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

[Matthew Wilcox]

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

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

Signed-off-by: Matthew Wilcox (Oracle) <wi...@infradead.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