Re: [PATCH/RFC v5 1/1] more cache effective symlink/directory detection

- Also introduce a 'void clear_lstat_cache(void)' function, which
  should be used to clean the cache before usage.  If for instance,
  you have changed the types of directories which should be cached,
  the cache could contain a path which was not wanted.

--- a/cache.h
+++ b/cache.h

@@ -719,7 +719,29 @@ struct checkout {
 };
 
 extern int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *topath);
-extern int has_symlink_leading_path(int len, const char *name);
+
+#define LSTAT_REG      (1u << 0)
+#define LSTAT_DIR      (1u << 1)
+#define LSTAT_NOENT    (1u << 2)
+#define LSTAT_SYMLINK  (1u << 3)
+#define LSTAT_LSTATERR (1u << 4)
+#define LSTAT_ERR      (1u << 5)
+#define LSTAT_FULLPATH (1u << 6)
+extern unsigned int lstat_cache(int len, const char *name,
+				unsigned int track_flags, int prefix_len_stat_func);
+extern void clear_lstat_cache(void);
+static inline unsigned int has_symlink_leading_path(int len, const char *name)
+{
+	return lstat_cache(len, name, LSTAT_SYMLINK|LSTAT_DIR, -1) &
+		LSTAT_SYMLINK;
+}
+#define clear_symlink_cache() clear_lstat_cache()
+static inline unsigned int has_symlink_or_noent_leading_path(int len, const char *name)
+{
+	return lstat_cache(len, name, LSTAT_SYMLINK|LSTAT_NOENT|LSTAT_DIR, -1) &
+		(LSTAT_SYMLINK|LSTAT_NOENT);
+}
+#define clear_symlink_or_noent_cache() clear_lstat_cache()

diff --git a/entry.c b/entry.c
index aa2ee46a84033585d8e07a585610c5a697af82c2..293400cf5be63fd66b797a68e17bf953c600fe99 100644
--- a/entry.c
+++ b/entry.c

@@ -8,35 +8,28 @@ static void create_directories(const char *path, const struct checkout *state)
 	const char *slash = path;
 
 	while ((slash = strchr(slash+1, '/')) != NULL) {
-		struct stat st;
-		int stat_status;
-
 		len = slash - path;
 		memcpy(buf, path, len);
 		buf[len] = 0;
 
-		if (len <= state->base_dir_len)
-			/*
-			 * checkout-index --prefix=<dir>; <dir> is
-			 * allowed to be a symlink to an existing
-			 * directory.
-			 */
-			stat_status = stat(buf, &st);
-		else
-			/*
-			 * if there currently is a symlink, we would
-			 * want to replace it with a real directory.
-			 */
-			stat_status = lstat(buf, &st);
-
-		if (!stat_status && S_ISDIR(st.st_mode))
+		/* For 'checkout-index --prefix=<dir>', <dir> is
+		 * allowed to be a symlink to an existing directory,
+		 * therefore we must give 'state->base_dir_len' to the
+		 * cache, such that we test path components of the
+		 * prefix with stat() instead of lstat()
+		 *
+		 * We must also tell the cache to test the complete
+		 * length of the buffer (the '|LSTAT_FULLPATH' part).
+		 */
+		if (lstat_cache(len, buf, LSTAT_DIR|LSTAT_FULLPATH,
+				state->base_dir_len) &
+		    LSTAT_DIR)
 			continue; /* ok, it is already a directory. */