[PATCH v2 3/4] packed-backend: extract munmap operation for `MMAP_TEMPORARY`

[shejialuo <shejialuo@gmail.com>]

"create_snapshot" would try to munmap the file when the "mmap_strategy"
is "MMAP_TEMPORARY". We also need to do this operation when checking the
consistency of the "packed-refs" file.

Create a new function "munmap_temporary_snapshot" to do above and
change "create_snapshot" to align with the behavior.

Suggested-by: Jeff King <peff@peff.net>
Suggested-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: shejialuo <shejialuo@gmail.com>
---
 refs/packed-backend.c | 36 +++++++++++++++++++++++-------------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index e582227772..ae6b6845a6 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -543,6 +543,27 @@ static int allocate_snapshot_buffer(struct snapshot *snapshot, int fd, struct st
 	return 1;
 }
 
+static void munmap_temporary_snapshot(struct snapshot *snapshot)
+{
+	char *buf_copy;
+	size_t size;
+
+	if (!snapshot)
+		return;
+
+	/*
+	 * We don't want to leave the file mmapped, so we are
+	 * forced to make a copy now:
+	 */
+	size = snapshot->eof - snapshot->start;
+	buf_copy = xmalloc(size);
+
+	memcpy(buf_copy, snapshot->start, size);
+	clear_snapshot_buffer(snapshot);
+	snapshot->buf = snapshot->start = buf_copy;
+	snapshot->eof = buf_copy + size;
+}
+
 /*
  * Depending on `mmap_strategy`, either mmap or read the contents of
  * the `packed-refs` file into the snapshot. Return 1 if the file
@@ -761,19 +782,8 @@ static struct snapshot *create_snapshot(struct packed_ref_store *refs)
 		verify_buffer_safe(snapshot);
 	}
 
-	if (mmap_strategy != MMAP_OK && snapshot->mmapped) {
-		/*
-		 * We don't want to leave the file mmapped, so we are
-		 * forced to make a copy now:
-		 */
-		size_t size = snapshot->eof - snapshot->start;
-		char *buf_copy = xmalloc(size);
-
-		memcpy(buf_copy, snapshot->start, size);
-		clear_snapshot_buffer(snapshot);
-		snapshot->buf = snapshot->start = buf_copy;
-		snapshot->eof = buf_copy + size;
-	}
+	if (mmap_strategy == MMAP_TEMPORARY && snapshot->mmapped)
+		munmap_temporary_snapshot(snapshot);
 
 	return snapshot;
 }
-- 
2.49.0