btrfs: avoid unnecessary next node searches when clearing bits from extent range

When clearing bits for a range in an io tree, at clear_state_bit(), we
always go search for the next node (through next_state() -> rb_next()) and
return it. However if the current extent state record ends at or after the
target range passed to btrfs_clear_extent_bit_changeset() or
btrfs_convert_extent_bit(), we are just wasting time finding that next
node since we won't use it in those functions.

Improve on this by skipping the next node search if the current node ends
at or after the target range.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent-io-tree.c b/fs/btrfs/extent-io-tree.c
index 0697afebb71dc4b65b0dd58f0a81254b1d081d32..d8d65a6a6cb1846e0d5a64d42c20fbe7a0ead20c 100644 (file)
--- a/fs/btrfs/extent-io-tree.c
+++ b/fs/btrfs/extent-io-tree.c
@@ -537,6 +537,18 @@ static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
        return 0;
 }
 
+/*
+ * Use this during tree iteration to avoid doing next node searches when it's
+ * not needed (the current record ends at or after the target range's end).
+ */
+static inline struct extent_state *next_search_state(struct extent_state *state, u64 end)
+{
+       if (state->end < end)
+               return next_state(state);
+
+       return NULL;
+}
+
 /*
  * Utility function to clear some bits in an extent state struct.  It will
  * optionally wake up anyone waiting on this state (wake == 1).
@@ -546,7 +558,7 @@ static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
  */
 static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
                                            struct extent_state *state,
-                                           u32 bits, int wake,
+                                           u32 bits, int wake, u64 end,
                                            struct extent_changeset *changeset)
 {
        struct extent_state *next;
@@ -562,7 +574,7 @@ static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
        if (wake)
                wake_up(&state->wq);
        if (state->state == 0) {
-               next = next_state(state);
+               next = next_search_state(state, end);
                if (extent_state_in_tree(state)) {
                        rb_erase(&state->rb_node, &tree->state);
                        RB_CLEAR_NODE(&state->rb_node);
@@ -572,7 +584,7 @@ static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
                }
        } else {
                merge_state(tree, state);
-               next = next_state(state);
+               next = next_search_state(state, end);
        }
        return next;
 }
@@ -666,7 +678,7 @@ hit_next:
 
        /* The state doesn't have the wanted bits, go ahead. */
        if (!(state->state & bits)) {
-               state = next_state(state);
+               state = next_search_state(state, end);
                goto next;
        }
 
@@ -696,7 +708,8 @@ hit_next:
                        goto out;
                }
                if (state->end <= end) {
-                       state = clear_state_bit(tree, state, bits, wake, changeset);
+                       state = clear_state_bit(tree, state, bits, wake, end,
+                                               changeset);
                        goto next;
                }
                if (need_resched())
@@ -726,13 +739,13 @@ hit_next:
                if (wake)
                        wake_up(&state->wq);
 
-               clear_state_bit(tree, prealloc, bits, wake, changeset);
+               clear_state_bit(tree, prealloc, bits, wake, end, changeset);
 
                prealloc = NULL;
                goto out;
        }
 
-       state = clear_state_bit(tree, state, bits, wake, changeset);
+       state = clear_state_bit(tree, state, bits, wake, end, changeset);
 next:
        if (last_end >= end)
                goto out;
@@ -1357,7 +1370,7 @@ hit_next:
        if (state->start == start && state->end <= end) {
                set_state_bits(tree, state, bits, NULL);
                cache_state(state, cached_state);
-               state = clear_state_bit(tree, state, clear_bits, 0, NULL);
+               state = clear_state_bit(tree, state, clear_bits, 0, end, NULL);
                if (last_end == (u64)-1)
                        goto out;
                start = last_end + 1;
@@ -1397,7 +1410,7 @@ hit_next:
                if (state->end <= end) {
                        set_state_bits(tree, state, bits, NULL);
                        cache_state(state, cached_state);
-                       state = clear_state_bit(tree, state, clear_bits, 0, NULL);
+                       state = clear_state_bit(tree, state, clear_bits, 0, end, NULL);
                        if (last_end == (u64)-1)
                                goto out;
                        start = last_end + 1;
@@ -1469,7 +1482,7 @@ hit_next:
 
                set_state_bits(tree, prealloc, bits, NULL);
                cache_state(prealloc, cached_state);
-               clear_state_bit(tree, prealloc, clear_bits, 0, NULL);
+               clear_state_bit(tree, prealloc, clear_bits, 0, end, NULL);
                prealloc = NULL;
                goto out;
        }