[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

[PATCH 05/10] ext4: Use pagevec_lookup_range() in ext4_find_unwritten_pgoff()

[Jan Kara]

Use pagevec_lookup_range() in ext4_find_unwritten_pgoff() since we are
interested only in pages in the given range. Simplify the logic as a
result of not getting pages out of range and index getting automatically
advanced.

CC: linux-ext4@vger.kernel.org
CC: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/file.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index ab09cb6fcce3..ac39a6a1ea5d 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -494,12 +494,11 @@ static int ext4_find_unwritten_pgoff(struct inode *inode,
 
 	pagevec_init(&pvec, 0);
 	do {
-		int i, num;
+		int i;
 		unsigned long nr_pages;
 
-		num = min_t(pgoff_t, end - index, PAGEVEC_SIZE - 1) + 1;
-		nr_pages = pagevec_lookup(&pvec, inode->i_mapping, &index,
-					  (pgoff_t)num);
+		nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping,
+					&index, end, PAGEVEC_SIZE);
 		if (nr_pages == 0)
 			break;
 
@@ -518,9 +517,6 @@ static int ext4_find_unwritten_pgoff(struct inode *inode,
 				goto out;
 			}
 
-			if (page->index > end)
-				goto out;

[PATCH 06/10] ext4: Use pagevec_lookup_range() in writeback code

[Jan Kara]

Both occurences of pagevec_lookup() actually want only pages from a
given range. Use pagevec_lookup_range() for the lookup.

CC: "Theodore Ts'o" <tytso@mit.edu>
CC: linux-ext4@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/inode.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 68d0166d5ebc..eb86c1baf40c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1676,13 +1676,13 @@ static void mpage_release_unused_pages(struct mpage_da_data *mpd,
 
 	pagevec_init(&pvec, 0);
 	while (index <= end) {
-		nr_pages = pagevec_lookup(&pvec, mapping, &index, PAGEVEC_SIZE);
+		nr_pages = pagevec_lookup_range(&pvec, mapping, &index, end,
+						PAGEVEC_SIZE);
 		if (nr_pages == 0)
 			break;
 		for (i = 0; i < nr_pages; i++) {
 			struct page *page = pvec.pages[i];
-			if (page->index > end)
-				break;
+
 			BUG_ON(!PageLocked(page));
 			BUG_ON(PageWriteback(page));
 			if (invalidate) {
@@ -2303,15 +2303,13 @@ static int mpage_map_and_submit_buffers(struct mpage_da_data *mpd)
 
 	pagevec_init(&pvec, 0);
 	while (start <= end) {
-		nr_pages = pagevec_lookup(&pvec, inode->i_mapping, &start,
-					  PAGEVEC_SIZE);
+		nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping,
+						&start, end, PAGEVEC_SIZE);
 		if (nr_pages == 0)
 			break;
 		for (i = 0; i < nr_pages; i++) {
 			struct page *page = pvec.pages[i];
 
-			if (page->index > end)
-				break;
 			bh = head = page_buffers(page);
 			do {
 				if (lblk < mpd->map.m_lblk)
-- 
2.12.3