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From: Christoph Hellwig <hch@lst.de>
To: viro@ZenIV.linux.org.uk, akpm@linux-foundation.org
Cc: linux-fsdevel@vger.kernel.org
Subject: [PATCH, RFC] prune back iprune_sem
Date: Tue, 2 Nov 2010 19:45:36 +0100	[thread overview]
Message-ID: <20101102184536.GA22941@lst.de> (raw)

iprune_sem is continously giving us lockdep warnings because we do take it in
read mode in the reclaim path, but we're also doing non-NOFS allocations under
it taken in write mode.

Taking a bit deeper look at it I think it's fixable quite trivially:

 - for invalidate_inodes we do not need iprune_sem at all.  We have an active
   reference on the superblock, so the filesystem is not going away until it
   has finished.
 - for evict_inodes we do need it, to make sure prune_icache has done it's
   work before we tear down the superblock.  But there is no reason to
   hold it over the actual reclaim operation - it's enough to cycle through
   it after the actual reclaim to make sure we wait for any pending
   prune_icache to complete.

Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/inode.c b/fs/inode.c
index ae2727a..cfa7722 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -492,8 +492,6 @@ void evict_inodes(struct super_block *sb)
 	struct inode *inode, *next;
 	LIST_HEAD(dispose);
 
-	down_write(&iprune_sem);
-
 	spin_lock(&inode_lock);
 	list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
 		if (atomic_read(&inode->i_count))
@@ -518,6 +516,13 @@ void evict_inodes(struct super_block *sb)
 	spin_unlock(&inode_lock);
 
 	dispose_list(&dispose);
+
+	/*
+	 * Cycle through iprune_sem to make sure any inode that prune_icache
+	 * moved off the list before we took the lock has been fully torn
+	 * down.
+	 */
+	down_write(&iprune_sem);
 	up_write(&iprune_sem);
 }
 
@@ -534,8 +539,6 @@ int invalidate_inodes(struct super_block *sb)
 	struct inode *inode, *next;
 	LIST_HEAD(dispose);
 
-	down_write(&iprune_sem);
-
 	spin_lock(&inode_lock);
 	list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
 		if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE))
@@ -559,7 +562,6 @@ int invalidate_inodes(struct super_block *sb)
 	spin_unlock(&inode_lock);
 
 	dispose_list(&dispose);
-	up_write(&iprune_sem);
 
 	return busy;
 }

             reply	other threads:[~2010-11-02 18:46 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-11-02 18:45 Christoph Hellwig [this message]
2010-11-04 23:32 ` [PATCH, RFC] prune back iprune_sem Jan Kara
2011-02-15 10:29 ` Christoph Hellwig
2011-02-15 14:49   ` Jan Kara
2011-02-15 14:53     ` Christoph Hellwig

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