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SubjectRe: [PATCH] fanotify: to differ file access event from different threads
From
How can this patch get merged?
Who is responsible for this?

We are developing some real-time antivirus software, the fanotify can make
it work without dirver/kenel-modues( like RedirFS).
But the bug costs a lot trouble.
If we used the patch, our software works great!

I think other antivirus or file-motoring softwares are influnced by the bug
too.


On Fri, Oct 14, 2011 at 2:56 PM, boyd yang <boyd.yang@gmail.com> wrote:
>
> Thanks, I updated the patch.
> Now it passed checkpatch.pl.
>
> I used the flag you mentioned.
>
> fanotify: to differ file access event from different threads
> When fanotify is monitoring the whole mount point "/", and multiple
> threads iterate the same direcotry, some thread will hang.
> This patch let fanotify to differ access events from different
> threads, prevent fanotify from merging access events from different
> threads.
> It also hide overflow events to reach user space.
> Signed-off-by: Boyd Yang <boyd.yang@gmail.com>
>
> diff -r -u linux-3.1-rc4_orig/fs/notify/fanotify/fanotify.c
> linux-3.1-rc4/fs/notify/fanotify/fanotify.c
> --- linux-3.1-rc4_orig/fs/notify/fanotify/fanotify.c    2011-08-29
> 12:16:01.000000000 +0800
> +++ linux-3.1-rc4/fs/notify/fanotify/fanotify.c 2011-10-14
> 14:17:53.055958000 +0800
> @@ -15,7 +15,8 @@
>
>        if (old->to_tell == new->to_tell &&
>            old->data_type == new->data_type &&
> -           old->tgid == new->tgid) {
> +           old->tgid == new->tgid &&
> +           old->pid == new->pid) {
>                switch (old->data_type) {
>                case (FSNOTIFY_EVENT_PATH):
>                        if ((old->path.mnt == new->path.mnt) &&
> @@ -144,11 +145,16 @@
>                return PTR_ERR(notify_event);
>
>  #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
> -       if (event->mask & FAN_ALL_PERM_EVENTS) {
> -               /* if we merged we need to wait on the new event */
> -               if (notify_event)
> -                       event = notify_event;
> -               ret = fanotify_get_response_from_access(group, event);
> +       /*if overflow, do not wait for response*/
> +       if (event->mask&FS_Q_OVERFLOW) {
> +               pr_debug("fanotify overflow!\n");
> +       }       else {
> +               if (event->mask & FAN_ALL_PERM_EVENTS) {
> +                       /* if we merged we need to wait on the new event */
> +                       if (notify_event)
> +                               event = notify_event;
> +                       ret = fanotify_get_response_from_access(group, event);
> +               }
>        }
>  #endif
>
> diff -r -u linux-3.1-rc4_orig/fs/notify/notification.c
> linux-3.1-rc4/fs/notify/notification.c
> --- linux-3.1-rc4_orig/fs/notify/notification.c 2011-08-29
> 12:16:01.000000000 +0800
> +++ linux-3.1-rc4/fs/notify/notification.c      2011-10-14 13:52:36.946608000 +0800
> @@ -95,6 +95,7 @@
>                BUG_ON(!list_empty(&event->private_data_list));
>
>                kfree(event->file_name);
> +               put_pid(event->pid);
>                put_pid(event->tgid);
>                kmem_cache_free(fsnotify_event_cachep, event);
>        }
> @@ -374,6 +375,7 @@
>                        return NULL;
>                }
>        }
> +       event->pid = get_pid(old_event->pid);
>        event->tgid = get_pid(old_event->tgid);
>        if (event->data_type == FSNOTIFY_EVENT_PATH)
>                path_get(&event->path);
> @@ -417,6 +419,7 @@
>                event->name_len = strlen(event->file_name);
>        }
>
> +       event->pid = get_pid(task_pid(current));
>        event->tgid = get_pid(task_tgid(current));
>        event->sync_cookie = cookie;
>        event->to_tell = to_tell;
> diff -r -u linux-3.1-rc4_orig/include/linux/fsnotify_backend.h
> linux-3.1-rc4/include/linux/fsnotify_backend.h
> --- linux-3.1-rc4_orig/include/linux/fsnotify_backend.h 2011-08-29
> 12:16:01.000000000 +0800
> +++ linux-3.1-rc4/include/linux/fsnotify_backend.h      2011-10-14
> 13:51:50.380168000 +0800
> @@ -238,6 +238,7 @@
>        u32 sync_cookie;        /* used to corrolate events, namely inotify mv events */
>        const unsigned char *file_name;
>        size_t name_len;
> +       struct pid *pid;
>        struct pid *tgid;
>
>  #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
>
>
>
>
>
> On Thu, Oct 13, 2011 at 9:38 PM, Josef Bacik <josef@redhat.com> wrote:
> > On Thu, Oct 13, 2011 at 04:56:43PM +0800, boyd yang wrote:
> >> This patch fixes a hang problem of Eric Paris's fs Notification/fanotify.
> >>
> >> Fanotify brings a way to intercept file access events.
> >> When multiple threadsiterate the same direcotry, some thread will hang.
> >> This patch let fanotify to differ access events from different
> >> threads, prevent fanotify from merging access events from different
> >> threads.
> >>
> >
> > You need to run this through checkpatch.pl, you have a ton of formatting
> > problems.  Also your email client seems to have word-wrapped parts of this, so
> > use a email client that doesn't word wrap.
> >
> >> =============================================================
> >>
> >> diff -r -u linux-3.1-rc4_orig/fs/notify/fanotify/fanotify.c
> >> linux-3.1-rc4/fs/notify/fanotify/fanotify.c
> >> --- linux-3.1-rc4_orig/fs/notify/fanotify/fanotify.c  2011-08-29
> >> 12:16:01.000000000 +0800
> >> +++ linux-3.1-rc4/fs/notify/fanotify/fanotify.c       2011-10-10
> >> 12:28:23.276847000 +0800
> >> @@ -15,7 +15,8 @@
> >>
> >>       if (old->to_tell == new->to_tell &&
> >>           old->data_type == new->data_type &&
> >> -         old->tgid == new->tgid) {
> >> +         old->tgid == new->tgid &&
> >> +         old->pid == new->pid) {
> >>               switch (old->data_type) {
> >>               case (FSNOTIFY_EVENT_PATH):
> >>                       if ((old->path.mnt == new->path.mnt) &&
> >> @@ -144,11 +145,19 @@
> >>               return PTR_ERR(notify_event);
> >>
> >>  #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
> >> -     if (event->mask & FAN_ALL_PERM_EVENTS) {
> >> -             /* if we merged we need to wait on the new event */
> >> -             if (notify_event)
> >> -                     event = notify_event;
> >> -             ret = fanotify_get_response_from_access(group, event);
> >> +     //if overflow, do not wait for response
> >> +     if(fsnotify_isoverflow(event))
> >> +     {
> >> +             pr_debug("fanotify overflow!\n");
> >> +     }
> >> +     else
> >> +     {
> >> +             if (event->mask & FAN_ALL_PERM_EVENTS) {
> >> +                     /* if we merged we need to wait on the new event */
> >> +                     if (notify_event)
> >> +                             event = notify_event;
> >> +                     ret = fanotify_get_response_from_access(group, event);
> >> +             }
> >>       }
> >
> > The overflow event should only have FS_Q_OVERFLOW set in it's mask right?  So
> > why is this test needed at all?  Thanks,
> >
> > Josef
> >
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