mm: implement find_get_pages_range()

Implement a variant of find_get_pages() that stops iterating at given
index.  This may be substantial performance gain if the mapping is
sparse.  See following commit for details.  Furthermore lots of users of
this function (through pagevec_lookup()) actually want a range lookup
and all of them are currently open-coding this.

Also create corresponding pagevec_lookup_range() function.

Link: http://lkml.kernel.org/r/20170726114704.7626-4-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 2 deletions

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 249b1b5964c7..5bbd6780f205 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -353,8 +353,16 @@ struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset);
 unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
                           unsigned int nr_entries, struct page **entries,
                           pgoff_t *indices);
-unsigned find_get_pages(struct address_space *mapping, pgoff_t *start,
-                        unsigned int nr_pages, struct page **pages);
+unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
+                        pgoff_t end, unsigned int nr_pages,
+                        struct page **pages);
+static inline unsigned find_get_pages(struct address_space *mapping,
+                        pgoff_t *start, unsigned int nr_pages,
+                        struct page **pages)
+{
+        return find_get_pages_range(mapping, start, (pgoff_t)-1, nr_pages,
+                                    pages);
+}
 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
                                unsigned int nr_pages, struct page **pages);
 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,