]

The first is a trival cleanup, the second a similarly trivial reduction
in memory usage.

[PATCH 1/2] raid5-cache: simplify r5l_move_io_unit_list

[Christoph Hellwig]

It's only used for one kind of move, so make that explicit.  Also clean
up the code a bit by using list_for_each_safe.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/raid5-cache.c | 32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index b887e04..3699c47 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -156,21 +156,6 @@ static void r5l_free_io_unit(struct r5l_log *log, struct r5l_io_unit *io)
 	kmem_cache_free(log->io_kc, io);
 }
 
-static void r5l_move_io_unit_list(struct list_head *from, struct list_head *to,
-				  enum r5l_io_unit_state state)
-{
-	struct r5l_io_unit *io;
-
-	while (!list_empty(from)) {
-		io = list_first_entry(from, struct r5l_io_unit, log_sibling);
-		/* don't change list order */
-		if (io->state >= state)
-			list_move_tail(&io->log_sibling, to);
-		else
-			break;
-	}
-}
-
 static void __r5l_set_io_unit_state(struct r5l_io_unit *io,
 				    enum r5l_io_unit_state state)
 {
@@ -206,6 +191,20 @@ static void r5l_log_run_stripes(struct r5l_log *log)
 	}
 }
 
+static void r5l_move_to_end_ios(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->io_end_ios);
+	}
+}
+
 static void r5l_log_endio(struct bio *bio)
 {
 	struct r5l_io_unit *io = bio->bi_private;
@@ -220,8 +219,7 @@ 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);
+		r5l_move_to_end_ios(log);
 	else
 		r5l_log_run_stripes(log);
 	spin_unlock_irqrestore(&log->io_list_lock, flags);
-- 
1.9.1

[PATCH 2/2] raid5-cache: free meta_page earlier

[Christoph Hellwig]

Once the I/O completed we don't need the meta page anymore.  As the iounits
can live on for a long time this reduces memory pressure a bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/raid5-cache.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 3699c47..668e973 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -150,12 +150,6 @@ static bool r5l_has_free_space(struct r5l_log *log, sector_t size)
 	return log->device_size > used_size + size;
 }
 
-static void r5l_free_io_unit(struct r5l_log *log, struct r5l_io_unit *io)
-{
-	__free_page(io->meta_page);
-	kmem_cache_free(log->io_kc, io);
-}
-
 static void __r5l_set_io_unit_state(struct r5l_io_unit *io,
 				    enum r5l_io_unit_state state)
 {
@@ -215,6 +209,7 @@ static void r5l_log_endio(struct bio *bio)
 		md_error(log->rdev->mddev, log->rdev);
 
 	bio_put(bio);
+	__free_page(io->meta_page);
 
 	spin_lock_irqsave(&log->io_list_lock, flags);
 	__r5l_set_io_unit_state(io, IO_UNIT_IO_END);
@@ -552,7 +547,7 @@ static bool r5l_complete_finished_ios(struct r5l_log *log)
 		log->next_cp_seq = io->seq;
 
 		list_del(&io->log_sibling);
-		r5l_free_io_unit(log, io);
+		kmem_cache_free(log->io_kc, io);
 
 		found = true;
 	}
-- 
1.9.1

Re: two small raid5 cache updates

[Shaohua Li]

On Wed, Dec 02, 2015 at 05:06:37PM +0100, Christoph Hellwig wrote:
> The first is a trival cleanup, the second a similarly trivial reduction
> in memory usage.

Looks good, thanks!

Reviewed-by: Shaohua Li <shli@fb.com>

Re: two small raid5 cache updates

[NeilBrown]

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On Thu, Dec 03 2015, Shaohua Li wrote:

> On Wed, Dec 02, 2015 at 05:06:37PM +0100, Christoph Hellwig wrote:
>> The first is a trival cleanup, the second a similarly trivial reduction
>> in memory usage.
>
> Looks good, thanks!
>
> Reviewed-by: Shaohua Li <shli@fb.com>

Both applied, thanks.

NeilBrown

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