keep iocb_flags() result cached in struct file

* calculate at the time we set FMODE_OPENED (do_dentry_open() for normal
opens, alloc_file() for pipe()/socket()/etc.)
* update when handling F_SETFL
* keep in a new field - file->f_iocb_flags; since that thing is needed only
before the refcount reaches zero, we can put it into the same anon union
where ->f_rcuhead and ->f_llist live - those are used only after refcount
reaches zero.

Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/nvme/target/io-cmd-file.c

@@ -112,7 +112,7 @@ static ssize_t nvmet_file_submit_bvec(struct nvmet_req *req, loff_t pos,
 
 	iocb->ki_pos = pos;
 	iocb->ki_filp = req->ns->file;
-	iocb->ki_flags = ki_flags | iocb_flags(req->ns->file);
+	iocb->ki_flags = ki_flags | iocb->ki_filp->f_iocb_flags;
 
 	return call_iter(iocb, &iter);
 }

fs/aio.c

@@ -1475,7 +1475,7 @@ static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb)
 	req->ki_complete = aio_complete_rw;
 	req->private = NULL;
 	req->ki_pos = iocb->aio_offset;
-	req->ki_flags = iocb_flags(req->ki_filp);
+	req->ki_flags = req->ki_filp->f_iocb_flags;
 	if (iocb->aio_flags & IOCB_FLAG_RESFD)
 		req->ki_flags |= IOCB_EVENTFD;
 	if (iocb->aio_flags & IOCB_FLAG_IOPRIO) {

fs/fcntl.c

@@ -78,6 +78,7 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
 	}
 	spin_lock(&filp->f_lock);
 	filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
+	filp->f_iocb_flags = iocb_flags(filp);
 	spin_unlock(&filp->f_lock);
 
  out:

fs/file_table.c

@@ -241,6 +241,7 @@ static struct file *alloc_file(const struct path *path, int flags,
 	if ((file->f_mode & FMODE_WRITE) &&
 	     likely(fop->write || fop->write_iter))
 		file->f_mode |= FMODE_CAN_WRITE;
+	file->f_iocb_flags = iocb_flags(file);
 	file->f_mode |= FMODE_OPENED;
 	file->f_op = fop;
 	if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)

fs/io_uring.c

@@ -4330,7 +4330,7 @@ static int io_rw_init_file(struct io_kiocb *req, fmode_t mode)
 	if (!io_req_ffs_set(req))
 		req->flags |= io_file_get_flags(file) << REQ_F_SUPPORT_NOWAIT_BIT;
 
-	kiocb->ki_flags = iocb_flags(file);
+	kiocb->ki_flags = file->f_iocb_flags;
 	ret = kiocb_set_rw_flags(kiocb, req->rw.flags);
 	if (unlikely(ret))
 		return ret;

fs/open.c

@@ -862,6 +862,7 @@ static int do_dentry_open(struct file *f,
 		f->f_mode |= FMODE_CAN_ODIRECT;
 
 	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
+	f->f_iocb_flags = iocb_flags(f);
 
 	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 

include/linux/fs.h

@@ -926,6 +926,7 @@ struct file {
 	union {
 		struct llist_node	f_llist;
 		struct rcu_head 	f_rcuhead;
+		unsigned int 		f_iocb_flags;
 	};
 	struct path		f_path;
 	struct inode		*f_inode;	/* cached value */
@@ -2199,13 +2200,11 @@ static inline bool HAS_UNMAPPED_ID(struct user_namespace *mnt_userns,
 	       !gid_valid(i_gid_into_mnt(mnt_userns, inode));
 }
 
-static inline int iocb_flags(struct file *file);
-
 static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 {
 	*kiocb = (struct kiocb) {
 		.ki_filp = filp,
-		.ki_flags = iocb_flags(filp),
+		.ki_flags = filp->f_iocb_flags,
 		.ki_ioprio = get_current_ioprio(),
 	};
 }