* [PATCH] block: zram: Replace GFP_ATOMIC with GFP_KERNEL
@ 2018-07-23 14:13 Jia-Ju Bai
2018-07-24 2:52 ` Sergey Senozhatsky
0 siblings, 1 reply; 2+ messages in thread
From: Jia-Ju Bai @ 2018-07-23 14:13 UTC (permalink / raw)
To: minchan, ngupta, sergey.senozhatsky.work, axboe
Cc: linux-kernel, linux-block, Jia-Ju Bai
read_from_bdev_async() and write_to_bdev() are never called in atomic
context. They call bio_alloc() with GFP_ATOMIC, which is not necessary.
GFP_ATOMIC can be replaced with GFP_KERNEL.
This is found by a static analysis tool named DCNS written by myself.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
drivers/block/zram/zram_drv.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 0f3fadd71230..b958ed0b8c35 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -450,7 +450,7 @@ static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec,
{
struct bio *bio;
- bio = bio_alloc(GFP_ATOMIC, 1);
+ bio = bio_alloc(GFP_KERNEL, 1);
if (!bio)
return -ENOMEM;
@@ -538,7 +538,7 @@ static int write_to_bdev(struct zram *zram, struct bio_vec *bvec,
struct bio *bio;
unsigned long entry;
- bio = bio_alloc(GFP_ATOMIC, 1);
+ bio = bio_alloc(GFP_KERNEL, 1);
if (!bio)
return -ENOMEM;
--
2.17.0
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH] block: zram: Replace GFP_ATOMIC with GFP_KERNEL
2018-07-23 14:13 [PATCH] block: zram: Replace GFP_ATOMIC with GFP_KERNEL Jia-Ju Bai
@ 2018-07-24 2:52 ` Sergey Senozhatsky
0 siblings, 0 replies; 2+ messages in thread
From: Sergey Senozhatsky @ 2018-07-24 2:52 UTC (permalink / raw)
To: Jia-Ju Bai
Cc: minchan, ngupta, sergey.senozhatsky.work, axboe, linux-kernel,
linux-block, Andrew Morton
On (07/23/18 22:13), Jia-Ju Bai wrote:
> read_from_bdev_async() and write_to_bdev() are never called in atomic
> context. They call bio_alloc() with GFP_ATOMIC, which is not necessary.
> GFP_ATOMIC can be replaced with GFP_KERNEL.
[..]
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 0f3fadd71230..b958ed0b8c35 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -450,7 +450,7 @@ static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec,
> {
> struct bio *bio;
>
> - bio = bio_alloc(GFP_ATOMIC, 1);
> + bio = bio_alloc(GFP_KERNEL, 1);
> if (!bio)
> return -ENOMEM;
>
> @@ -538,7 +538,7 @@ static int write_to_bdev(struct zram *zram, struct bio_vec *bvec,
> struct bio *bio;
> unsigned long entry;
>
> - bio = bio_alloc(GFP_ATOMIC, 1);
> + bio = bio_alloc(GFP_KERNEL, 1);
> if (!bio)
> return -ENOMEM;
I think the intent here is different and is not related to atomic
contexts.
Consider the following
OMM -> swapout -> __zram_bvec_write() -> write_to_bdev() -> bio_alloc(GFP_KERNEL) -> [OOM?]
So maybe we can do a bit better than GFP_ATOMIC (NOIO, etc.), but in general,
I believe, we can't use GFP_KERNEL [at least in write_to_bdev()].
-ss
^ permalink raw reply [flat|nested] 2+ messages in thread
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