---

yaml
---
r: 135860
b: refs/heads/master
c: 7639842
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: db1dd4d376134eba0e08af523b61cc566a4ea1cd
+refs/heads/master: 76398425bb06b07cc3a3b1ce169c67dc9d6874ed

trunk/Documentation/filesystems/Locking

@@ -437,8 +437,11 @@ grab BKL for cases when we close a file that had been opened r/w, but that
 can and should be done using the internal locking with smaller critical areas).
 Current worst offender is ext2_get_block()...
 
-->fasync() is a mess. This area needs a big cleanup and that will probably
-affect locking.
+->fasync() is called without BKL protection, and is responsible for
+maintaining the FASYNC bit in filp->f_flags.  Most instances call
+fasync_helper(), which does that maintenance, so it's not normally
+something one needs to worry about.  Return values > 0 will be mapped to
+zero in the VFS layer.
 
 ->readdir() and ->ioctl() on directories must be changed. Ideally we would
 move ->readdir() to inode_operations and use a separate method for directory

trunk/fs/fcntl.c

@@ -141,7 +141,7 @@ SYSCALL_DEFINE1(dup, unsigned int, fildes)
 	return ret;
 }
 
-#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT | O_NOATIME)
+#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME)
 
 static int setfl(int fd, struct file * filp, unsigned long arg)
 {
@@ -177,23 +177,19 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
 		return error;
 
 	/*
-	 * We still need a lock here for now to keep multiple FASYNC calls
-	 * from racing with each other.
+	 * ->fasync() is responsible for setting the FASYNC bit.
 	 */
-	lock_kernel();
-	if ((arg ^ filp->f_flags) & FASYNC) {
-		if (filp->f_op && filp->f_op->fasync) {
-			error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
-			if (error < 0)
-				goto out;
-		}
+	if (((arg ^ filp->f_flags) & FASYNC) && filp->f_op &&
+			filp->f_op->fasync) {
+		error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
+		if (error < 0)
+			goto out;
 	}
-
 	spin_lock(&filp->f_lock);
 	filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
 	spin_unlock(&filp->f_lock);
+
  out:
-	unlock_kernel();
 	return error;
 }
 
@@ -518,7 +514,7 @@ static DEFINE_RWLOCK(fasync_lock);
 static struct kmem_cache *fasync_cache __read_mostly;
 
 /*
- * fasync_helper() is used by some character device drivers (mainly mice)
+ * fasync_helper() is used by almost all character device drivers
  * to set up the fasync queue. It returns negative on error, 0 if it did
  * no changes and positive if it added/deleted the entry.
  */
@@ -557,6 +553,13 @@ int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fap
 		result = 1;
 	}
 out:
+	/* Fix up FASYNC bit while still holding fasync_lock */
+	spin_lock(&filp->f_lock);
+	if (on)
+		filp->f_flags |= FASYNC;
+	else
+		filp->f_flags &= ~FASYNC;
+	spin_unlock(&filp->f_lock);
 	write_unlock_irq(&fasync_lock);
 	return result;
 }

trunk/fs/ioctl.c

@@ -427,19 +427,11 @@ static int ioctl_fioasync(unsigned int fd, struct file *filp,
 	/* Did FASYNC state change ? */
 	if ((flag ^ filp->f_flags) & FASYNC) {
 		if (filp->f_op && filp->f_op->fasync)
+			/* fasync() adjusts filp->f_flags */
 			error = filp->f_op->fasync(fd, filp, on);
 		else
 			error = -ENOTTY;
 	}
-	if (error)
-		return error;
-
-	spin_lock(&filp->f_lock);
-	if (on)
-		filp->f_flags |= FASYNC;
-	else
-		filp->f_flags &= ~FASYNC;
-	spin_unlock(&filp->f_lock);
 	return error;
 }
 
@@ -507,10 +499,7 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
 		break;
 
 	case FIOASYNC:
-		/* BKL needed to avoid races tweaking f_flags */
-		lock_kernel();
 		error = ioctl_fioasync(fd, filp, argp);
-		unlock_kernel();
 		break;
 
 	case FIOQSIZE:

trunk/net/socket.c

@@ -1030,6 +1030,13 @@ static int sock_fasync(int fd, struct file *filp, int on)
 
 	lock_sock(sk);
 
+	spin_lock(&filp->f_lock);
+	if (on)
+		filp->f_flags |= FASYNC;
+	else
+		filp->f_flags &= ~FASYNC;
+	spin_unlock(&filp->f_lock);
+
 	prev = &(sock->fasync_list);
 
 	for (fa = *prev; fa != NULL; prev = &fa->fa_next, fa = *prev)