Commit c7bc6319 authored Nov 03, 2014 by Filipe Manana Committed by Chris Mason Nov 20, 2014

Btrfs: avoid premature -ENOMEM in clear_extent_bit()

We try to allocate an extent state structure before acquiring the extent
state tree's spinlock as we might need a new one later and therefore avoid
doing later an atomic allocation while holding the tree's spinlock. However
we returned -ENOMEM if that initial non-atomic allocation failed, which is
a bit excessive since we might end up not needing the pre-allocated extent
state at all - for the case where the tree doesn't have any extent states
that cover the input range and cover too any other range. Therefore don't
return -ENOMEM if that pre-allocation fails.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

parent 7e33fd99

fs/btrfs/extent_io.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -595,9 +595,14 @@ int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
		clear = 1;
		again:
		if (!prealloc && (mask & __GFP_WAIT)) {
		/*
		* Don't care for allocation failure here because we might end
		* up not needing the pre-allocated extent state at all, which
		* is the case if we only have in the tree extent states that
		* cover our input range and don't cover too any other range.
		* If we end up needing a new extent state we allocate it later.
		*/
		prealloc = alloc_extent_state(mask);
		if (!prealloc)
		return -ENOMEM;
		}

		spin_lock(&tree->lock);