@@ -440,6 +440,8 @@ prototypes:
ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
int (*iterate) (struct file *, struct dir_context *);
__poll_t (*poll) (struct file *, struct poll_table_struct *);
+ struct wait_queue_head * (*get_poll_head)(struct file *, __poll_t);
+ __poll_t (*poll_mask) (struct file *, __poll_t);
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);
@@ -470,7 +472,7 @@ prototypes:
};
locking rules:
- All may block.
+ All except for ->poll_mask may block.
->llseek() locking has moved from llseek to the individual llseek
implementations. If your fs is not using generic_file_llseek, you
@@ -498,6 +500,9 @@ in sys_read() and friends.
the lease within the individual filesystem to record the result of the
operation
+->poll_mask can be called with or without the waitqueue lock for the waitqueue
+returned from ->get_poll_head.
+
--------------------------- dquot_operations -------------------------------
prototypes:
int (*write_dquot) (struct dquot *);
@@ -857,6 +857,8 @@ struct file_operations {
ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
int (*iterate) (struct file *, struct dir_context *);
__poll_t (*poll) (struct file *, struct poll_table_struct *);
+ struct wait_queue_head * (*get_poll_head)(struct file *, __poll_t);
+ __poll_t (*poll_mask) (struct file *, __poll_t);
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);
@@ -901,6 +903,15 @@ otherwise noted.
activity on this file and (optionally) go to sleep until there
is activity. Called by the select(2) and poll(2) system calls
+ get_poll_head: Returns the struct wait_queue_head that poll, select,
+ epoll or aio poll should wait on in case this instance only has single
+ waitqueue. Can return NULL to indicate polling is not supported.
+
+ poll_mask: return the mask of POLL* values describing the file descriptor
+ state. Called before going to sleep on the waitqueue returned by
+ get_poll_head, and after it has been woken. If ->get_poll_head and
+ ->poll_mask are implemented ->poll does not need to be implement.
+
unlocked_ioctl: called by the ioctl(2) system call.
compat_ioctl: called by the ioctl(2) system call when 32 bit system calls
@@ -34,6 +34,35 @@
#include <linux/uaccess.h>
+__poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
+{
+ unsigned int events = poll_requested_events(pt), mask;
+ struct wait_queue_head *head;
+
+ if (unlikely(!file_can_poll(file)))
+ return DEFAULT_POLLMASK;
+
+ if (file->f_op->poll)
+ return file->f_op->poll(file, pt);
+
+ /*
+ * Only get the poll head and do the first mask check if we are actually
+ * going to sleep on this file:
+ */
+ if (pt && pt->_qproc) {
+ head = vfs_get_poll_head(file, events);
+ if (!head)
+ return DEFAULT_POLLMASK;
+ mask = file->f_op->poll_mask(file, events);
+ if (mask)
+ return mask;
+
+ pt->_qproc(file, head, pt);
+ }
+
+ return file->f_op->poll_mask(file, events);
+}
+EXPORT_SYMBOL_GPL(vfs_poll);
/*
* Estimate expected accuracy in ns from a timeval.
@@ -1699,6 +1699,8 @@ struct file_operations {
int (*iterate) (struct file *, struct dir_context *);
int (*iterate_shared) (struct file *, struct dir_context *);
__poll_t (*poll) (struct file *, struct poll_table_struct *);
+ struct wait_queue_head * (*get_poll_head)(struct file *, __poll_t);
+ __poll_t (*poll_mask) (struct file *, __poll_t);
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);
@@ -75,16 +75,27 @@ static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
static inline bool file_can_poll(struct file *file)
{
- return file->f_op->poll;
+ return file->f_op->poll ||
+ (file->f_op->get_poll_head && file->f_op->poll_mask);
}
-static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
+static inline struct wait_queue_head *vfs_get_poll_head(struct file *file,
+ __poll_t events)
{
- if (unlikely(!file->f_op->poll))
+ if (unlikely(!file->f_op->get_poll_head || !file->f_op->poll_mask))
+ return NULL;
+ return file->f_op->get_poll_head(file, events);
+}
+
+static inline __poll_t vfs_poll_mask(struct file *file, __poll_t events)
+{
+ if (unlikely(!file->f_op->poll_mask))
return DEFAULT_POLLMASK;
- return file->f_op->poll(file, pt);
+ return file->f_op->poll_mask(file, events) & events;
}
+__poll_t vfs_poll(struct file *file, struct poll_table_struct *pt);
+
struct poll_table_entry {
struct file *filp;
__poll_t key;
->get_poll_head returns the waitqueue that the poll operation is going to sleep on. Note that this means we can only use a single waitqueue for the poll, unlike some current drivers that use two waitqueues for different events. But now that we have keyed wakeups and heavily use those for poll there aren't that many good reason left to keep the multiple waitqueues, and if there are any ->poll is still around, the driver just won't support aio poll. ->poll_mask is called before going to sleep to check for already pending events, and after the wakeup to return the actual mask of events reported by poll. It can be called with the waitqueue lock held to gurantee race free checking for events and to be called from the waitqueue wake callback, but the legacy callers don't hold it yet. Signed-off-by: Christoph Hellwig <hch@lst.de> --- Documentation/filesystems/Locking | 7 ++++++- Documentation/filesystems/vfs.txt | 11 +++++++++++ fs/select.c | 29 +++++++++++++++++++++++++++++ include/linux/fs.h | 2 ++ include/linux/poll.h | 19 +++++++++++++++---- 5 files changed, 63 insertions(+), 5 deletions(-)