[PATCH 7/9] iomap: Convert write_count to byte count

[Matthew Wilcox (Oracle)]

Instead of counting bio segments, count the number of bytes submitted.
This insulates us from the block layer's definition of what a 'same page'
is, which is not necessarily clear once THPs are involved.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 fs/iomap/buffered-io.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index c9b44f86d166..8c6187a6f34e 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1050,7 +1050,7 @@ EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
 
 static void
 iomap_finish_page_writeback(struct inode *inode, struct page *page,
-		int error)
+		int error, unsigned int len)
 {
 	struct iomap_page *iop = to_iomap_page(page);
 
@@ -1062,7 +1062,7 @@ iomap_finish_page_writeback(struct inode *inode, struct page *page,
 	WARN_ON_ONCE(i_blocks_per_page(inode, page) > 1 && !iop);
 	WARN_ON_ONCE(iop && atomic_read(&iop->write_count) <= 0);
 
-	if (!iop || atomic_dec_and_test(&iop->write_count))
+	if (!iop || atomic_sub_and_test(len, &iop->write_count))
 		end_page_writeback(page);
 }
 
@@ -1096,7 +1096,8 @@ iomap_finish_ioend(struct iomap_ioend *ioend, int error)
 
 		/* walk each page on bio, ending page IO on them */
 		bio_for_each_segment_all(bv, bio, iter_all)
-			iomap_finish_page_writeback(inode, bv->bv_page, error);
+			iomap_finish_page_writeback(inode, bv->bv_page, error,
+					bv->bv_len);
 		bio_put(bio);
 	}
 	/* The ioend has been freed by bio_put() */
@@ -1312,8 +1313,8 @@ iomap_add_to_ioend(struct inode *inode, loff_t offset, struct page *page,
 
 	merged = __bio_try_merge_page(wpc->ioend->io_bio, page, len, poff,
 			&same_page);
-	if (iop && !same_page)
-		atomic_inc(&iop->write_count);
+	if (iop)
+		atomic_add(len, &iop->write_count);
 
 	if (!merged) {
 		if (bio_full(wpc->ioend->io_bio, len)) {
-- 
2.28.0