linux-kernel - Re: [PATCH] fs/fuse/dev.c: use zero_user

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Message-ID: <a8e1da0707200309n377eca1fwa640eeceb920959b@mail.gmail.com>
Date:	Fri, 20 Jul 2007 10:09:10 +0000
From:	"Dave Young" <hidave.darkstar@...il.com>
To:	"Denis Cheng" <crquan@...il.com>
Cc:	"Miklos Szeredi" <miklos@...redi.hu>,
	fuse-devel@...ts.sourceforge.net, viro@...iv.linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/fuse/dev.c: use zero_user_page instead

>On 7/20/07, Denis Cheng <crquan@...il.com> wrote:
> Signed-off-by: Denis Cheng <crquan@...il.com>
> ---
> I'm not very sure zero_user_page is correctly used here,
> so please feel free to give comments.
>
> and why here it uses KM_USER1 not KM_USER0, What are the differences?
>
>  fs/fuse/dev.c |    8 +++-----
>  1 files changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 3ad22be..e55b5e8 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -533,11 +533,9 @@ static int fuse_copy_do(struct fuse_copy_state *cs, void **val, unsigned *size)
>  static int fuse_copy_page(struct fuse_copy_state *cs, struct page *page,
>                           unsigned offset, unsigned count, int zeroing)
>  {
> -       if (page && zeroing && count < PAGE_SIZE) {
> -               void *mapaddr = kmap_atomic(page, KM_USER1);
> -               memset(mapaddr, 0, PAGE_SIZE);
> -               kunmap_atomic(mapaddr, KM_USER1);
> -       }
> +       if (page && zeroing && count < PAGE_SIZE)
> +               zero_user_page(page, 0, PAGE_SIZE, KM_USER1);
Why clear all page? IMHO,only count bytes need to be cleared.
> +
>         while (count) {
>                 int err;
>                 if (!cs->len && (err = fuse_copy_fill(cs)))
-
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