io_uring: for requests that require async, force it

Some requests require being run async as they do not support
non-blocking. Instead of trying to issue these requests, getting -EAGAIN
and then queueing them for async issue, rather just force async upfront.

Add WARN_ON_ONCE to make sure surprising code paths do not come up,
however in those cases the bug would end up being a blocking
io_uring_enter(2) which should not be critical.

Signed-off-by: Dylan Yudaken <dylany@meta.com>
Link: https://lore.kernel.org/r/20230127135227.3646353-3-dylany@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

7 files changed, 33 insertions, 34 deletions

diff --git a/io_uring/advise.c b/io_uring/advise.c
index 449c6f14649f..cf600579bffe 100644
--- a/io_uring/advise.c
+++ b/io_uring/advise.c
@@ -39,6 +39,7 @@ int io_madvise_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	ma->addr = READ_ONCE(sqe->addr);
 	ma->len = READ_ONCE(sqe->len);
 	ma->advice = READ_ONCE(sqe->fadvise_advice);
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 #else
 	return -EOPNOTSUPP;
@@ -51,8 +52,7 @@ int io_madvise(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_madvise *ma = io_kiocb_to_cmd(req, struct io_madvise);
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	ret = do_madvise(current->mm, ma->addr, ma->len, ma->advice);
 	io_req_set_res(req, ret, 0);
diff --git a/io_uring/fs.c b/io_uring/fs.c
index 7100c293c13a..f6a69a549fd4 100644
--- a/io_uring/fs.c
+++ b/io_uring/fs.c
@@ -74,6 +74,7 @@ int io_renameat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	}
 
 	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -82,8 +83,7 @@ int io_renameat(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename);
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	ret = do_renameat2(ren->old_dfd, ren->oldpath, ren->new_dfd,
 				ren->newpath, ren->flags);
@@ -123,6 +123,7 @@ int io_unlinkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return PTR_ERR(un->filename);
 
 	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -131,8 +132,7 @@ int io_unlinkat(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_unlink *un = io_kiocb_to_cmd(req, struct io_unlink);
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	if (un->flags & AT_REMOVEDIR)
 		ret = do_rmdir(un->dfd, un->filename);
@@ -170,6 +170,7 @@ int io_mkdirat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return PTR_ERR(mkd->filename);
 
 	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -178,8 +179,7 @@ int io_mkdirat(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_mkdir *mkd = io_kiocb_to_cmd(req, struct io_mkdir);
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	ret = do_mkdirat(mkd->dfd, mkd->filename, mkd->mode);
 
@@ -220,6 +220,7 @@ int io_symlinkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	}
 
 	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -228,8 +229,7 @@ int io_symlinkat(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_link *sl = io_kiocb_to_cmd(req, struct io_link);
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	ret = do_symlinkat(sl->oldpath, sl->new_dfd, sl->newpath);
 
@@ -265,6 +265,7 @@ int io_linkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	}
 
 	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -273,8 +274,7 @@ int io_linkat(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_link *lnk = io_kiocb_to_cmd(req, struct io_link);
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	ret = do_linkat(lnk->old_dfd, lnk->oldpath, lnk->new_dfd,
 				lnk->newpath, lnk->flags);
diff --git a/io_uring/net.c b/io_uring/net.c
index 90326b279965..aeb1d016e2e9 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -90,6 +90,7 @@ int io_shutdown_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return -EINVAL;
 
 	shutdown->how = READ_ONCE(sqe->len);
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -99,8 +100,7 @@ int io_shutdown(struct io_kiocb *req, unsigned int issue_flags)
 	struct socket *sock;
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	sock = sock_from_file(req->file);
 	if (unlikely(!sock))
diff --git a/io_uring/splice.c b/io_uring/splice.c
index 53e4232d0866..2a4bbb719531 100644
--- a/io_uring/splice.c
+++ b/io_uring/splice.c
@@ -34,6 +34,7 @@ static int __io_splice_prep(struct io_kiocb *req,
 	if (unlikely(sp->flags & ~valid_flags))
 		return -EINVAL;
 	sp->splice_fd_in = READ_ONCE(sqe->splice_fd_in);
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -52,8 +53,7 @@ int io_tee(struct io_kiocb *req, unsigned int issue_flags)
 	struct file *in;
 	long ret = 0;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	if (sp->flags & SPLICE_F_FD_IN_FIXED)
 		in = io_file_get_fixed(req, sp->splice_fd_in, issue_flags);
@@ -94,8 +94,7 @@ int io_splice(struct io_kiocb *req, unsigned int issue_flags)
 	struct file *in;
 	long ret = 0;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	if (sp->flags & SPLICE_F_FD_IN_FIXED)
 		in = io_file_get_fixed(req, sp->splice_fd_in, issue_flags);
diff --git a/io_uring/statx.c b/io_uring/statx.c
index d8fc933d3f59..abb874209caa 100644
--- a/io_uring/statx.c
+++ b/io_uring/statx.c
@@ -48,6 +48,7 @@ int io_statx_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	}
 
 	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -56,8 +57,7 @@ int io_statx(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_statx *sx = io_kiocb_to_cmd(req, struct io_statx);
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	ret = do_statx(sx->dfd, sx->filename, sx->flags, sx->mask, sx->buffer);
 	io_req_set_res(req, ret, 0);
diff --git a/io_uring/sync.c b/io_uring/sync.c
index 64e87ea2b8fb..255f68c37e55 100644
--- a/io_uring/sync.c
+++ b/io_uring/sync.c
@@ -32,6 +32,8 @@ int io_sfr_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	sync->off = READ_ONCE(sqe->off);
 	sync->len = READ_ONCE(sqe->len);
 	sync->flags = READ_ONCE(sqe->sync_range_flags);
+	req->flags |= REQ_F_FORCE_ASYNC;
+
 	return 0;
 }
 
@@ -41,8 +43,7 @@ int io_sync_file_range(struct io_kiocb *req, unsigned int issue_flags)
 	int ret;
 
 	/* sync_file_range always requires a blocking context */
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	ret = sync_file_range(req->file, sync->off, sync->len, sync->flags);
 	io_req_set_res(req, ret, 0);
@@ -62,6 +63,7 @@ int io_fsync_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
 	sync->off = READ_ONCE(sqe->off);
 	sync->len = READ_ONCE(sqe->len);
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -72,8 +74,7 @@ int io_fsync(struct io_kiocb *req, unsigned int issue_flags)
 	int ret;
 
 	/* fsync always requires a blocking context */
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	ret = vfs_fsync_range(req->file, sync->off, end > 0 ? end : LLONG_MAX,
 				sync->flags & IORING_FSYNC_DATASYNC);
@@ -91,6 +92,7 @@ int io_fallocate_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	sync->off = READ_ONCE(sqe->off);
 	sync->len = READ_ONCE(sqe->addr);
 	sync->mode = READ_ONCE(sqe->len);
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -100,8 +102,8 @@ int io_fallocate(struct io_kiocb *req, unsigned int issue_flags)
 	int ret;
 
 	/* fallocate always requiring blocking context */
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
 	ret = vfs_fallocate(req->file, sync->mode, sync->off, sync->len);
 	if (ret >= 0)
 		fsnotify_modify(req->file);
diff --git a/io_uring/xattr.c b/io_uring/xattr.c
index 6201a9f442c6..e1c810e0b85a 100644
--- a/io_uring/xattr.c
+++ b/io_uring/xattr.c
@@ -75,6 +75,7 @@ static int __io_getxattr_prep(struct io_kiocb *req,
 	}
 
 	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -109,8 +110,7 @@ int io_fgetxattr(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	ret = do_getxattr(mnt_idmap(req->file->f_path.mnt),
 			req->file->f_path.dentry,
@@ -127,8 +127,7 @@ int io_getxattr(struct io_kiocb *req, unsigned int issue_flags)
 	struct path path;
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 retry:
 	ret = filename_lookup(AT_FDCWD, ix->filename, lookup_flags, &path, NULL);
@@ -174,6 +173,7 @@ static int __io_setxattr_prep(struct io_kiocb *req,
 	}
 
 	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
 	return 0;
 }
 
@@ -222,8 +222,7 @@ int io_fsetxattr(struct io_kiocb *req, unsigned int issue_flags)
 {
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 	ret = __io_setxattr(req, issue_flags, &req->file->f_path);
 	io_xattr_finish(req, ret);
@@ -237,8 +236,7 @@ int io_setxattr(struct io_kiocb *req, unsigned int issue_flags)
 	struct path path;
 	int ret;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
 retry:
 	ret = filename_lookup(AT_FDCWD, ix->filename, lookup_flags, &path, NULL);