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authorChristoph Hellwig <hch@lst.de>2018-01-09 17:29:24 +0300
committerChristoph Hellwig <hch@lst.de>2018-05-26 10:16:44 +0300
commit3deb642f0de4c14f37437dd247f9c77839f043f8 (patch)
tree56f6867ac66e6fa881295a6c9af52349471374e4 /Documentation/filesystems/vfs.txt
parent9965ed174e7d38896e5d2582159d8ef31ecd4cb5 (diff)
downloadlinux-3deb642f0de4c14f37437dd247f9c77839f043f8.tar.xz
fs: introduce new ->get_poll_head and ->poll_mask methods
->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. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Diffstat (limited to 'Documentation/filesystems/vfs.txt')
-rw-r--r--Documentation/filesystems/vfs.txt13
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index f608180ad59d..829a7b7857a4 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -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 +903,17 @@ 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 callers can
+ wait on. Callers need to check the returned events using ->poll_mask
+ once woken. Can return NULL to indicate polling is not supported,
+ or any error code using the ERR_PTR convention to indicate that a
+ grave error occured and ->poll_mask shall not be called.
+
+ poll_mask: return the mask of EPOLL* values describing the file descriptor
+ state. Called either before going to sleep on the waitqueue returned by
+ get_poll_head, or 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