[PATCH 06/12] btrfs: Convert from readpages to readahead

Matthew Wilcox
2020-01-25T01:36:38Z

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

Use the new readahead operation in btrfs

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: linux-btrfs@vger.kernel.org
---
fs/btrfs/extent_io.c | 15 ++++-----------
fs/btrfs/extent_io.h | 2 +-
fs/btrfs/inode.c | 18 +++++++++---------
3 files changed, 14 insertions(+), 21 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 2f4802f405a2..b1e2acbec165 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4283,7 +4283,7 @@ int extent_writepages(struct address_space *mapping,
return ret;
}

-int extent_readpages(struct address_space *mapping, struct list_head *pages,
+unsigned extent_readahead(struct address_space *mapping, pgoff_t start,
unsigned nr_pages)
{
struct bio *bio = NULL;
@@ -4294,20 +4294,13 @@ int extent_readpages(struct address_space *mapping, struct list_head *pages,
int nr = 0;
u64 prev_em_start = (u64)-1;

- while (!list_empty(pages)) {
+ while (nr_pages) {
u64 contig_end = 0;

- for (nr = 0; nr < ARRAY_SIZE(pagepool) && !list_empty(pages);) {
- struct page *page = lru_to_page(pages);
+ for (nr = 0; nr < ARRAY_SIZE(pagepool) && nr_pages--;) {
+ struct page *page = readahead_page(mapping, start++);

prefetchw(&page->flags);
- list_del(&page->lru);
- if (add_to_page_cache_lru(page, mapping, page->index,
- readahead_gfp_mask(mapping))) {
- put_page(page);
- break;
- }
-
pagepool[nr++] = page;
contig_end = page_offset(page) + PAGE_SIZE - 1;
}
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index a8551a1f56e2..d0f154766a02 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -200,7 +200,7 @@ int extent_writepages(struct address_space *mapping,
struct writeback_control *wbc);
int btree_write_cache_pages(struct address_space *mapping,
struct writeback_control *wbc);
-int extent_readpages(struct address_space *mapping, struct list_head *pages,
+unsigned extent_readahead(struct address_space *mapping, pgoff_t start,
unsigned nr_pages);
int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
__u64 start, __u64 len);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c70baafb2a39..4f223b4f7dff 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5395,8 +5395,8 @@ static void evict_inode_truncate_pages(struct inode *inode)

/*
* Keep looping until we have no more ranges in the io tree.
- * We can have ongoing bios started by readpages (called from readahead)
- * that have their endio callback (extent_io.c:end_bio_extent_readpage)
+ * We can have ongoing bios started by readahead that have
+ * their endio callback (extent_io.c:end_bio_extent_readpage)
* still in progress (unlocked the pages in the bio but did not yet
* unlocked the ranges in the io tree). Therefore this means some
* ranges can still be locked and eviction started because before
@@ -7586,11 +7586,11 @@ static int lock_extent_direct(struct inode *inode, u64 lockstart, u64 lockend,
* for it to complete) and then invalidate the pages for
* this range (through invalidate_inode_pages2_range()),
* but that can lead us to a deadlock with a concurrent
- * call to readpages() (a buffered read or a defrag call
+ * call to readahead (a buffered read or a defrag call
* triggered a readahead) on a page lock due to an
* ordered dio extent we created before but did not have
* yet a corresponding bio submitted (whence it can not
- * complete), which makes readpages() wait for that
+ * complete), which makes readahead wait for that
* ordered extent to complete while holding a lock on
* that page.
*/
@@ -8829,11 +8829,11 @@ static int btrfs_writepages(struct address_space *mapping,
return extent_writepages(mapping, wbc);
}

-static int
-btrfs_readpages(struct file *file, struct address_space *mapping,
- struct list_head *pages, unsigned nr_pages)
+static unsigned
+btrfs_readahead(struct file *file, struct address_space *mapping,
+ pgoff_t start, unsigned nr_pages)
{
- return extent_readpages(mapping, pages, nr_pages);
+ return extent_readahead(mapping, start, nr_pages);
}

static int __btrfs_releasepage(struct page *page, gfp_t gfp_flags)
@@ -11045,7 +11045,7 @@ static const struct address_space_operations btrfs_aops = {
.readpage = btrfs_readpage,
.writepage = btrfs_writepage,
.writepages = btrfs_writepages,
- .readpages = btrfs_readpages,
+ .readahead = btrfs_readahead,
.direct_IO = btrfs_direct_IO,
.invalidatepage = btrfs_invalidatepage,
.releasepage = btrfs_releasepage,
--
2.24.1