[PATCH v3 4/4] fsmonitor: Delay updating state until after split index is merged

[Alex Vandiver <alexmv@dropbox.com>]

If the fsmonitor extension is used in conjunction with the split index
extension, the set of entries in the index when it is first loaded is
only a subset of the real index.  This leads to only the non-"base"
index being marked as CE_FSMONITOR_VALID.

Delay the expansion of the ewah bitmap until after tweak_split_index
has been called to merge in the base index as well.

The new fsmonitor_dirty is kept from being leaked by dint of being
cleaned up in post_read_index_from, which is guaranteed to be called
after do_read_index in read_index_from.

Signed-off-by: Alex Vandiver <alexmv@dropbox.com>
---
 cache.h     |  1 +
 fsmonitor.c | 39 ++++++++++++++++++++++++---------------
 2 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/cache.h b/cache.h
index 25adcf681..0a4f43ec2 100644
--- a/cache.h
+++ b/cache.h
@@ -348,6 +348,7 @@ struct index_state {
 	unsigned char sha1[20];
 	struct untracked_cache *untracked;
 	uint64_t fsmonitor_last_update;
+	struct ewah_bitmap *fsmonitor_dirty;
 };
 
 extern struct index_state the_index;
diff --git a/fsmonitor.c b/fsmonitor.c
index 4ea44dcc6..417759224 100644
--- a/fsmonitor.c
+++ b/fsmonitor.c
@@ -49,20 +49,7 @@ int read_fsmonitor_extension(struct index_state *istate, const void *data,
 		ewah_free(fsmonitor_dirty);
 		return error("failed to parse ewah bitmap reading fsmonitor index extension");
 	}
-
-	if (git_config_get_fsmonitor()) {
-		/* Mark all entries valid */
-		for (i = 0; i < istate->cache_nr; i++)
-			istate->cache[i]->ce_flags |= CE_FSMONITOR_VALID;
-
-		/* Mark all previously saved entries as dirty */
-		ewah_each_bit(fsmonitor_dirty, fsmonitor_ewah_callback, istate);
-
-		/* Now mark the untracked cache for fsmonitor usage */
-		if (istate->untracked)
-			istate->untracked->use_fsmonitor = 1;
-	}
-	ewah_free(fsmonitor_dirty);
+	istate->fsmonitor_dirty = fsmonitor_dirty;
 
 	trace_printf_key(&trace_fsmonitor, "read fsmonitor extension successful");
 	return 0;
@@ -239,7 +226,29 @@ void remove_fsmonitor(struct index_state *istate)
 
 void tweak_fsmonitor(struct index_state *istate)
 {
-	switch (git_config_get_fsmonitor()) {
+	int i;
+	int fsmonitor_enabled = git_config_get_fsmonitor();
+
+	if (istate->fsmonitor_dirty) {
+		if (fsmonitor_enabled) {
+			/* Mark all entries valid */
+			for (i = 0; i < istate->cache_nr; i++) {
+				istate->cache[i]->ce_flags |= CE_FSMONITOR_VALID;
+			}
+
+			/* Mark all previously saved entries as dirty */
+			ewah_each_bit(istate->fsmonitor_dirty, fsmonitor_ewah_callback, istate);
+
+			/* Now mark the untracked cache for fsmonitor usage */
+			if (istate->untracked)
+				istate->untracked->use_fsmonitor = 1;
+		}
+
+		ewah_free(istate->fsmonitor_dirty);
+		istate->fsmonitor_dirty = NULL;
+	}
+
+	switch (fsmonitor_enabled) {
 	case -1: /* keep: do nothing */
 		break;
 	case 0: /* false */
-- 
2.15.0.rc1.413.g76aedb451