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>

1 files changed, 7 insertions, 1 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index d39e2241ceb7..8707bcc615ff 100644
--- 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);