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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]>
Subject: [PATCH 04/12] mm: add support for async page locking
Date: Tue, 26 May 2020 13:51:15 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

Normally waiting for a page to become unlocked, or locking the page,
requires waiting for IO to complete. Add support for lock_page_async()
and wait_on_page_locked_async(), which are callback based instead. This
allows a caller to get notified when a page becomes unlocked, rather
than wait for it.

We add a new iocb field, ki_waitq, to pass in the necessary data for this
to happen. We can unionize this with ki_cookie, since that is only used
for polled IO. Polled IO can never co-exist with async callbacks, as it is
(by definition) polled completions. struct wait_page_key is made public,
and we define struct wait_page_async as the interface between the caller
and the core.

Signed-off-by: Jens Axboe <[email protected]>
---
 include/linux/fs.h      |  7 ++++++-
 include/linux/pagemap.h |  9 +++++++++
 mm/filemap.c            | 41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index d3ebb49189df..ba1fff0e7bca 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -314,6 +314,8 @@ enum rw_hint {
 #define IOCB_SYNC		(1 << 5)
 #define IOCB_WRITE		(1 << 6)
 #define IOCB_NOWAIT		(1 << 7)
+/* iocb->ki_waitq is valid */
+#define IOCB_WAITQ		(1 << 8)
 
 struct kiocb {
 	struct file		*ki_filp;
@@ -327,7 +329,10 @@ struct kiocb {
 	int			ki_flags;
 	u16			ki_hint;
 	u16			ki_ioprio; /* See linux/ioprio.h */
-	unsigned int		ki_cookie; /* for ->iopoll */
+	union {
+		unsigned int		ki_cookie; /* for ->iopoll */
+		struct wait_page_queue	*ki_waitq; /* for async buffered IO */
+	};
 
 	randomized_struct_fields_end
 };
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 53d980f2208d..d3e63c9c61ae 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -495,6 +495,7 @@ static inline int wake_page_match(struct wait_page_queue *wait_page,
 
 extern void __lock_page(struct page *page);
 extern int __lock_page_killable(struct page *page);
+extern int __lock_page_async(struct page *page, struct wait_page_queue *wait);
 extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
 				unsigned int flags);
 extern void unlock_page(struct page *page);
@@ -531,6 +532,14 @@ static inline int lock_page_killable(struct page *page)
 	return 0;
 }
 
+static inline int lock_page_async(struct page *page,
+				  struct wait_page_queue *wait)
+{
+	if (!trylock_page(page))
+		return __lock_page_async(page, wait);
+	return 0;
+}
+
 /*
  * lock_page_or_retry - Lock the page, unless this would block and the
  * caller indicated that it can handle a retry.
diff --git a/mm/filemap.c b/mm/filemap.c
index e891b5bee8fd..c746541b1d49 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1183,6 +1183,42 @@ int wait_on_page_bit_killable(struct page *page, int bit_nr)
 }
 EXPORT_SYMBOL(wait_on_page_bit_killable);
 
+static int __wait_on_page_locked_async(struct page *page,
+				       struct wait_page_queue *wait, bool set)
+{
+	struct wait_queue_head *q = page_waitqueue(page);
+	int ret = 0;
+
+	wait->page = page;
+	wait->bit_nr = PG_locked;
+
+	spin_lock_irq(&q->lock);
+	if (set)
+		ret = !trylock_page(page);
+	else
+		ret = PageLocked(page);
+	if (ret) {
+		__add_wait_queue_entry_tail(q, &wait->wait);
+		SetPageWaiters(page);
+		if (set)
+			ret = !trylock_page(page);
+		else
+			ret = PageLocked(page);
+		/*
+		 * If we were succesful now, we know we're still on the
+		 * waitqueue as we're still under the lock. This means it's
+		 * safe to remove and return success, we know the callback
+		 * isn't going to trigger.
+		 */
+		if (!ret)
+			__remove_wait_queue(q, &wait->wait);
+		else
+			ret = -EIOCBQUEUED;
+	}
+	spin_unlock_irq(&q->lock);
+	return ret;
+}
+
 /**
  * put_and_wait_on_page_locked - Drop a reference and wait for it to be unlocked
  * @page: The page to wait for.
@@ -1345,6 +1381,11 @@ int __lock_page_killable(struct page *__page)
 }
 EXPORT_SYMBOL_GPL(__lock_page_killable);
 
+int __lock_page_async(struct page *page, struct wait_page_queue *wait)
+{
+	return __wait_on_page_locked_async(page, wait, true);
+}
+
 /*
  * Return values:
  * 1 - page is locked; mmap_sem is still held.
-- 
2.26.2


  parent reply	other threads:[~2020-05-26 19:51 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-26 19:51 [PATCHSET v5 0/12] Add support for async buffered reads Jens Axboe
2020-05-26 19:51 ` [PATCH 01/12] block: read-ahead submission should imply no-wait as well Jens Axboe
2020-05-26 19:51 ` [PATCH 02/12] mm: allow read-ahead with IOCB_NOWAIT set Jens Axboe
2020-05-26 20:45   ` Johannes Weiner
2020-05-26 19:51 ` [PATCH 03/12] mm: abstract out wake_page_match() from wake_page_function() Jens Axboe
2020-05-26 21:02   ` Johannes Weiner
2020-06-01 14:16   ` Matthew Wilcox
2020-05-26 19:51 ` Jens Axboe [this message]
2020-05-26 21:59   ` [PATCH 04/12] mm: add support for async page locking Johannes Weiner
2020-05-26 22:01     ` Jens Axboe
2020-05-27 16:02       ` Johannes Weiner
2020-06-01 14:26   ` Matthew Wilcox
2020-06-01 17:15     ` Jens Axboe
2020-05-26 19:51 ` [PATCH 05/12] mm: support async buffered reads in generic_file_buffered_read() Jens Axboe
2020-05-26 22:00   ` Johannes Weiner
2020-05-26 19:51 ` [PATCH 06/12] fs: add FMODE_BUF_RASYNC Jens Axboe
2020-05-26 19:51 ` [PATCH 07/12] ext4: flag as supporting buffered async reads Jens Axboe
2020-05-26 19:51 ` [PATCH 08/12] block: flag block devices as supporting IOCB_WAITQ Jens Axboe
2020-05-26 19:51 ` [PATCH 09/12] xfs: flag files as supporting buffered async reads Jens Axboe
2020-05-28 17:53   ` Darrick J. Wong
2020-05-28 19:23     ` Jens Axboe
2020-05-26 19:51 ` [PATCH 10/12] btrfs: " Jens Axboe
2020-05-26 19:57   ` Chris Mason
2020-05-26 19:51 ` [PATCH 11/12] mm: add kiocb_wait_page_queue_init() helper Jens Axboe
2020-05-26 22:01   ` Johannes Weiner
2020-05-26 19:51 ` [PATCH 12/12] io_uring: support true async buffered reads, if file provides it Jens Axboe
     [not found] ` <CA+icZUWfX+QmroE6j74C7o-BdfMF5=6PdYrA=5W_JCKddqkJgQ@mail.gmail.com>
2020-05-28 17:06   ` [PATCHSET v5 0/12] Add support for async buffered reads Jens Axboe
2020-05-28 17:12     ` Sedat Dilek
2020-05-28 17:14       ` Jens Axboe
2020-05-28 18:20         ` Sedat Dilek
2020-05-29 10:02     ` Sedat Dilek
2020-05-29 11:22       ` Sedat Dilek
2020-05-30 13:36         ` Sedat Dilek
2020-05-30 18:57           ` Sedat Dilek
2020-05-31  1:57             ` Jens Axboe
     [not found]               ` <CA+icZUXxmOA-5+dukCgxfSp4eVHB+QaAHO6tsgq0iioQs3Af-w@mail.gmail.com>
2020-05-31  7:12                 ` Sedat Dilek
2020-06-01 13:35                   ` Sedat Dilek
2020-06-01 14:04                     ` Jens Axboe
2020-06-01 14:13                       ` Sedat Dilek
2020-06-01 14:14                         ` Jens Axboe
2020-06-01 14:35                           ` Jens Axboe
2020-06-01 14:43                             ` Sedat Dilek
2020-06-01 14:46                               ` Jens Axboe
2020-06-01 14:51                                 ` Sedat Dilek
2020-06-01 20:18                                 ` Sedat Dilek
     [not found] ` <[email protected]>
2020-06-04  1:04   ` Jens Axboe
2020-06-04  1:30     ` Andres Freund
2020-06-05 19:56       ` Andres Freund
2020-06-05 14:42     ` Jens Axboe
2020-06-05 20:20       ` Andres Freund
2020-06-05 20:21         ` Jens Axboe
2020-06-05 20:36         ` Andres Freund
2020-06-05 20:53           ` Jens Axboe
2020-06-05 21:13             ` Jens Axboe
2020-06-05 21:21               ` Jens Axboe
2020-06-05 22:30                 ` Andres Freund
2020-06-05 22:36                   ` Andres Freund
2020-06-05 22:49                     ` Jens Axboe
2020-06-05 22:54                       ` Andres Freund
2020-06-05 22:56                         ` Jens Axboe
2020-06-05 23:02                           ` Andres Freund
2020-06-06  0:33                 ` Sedat Dilek
2020-06-06 16:04                   ` Jens Axboe
  -- strict thread matches above, loose matches on Subject: below --
2020-05-24 19:21 [PATCHSET v4 " Jens Axboe
2020-05-24 19:21 ` [PATCH 04/12] mm: add support for async page locking Jens Axboe
2020-05-23 18:57 [PATCHSET v2 0/12] Add support for async buffered reads Jens Axboe
2020-05-23 18:57 ` [PATCH 04/12] mm: add support for async page locking Jens Axboe

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