io_uring: offload write to async worker in case of -EAGAIN

In case of direct write -EAGAIN will be returned if page cache was
previously populated.  To avoid immediate completion of a request
with -EAGAIN error write has to be offloaded to the async worker,
like io_read() does.

Signed-off-by: Roman Penyaev <rpenyaev@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 15 insertions, 1 deletions

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 8f48d29abf76..bbdbd56cf2ac 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1022,6 +1022,8 @@ static int io_write(struct io_kiocb *req, const struct sqe_submit *s,
 
         ret = rw_verify_area(WRITE, file, &kiocb->ki_pos, iov_count);
         if (!ret) {
+                ssize_t ret2;
+
                 /*
                  * Open-code file_start_write here to grab freeze protection,
                  * which will be released by another thread in
@@ -1036,7 +1038,19 @@ static int io_write(struct io_kiocb *req, const struct sqe_submit *s,
                                                 SB_FREEZE_WRITE);
                 }
                 kiocb->ki_flags |= IOCB_WRITE;
-                io_rw_done(kiocb, call_write_iter(file, kiocb, &iter));
+
+                ret2 = call_write_iter(file, kiocb, &iter);
+                if (!force_nonblock || ret2 != -EAGAIN) {
+                        io_rw_done(kiocb, ret2);
+                } else {
+                        /*
+                         * If ->needs_lock is true, we're already in async
+                         * context.
+                         */
+                        if (!s->needs_lock)
+                                io_async_list_note(WRITE, req, iov_count);
+                        ret = -EAGAIN;
+                }
         }
 out_free:
         kfree(iovec);