2018-04-09 14:35:49

by Jia-Ju Bai

Subject: [PATCH] fs: quota: Replace GFP_ATOMIC with GFP_KERNEL in dquot_init

dquot_init() is never called in atomic context.
This function is only set as a parameter of fs_initcall().

Despite never getting called from atomic context,
dquot_init() calls __get_free_pages() with GFP_ATOMIC,
which waits busily for allocation.
GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
to avoid busy waiting and improve the possibility of sucessful allocation.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
fs/quota/dquot.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 8381db9..d6e111e 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -2944,7 +2944,7 @@ static int __init dquot_init(void)
NULL);

order = 0;
- dquot_hash = (struct hlist_head *)__get_free_pages(GFP_ATOMIC, order);
+ dquot_hash = (struct hlist_head *)__get_free_pages(GFP_KERNEL, order);
if (!dquot_hash)
panic("Cannot create dquot hash table");

--
1.9.1

2018-04-09 15:54:09

by Jan Kara

Subject: Re: [PATCH] fs: quota: Replace GFP_ATOMIC with GFP_KERNEL in dquot_init

On Mon 09-04-18 22:31:19, Jia-Ju Bai wrote:
> dquot_init() is never called in atomic context.
> This function is only set as a parameter of fs_initcall().
>
> Despite never getting called from atomic context,
> dquot_init() calls __get_free_pages() with GFP_ATOMIC,
> which waits busily for allocation.
> GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
> to avoid busy waiting and improve the possibility of sucessful allocation.
>
> This is found by a static analysis tool named DCNS written by myself.
> And I also manually check it.
>
> Signed-off-by: Jia-Ju Bai <[email protected]>

Thanks, I have added the patch to my tree.

Honza


> ---
> fs/quota/dquot.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> index 8381db9..d6e111e 100644
> --- a/fs/quota/dquot.c
> +++ b/fs/quota/dquot.c
> @@ -2944,7 +2944,7 @@ static int __init dquot_init(void)
> NULL);
>
> order = 0;
> - dquot_hash = (struct hlist_head *)__get_free_pages(GFP_ATOMIC, order);
> + dquot_hash = (struct hlist_head *)__get_free_pages(GFP_KERNEL, order);
> if (!dquot_hash)
> panic("Cannot create dquot hash table");
>
> --
> 1.9.1
>
>
--
Jan Kara <[email protected]>
SUSE Labs, CR