Commit 0420177c authored Sep 14, 2020 by Nikolay Borisov Committed by David Sterba Oct 07, 2020

btrfs: simplify metadata pages reading



Metadata pages currently use __do_readpage to read metadata pages,
unfortunately this function is also used to deal with ordinary data
pages. This makes the metadata pages reading code to go through multiple
hoops in order to adhere to __do_readpage invariants. Most of these are
necessary for data pages which could be compressed. For metadata it's
enough to simply build a bio and submit it.

To this effect simply call submit_extent_page directly from
read_extent_buffer_pages which is the only callpath used to populate
extent_buffers with data. This in turn enables further cleanups.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent 2f1d3e4b

fs/btrfs/extent_io.c

+10 −11

Original line number	Diff line number	Diff line
		@@ -5573,20 +5573,19 @@ int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num)
		}

		ClearPageError(page);
		err = __extent_read_full_page(page,
		btree_get_extent, &bio,
		mirror_num, &bio_flags,
		REQ_META);
		err = submit_extent_page(REQ_OP_READ \| REQ_META, NULL,
		page, page_offset(page), PAGE_SIZE, 0,
		&bio, end_bio_extent_readpage,
		mirror_num, 0, 0, false);
		if (err) {
		ret = err;
		/*
		* We use &bio in above __extent_read_full_page,
		* so we ensure that if it returns error, the
		* current page fails to add itself to bio and
		* it's been unlocked.
		*
		* We must dec io_pages by ourselves.
		* We failed to submit the bio so it's the
		* caller's responsibility to perform cleanup
		* i.e unlock page/set error bit.
		*/
		ret = err;
		SetPageError(page);
		unlock_page(page);
		atomic_dec(&eb->io_pages);
		}
		} else {

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