vfs: fix lock inversion in drop_pagecache_sb()

eccb95ce · Jan Kara <[email protected]> · 2008-04-29 00:59:37 -07:00

Fix longstanding lock inversion in drop_pagecache_sb by dropping inode_lock
before calling __invalidate_mapping_pages().  We just have to make sure inode
won't go away from under us by keeping reference to it and putting the
reference only after we have safely resumed the scan of the inode list.  A bit
tricky but not too bad...

Signed-off-by: Jan Kara <[email protected]>
Cc: Fengguang Wu <[email protected]>
Cc: David Chinner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: eccb95cee4f0d56faa46ef22fb94dd4a3578d3eb
Parents: a8522509

Changes

1 files changed · +7 −1

File	Status	Add	Del	Content
fs/drop_caches.c	modified	+7	−1	View file

fs/drop_caches.c

View file

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index e2c6b65..50f9087 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -14,15 +14,21 @@ int sysctl_drop_caches;
 
 static void drop_pagecache_sb(struct super_block *sb)
 {
-	struct inode *inode;
+	struct inode *inode, *toput_inode = NULL;
 
 	spin_lock(&inode_lock);
 	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
 		if (inode->i_state & (I_FREEING|I_WILL_FREE))
 			continue;
+		__iget(inode);
+		spin_unlock(&inode_lock);
 		__invalidate_mapping_pages(inode->i_mapping, 0, -1, true);
+		iput(toput_inode);
+		toput_inode = inode;
+		spin_lock(&inode_lock);
 	}
 	spin_unlock(&inode_lock);
+	iput(toput_inode);
 }
 
 static void drop_pagecache(void)