[PATCH 0/10 v2] Ranged pagevec lookup

[PATCH 0/10 v2] Ranged pagevec lookup

[Jan Kara]

Hello,

This patch series was split out of the larger series to clean up pagevec APIs
and provide ranged lookups. In this series I make pagevec_lookup() update the
index (to be consistent with pagevec_lookup_tag() and also as a preparation
for ranged lookups), provide ranged variant of pagevec_lookup() and use it
in places where it makes sense. This not only removes some common code but
is also a measurable performance win for some use cases (see patch 4/10) where
radix tree is sparse and searching & grabing of a page after the end of the
range has measurable overhead.

Andrew, can you please consider merging this series?

Full series including dependencies can be also obtained from my git tree:

git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git find_get_pages_range

Opinions and review welcome!

								Honza

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[PATCH 08/10] fs: Use pagevec_lookup_range() in page_cache_seek_hole_data()

[Jan Kara]

We want only pages from given range in page_cache_seek_hole_data(). Use
pagevec_lookup_range() instead of pagevec_lookup() and remove
unnecessary code. Note that the check for getting less pages than
desired can be removed because index gets updated by
pagevec_lookup_range().

CC: linux-fsdevel@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/buffer.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 7e531bb356bd..8770b58ca569 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3549,11 +3549,10 @@ page_cache_seek_hole_data(struct inode *inode, loff_t offset, loff_t length,
 	pagevec_init(&pvec, 0);
 
 	do {
-		unsigned want, nr_pages, i;
+		unsigned nr_pages, i;
 
-		want = min_t(unsigned, end - index, PAGEVEC_SIZE);
-		nr_pages = pagevec_lookup(&pvec, inode->i_mapping, &index,
-					  want);
+		nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping, &index,
+						end - 1, PAGEVEC_SIZE);
 		if (nr_pages == 0)
 			break;
 
@@ -3574,10 +3573,6 @@ page_cache_seek_hole_data(struct inode *inode, loff_t offset, loff_t length,
 			    lastoff < page_offset(page))
 				goto check_range;
 
-			/* Searching done if the page index is out of range. */
-			if (page->index >= end)
-				goto not_found;
-
 			lock_page(page);
 			if (likely(page->mapping == inode->i_mapping) &&
 			    page_has_buffers(page)) {
@@ -3590,11 +3585,6 @@ page_cache_seek_hole_data(struct inode *inode, loff_t offset, loff_t length,
 			unlock_page(page);
 			lastoff = page_offset(page) + PAGE_SIZE;
 		}
-
-		/* Searching done if fewer pages returned than wanted. */
-		if (nr_pages < want)
-			break;
-
 		pagevec_release(&pvec);
 	} while (index < end);
 
-- 
2.12.3

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