Commit b1793929 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

writeback: factor folio_prepare_writeback() out of write_cache_pages() 

Reduce write_cache_pages() by about 30 lines; much of it is commentary,
but it all bundles nicely into an obvious function.

[hch@lst.de: rename should_writeback_folio to folio_prepare_writeback per Jan]
Link: https://lkml.kernel.org/r/20240215063649.2164017-8-hch@lst.de


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarBrian Foster <bfoster@redhat.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Acked-by: default avatarDave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f946e0d2

mm/page-writeback.c

+34 −27
Original line number Diff line number Diff line
@@ -2360,6 +2360,38 @@ void tag_pages_for_writeback(struct address_space *mapping, 
}

EXPORT_SYMBOL(tag_pages_for_writeback);



static bool folio_prepare_writeback(struct address_space *mapping,

		struct writeback_control *wbc, struct folio *folio)

{

	/*

	 * Folio truncated or invalidated. We can freely skip it then,

	 * even for data integrity operations: the folio has disappeared

	 * concurrently, so there could be no real expectation of this

	 * data integrity operation even if there is now a new, dirty

	 * folio at the same pagecache index.

	 */

	if (unlikely(folio->mapping != mapping))

		return false;



	/*

	 * Did somebody else write it for us?

	 */

	if (!folio_test_dirty(folio))

		return false;



	if (folio_test_writeback(folio)) {

		if (wbc->sync_mode == WB_SYNC_NONE)

			return false;

		folio_wait_writeback(folio);

	}

	BUG_ON(folio_test_writeback(folio));



	if (!folio_clear_dirty_for_io(folio))

		return false;



	return true;

}



/**

 * write_cache_pages - walk the list of dirty pages of the given address space and write all of them.

 * @mapping: address space structure to write
@@ -2430,38 +2462,13 @@ int write_cache_pages(struct address_space *mapping, 
		for (i = 0; i < nr_folios; i++) {

			folio = fbatch.folios[i];

			folio_lock(folio);



			/*

			 * Page truncated or invalidated. We can freely skip it

			 * then, even for data integrity operations: the page

			 * has disappeared concurrently, so there could be no

			 * real expectation of this data integrity operation

			 * even if there is now a new, dirty page at the same

			 * pagecache address.

			 */

			if (unlikely(folio->mapping != mapping)) {

continue_unlock:

			if (!folio_prepare_writeback(mapping, wbc, folio)) {

				folio_unlock(folio);

				continue;

			}



			if (!folio_test_dirty(folio)) {

				/* someone wrote it for us */

				goto continue_unlock;

			}



			if (folio_test_writeback(folio)) {

				if (wbc->sync_mode != WB_SYNC_NONE)

					folio_wait_writeback(folio);

				else

					goto continue_unlock;

			}



			BUG_ON(folio_test_writeback(folio));

			if (!folio_clear_dirty_for_io(folio))

				goto continue_unlock;



			trace_wbc_writepage(wbc, inode_to_bdi(mapping->host));



			error = writepage(folio, wbc, data);

			wbc->nr_to_write -= folio_nr_pages(folio);