zram: delay pending free request in read path

Sergey reported 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@kernel.org>
Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 9b353db16d18f87242337e3e61a948c023505a65)
Signed-off-by: Alex Shi <alex.shi@linaro.org>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 1a377872729d2543d4d6c66b85e734d8a93b0df5..8b88a8d064aff2e4601b7457367681dcb71b4ca8 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -534,7 +534,6 @@ 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 {