linux-kernel - [PATCH v5 37/39] mm: Allow PageReadahead to be set on head pages

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Date:   Thu, 28 May 2020 19:58:22 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     linux-fsdevel@...r.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH v5 37/39] mm: Allow PageReadahead to be set on head pages

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

Adjust the callers to only call PageReadahead on the head page.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 include/linux/page-flags.h |  4 ++--
 mm/filemap.c               | 14 +++++++-------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 979460df4768..a3110d675cd0 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -377,8 +377,8 @@ PAGEFLAG(MappedToDisk, mappedtodisk, PF_NO_TAIL)
 /* PG_readahead is only used for reads; PG_reclaim is only for writes */
 PAGEFLAG(Reclaim, reclaim, PF_NO_TAIL)
 	TESTCLEARFLAG(Reclaim, reclaim, PF_NO_TAIL)
-PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
-	TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)
+PAGEFLAG(Readahead, reclaim, PF_ONLY_HEAD)
+	TESTCLEARFLAG(Readahead, reclaim, PF_ONLY_HEAD)
 
 #ifdef CONFIG_HIGHMEM
 /*
diff --git a/mm/filemap.c b/mm/filemap.c
index 56eb086acef8..7d38eb9c2229 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2067,9 +2067,9 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
 			if (unlikely(page == NULL))
 				goto no_cached_page;
 		}
-		if (PageReadahead(page)) {
+		if (PageReadahead(compound_head(page))) {
 			page_cache_async_readahead(mapping,
-					ra, filp, page,
+					ra, filp, compound_head(page),
 					index, last_index - index);
 		}
 		if (!PageUptodate(page)) {
@@ -2454,10 +2454,10 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
 		return fpin;
 	if (ra->mmap_miss > 0)
 		ra->mmap_miss--;
-	if (PageReadahead(page)) {
+	if (PageReadahead(compound_head(page))) {
 		fpin = maybe_unlock_mmap_for_io(vmf, fpin);
 		page_cache_async_readahead(mapping, ra, file,
-					   page, offset, ra->ra_pages);
+				compound_head(page), offset, ra->ra_pages);
 	}
 	return fpin;
 }
@@ -2640,11 +2640,11 @@ void filemap_map_pages(struct vm_fault *vmf,
 		/* Has the page moved or been split? */
 		if (unlikely(page != xas_reload(&xas)))
 			goto skip;
+		if (PageReadahead(page))
+			goto skip;
 		page = find_subpage(page, xas.xa_index);
 
-		if (!PageUptodate(page) ||
-				PageReadahead(page) ||
-				PageHWPoison(page))
+		if (!PageUptodate(page) || PageHWPoison(page))
 			goto skip;
 		if (!trylock_page(page))
 			goto skip;
-- 
2.26.2