[PATCH v2 16/25] iomap: Support large pages in read paths

Matthew Wilcox
2020-02-12T04:19:42Z

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

Use thp_size() instead of PAGE_SIZE, use offset_in_this_page() and
abstract away how to access the list of readahead pages.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
fs/iomap/buffered-io.c | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index e522039f627f..68f8903ecd6d 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -179,14 +179,16 @@ iomap_read_finish(struct iomap_page *iop, struct page *page)
static void
iomap_read_page_end_io(struct bio_vec *bvec, int error)
{
- struct page *page = bvec->bv_page;
+ struct page *page = compound_head(bvec->bv_page);
struct iomap_page *iop = to_iomap_page(page);
+ unsigned offset = bvec->bv_offset +
+ PAGE_SIZE * (bvec->bv_page - page);

if (unlikely(error)) {
ClearPageUptodate(page);
SetPageError(page);
} else {
- iomap_set_range_uptodate(page, bvec->bv_offset, bvec->bv_len);
+ iomap_set_range_uptodate(page, offset, bvec->bv_len);
}

iomap_read_finish(iop, page);
@@ -239,6 +241,16 @@ static inline bool iomap_block_needs_zeroing(struct inode *inode,
pos >= i_size_read(inode);
}

+/*
+ * Estimate the number of vectors we need based on the current page size;
+ * if we're wrong we'll end up doing an overly large allocation or needing
+ * to do a second allocation, neither of which is a big deal.
+ */
+static unsigned int iomap_nr_vecs(struct page *page, loff_t length)
+{
+ return (length + thp_size(page) - 1) >> page_shift(page);
+}
+
static loff_t
iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
struct iomap *iomap, struct iomap *srcmap)
@@ -263,7 +275,7 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
goto done;

if (iomap_block_needs_zeroing(inode, iomap, pos)) {
- zero_user(page, poff, plen);
+ zero_user_large(page, poff, plen);
iomap_set_range_uptodate(page, poff, plen);
goto done;
}
@@ -294,7 +306,7 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,

if (!ctx->bio || !is_contig || bio_full(ctx->bio, plen)) {
gfp_t gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL);
- int nr_vecs = (length + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ int nr_vecs = iomap_nr_vecs(page, length);

if (ctx->bio)
submit_bio(ctx->bio);
@@ -331,9 +343,9 @@ iomap_readpage(struct page *page, const struct iomap_ops *ops)

trace_iomap_readpage(page->mapping->host, 1);

- for (poff = 0; poff < PAGE_SIZE; poff += ret) {
- ret = iomap_apply(inode, page_offset(page) + poff,
- PAGE_SIZE - poff, 0, ops, &ctx,
+ for (poff = 0; poff < thp_size(page); poff += ret) {
+ ret = iomap_apply(inode, file_offset_of_page(page) + poff,
+ thp_size(page) - poff, 0, ops, &ctx,
iomap_readpage_actor);
if (ret <= 0) {
WARN_ON_ONCE(ret == 0);
@@ -376,7 +388,7 @@ iomap_readahead_actor(struct inode *inode, loff_t pos, loff_t length,
if (WARN_ON(ret == 0))
break;
done += ret;
- if (offset_in_page(pos + done) == 0) {
+ if (offset_in_this_page(ctx->cur_page, pos + done) == 0) {
ctx->rac->nr_pages -= ctx->rac->batch_count;
if (!ctx->cur_page_in_bio)
unlock_page(ctx->cur_page);
--
2.25.0