linux-kernel - [PATCH mmotm] fsnotify: don't slow everything down

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Date:	Sun, 17 May 2009 14:52:32 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Eric Paris <eparis@...hat.com>, Al Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@....de>, linux-kernel@...r.kernel.org
Subject: [PATCH mmotm] fsnotify: don't slow everything down

Two little fixes to mmotm's fsnotify-parent-event-notification.patch:

Why is copying or building a kernel tree using twice as much system time
as before?  Lots of time spent in __fsnotify_update_child_dentry_flags()
when it shouldn't even get called.  Fix | to & in __fsnotify_parent().

And it's probably a bad idea to have DCACHE_FSNOTIFY_PARENT_WATCHED
sharing the same d_flags bit as DCACHE_COOKIE: though the COOKIE bit has
prior claim, change it to keep the NOTIFY_PARENT_WATCHED bits together.

Signed-off-by: Hugh Dickins <hugh@...itas.com>
---

 fs/notify/fsnotify.c   |    2 +-
 include/linux/dcache.h |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- mmotm/fs/notify/fsnotify.c	2009-05-14 11:27:38.000000000 +0100
+++ linux/fs/notify/fsnotify.c	2009-05-17 13:31:23.000000000 +0100
@@ -84,7 +84,7 @@ void __fsnotify_parent(struct dentry *de
 	bool send = false;
 	bool should_update_children = false;
 
-	if (!(dentry->d_flags | DCACHE_FSNOTIFY_PARENT_WATCHED))
+	if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
 		return;
 
 	spin_lock(&dentry->d_lock);
--- mmotm/include/linux/dcache.h	2009-05-14 11:27:39.000000000 +0100
+++ linux/include/linux/dcache.h	2009-05-17 13:31:23.000000000 +0100
@@ -183,7 +183,7 @@ d_iput:		no		no		no       yes
 #define DCACHE_INOTIFY_PARENT_WATCHED	0x0020 /* Parent inode is watched by inotify */
 #define DCACHE_FSNOTIFY_PARENT_WATCHED	0x0040 /* Parent inode is watched by some fsnotify listener */
 
-#define DCACHE_COOKIE		0x0040	/* For use by dcookie subsystem */
+#define DCACHE_COOKIE		0x0080	/* For use by dcookie subsystem */
 
 extern spinlock_t dcache_lock;
 extern seqlock_t rename_lock;
--
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