linux-kernel - [PATCH 2/2] ocfs2: Use MAY_CREATE in ocfs2

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Date:	Wed, 14 Oct 2009 02:57:41 -0700
From:	Joel Becker <joel.becker@...CLE.COM>
To:	ocfs2-devel@....oracle.com, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
	hch@...radead.org, torvalds@...ux-foundation.org
Subject: [PATCH 2/2] ocfs2: Use MAY_CREATE in ocfs2_permission()

ocfs2 has a problem with open(O_CREAT|O_EXCL).  Once you've created the
file, you can't restart the open(), because O_CREAT|O_EXCL will trigger
-EEXIST.

The problem is that ocfs2 is catching the signal ->permission(), called
by may_open().  This happens after ->create() has successfully created
the file.  ocfs2_permission() has to get a cluster lock, and this is
what can be interrupted by a signal.  Now, obviously we want to block
signals in the O_CREAT|O_EXCL case, but ocfs2_permission() has no way of
knowing it just got called from open_namei_create().

We key on the MAY_CREATE flag passed to permission to block signals.

Signed-off-by: Joel Becker <joel.becker@...cle.com>
---
 fs/ocfs2/file.c |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 89fc8ee..b8749fa 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -1141,9 +1141,18 @@ bail:
 int ocfs2_permission(struct inode *inode, int mask)
 {
 	int ret;
+	sigset_t oldset;
 
 	mlog_entry_void();
 
+	/*
+	 * If this inode was just created by open(O_CREAT|O_EXCL), we
+	 * can't allow signal restarting.  So we need to block signals
+	 * around the cluster locking.
+	 */
+	if (mask & MAY_CREATE)
+		ocfs2_block_signals(&oldset);
+
 	ret = ocfs2_inode_lock(inode, NULL, 0);
 	if (ret) {
 		if (ret != -ENOENT)
@@ -1154,7 +1163,11 @@ int ocfs2_permission(struct inode *inode, int mask)
 	ret = generic_permission(inode, mask, ocfs2_check_acl);
 
 	ocfs2_inode_unlock(inode, 0);
+
 out:
+	if (mask & MAY_CREATE)
+		ocfs2_unblock_signals(&oldset);
+
 	mlog_exit(ret);
 	return ret;
 }
-- 
1.6.3.3

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