fs: add an iopoll method to struct file_operations

This new methods is used to explicitly poll for I/O completion for an
iocb.  It must be called for any iocb submitted asynchronously (that
is with a non-null ki_complete) which has the IOCB_HIPRI flag set.

The method is assisted by a new ki_cookie field in struct iocb to store
the polling cookie.

Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 29d8e2cfed0e..dedcc2e9265c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -310,6 +310,7 @@ struct kiocb {
         int                     ki_flags;
         u16                     ki_hint;
         u16                     ki_ioprio; /* See linux/ioprio.h */
+        unsigned int            ki_cookie; /* for ->iopoll */
 } __randomize_layout;
 
 static inline bool is_sync_kiocb(struct kiocb *kiocb)
@@ -1787,6 +1788,7 @@ struct file_operations {
         ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
         ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
         ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
+        int (*iopoll)(struct kiocb *kiocb, bool spin);
         int (*iterate) (struct file *, struct dir_context *);
         int (*iterate_shared) (struct file *, struct dir_context *);
         __poll_t (*poll) (struct file *, struct poll_table_struct *);