Commit 28187ae5 authored Jul 04, 2018 by Nikolay Borisov Committed by David Sterba Aug 06, 2018

btrfs: Simplify page unlocking in alloc_extent_buffer



Current version of the page unlocking code was added in
727011e0 ("Btrfs: allow metadata blocks larger than the page size")
but even in this commit that particular flag was never used per-se. In
fact, btrfs only uses PageChecked for data pages to identify pages
which have been dirtied but don't have ORDERED bit set. For more
information see 247e743c ("Btrfs: Use async helpers to deal with
pages that have been improperly dirtied").

However, this doesn't apply to extent buffer pages. The important bit
here is that the pages are unlocked AFTER the extent buffer has been
properly recorded in the radix tree to avoid races with
btree_releasepage. Let's exploit this fact and simplify the page
unlocking sequence by unlocking the pages in-order and removing the
redundant PageChecked flag setting/clearing.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent 8b9b6f25

fs/btrfs/extent_io.c

+2 −7

Original line number	Diff line number	Diff line
		@@ -5047,13 +5047,8 @@ again:
		* after the extent buffer is in the radix tree so
		* it doesn't get lost
		*/
		SetPageChecked(eb->pages[0]);
		for (i = 1; i < num_pages; i++) {
		p = eb->pages[i];
		ClearPageChecked(p);
		unlock_page(p);
		}
		unlock_page(eb->pages[0]);
		for (i = 0; i < num_pages; i++)
		unlock_page(eb->pages[i]);
		return eb;

		free_eb:

Admin message