fsmonitor: store fsmonitor bitmap before splitting index

ba1b9cac ("fsmonitor: delay updating state until after split index
is merged", 2017-10-27) resolved the problem of the fsmonitor data
being applied to the non-base index when reading; however, a similar
problem exists when writing the index.  Specifically, writing of the
fsmonitor extension happens only after the work to split the index
has been applied -- as such, the information in the index is only
for the non-"base" index, and thus the extension information
contains only partial data.

When saving, compute the ewah bitmap before the index is split, and
store it in the fsmonitor_dirty field, mirroring the behavior that
occurred during reading.  fsmonitor_dirty is kept from being leaked by
being freed when the extension data is written -- which always happens
precisely once, no matter the split index configuration.

Signed-off-by: Alex Vandiver <alexmv@dropbox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 12 insertions, 8 deletions

diff --git a/fsmonitor.c b/fsmonitor.c
index f494a866d5..0af7c4edba 100644
--- a/fsmonitor.c
+++ b/fsmonitor.c
@@ -54,12 +54,19 @@ int read_fsmonitor_extension(struct index_state *istate, const void *data,
 	return 0;
 }
 
+void fill_fsmonitor_bitmap(struct index_state *istate)
+{
+	int i;
+	istate->fsmonitor_dirty = ewah_new();
+	for (i = 0; i < istate->cache_nr; i++)
+		if (!(istate->cache[i]->ce_flags & CE_FSMONITOR_VALID))
+			ewah_set(istate->fsmonitor_dirty, i);
+}
+
 void write_fsmonitor_extension(struct strbuf *sb, struct index_state *istate)
 {
 	uint32_t hdr_version;
 	uint64_t tm;
-	struct ewah_bitmap *bitmap;
-	int i;
 	uint32_t ewah_start;
 	uint32_t ewah_size = 0;
 	int fixup = 0;
@@ -73,12 +80,9 @@ void write_fsmonitor_extension(struct strbuf *sb, struct index_state *istate)
 	strbuf_add(sb, &ewah_size, sizeof(uint32_t)); /* we'll fix this up later */
 
 	ewah_start = sb->len;
-	bitmap = ewah_new();
-	for (i = 0; i < istate->cache_nr; i++)
-		if (!(istate->cache[i]->ce_flags & CE_FSMONITOR_VALID))
-			ewah_set(bitmap, i);
-	ewah_serialize_strbuf(bitmap, sb);
-	ewah_free(bitmap);
+	ewah_serialize_strbuf(istate->fsmonitor_dirty, sb);
+	ewah_free(istate->fsmonitor_dirty);
+	istate->fsmonitor_dirty = NULL;
 
 	/* fix up size field */
 	put_be32(&ewah_size, sb->len - ewah_start);