Re: [PATCH] fanotify: to differ file access event from different threads

[boyd yang]

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@xxxxxxxxx>

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@xxxxxxxxxx> 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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