linux-kernel - [PATCH 2/7] zram: delay pending free request in read path

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Date:	Mon, 13 Jan 2014 20:18:57 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Minchan Kim <minchan@...nel.org>
Subject: [PATCH 2/7] zram: delay pending free request in read path

Sergey Senozhatsky reporetd we don't need to handle pending free
request every I/O so that this patch removes it in read path while
we remain it in write path.

Let's consider below example.

Swap subsystem ask to zram "A" block free by swap_slot_free_notify
but zram had been pended it without real freeing.
Swap subsystem allocates "A" block for new data but request pended
for a long time just handled and zram blindly free new data on
the "A" block. :(

That's why we couldn't remove handle pending free request right before
zram-write.

Signed-off-by: Minchan Kim <minchan@...nel.org>
---
 drivers/block/zram/zram_drv.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 213dfc1..d87c7e9 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -535,7 +535,6 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,

 	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 {
-- 
1.8.4.3

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