fsmonitor: do not compare bitmap size with size of split index

3444ec2e ("fsmonitor: don't fill bitmap with entries to be removed",
2019-10-11) added a handful of sanity checks that make sure that a
bit position in fsmonitor bitmap does not go beyond the end of the
index.  As each bit in the bitmap corresponds to a path in the
index, this is the right check most of the time.

Except for the case when we are in the split-index mode and looking
at a delta index that is to be overlayed on the base index but
before the base index has actually been merged in, namely in read_
and write_fsmonitor_extension().  In these codepaths, the entries in
the split/delta index is typically a small subset of the entire set
of paths (otherwise why would we be using split-index?), so the
bitmap used by the fsmonitor is almost always larger than the number
of entries in the partial index, and the incorrect comparison would
trigger the BUG().

Reported-by: Utsav Shah <ukshah2@illinois.edu>
Helped-by: Kevin Willford <Kevin.Willford@microsoft.com>
Helped-by: William Baker <William.Baker@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/fsmonitor.c b/fsmonitor.c
index 1f4aa1b150dbe948910705c9ff4e75ad0a6a12a1..0477500b392b2baee699b51f2afa39381e66504d 100644 (file)
--- a/fsmonitor.c
+++ b/fsmonitor.c
@@ -55,7 +55,8 @@ int read_fsmonitor_extension(struct index_state *istate, const void *data,
        }
        istate->fsmonitor_dirty = fsmonitor_dirty;
 
-       if (istate->fsmonitor_dirty->bit_size > istate->cache_nr)
+       if (!istate->split_index &&
+           istate->fsmonitor_dirty->bit_size > istate->cache_nr)
                BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" > %u)",
                    (uintmax_t)istate->fsmonitor_dirty->bit_size, istate->cache_nr);
 
@@ -83,7 +84,8 @@ void write_fsmonitor_extension(struct strbuf *sb, struct index_state *istate)
        uint32_t ewah_size = 0;
        int fixup = 0;
 
-       if (istate->fsmonitor_dirty->bit_size > istate->cache_nr)
+       if (!istate->split_index &&
+           istate->fsmonitor_dirty->bit_size > istate->cache_nr)
                BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" > %u)",
                    (uintmax_t)istate->fsmonitor_dirty->bit_size, istate->cache_nr);