linux-kernel - [PATCH] proc: avoid extra pde_put() in proc_fill

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Date:	Tue, 22 Jan 2013 21:03:26 +0400
From:	Maxim Patlasov <mpatlasov@...allels.com>
To:	ebiederm@...ssion.com
Cc:	linux-kernel@...r.kernel.org, dhowells@...hat.com,
	viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
	fengguang.wu@...el.com, devel@...nvz.org
Subject: [PATCH] proc: avoid extra pde_put() in proc_fill_super()

If proc_get_inode() succeeded, but d_make_root() failed, pde_put() for
proc_root will be called twice: the first time due to iput() called from
d_make_root() and the second time directly in the end of proc_fill_super().

Signed-off-by: Maxim Patlasov <mpatlasov@...allels.com>
---
 fs/proc/inode.c |   21 +++++++++++++++------
 1 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 439ae688..c7f8b24 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -486,6 +486,8 @@ struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
 
 int proc_fill_super(struct super_block *s)
 {
+	struct inode *root_inode;
+
 	s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
 	s->s_blocksize = 1024;
 	s->s_blocksize_bits = 10;
@@ -494,11 +496,18 @@ int proc_fill_super(struct super_block *s)
 	s->s_time_gran = 1;
 	
 	pde_get(&proc_root);
-	s->s_root = d_make_root(proc_get_inode(s, &proc_root));
-	if (s->s_root)
-		return 0;
+	root_inode = proc_get_inode(s, &proc_root);
+	if (!root_inode) {
+		printk(KERN_ERR "proc_fill_super: get root inode failed\n");
+		pde_put(&proc_root);
+		return -ENOMEM;
+	}
 
-	printk("proc_read_super: get root inode failed\n");
-	pde_put(&proc_root);
-	return -ENOMEM;
+	s->s_root = d_make_root(root_inode);
+	if (!s->s_root) {
+		printk(KERN_ERR "proc_fill_super: allocate dentry failed\n");
+		return -ENOMEM;
+	}
+
+	return 0;
 }

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