btrfs: make state preallocation more speculative in __set_extent_bit

Similar to __clear_extent_bit, do not fail if the state preallocation
fails as we might not need it. One less BUG_ON.

Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index d39e224..8707bcc 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -873,8 +873,14 @@ __set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
        bits |= EXTENT_FIRST_DELALLOC;
 again:
        if (!prealloc && gfpflags_allow_blocking(mask)) {
+               /*
+                * 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);
-               BUG_ON(!prealloc);
        }
 
        spin_lock(&tree->lock);