linux-kernel - [PATCH 3/3] reiserfs: Relax lock on xattr removing

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Date:	Tue,  5 Jan 2010 08:02:38 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Christian Kujau <lists@...dbynature.de>,
	Alexander Beregalov <a.beregalov@...il.com>,
	Chris Mason <chris.mason@...cle.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: [PATCH 3/3] reiserfs: Relax lock on xattr removing

When we remove an xattr, we call lookup_and_delete_xattr()
that takes some private xattr inodes mutexes. But we hold
the reiserfs lock at this time, which leads to dependency
inversions.

We can safely call lookup_and_delete_xattr() without the
reiserfs lock, where xattr inodes lookups only need the
xattr inodes mutexes.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Christian Kujau <lists@...dbynature.de>
Cc: Alexander Beregalov <a.beregalov@...il.com>
Cc: Chris Mason <chris.mason@...cle.com>
Cc: Ingo Molnar <mingo@...e.hu>
---
 fs/reiserfs/xattr.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c
index 75d3706..4899d78 100644
--- a/fs/reiserfs/xattr.c
+++ b/fs/reiserfs/xattr.c
@@ -451,7 +451,9 @@ static int lookup_and_delete_xattr(struct inode *inode, const char *name)
 	}
 
 	if (dentry->d_inode) {
+		reiserfs_write_lock(inode->i_sb);
 		err = xattr_unlink(xadir->d_inode, dentry);
+		reiserfs_write_unlock(inode->i_sb);
 		update_ctime(inode);
 	}
 
@@ -485,10 +487,14 @@ reiserfs_xattr_set_handle(struct reiserfs_transaction_handle *th,
 	if (get_inode_sd_version(inode) == STAT_DATA_V1)
 		return -EOPNOTSUPP;
 
-	if (!buffer)
-		return lookup_and_delete_xattr(inode, name);
-
 	reiserfs_write_unlock(inode->i_sb);
+
+	if (!buffer) {
+		err = lookup_and_delete_xattr(inode, name);
+		reiserfs_write_lock(inode->i_sb);
+		return err;
+	}
+
 	dentry = xattr_lookup(inode, name, flags);
 	if (IS_ERR(dentry)) {
 		reiserfs_write_lock(inode->i_sb);
-- 
1.6.2.3

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