From: Nathan Zimmer <nzimmer@sgi.com>
Date: Wed, 20 Mar 2013 04:08:32 +0000 (+1100)
Subject: procfs-improve-scaling-in-proc-v5
X-Git-Tag: next-20130322~1^2~94
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=a20be10130a8792f1fb254a90cacf2d4476bc8e8;p=karo-tx-linux.git

procfs-improve-scaling-in-proc-v5

v5: Corrected some warnings from sparce including the supplied by Sasha.

Signed-off-by: Nathan Zimmer <nzimmer@sgi.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 6cccc4d7a106..f53660a471c2 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -284,7 +284,7 @@ static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned
 		return rv;
 	}
 	atomic_inc(&pde->pde_users);
-	compat_ioctl = pde->proc_fops->compat_ioctl;
+	compat_ioctl = fops->compat_ioctl;
 	rcu_read_unlock();
 
 	if (compat_ioctl)
@@ -309,7 +309,7 @@ static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
 		return rv;
 	}
 	atomic_inc(&pde->pde_users);
-	mmap = pde->proc_fops->mmap;
+	mmap = fops->mmap;
 	rcu_read_unlock();
 
 	if (mmap)
@@ -352,7 +352,7 @@ static int proc_reg_open(struct inode *inode, struct file *file)
 	atomic_inc(&pde->pde_users);
 	open = fops->open;
 	release = fops->release;
-	rcu_read_lock();
+	rcu_read_unlock();
 
 	if (open)
 		rv = open(inode, file);
@@ -400,6 +400,7 @@ static int proc_reg_release(struct inode *inode, struct file *file)
 	rcu_read_lock();
 	fops = rcu_dereference(pde->proc_fops);
 	if (!fops) {
+		rcu_read_unlock();
 		/*
 		 * Can't simply exit, __fput() will think that everything is OK,
 		 * and move on to freeing struct file. remove_proc_entry() will
@@ -464,6 +465,7 @@ static const struct file_operations proc_reg_file_ops_no_compat = {
 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
 {
 	struct inode *inode = iget_locked(sb, de->low_ino);
+	const struct file_operations *fops;
 
 	if (inode && (inode->i_state & I_NEW)) {
 		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
@@ -480,19 +482,22 @@ struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
 			set_nlink(inode, de->nlink);
 		if (de->proc_iops)
 			inode->i_op = de->proc_iops;
-		if (de->proc_fops) {
+		rcu_read_lock();
+		fops = rcu_dereference(de->proc_fops);
+		if (fops) {
 			if (S_ISREG(inode->i_mode)) {
 #ifdef CONFIG_COMPAT
-				if (!de->proc_fops->compat_ioctl)
+				if (!fops->compat_ioctl)
 					inode->i_fop =
 						&proc_reg_file_ops_no_compat;
 				else
 #endif
 					inode->i_fop = &proc_reg_file_ops;
 			} else {
-				inode->i_fop = de->proc_fops;
+				inode->i_fop = fops;
 			}
 		}
+		rcu_read_unlock();
 		unlock_new_inode(inode);
 	} else
 	       pde_put(de);