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Subject[PATCH v4 15/36] iomap: Support large pages in read paths
Date
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Use thp_size() instead of PAGE_SIZE, offset_in_thp() instead of
offset_in_page() and bio_for_each_thp_segment_all().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
fs/iomap/buffered-io.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 423ffc9d4a97..75f42c0d4cd9 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -198,7 +198,7 @@ iomap_read_end_io(struct bio *bio)
struct bio_vec *bvec;
struct bvec_iter_all iter_all;

- bio_for_each_segment_all(bvec, bio, iter_all)
+ bio_for_each_thp_segment_all(bvec, bio, iter_all)
iomap_read_page_end_io(bvec, error);
bio_put(bio);
}
@@ -238,6 +238,16 @@ 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)
@@ -294,7 +304,7 @@ 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);
gfp_t orig_gfp = gfp;
- int nr_vecs = (length + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ int nr_vecs = iomap_nr_vecs(page, length);

if (ctx->bio)
submit_bio(ctx->bio);
@@ -338,9 +348,9 @@ 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) {
+ for (poff = 0; poff < thp_size(page); poff += ret) {
ret = iomap_apply(inode, page_offset(page) + poff,
- PAGE_SIZE - poff, 0, ops, &ctx,
+ thp_size(page) - poff, 0, ops, &ctx,
iomap_readpage_actor);
if (ret <= 0) {
WARN_ON_ONCE(ret == 0);
@@ -374,7 +384,8 @@ iomap_readahead_actor(struct inode *inode, loff_t pos, loff_t length,
loff_t done, ret;

for (done = 0; done < length; done += ret) {
- if (ctx->cur_page && offset_in_page(pos + done) == 0) {
+ if (ctx->cur_page &&
+ offset_in_thp(ctx->cur_page, pos + done) == 0) {
if (!ctx->cur_page_in_bio)
unlock_page(ctx->cur_page);
put_page(ctx->cur_page);
--
2.26.2
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