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>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 8f48d29abf76c0b3a811ff0dc03f4c72041daae7..bbdbd56cf2ac9384b83e78945b2c6c0031cc346d 100644 (file)
--- 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);