Commit 368a83ce authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Theodore Ts'o
Browse files

ext4: pipeline buffer reads in mext_page_mkuptodate() 



Instead of synchronously reading one buffer at a time, submit reads
as we walk the buffers in the first loop, then wait for them in the
second loop.  This should be significantly more efficient, particularly
on HDDs, but I have not measured.

Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Link: https://patch.msgid.link/20240718223005.568869-2-willy@infradead.org


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent e37c9e17

fs/ext4/move_extent.c

+15 −8
Original line number Diff line number Diff line
@@ -174,7 +174,9 @@ mext_page_mkuptodate(struct folio *folio, unsigned from, unsigned to) 
	sector_t block;

	struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];

	unsigned int blocksize, block_start, block_end;

	int i, err,  nr = 0, partial = 0;

	int i, nr = 0;

	bool partial = false;



	BUG_ON(!folio_test_locked(folio));

	BUG_ON(folio_test_writeback(folio));
@@ -192,13 +194,13 @@ mext_page_mkuptodate(struct folio *folio, unsigned from, unsigned to) 
		block_end = block_start + blocksize;

		if (block_end <= from || block_start >= to) {

			if (!buffer_uptodate(bh))

				partial = 1;

				partial = true;

			continue;

		}

		if (buffer_uptodate(bh))

			continue;

		if (!buffer_mapped(bh)) {

			err = ext4_get_block(inode, block, bh, 0);

			int err = ext4_get_block(inode, block, bh, 0);

			if (err)

				return err;

			if (!buffer_mapped(bh)) {
@@ -207,6 +209,12 @@ mext_page_mkuptodate(struct folio *folio, unsigned from, unsigned to) 
				continue;

			}

		}

		lock_buffer(bh);

		if (buffer_uptodate(bh)) {

			unlock_buffer(bh);

			continue;

		}

		ext4_read_bh_nowait(bh, 0, NULL);

		BUG_ON(nr >= MAX_BUF_PER_PAGE);

		arr[nr++] = bh;

	}
@@ -216,11 +224,10 @@ mext_page_mkuptodate(struct folio *folio, unsigned from, unsigned to) 


	for (i = 0; i < nr; i++) {

		bh = arr[i];

		if (!bh_uptodate_or_lock(bh)) {

			err = ext4_read_bh(bh, 0, NULL);

			if (err)

				return err;

		}

		wait_on_buffer(bh);

		if (buffer_uptodate(bh))

			continue;

		return -EIO;

	}

out:

	if (!partial)