linux-kernel - [PATCH 1/2] staging: zram: minimize `slot_free

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Message-ID: <20130906134706.GA2238@swordfish.minsk.epam.com>
Date:	Fri, 6 Sep 2013 16:47:06 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Minchan Kim <minchan@...nel.org>, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] staging: zram: minimize `slot_free_lock' usage

Calling handle_pending_slot_free() for every RW operation may
cause unneccessary slot_free_lock locking, because most likely
process will see NULL slot_free_rq. handle_pending_slot_free()
only when current detects that slot_free_rq is not NULL.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

---

 drivers/staging/zram/zram_drv.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index 91d94b5..17386e2 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -532,14 +532,15 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 {
 	int ret;
 
+	if (zram->slot_free_rq)
+		handle_pending_slot_free(zram);
+
 	if (rw == READ) {
 		down_read(&zram->lock);
-		handle_pending_slot_free(zram);
 		ret = zram_bvec_read(zram, bvec, index, offset, bio);
 		up_read(&zram->lock);
 	} else {
 		down_write(&zram->lock);
-		handle_pending_slot_free(zram);
 		ret = zram_bvec_write(zram, bvec, index, offset);
 		up_write(&zram->lock);
 	}

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