fasync: re-organize fasync entry insertion to allow it under a spinlock

[pandora-kernel.git] / fs / fcntl.c

diff --git a/fs/fcntl.c b/fs/fcntl.c
index f8cc34f..dcdbc6f 100644 (file)
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -640,7 +640,7 @@ static void fasync_free_rcu(struct rcu_head *head)
  * match the state "is the filp on a fasync list".
  *
  */
-static int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
+int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
 {
        struct fasync_struct *fa, **fp;
        int result = 0;
@@ -666,21 +666,28 @@ static int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
        return result;
 }
 
+struct fasync_struct *fasync_alloc(void)
+{
+       return kmem_cache_alloc(fasync_cache, GFP_KERNEL);
+}
+
 /*
- * Add a fasync entry. Return negative on error, positive if
- * added, and zero if did nothing but change an existing one.
- *
- * NOTE! It is very important that the FASYNC flag always
- * match the state "is the filp on a fasync list".
+ * NOTE! This can be used only for unused fasync entries:
+ * entries that actually got inserted on the fasync list
+ * need to be released by rcu - see fasync_remove_entry.
  */
-static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
+void fasync_free(struct fasync_struct *new)
 {
-       struct fasync_struct *new, *fa, **fp;
-       int result = 0;
+       kmem_cache_free(fasync_cache, new);
+}
 
-       new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
-       if (!new)
-               return -ENOMEM;
+/*
+ * Insert a new entry into the fasync list.  Return the pointer to the
+ * old one if we didn't use the new one.
+ */
+struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasync_struct **fapp, struct fasync_struct *new)
+{
+        struct fasync_struct *fa, **fp;
 
        spin_lock(&filp->f_lock);
        spin_lock(&fasync_lock);
@@ -691,8 +698,6 @@ static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fa
                spin_lock_irq(&fa->fa_lock);
                fa->fa_fd = fd;
                spin_unlock_irq(&fa->fa_lock);
-
-               kmem_cache_free(fasync_cache, new);
                goto out;
        }
 
@@ -702,13 +707,42 @@ static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fa
        new->fa_fd = fd;
        new->fa_next = *fapp;
        rcu_assign_pointer(*fapp, new);
-       result = 1;
        filp->f_flags |= FASYNC;
 
 out:
        spin_unlock(&fasync_lock);
        spin_unlock(&filp->f_lock);
-       return result;
+       return fa;
+}
+
+/*
+ * Add a fasync entry. Return negative on error, positive if
+ * added, and zero if did nothing but change an existing one.
+ *
+ * NOTE! It is very important that the FASYNC flag always
+ * match the state "is the filp on a fasync list".
+ */
+static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
+{
+       struct fasync_struct *new;
+
+       new = fasync_alloc();
+       if (!new)
+               return -ENOMEM;
+
+       /*
+        * fasync_insert_entry() returns the old (update) entry if
+        * it existed.
+        *
+        * So free the (unused) new entry and return 0 to let the
+        * caller know that we didn't add any new fasync entries.
+        */
+       if (fasync_insert_entry(fd, filp, fapp, new)) {
+               fasync_free(new);
+               return 0;
+       }
+
+       return 1;
 }
 
 /*