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From: Jens Axboe <axboe@kernel.dk>
To: io-uring@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, Jens Axboe <axboe@kernel.dk>
Subject: [PATCH 04/11] mm: support async buffered reads in generic_file_buffered_read()
Date: Fri, 22 May 2020 19:50:42 -0600
Message-ID: <20200523015049.14808-5-axboe@kernel.dk> (raw)
In-Reply-To: <20200523015049.14808-1-axboe@kernel.dk>

Use the async page locking infrastructure, if IOCB_WAITQ is set in the
passed in iocb. The caller must expect an -EIOCBQUEUED return value,
which means that IO is started but not done yet. This is similar to how
O_DIRECT signals the same operation. Once the callback is received by
the caller for IO completion, the caller must retry the operation.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 mm/filemap.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index a01daafd49fd..b49836ff0fdc 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2086,17 +2086,25 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
 					index, last_index - index);
 		}
 		if (!PageUptodate(page)) {
-			if (iocb->ki_flags & IOCB_NOWAIT) {
-				put_page(page);
-				goto would_block;
-			}
-
 			/*
 			 * See comment in do_read_cache_page on why
 			 * wait_on_page_locked is used to avoid unnecessarily
 			 * serialisations and why it's safe.
 			 */
-			error = wait_on_page_locked_killable(page);
+			if (iocb->ki_flags & IOCB_WAITQ) {
+				if (written) {
+					put_page(page);
+					goto out;
+				}
+				error = wait_on_page_locked_async(page,
+								iocb->private);
+			} else {
+				if (iocb->ki_flags & IOCB_NOWAIT) {
+					put_page(page);
+					goto would_block;
+				}
+				error = wait_on_page_locked_killable(page);
+			}
 			if (unlikely(error))
 				goto readpage_error;
 			if (PageUptodate(page))
@@ -2184,7 +2192,10 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
 
 page_not_up_to_date:
 		/* Get exclusive access to the page ... */
-		error = lock_page_killable(page);
+		if (iocb->ki_flags & IOCB_WAITQ)
+			error = lock_page_async(page, iocb->private);
+		else
+			error = lock_page_killable(page);
 		if (unlikely(error))
 			goto readpage_error;
 
-- 
2.26.2


  parent reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-23  1:50 [PATCHSET v2 RFC 0/11] Add support for async buffered reads Jens Axboe
2020-05-23  1:50 ` [PATCH 01/11] block: read-ahead submission should imply no-wait as well Jens Axboe
2020-05-23  1:50 ` [PATCH 02/11] mm: allow read-ahead with IOCB_NOWAIT set Jens Axboe
2020-05-23  1:50 ` [PATCH 03/11] mm: add support for async page locking Jens Axboe
2020-05-23  1:50 ` Jens Axboe [this message]
2020-05-23  1:50 ` [PATCH 05/11] fs: add FMODE_BUF_RASYNC Jens Axboe
2020-05-23  1:50 ` [PATCH 06/11] ext4: flag as supporting buffered async reads Jens Axboe
2020-05-23  1:50 ` [PATCH 07/11] block: flag block devices as supporting IOCB_WAITQ Jens Axboe
2020-05-23  1:50 ` [PATCH 08/11] xfs: flag files as supporting buffered async reads Jens Axboe
2020-05-23  1:50 ` [PATCH 09/11] btrfs: " Jens Axboe
2020-05-23  1:50 ` [PATCH 10/11] mm: add kiocb_wait_page_async_init() helper Jens Axboe
2020-05-23  1:50 ` [PATCH 11/11] io_uring: support true async buffered reads, if file provides it Jens Axboe
  -- strict thread matches above, loose matches on Subject: below --
2020-05-22 20:23 [PATCHSET RFC 0/11] Add support for async buffered reads Jens Axboe
2020-05-22 20:23 ` [PATCH 04/11] mm: support async buffered reads in generic_file_buffered_read() Jens Axboe

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