From c8d317aa1887b40b188ec3aaa6e9e524333caed1 Mon Sep 17 00:00:00 2001
From: Hao Xu <haoxu@linux.alibaba.com>
Date: Tue, 29 Sep 2020 20:00:45 +0800
Subject: [PATCH] io_uring: fix async buffered reads when readahead is disabled
The async buffered reads feature is not working when readahead is
turned off. There are two things to concern:
- when doing retry in io_read, not only the IOCB_WAITQ flag but also
the IOCB_NOWAIT flag is still set, which makes it goes to would_block
phase in generic_file_buffered_read() and then return -EAGAIN. After
that, the io-wq thread work is queued, and later doing the async
reads in the old way.
- even if we remove IOCB_NOWAIT when doing retry, the feature is still
not running properly, since in generic_file_buffered_read() it goes to
lock_page_killable() after calling mapping->a_ops->readpage() to do
IO, and thus causing process to sleep.
Fixes: 1a0a7853b901 ("mm: support async buffered reads in generic_file_buffered_read()")
Fixes: 3b2a4439e0ae ("io_uring: get rid of kiocb_wait_page_queue_init()")
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
fs/io_uring.c | 2 ++
mm/filemap.c | 6 +++++-
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 556e4a2ead07..b89cc87830b1 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3049,6 +3049,7 @@ static int io_async_buf_func(struct wait_queue_entry *wait, unsigned mode,
if (!wake_page_match(wpq, key))
return 0;
+ req->rw.kiocb.ki_flags &= ~IOCB_WAITQ;
list_del_init(&wait->entry);
init_task_work(&req->task_work, io_req_task_submit);
@@ -3106,6 +3107,7 @@ static bool io_rw_should_retry(struct io_kiocb *req)
wait->wait.flags = 0;
INIT_LIST_HEAD(&wait->wait.entry);
kiocb->ki_flags |= IOCB_WAITQ;
+ kiocb->ki_flags &= ~IOCB_NOWAIT;
kiocb->ki_waitq = wait;
io_get_req_task(req);
diff --git a/mm/filemap.c b/mm/filemap.c
index 1aaea26556cc..ea383478fc22 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2267,7 +2267,11 @@ readpage:
}
if (!PageUptodate(page)) {
- error = lock_page_killable(page);
+ if (iocb->ki_flags & IOCB_WAITQ)
+ error = lock_page_async(page, iocb->ki_waitq);
+ else
+ error = lock_page_killable(page);
+
if (unlikely(error))
goto readpage_error;
if (!PageUptodate(page)) {