linux-kernel - Re: [fs] inode_lru_isolate(): Move counter increment into spinlock section

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Date:	Fri, 20 Dec 2013 12:05:29 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Dave Chinner <david@...morbit.com>
cc:	Dave Chinner <dchinner@...hat.com>, linux-kernel@...r.kernel.org,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [fs] inode_lru_isolate(): Move counter increment into spinlock
 section

On Fri, 20 Dec 2013, Dave Chinner wrote:

> If count_vm_events requires irqs to be disabled to behave correctly,
> then putting __count_vm_events under a spin lock is still not irq
> safe. Either way, this isn't in a performance critical path, so I'd
> much prefer the simpler, safer option be used rather than leave a
> landmine for other unsuspecting developers.


Subject: [fs] Use safe counter increment operations

The counter increment in inode_lru_isolate is happening with
preemption on using __count_vm_events making counter
increment races possible.

Use count_vm_events instead.

Signed-off-by: Christoph Lameter <cl@...ux.com>

Index: linux/fs/inode.c
===================================================================
--- linux.orig/fs/inode.c	2013-12-20 12:02:14.409583380 -0600
+++ linux/fs/inode.c	2013-12-20 12:02:14.409583380 -0600
@@ -722,9 +722,9 @@ inode_lru_isolate(struct list_head *item
 			unsigned long reap;
 			reap = invalidate_mapping_pages(&inode->i_data, 0, -1);
 			if (current_is_kswapd())
-				__count_vm_events(KSWAPD_INODESTEAL, reap);
+				count_vm_events(KSWAPD_INODESTEAL, reap);
 			else
-				__count_vm_events(PGINODESTEAL, reap);
+				count_vm_events(PGINODESTEAL, reap);
 			if (current->reclaim_state)
 				current->reclaim_state->reclaimed_slab += reap;
 		}
--
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