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From: Matthew Wilcox <willy@infradead.org>
To: linux-fsdevel@vger.kernel.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org,
	linux-ext4@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com,
	ocfs2-devel@oss.oracle.com, linux-xfs@vger.kernel.org
Subject: [PATCH v8 14/25] mm: Document why we don't set PageReadahead
Date: Tue, 25 Feb 2020 13:48:27 -0800	[thread overview]
Message-ID: <20200225214838.30017-15-willy@infradead.org> (raw)
In-Reply-To: <20200225214838.30017-1-willy@infradead.org>

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

If the page is already in cache, we don't set PageReadahead on it.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/readahead.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/mm/readahead.c b/mm/readahead.c
index 8ee9036fd681..0afb55a49909 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -195,9 +195,12 @@ void page_cache_readahead_unbounded(struct address_space *mapping,
 
 		if (page && !xa_is_value(page)) {
 			/*
-			 * Page already present?  Kick off the current batch of
-			 * contiguous pages before continuing with the next
-			 * batch.
+			 * Page already present?  Kick off the current batch
+			 * of contiguous pages before continuing with the
+			 * next batch.  This page may be the one we would
+			 * have intended to mark as Readahead, but we don't
+			 * have a stable reference to this page, and it's
+			 * not worth getting one just for that.
 			 */
 			read_pages(&rac, &page_pool, true);
 			continue;
-- 
2.25.0


  parent reply	other threads:[~2020-02-25 21:50 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-25 21:48 [PATCH v8 00/25] Change readahead API Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 01/25] mm: Move readahead prototypes from mm.h Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 02/25] mm: Return void from various readahead functions Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 03/25] mm: Ignore return value of ->readpages Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 04/25] mm: Move readahead nr_pages check into read_pages Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 05/25] mm: Add new readahead_control API Matthew Wilcox
2020-02-26 17:01   ` Christoph Hellwig
2020-02-25 21:48 ` [PATCH v8 06/25] mm: Use readahead_control to pass arguments Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 07/25] mm: Rename various 'offset' parameters to 'index' Matthew Wilcox
2020-02-26 17:13   ` Zi Yan
2020-02-25 21:48 ` [PATCH v8 08/25] mm: rename readahead loop variable to 'i' Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 09/25] mm: Remove 'page_offset' from readahead loop Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 10/25] mm: Put readahead pages in cache earlier Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 11/25] mm: Add readahead address space operation Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 12/25] mm: Move end_index check out of readahead loop Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 13/25] mm: Add page_cache_readahead_unbounded Matthew Wilcox
2020-02-25 21:48 ` Matthew Wilcox [this message]
2020-02-26 17:03   ` [PATCH v8 14/25] mm: Document why we don't set PageReadahead Christoph Hellwig
2020-02-25 21:48 ` [PATCH v8 15/25] mm: Use memalloc_nofs_save in readahead path Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 16/25] fs: Convert mpage_readpages to mpage_readahead Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 17/25] btrfs: Convert from readpages to readahead Matthew Wilcox
2020-02-26 17:05   ` Christoph Hellwig
2020-02-28 14:08     ` David Sterba
2020-02-25 21:48 ` [PATCH v8 18/25] erofs: Convert uncompressed files " Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 19/25] erofs: Convert compressed " Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 20/25] ext4: Convert " Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 21/25] ext4: Pass the inode to ext4_mpage_readpages Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 22/25] f2fs: Convert from readpages to readahead Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 23/25] f2fs: Pass the inode to f2fs_mpage_readpages Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 24/25] fuse: Convert from readpages to readahead Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 25/25] iomap: " Matthew Wilcox
2020-02-26 17:04   ` Darrick J. Wong
2020-02-26 17:07     ` Christoph Hellwig
2020-02-26 17:10       ` Darrick J. Wong
2020-02-26 17:07   ` Christoph Hellwig
2020-03-19 10:20 ` [PATCH v8 00/25] Change readahead API Christoph Hellwig
2020-03-19 11:57   ` Matthew Wilcox
2020-03-19 11:49 ` William Kucharski

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