Commit 48acc47d authored Oct 14, 2022 by Josef Bacik Committed by David Sterba Dec 05, 2022

btrfs: do not use GFP_ATOMIC in the read endio



We have done read endio in an async thread for a very, very long time,
which makes the use of GFP_ATOMIC and unlock_extent_atomic() unneeded in
our read endio path.  We've noticed under heavy memory pressure in our
fleet that we can fail these allocations, and then often trip a
BUG_ON(!allocation), which isn't an ideal outcome.  Begin to address
this by simply not using GFP_ATOMIC, which will allow us to do things
like actually allocate a extent state when doing
set_extent_bits(UPTODATE) in the endio handler.

End io handlers are not called in atomic context, besides we have been
allocating failrec with GFP_NOFS so we'd notice there's a problem.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent 7248e0ce

fs/btrfs/extent_io.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -897,8 +897,8 @@ static void end_sector_io(struct page *page, u64 offset, bool uptodate)
		end_page_read(page, uptodate, offset, sectorsize);
		if (uptodate)
		set_extent_uptodate(&inode->io_tree, offset,
		offset + sectorsize - 1, &cached, GFP_ATOMIC);
		unlock_extent_atomic(&inode->io_tree, offset, offset + sectorsize - 1,
		offset + sectorsize - 1, &cached, GFP_NOFS);
		unlock_extent(&inode->io_tree, offset, offset + sectorsize - 1,
		&cached);
		}

		@@ -1103,7 +1103,7 @@ static void endio_readpage_release_extent(struct processed_extent *processed,
		* Now we don't have range contiguous to the processed range, release
		* the processed range now.
		*/
		unlock_extent_atomic(tree, processed->start, processed->end, &cached);
		unlock_extent(tree, processed->start, processed->end, &cached);

		update:
		/* Update processed to current range */