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-rw-r--r--fs/fcntl.c102
1 files changed, 66 insertions, 36 deletions
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 2cf93ec..97e01dc 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -618,60 +618,90 @@ static DEFINE_RWLOCK(fasync_lock);
static struct kmem_cache *fasync_cache __read_mostly;
/*
- * 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.
+ * Remove a fasync entry. If successfully removed, return
+ * positive and clear the FASYNC flag. If no entry exists,
+ * do nothing and return 0.
+ *
+ * NOTE! It is very important that the FASYNC flag always
+ * match the state "is the filp on a fasync list".
+ *
+ * We always take the 'filp->f_lock', in since fasync_lock
+ * needs to be irq-safe.
*/
-int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
+static int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
{
struct fasync_struct *fa, **fp;
- struct fasync_struct *new = NULL;
int result = 0;
- if (on) {
- new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
- if (!new)
- return -ENOMEM;
+ spin_lock(&filp->f_lock);
+ write_lock_irq(&fasync_lock);
+ for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
+ if (fa->fa_file != filp)
+ continue;
+ *fp = fa->fa_next;
+ kmem_cache_free(fasync_cache, fa);
+ filp->f_flags &= ~FASYNC;
+ result = 1;
+ break;
}
+ write_unlock_irq(&fasync_lock);
+ spin_unlock(&filp->f_lock);
+ return result;
+}
+
+/*
+ * 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, *fa, **fp;
+ int result = 0;
+
+ new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
+ if (!new)
+ return -ENOMEM;
- /*
- * We need to take f_lock first since it's not an IRQ-safe
- * lock.
- */
spin_lock(&filp->f_lock);
write_lock_irq(&fasync_lock);
for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
- if (fa->fa_file == filp) {
- if(on) {
- fa->fa_fd = fd;
- kmem_cache_free(fasync_cache, new);
- } else {
- *fp = fa->fa_next;
- kmem_cache_free(fasync_cache, fa);
- result = 1;
- }
- goto out;
- }
+ if (fa->fa_file != filp)
+ continue;
+ fa->fa_fd = fd;
+ kmem_cache_free(fasync_cache, new);
+ goto out;
}
- if (on) {
- new->magic = FASYNC_MAGIC;
- new->fa_file = filp;
- new->fa_fd = fd;
- new->fa_next = *fapp;
- *fapp = new;
- result = 1;
- }
+ new->magic = FASYNC_MAGIC;
+ new->fa_file = filp;
+ new->fa_fd = fd;
+ new->fa_next = *fapp;
+ *fapp = new;
+ result = 1;
+ filp->f_flags |= FASYNC;
+
out:
- if (on)
- filp->f_flags |= FASYNC;
- else
- filp->f_flags &= ~FASYNC;
write_unlock_irq(&fasync_lock);
spin_unlock(&filp->f_lock);
return result;
}
+/*
+ * fasync_helper() is used by almost all character device drivers
+ * to set up the fasync queue, and for regular files by the file
+ * lease code. It returns negative on error, 0 if it did no changes
+ * and positive if it added/deleted the entry.
+ */
+int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
+{
+ if (!on)
+ return fasync_remove_entry(filp, fapp);
+ return fasync_add_entry(fd, filp, fapp);
+}
+
EXPORT_SYMBOL(fasync_helper);
void __kill_fasync(struct fasync_struct *fa, int sig, int band)
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