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

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Message-ID: <00000143072add16-956bfa6c-d7d5-4df9-aabc-05a904a0edc4-000000@email.amazonses.com>
Date:	Wed, 18 Dec 2013 19:24:46 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Dave Chinner <dchinner@...hat.com>
cc:	linux-kernel@...r.kernel.org,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: [fs] inode_lru_isolate(): Move counter increment into spinlock
 section

The counter increment in inode_lru_isolate is happening after
spinlocks have been dropped with preemption on using __count_vm_events
making counter increment races possible.

Move the counter increments to be done when the spinlock is
reacquired later so that the counter can be safely incremented.

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

Index: linux/fs/inode.c
===================================================================
--- linux.orig/fs/inode.c	2013-12-18 13:14:43.211693438 -0600
+++ linux/fs/inode.c	2013-12-18 13:15:58.489266129 -0600
@@ -715,21 +715,21 @@ inode_lru_isolate(struct list_head *item
 	}

 	if (inode_has_buffers(inode) || inode->i_data.nrpages) {
+		unsigned long reap = 0;
 		__iget(inode);
 		spin_unlock(&inode->i_lock);
 		spin_unlock(lru_lock);
 		if (remove_inode_buffers(inode)) {
-			unsigned long reap;
 			reap = invalidate_mapping_pages(&inode->i_data, 0, -1);
-			if (current_is_kswapd())
-				__count_vm_events(KSWAPD_INODESTEAL, reap);
-			else
-				__count_vm_events(PGINODESTEAL, reap);
 			if (current->reclaim_state)
 				current->reclaim_state->reclaimed_slab += reap;
 		}
 		iput(inode);
 		spin_lock(lru_lock);
+		if (current_is_kswapd())
+			__count_vm_events(KSWAPD_INODESTEAL, reap);
+		else
+			__count_vm_events(PGINODESTEAL, reap);
 		return LRU_RETRY;
 	}

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