Commit 66448b9d authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: subpage: make extent_write_locked_range() compatible 



There are two sites are not subpage compatible yet for
extent_write_locked_range():

- How @nr_pages are calculated
  For subpage we can have the following range with 64K page size:

  0   32K  64K   96K 128K
  |   |////|/////|   |

  In that case, although 96K - 32K == 64K, thus it looks like one page
  is enough, but the range spans two pages, not one.

  Fix it by doing proper round_up() and round_down() to calculate
  @nr_pages.

  Also add some extra ASSERT()s to ensure the range passed in is already
  aligned.

- How the page end is calculated
  Currently we just use cur + PAGE_SIZE - 1 to calculate the page end.

  Which can't handle the above range layout, and will trigger ASSERT()
  in btrfs_writepage_endio_finish_ordered(), as the range is no longer
  covered by the page range.

  Fix it by taking page end into consideration.

Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 741ec653

fs/btrfs/extent_io.c

+11 −4
Original line number Diff line number Diff line
@@ -5086,15 +5086,14 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end) 
	struct address_space *mapping = inode->i_mapping;

	struct page *page;

	u64 cur = start;

	unsigned long nr_pages = (end - start + PAGE_SIZE) >>

		PAGE_SHIFT;

	unsigned long nr_pages;

	const u32 sectorsize = btrfs_sb(inode->i_sb)->sectorsize;

	struct extent_page_data epd = {

		.bio_ctrl = { 0 },

		.extent_locked = 1,

		.sync_io = 1,

	};

	struct writeback_control wbc_writepages = {

		.nr_to_write	= nr_pages * 2,

		.sync_mode	= WB_SYNC_ALL,

		.range_start	= start,

		.range_end	= end + 1,
@@ -5103,14 +5102,22 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end) 
		.no_cgroup_owner = 1,

	};



	ASSERT(IS_ALIGNED(start, sectorsize) && IS_ALIGNED(end + 1, sectorsize));

	nr_pages = (round_up(end, PAGE_SIZE) - round_down(start, PAGE_SIZE)) >>

		   PAGE_SHIFT;

	wbc_writepages.nr_to_write = nr_pages * 2;



	wbc_attach_fdatawrite_inode(&wbc_writepages, inode);

	while (cur <= end) {

		u64 cur_end = min(round_down(cur, PAGE_SIZE) + PAGE_SIZE - 1, end);



		page = find_get_page(mapping, cur >> PAGE_SHIFT);

		/*

		 * All pages in the range are locked since

		 * btrfs_run_delalloc_range(), thus there is no way to clear

		 * the page dirty flag.

		 */

		ASSERT(PageLocked(page));

		ASSERT(PageDirty(page));

		clear_page_dirty_for_io(page);

		ret = __extent_writepage(page, &wbc_writepages, &epd);
@@ -5120,7 +5127,7 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end) 
			first_error = ret;

		}

		put_page(page);

		cur += PAGE_SIZE;

		cur = cur_end + 1;

	}



	if (!found_error)