From 079458e82cae127564014508cbc77d5b5728679f Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 22 May 2020 09:18:38 -0600 Subject: [PATCH 2083/2944] mm: support async buffered reads in generic_file_buffered_read() to #29998112 commit 1a0a7853b901c35a742b3bf176cf4701a5c5817c upstream 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 Signed-off-by: Jens Axboe Signed-off-by: Hao Xu Reviewed-by: Joseph Qi --- mm/filemap.c | 38 +++++++++++++++++++++++++++----------- 1 file changed, 27 insertions(+), 11 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index fba13e6..82ce70d 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1190,6 +1190,14 @@ 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); +} + /** * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue * @page: Page defining the wait queue of interest @@ -2164,17 +2172,25 @@ 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->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)) @@ -2262,7 +2278,10 @@ 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->ki_waitq); + else + error = lock_page_killable(page); if (unlikely(error)) goto readpage_error; @@ -2305,10 +2324,7 @@ static 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)) { -- 1.8.3.1