linux-kernel - Re: [PATCH 2/5] inotify: use ZERO_PAGE instead of private static declaration

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Date:	Mon, 10 Aug 2009 10:12:55 -0400
From:	Eric Paris <eparis@...isplace.org>
To:	Eric Paris <eparis@...hat.com>
Cc:	linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk
Subject: Re: [PATCH 2/5] inotify: use ZERO_PAGE instead of private static 
	declaration

On Sun, Aug 9, 2009 at 5:59 PM, Eric Paris<eparis@...hat.com> wrote:
> inotify needs to pad filenames to an inotify event length.  Currently this
> is done by copying 0s from an event declared globally.  This patch doesn't
> waste global address space just to have some 0s and instead uses
> clear_user()
>
> Signed-off-by: Eric Paris <eparis@...hat.com>

Crap, the subject of this message is wrong.  I'll fix the subject when
I commit, the summary and patch are correct.

-Eric

> ---
>
>  fs/notify/inotify/inotify_user.c |    9 +++------
>  1 files changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
> index c17d5a3..c3086b0 100644
> --- a/fs/notify/inotify/inotify_user.c
> +++ b/fs/notify/inotify/inotify_user.c
> @@ -47,9 +47,6 @@
>
>  static struct vfsmount *inotify_mnt __read_mostly;
>
> -/* this just sits here and wastes global memory.  used to just pad userspace messages with zeros */
> -static struct inotify_event nul_inotify_event;
> -
>  /* these are configurable via /proc/sys/fs/inotify/ */
>  static int inotify_max_user_instances __read_mostly;
>  static int inotify_max_queued_events __read_mostly;
> @@ -215,7 +212,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
>        /*
>         * fsnotify only stores the pathname, so here we have to send the pathname
>         * and then pad that pathname out to a multiple of sizeof(inotify_event)
> -        * with zeros.  I get my zeros from the nul_inotify_event.
> +        * with zeros.
>         */
>        if (name_len) {
>                unsigned int len_to_zero = name_len - event->name_len;
> @@ -224,8 +221,8 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
>                        return -EFAULT;
>                buf += event->name_len;
>
> -               /* fill userspace with 0's from nul_inotify_event */
> -               if (copy_to_user(buf, &nul_inotify_event, len_to_zero))
> +               /* fill userspace with 0's */
> +               if (clear_user(buf, len_to_zero))
>                        return -EFAULT;
>                buf += len_to_zero;
>                event_size += name_len;
>
> --
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