poll: avoid extra wakeups in select/poll

[sfrench/cifs-2.6.git] / fs / select.c

diff --git a/fs/select.c b/fs/select.c
index 0fe0e1469df31f386845dd443fdfe89a01543d92..d870237e42c74f018b2824304345aa44a90b8607 100644 (file)
--- a/fs/select.c
+++ b/fs/select.c
@@ -168,7 +168,7 @@ static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p)
        return table->entry++;
 }
 
-static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
+static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
 {
        struct poll_wqueues *pwq = wait->private;
        DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
@@ -194,6 +194,16 @@ static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
        return default_wake_function(&dummy_wait, mode, sync, key);
 }
 
+static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
+{
+       struct poll_table_entry *entry;
+
+       entry = container_of(wait, struct poll_table_entry, wait);
+       if (key && !((unsigned long)key & entry->key))
+               return 0;
+       return __pollwake(wait, mode, sync, key);
+}
+
 /* Add a new entry */
 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
                                poll_table *p)
@@ -205,6 +215,7 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
        get_file(filp);
        entry->filp = filp;
        entry->wait_address = wait_address;
+       entry->key = p->key;
        init_waitqueue_func_entry(&entry->wait, pollwake);
        entry->wait.private = pwq;
        add_wait_queue(wait_address, &entry->wait);
@@ -362,6 +373,18 @@ get_max:
 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 #define POLLEX_SET (POLLPRI)
 
+static inline void wait_key_set(poll_table *wait, unsigned long in,
+                               unsigned long out, unsigned long bit)
+{
+       if (wait) {
+               wait->key = POLLEX_SET;
+               if (in & bit)
+                       wait->key |= POLLIN_SET;
+               if (out & bit)
+                       wait->key |= POLLOUT_SET;
+       }
+}
+
 int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 {
        ktime_t expire, *to = NULL;
@@ -418,20 +441,25 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
                                if (file) {
                                        f_op = file->f_op;
                                        mask = DEFAULT_POLLMASK;
-                                       if (f_op && f_op->poll)
-                                               mask = (*f_op->poll)(file, retval ? NULL : wait);
+                                       if (f_op && f_op->poll) {
+                                               wait_key_set(wait, in, out, bit);
+                                               mask = (*f_op->poll)(file, wait);
+                                       }
                                        fput_light(file, fput_needed);
                                        if ((mask & POLLIN_SET) && (in & bit)) {
                                                res_in |= bit;
                                                retval++;
+                                               wait = NULL;
                                        }
                                        if ((mask & POLLOUT_SET) && (out & bit)) {
                                                res_out |= bit;
                                                retval++;
+                                               wait = NULL;
                                        }
                                        if ((mask & POLLEX_SET) && (ex & bit)) {
                                                res_ex |= bit;
                                                retval++;
+                                               wait = NULL;
                                        }
                                }
                        }
@@ -685,8 +713,12 @@ static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
                mask = POLLNVAL;
                if (file != NULL) {
                        mask = DEFAULT_POLLMASK;
-                       if (file->f_op && file->f_op->poll)
+                       if (file->f_op && file->f_op->poll) {
+                               if (pwait)
+                                       pwait->key = pollfd->events |
+                                                       POLLERR | POLLHUP;
                                mask = file->f_op->poll(file, pwait);
+                       }
                        /* Mask out unneeded events. */
                        mask &= pollfd->events | POLLERR | POLLHUP;
                        fput_light(file, fput_needed);