[Devel] [PATCH -mm] proc: introduce and use pde_users_dec()

[Alexey Dobriyan]

Signed-off-by: Alexey Dobriyan <adobriyan at sw.ru>
---

 Please, fold into fix-rmmod-read-write-races-in-proc-entries.patch
 This should address last review comment.

 fs/proc/inode.c |  135 ++++++++++++++++++++++----------------------------------
 1 file changed, 54 insertions(+), 81 deletions(-)

--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -141,6 +141,15 @@ static const struct super_operations pro
 	.remount_fs	= proc_remount,
 };
 
+static void pde_users_dec(struct proc_dir_entry *pde)
+{
+	spin_lock(&pde->pde_unload_lock);
+	pde->pde_users--;
+	if (pde->pde_unload_completion && pde->pde_users == 0)
+		complete(pde->pde_unload_completion);
+	spin_unlock(&pde->pde_unload_lock);
+}
+
 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
 {
 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
@@ -152,8 +161,10 @@ static loff_t proc_reg_llseek(struct fil
 	 * remove_proc_entry() is going to delete PDE (as part of module
 	 * cleanup sequence). No new callers into module allowed.
 	 */
-	if (!pde->proc_fops)
-		goto out_unlock;
+	if (!pde->proc_fops) {
+		spin_unlock(&pde->pde_unload_lock);
+		return rv;
+	}
 	/*
 	 * Bump refcount so that remove_proc_entry will wail for ->llseek to
 	 * complete.
@@ -170,13 +181,7 @@ static loff_t proc_reg_llseek(struct fil
 		llseek = default_llseek;
 	rv = llseek(file, offset, whence);
 
-	spin_lock(&pde->pde_unload_lock);
-	pde->pde_users--;
-	if (pde->pde_unload_completion && pde->pde_users == 0)
-		complete(pde->pde_unload_completion);
-out_unlock:
-	spin_unlock(&pde->pde_unload_lock);
-
+	pde_users_dec(pde);
 	return rv;
 }
 
@@ -187,8 +192,10 @@ static ssize_t proc_reg_read(struct file
 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
 
 	spin_lock(&pde->pde_unload_lock);
-	if (!pde->proc_fops)
-		goto out_unlock;
+	if (!pde->proc_fops) {
+		spin_unlock(&pde->pde_unload_lock);
+		return rv;
+	}
 	pde->pde_users++;
 	read = pde->proc_fops->read;
 	spin_unlock(&pde->pde_unload_lock);
@@ -196,13 +203,7 @@ static ssize_t proc_reg_read(struct file
 	if (read)
 		rv = read(file, buf, count, ppos);
 
-	spin_lock(&pde->pde_unload_lock);
-	pde->pde_users--;
-	if (pde->pde_unload_completion && pde->pde_users == 0)
-		complete(pde->pde_unload_completion);
-out_unlock:
-	spin_unlock(&pde->pde_unload_lock);
-
+	pde_users_dec(pde);
 	return rv;
 }
 
@@ -213,8 +214,10 @@ static ssize_t proc_reg_write(struct fil
 	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
 
 	spin_lock(&pde->pde_unload_lock);
-	if (!pde->proc_fops)
-		goto out_unlock;
+	if (!pde->proc_fops) {
+		spin_unlock(&pde->pde_unload_lock);
+		return rv;
+	}
 	pde->pde_users++;
 	write = pde->proc_fops->write;
 	spin_unlock(&pde->pde_unload_lock);
@@ -222,13 +225,7 @@ static ssize_t proc_reg_write(struct fil
 	if (write)
 		rv = write(file, buf, count, ppos);
 
-	spin_lock(&pde->pde_unload_lock);
-	pde->pde_users--;
-	if (pde->pde_unload_completion && pde->pde_users == 0)
-		complete(pde->pde_unload_completion);
-out_unlock:
-	spin_unlock(&pde->pde_unload_lock);
-
+	pde_users_dec(pde);
 	return rv;
 }
 
@@ -239,8 +236,10 @@ static unsigned int proc_reg_poll(struct
 	unsigned int (*poll)(struct file *, struct poll_table_struct *);
 
 	spin_lock(&pde->pde_unload_lock);
-	if (!pde->proc_fops)
-		goto out_unlock;
+	if (!pde->proc_fops) {
+		spin_unlock(&pde->pde_unload_lock);
+		return rv;
+	}
 	pde->pde_users++;
 	poll = pde->proc_fops->poll;
 	spin_unlock(&pde->pde_unload_lock);
@@ -248,13 +247,7 @@ static unsigned int proc_reg_poll(struct
 	if (poll)
 		rv = poll(file, pts);
 
-	spin_lock(&pde->pde_unload_lock);
-	pde->pde_users--;
-	if (pde->pde_unload_completion && pde->pde_users == 0)
-		complete(pde->pde_unload_completion);
-out_unlock:
-	spin_unlock(&pde->pde_unload_lock);
-
+	pde_users_dec(pde);
 	return rv;
 }
 
@@ -266,8 +259,10 @@ static long proc_reg_unlocked_ioctl(stru
 	int (*ioctl)(struct inode *, struct file *, unsigned int, unsigned long);
 
 	spin_lock(&pde->pde_unload_lock);
-	if (!pde->proc_fops)
-		goto out_unlock;
+	if (!pde->proc_fops) {
+		spin_unlock(&pde->pde_unload_lock);
+		return rv;
+	}
 	pde->pde_users++;
 	unlocked_ioctl = pde->proc_fops->unlocked_ioctl;
 	ioctl = pde->proc_fops->ioctl;
@@ -283,13 +278,7 @@ static long proc_reg_unlocked_ioctl(stru
 		unlock_kernel();
 	}
 
-	spin_lock(&pde->pde_unload_lock);
-	pde->pde_users--;
-	if (pde->pde_unload_completion && pde->pde_users == 0)
-		complete(pde->pde_unload_completion);
-out_unlock:
-	spin_unlock(&pde->pde_unload_lock);
-
+	pde_users_dec(pde);
 	return rv;
 }
 
@@ -301,8 +290,10 @@ static long proc_reg_compat_ioctl(struct
 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
 
 	spin_lock(&pde->pde_unload_lock);
-	if (!pde->proc_fops)
-		goto out_unlock;
+	if (!pde->proc_fops) {
+		spin_unlock(&pde->pde_unload_lock);
+		return rv;
+	}
 	pde->pde_users++;
 	compat_ioctl = pde->proc_fops->compat_ioctl;
 	spin_unlock(&pde->pde_unload_lock);
@@ -310,13 +301,7 @@ static long proc_reg_compat_ioctl(struct
 	if (compat_ioctl)
 		rv = compat_ioctl(file, cmd, arg);
 
-	spin_lock(&pde->pde_unload_lock);
-	pde->pde_users--;
-	if (pde->pde_unload_completion && pde->pde_users == 0)
-		complete(pde->pde_unload_completion);
-out_unlock:
-	spin_unlock(&pde->pde_unload_lock);
-
+	pde_users_dec(pde);
 	return rv;
 }
 #endif
@@ -328,8 +313,10 @@ static int proc_reg_mmap(struct file *fi
 	int (*mmap)(struct file *, struct vm_area_struct *);
 
 	spin_lock(&pde->pde_unload_lock);
-	if (!pde->proc_fops)
-		goto out_unlock;
+	if (!pde->proc_fops) {
+		spin_unlock(&pde->pde_unload_lock);
+		return rv;
+	}
 	pde->pde_users++;
 	mmap = pde->proc_fops->mmap;
 	spin_unlock(&pde->pde_unload_lock);
@@ -337,13 +324,7 @@ static int proc_reg_mmap(struct file *fi
 	if (mmap)
 		rv = mmap(file, vma);
 
-	spin_lock(&pde->pde_unload_lock);
-	pde->pde_users--;
-	if (pde->pde_unload_completion && pde->pde_users == 0)
-		complete(pde->pde_unload_completion);
-out_unlock:
-	spin_unlock(&pde->pde_unload_lock);
-
+	pde_users_dec(pde);
 	return rv;
 }
 
@@ -354,8 +335,10 @@ static int proc_reg_open(struct inode *i
 	int (*open)(struct inode *, struct file *);
 
 	spin_lock(&pde->pde_unload_lock);
-	if (!pde->proc_fops)
-		goto out_unlock;
+	if (!pde->proc_fops) {
+		spin_unlock(&pde->pde_unload_lock);
+		return rv;
+	}
 	pde->pde_users++;
 	open = pde->proc_fops->open;
 	spin_unlock(&pde->pde_unload_lock);
@@ -363,13 +346,7 @@ static int proc_reg_open(struct inode *i
 	if (open)
 		rv = open(inode, file);
 
-	spin_lock(&pde->pde_unload_lock);
-	pde->pde_users--;
-	if (pde->pde_unload_completion && pde->pde_users == 0)
-		complete(pde->pde_unload_completion);
-out_unlock:
-	spin_unlock(&pde->pde_unload_lock);
-
+	pde_users_dec(pde);
 	return rv;
 }
 
@@ -380,8 +357,10 @@ static int proc_reg_release(struct inode
 	int (*release)(struct inode *, struct file *);
 
 	spin_lock(&pde->pde_unload_lock);
-	if (!pde->proc_fops)
-		goto out_unlock;
+	if (!pde->proc_fops) {
+		spin_unlock(&pde->pde_unload_lock);
+		return rv;
+	}
 	pde->pde_users++;
 	release = pde->proc_fops->release;
 	spin_unlock(&pde->pde_unload_lock);
@@ -389,13 +368,7 @@ static int proc_reg_release(struct inode
 	if (release)
 		rv = release(inode, file);
 
-	spin_lock(&pde->pde_unload_lock);
-	pde->pde_users--;
-	if (pde->pde_unload_completion && pde->pde_users == 0)
-		complete(pde->pde_unload_completion);
-out_unlock:
-	spin_unlock(&pde->pde_unload_lock);
-
+	pde_users_dec(pde);
 	return rv;
 }