1 files changed, 20 insertions, 13 deletions

diff --git a/fs/fcntl.c b/fs/fcntl.c
index bd215cc791da..d865ca66ccba 100644
--- a/fs/fcntl.c
+++ b/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)
 {
@@ -177,21 +177,21 @@ 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;
+                if (error > 0)
+                        error = 0;
         }
-
+        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;
 }
 
@@ -516,7 +516,7 @@ 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.
  */
@@ -555,6 +555,13 @@ 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;
 }