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From: Jens Axboe <[email protected]>
To: [email protected]
Cc: [email protected], [email protected],
	[email protected], [email protected],
	Jens Axboe <[email protected]>,
	Johannes Weiner <[email protected]>
Subject: [PATCH 08/15] mm: support async buffered reads in generic_file_buffered_read()
Date: Thu, 18 Jun 2020 08:43:48 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

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.

Acked-by: Johannes Weiner <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
---
 mm/filemap.c | 38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index e8aaf43bee9f..a5b1fa8f7ce4 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1210,6 +1210,14 @@ static int __wait_on_page_locked_async(struct page *page,
 	return ret;
 }
 
+static int wait_on_page_locked_async(struct page *page,
+				     struct wait_page_queue *wait)
+{
+	if (!PageLocked(page))
+		return 0;
+	return __wait_on_page_locked_async(compound_head(page), wait, false);
+}
+
 /**
  * put_and_wait_on_page_locked - Drop a reference and wait for it to be unlocked
  * @page: The page to wait for.
@@ -2049,17 +2057,25 @@ 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->ki_waitq);
+			} 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))
@@ -2147,7 +2163,10 @@ 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->ki_waitq);
+		else
+			error = lock_page_killable(page);
 		if (unlikely(error))
 			goto readpage_error;
 
@@ -2190,10 +2209,7 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,
 		}
 
 		if (!PageUptodate(page)) {
-			if (iocb->ki_flags & IOCB_WAITQ)
-				error = lock_page_async(page, iocb->ki_waitq);
-			else
-				error = lock_page_killable(page);
+			error = lock_page_killable(page);
 			if (unlikely(error))
 				goto readpage_error;
 			if (!PageUptodate(page)) {
-- 
2.27.0


  parent reply	other threads:[~2020-06-18 14:45 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-18 14:43 Jens Axboe
2020-06-18 14:43 ` [PATCH 01/15] block: provide plug based way of signaling forced no-wait semantics Jens Axboe
2020-06-18 14:43 ` [PATCH 02/15] io_uring: always plug for any number of IOs Jens Axboe
2020-06-18 14:43 ` [PATCH 03/15] io_uring: catch -EIO from buffered issue request failure Jens Axboe
2020-06-18 14:43 ` [PATCH 04/15] io_uring: re-issue block requests that failed because of resources Jens Axboe
2020-06-19 14:12   ` Pavel Begunkov
2020-06-19 14:22     ` Jens Axboe
2020-06-19 14:30       ` Pavel Begunkov
2020-06-19 14:36         ` Jens Axboe
2020-06-18 14:43 ` [PATCH 05/15] mm: allow read-ahead with IOCB_NOWAIT set Jens Axboe
2020-06-24  1:02   ` Dave Chinner
2020-06-24  1:46     ` Matthew Wilcox
2020-06-24 15:00       ` Jens Axboe
2020-06-24 15:35         ` Jens Axboe
2020-06-24 16:41           ` Matthew Wilcox
2020-06-24 16:44             ` Jens Axboe
2020-07-07 11:38               ` Andreas Grünbacher
2020-07-07 14:31                 ` Jens Axboe
2020-08-10 22:56               ` Dave Chinner
2020-08-10 23:03                 ` Jens Axboe
2020-06-24  4:38   ` Dave Chinner
2020-06-24 15:01     ` Jens Axboe
2020-06-18 14:43 ` [PATCH 06/15] mm: abstract out wake_page_match() from wake_page_function() Jens Axboe
2020-06-18 14:43 ` [PATCH 07/15] mm: add support for async page locking Jens Axboe
2020-07-07 11:32   ` Andreas Grünbacher
2020-07-07 14:32     ` Jens Axboe
2020-06-18 14:43 ` Jens Axboe [this message]
2020-06-18 14:43 ` [PATCH 09/15] fs: add FMODE_BUF_RASYNC Jens Axboe
2020-06-18 14:43 ` [PATCH 10/15] block: flag block devices as supporting IOCB_WAITQ Jens Axboe
2020-06-18 14:43 ` [PATCH 11/15] xfs: flag files as supporting buffered async reads Jens Axboe
2020-06-18 14:43 ` [PATCH 12/15] btrfs: " Jens Axboe
2020-06-19 11:11   ` David Sterba
2020-06-18 14:43 ` [PATCH 13/15] ext4: flag " Jens Axboe
2020-06-18 14:43 ` [PATCH 14/15] mm: add kiocb_wait_page_queue_init() helper Jens Axboe
2020-06-18 14:43 ` [PATCH 15/15] io_uring: support true async buffered reads, if file provides it Jens Axboe
2020-06-23 12:39   ` Pavel Begunkov
2020-06-23 14:38     ` Jens Axboe
2020-06-18 14:45 ` [PATCHSET v7 0/12] Add support for async buffered reads Jens Axboe

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