linux-kernel - [PATCH] vfs: clean up real

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <1253808660-20473-2-git-send-email-sage@newdream.net>
Date:	Thu, 24 Sep 2009 09:11:00 -0700
From:	Sage Weil <sage@...dream.net>
To:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	viro@...IV.linux.org.uk, hch@...radead.org, adilger@....com,
	yehuda@...dream.net, garlick@...l.gov, raven@...maw.net,
	Sage Weil <sage@...dream.net>
Subject: [PATCH] vfs: clean up real_lookup

Get rid of the goto by flipping the if (!result) over.  Make the
comments a bit more descriptive.  Fix a few kernel style problems.
No functional changes.

CC: Ian Kent <raven@...maw.net>
CC: Christoph Hellwig <hch@...radead.org>
Signed-off-by: Yehuda Sadeh <yehuda@...dream.net>
Signed-off-by: Sage Weil <sage@...dream.net>
---
 fs/namei.c |   65 +++++++++++++++++++++++++++++++----------------------------
 1 files changed, 34 insertions(+), 31 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index f74ddb3..6770dde 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -469,19 +469,20 @@ ok:
  * This is called when everything else fails, and we actually have
  * to go to the low-level filesystem to find out what we should do..
  *
- * We get the directory semaphore, and after getting that we also
+ * We get the directory mutex, and after getting that we also
  * make sure that nobody added the entry to the dcache in the meantime..
  * SMP-safe
  */
-static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
+static struct dentry *real_lookup(struct dentry *parent, struct qstr *name,
+				  struct nameidata *nd)
 {
-	struct dentry * result;
+	struct dentry *result, *dentry;
 	struct inode *dir = parent->d_inode;
 
 	mutex_lock(&dir->i_mutex);
 	/*
 	 * First re-do the cached lookup just in case it was created
-	 * while we waited for the directory semaphore..
+	 * while we waited for the directory mutex.
 	 *
 	 * FIXME! This could use version numbering or similar to
 	 * avoid unnecessary cache lookups.
@@ -494,38 +495,40 @@ static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, s
 	 * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
 	 */
 	result = d_lookup(parent, name);
-	if (!result) {
-		struct dentry *dentry;
-
-do_the_lookup:
-		/* Don't create child dentry for a dead directory. */
-		result = ERR_PTR(-ENOENT);
-		if (IS_DEADDIR(dir))
-			goto out_unlock;
-
-		dentry = d_alloc(parent, name);
-		result = ERR_PTR(-ENOMEM);
-		if (dentry) {
-			result = dir->i_op->lookup(dir, dentry, nd);
+	if (result) {
+		/*
+		 * The cache was re-populated while we waited on the
+		 * mutex.  We need to revalidate, this time while
+		 * holding i_mutex (to avoid another race).
+		 */
+		if (result->d_op && result->d_op->d_revalidate) {
+			result = do_revalidate(result, nd);
 			if (result)
-				dput(dentry);
-			else
-				result = dentry;
+				goto out_unlock;
+			/*
+			 * The dentry was left behind invalid.  Just
+			 * do the lookup.
+			 */
+		} else {
+			goto out_unlock;
 		}
-out_unlock:
-		mutex_unlock(&dir->i_mutex);
-		return result;
 	}
 
-	/*
-	 * Uhhuh! Nasty case: the cache was re-populated while
-	 * we waited on the semaphore. Need to revalidate.
-	 */
-	if (result->d_op && result->d_op->d_revalidate) {
-		result = do_revalidate(result, nd);
-		if (!result)
-			goto do_the_lookup;
+	/* Don't create child dentry for a dead directory. */
+	result = ERR_PTR(-ENOENT);
+	if (IS_DEADDIR(dir))
+		goto out_unlock;
+
+	dentry = d_alloc(parent, name);
+	result = ERR_PTR(-ENOMEM);
+	if (dentry) {
+		result = dir->i_op->lookup(dir, dentry, nd);
+		if (result)
+			dput(dentry);
+		else
+			result = dentry;
 	}
+out_unlock:
 	mutex_unlock(&dir->i_mutex);
 	return result;
 }
-- 
1.5.6.5

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/