bcachefs: Heap code fix

When deleting an entry from a heap that was at entry h->used - 1, we'd
end up calling heap_sift() on an entry outside the heap - the entry we
just removed - which would end up re-adding it to the heap and deleting
something we didn't want to delete. Oops...

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

diff --git a/fs/bcachefs/util.h b/fs/bcachefs/util.h
index f2df4d7fbec98844fcd522fb6eeea0b2c47c1bf2..fd776fb281b74209edc401be8e788412d0c5ef01 100644 (file)
--- a/fs/bcachefs/util.h
+++ b/fs/bcachefs/util.h
@@ -210,9 +210,11 @@ do {                                                                       \
                                                                        \
        BUG_ON(_i >= (h)->used);                                        \
        (h)->used--;                                                    \
-       heap_swap(h, _i, (h)->used, set_backpointer);                   \
-       heap_sift_up(h, _i, cmp, set_backpointer);                      \
-       heap_sift_down(h, _i, cmp, set_backpointer);                    \
+       if ((_i) < (h)->used) {                                         \
+               heap_swap(h, _i, (h)->used, set_backpointer);           \
+               heap_sift_up(h, _i, cmp, set_backpointer);              \
+               heap_sift_down(h, _i, cmp, set_backpointer);            \
+       }                                                               \
 } while (0)
 
 #define heap_pop(h, d, cmp, set_backpointer)                           \