[PATCH 4/3] Avoid using 'lstat()' to figure out directories

[Linus Torvalds <torvalds@linux-foundation.org>]

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 9 Jul 2009 13:14:28 -0700
Subject: [PATCH 4/3] Avoid using 'lstat()' to figure out directories

If we have an up-to-date index entry for a file in that directory, we
can know that the directories leading up to that file must be
directories.  No need to do an lstat() on the directory.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

This is the patch I already sent out earlier. Now it's just numbered. 
There's going to be an additional three patches to actually give the right 
behavior for index preloading, so that we can really say "if CE_UPTODATE 
is set, then the whole directory structure is valid".

 dir.c |   47 ++++++++++++++++++++++++++++++++++++++++++-----
 1 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/dir.c b/dir.c
index 8a9e7d8..e05b850 100644
--- a/dir.c
+++ b/dir.c
@@ -566,18 +566,55 @@ static int in_pathspec(const char *path, int len, const struct path_simplify *si
 	return 0;
 }
 
+static int get_index_dtype(const char *path, int len)
+{
+	int pos;
+	struct cache_entry *ce;
+
+	ce = cache_name_exists(path, len, 0);
+	if (ce) {
+		if (!ce_uptodate(ce))
+			return DT_UNKNOWN;
+		if (S_ISGITLINK(ce->ce_mode))
+			return DT_DIR;
+		/*
+		 * Nobody actually cares about the
+		 * difference between DT_LNK and DT_REG
+		 */
+		return DT_REG;
+	}
+
+	/* Try to look it up as a directory */
+	pos = cache_name_pos(path, len);
+	if (pos >= 0)
+		return DT_UNKNOWN;
+	pos = -pos-1;
+	while (pos < active_nr) {
+		ce = active_cache[pos++];
+		if (strncmp(ce->name, path, len))
+			break;
+		if (ce->name[len] > '/')
+			break;
+		if (ce->name[len] < '/')
+			continue;
+		if (!ce_uptodate(ce))
+			break;	/* continue? */
+		return DT_DIR;
+	}
+	return DT_UNKNOWN;
+}
+
 static int get_dtype(struct dirent *de, const char *path, int len)
 {
 	int dtype = de ? DTYPE(de) : DT_UNKNOWN;
-	struct cache_entry *ce;
 	struct stat st;
 
 	if (dtype != DT_UNKNOWN)
 		return dtype;
-	ce = cache_name_exists(path, len, 0);
-	if (ce && ce_uptodate(ce))
-		st.st_mode = ce->ce_mode;
-	else if (lstat(path, &st))
+	dtype = get_index_dtype(path, len);
+	if (dtype != DT_UNKNOWN)
+		return dtype;
+	if (lstat(path, &st))
 		return dtype;
 	if (S_ISREG(st.st_mode))
 		return DT_REG;
-- 
1.6.3.3.415.ga8877