Commit 1a0a7853 authored by Jens Axboe's avatar Jens Axboe
Browse files

mm: support async buffered reads in generic_file_buffered_read() 



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: default avatarJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent dd3e6d50

mm/filemap.c

+27 −11
Original line number Diff line number Diff line
@@ -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 @@ find_page: 
					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.

			 */

			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))
@@ -2147,6 +2163,9 @@ page_ok: 


page_not_up_to_date:

		/* Get exclusive access to the 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;
@@ -2190,9 +2209,6 @@ readpage: 
		}



		if (!PageUptodate(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;

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