In some cases, especially inside the unpack-trees.c file, and inside
the verify_absent() function, we can avoid some unnecessary calls to
lstat(), if the lstat_cache() function can also be told to keep track
of non-existing directories.
So we update the lstat_cache() function to handle this new fact,
introduce a new wrapper function, and the result is that we save lots
of lstat() calls for a removed directory which previously contained
lots of files, when we call this new wrapper of lstat_cache() instead
of the old one.
We do similar changes inside the unlink_entry() function, since if we
can already say that the leading directory component of a pathname
does not exist, it is not necessary to try to remove a pathname below
it!
Thanks to Junio C Hamano, Linus Torvalds and Rene Scharfe for valuable
comments to this patch!
Signed-off-by: Kjetil Barvik <barvik@xxxxxxxxxxxx>
---
cache.h | 1 +
symlinks.c | 94 +++++++++++++++++++++++++++++++++++--------------------
unpack-trees.c | 4 +-
3 files changed, 63 insertions(+), 36 deletions(-)
diff --git a/cache.h b/cache.h
index 8e1af26..518e4c7 100644
--- a/cache.h
+++ b/cache.h
@@ -717,6 +717,7 @@ 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);
+extern int has_symlink_or_noent_leading_path(int len, const char *name);
extern struct alternate_object_database {
struct alternate_object_database *next;
diff --git a/symlinks.c b/symlinks.c
index 49fb4d8..c69556a 100644
--- a/symlinks.c
+++ b/symlinks.c
@@ -4,6 +4,7 @@ static struct cache_def {
char path[PATH_MAX];
int len;
int flags;
+ int track_flags;
} cache;
/*
@@ -30,21 +31,23 @@ static inline int longest_match_lstat_cache(int len, const char *name)
return match_len;
}
-static inline void reset_lstat_cache(void)
+static inline void reset_lstat_cache(int track_flags)
{
cache.path[0] = '\0';
cache.len = 0;
cache.flags = 0;
+ cache.track_flags = track_flags;
}
#define FL_DIR (1 << 0)
-#define FL_SYMLINK (1 << 1)
-#define FL_LSTATERR (1 << 2)
-#define FL_ERR (1 << 3)
+#define FL_NOENT (1 << 1)
+#define FL_SYMLINK (1 << 2)
+#define FL_LSTATERR (1 << 3)
+#define FL_ERR (1 << 4)
/*
* Check if name 'name' of length 'len' has a symlink leading
- * component, or if the directory exists and is real.
+ * component, or if the directory exists and is real, or not.
*
* To speed up the check, some information is allowed to be cached.
* This can be indicated by the 'track_flags' argument.
@@ -56,25 +59,35 @@ static int lstat_cache(int len, const char *name,
int match_flags, ret_flags, save_flags, max_len;
struct stat st;
- /*
- * Check to see if we have a match from the cache for the
- * symlink path type.
- */
- match_len = last_slash = longest_match_lstat_cache(len, name);
- match_flags = cache.flags & track_flags & FL_SYMLINK;
- if (match_flags && match_len == cache.len)
- return match_flags;
- /*
- * If we now have match_len > 0, we would know that the
- * matched part will always be a directory.
- *
- * Also, if we are tracking directories and 'name' is a
- * substring of the cache on a path component basis, we can
- * return immediately.
- */
- match_flags = track_flags & FL_DIR;
- if (match_flags && len == match_len)
- return match_flags;
+ if (cache.track_flags != track_flags) {
+ /*
+ * As a safeguard we clear the cache if the value of
+ * track_flags does not match with the last supplied
+ * value.
+ */
+ reset_lstat_cache(track_flags);
+ match_len = last_slash = 0;
+ } else {
+ /*
+ * Check to see if we have a match from the cache for
+ * the 2 "excluding" path types.
+ */
+ match_len = last_slash = longest_match_lstat_cache(len, name);
+ match_flags = cache.flags & track_flags & (FL_NOENT|FL_SYMLINK);
+ if (match_flags && match_len == cache.len)
+ return match_flags;
+ /*
+ * If we now have match_len > 0, we would know that
+ * the matched part will always be a directory.
+ *
+ * Also, if we are tracking directories and 'name' is
+ * a substring of the cache on a path component basis,
+ * we can return immediately.
+ */
+ match_flags = track_flags & FL_DIR;
+ if (match_flags && len == match_len)
+ return match_flags;
+ }
/*
* Okay, no match from the cache so far, so now we have to
@@ -95,6 +108,8 @@ static int lstat_cache(int len, const char *name,
if (lstat(cache.path, &st)) {
ret_flags = FL_LSTATERR;
+ if (errno == ENOENT)
+ ret_flags |= FL_NOENT;
} else if (S_ISDIR(st.st_mode)) {
last_slash_dir = last_slash;
continue;
@@ -107,11 +122,11 @@ static int lstat_cache(int len, const char *name,
}
/*
- * At the end update the cache. Note that max 2 different
- * path types, FL_SYMLINK and FL_DIR, can be cached for the
- * moment!
+ * At the end update the cache. Note that max 3 different
+ * path types, FL_NOENT, FL_SYMLINK and FL_DIR, can be cached
+ * for the moment!
*/
- save_flags = ret_flags & track_flags & FL_SYMLINK;
+ save_flags = ret_flags & track_flags & (FL_NOENT|FL_SYMLINK);
if (save_flags && last_slash > 0 && last_slash < PATH_MAX) {
cache.path[last_slash] = '\0';
cache.len = last_slash;
@@ -120,20 +135,20 @@ static int lstat_cache(int len, const char *name,
last_slash_dir > 0 && last_slash_dir < PATH_MAX) {
/*
* We have a separate test for the directory case,
- * since it could be that we have found a symlink and
- * the track_flags says that we cannot cache this
- * fact, so the cache would then have been left empty
- * in this case.
+ * since it could be that we have found a symlink or a
+ * non-existing directory and the track_flags says
+ * that we cannot cache this fact, so the cache would
+ * then have been left empty in this case.
*
* But if we are allowed to track real directories, we
* can still cache the path components before the last
- * one (the found symlink component).
+ * one (the found symlink or non-existing component).
*/
cache.path[last_slash_dir] = '\0';
cache.len = last_slash_dir;
cache.flags = FL_DIR;
} else {
- reset_lstat_cache();
+ reset_lstat_cache(track_flags);
}
return ret_flags;
}
@@ -147,3 +162,14 @@ int has_symlink_leading_path(int len, const char *name)
FL_SYMLINK|FL_DIR) &
FL_SYMLINK;
}
+
+/*
+ * Return non-zero if path 'name' has a leading symlink component or
+ * if some leading path component does not exists.
+ */
+int has_symlink_or_noent_leading_path(int len, const char *name)
+{
+ return lstat_cache(len, name,
+ FL_SYMLINK|FL_NOENT|FL_DIR) &
+ (FL_SYMLINK|FL_NOENT);
+}
diff --git a/unpack-trees.c b/unpack-trees.c
index 15c9ef5..16bc2ca 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -61,7 +61,7 @@ static void unlink_entry(struct cache_entry *ce)
char *cp, *prev;
char *name = ce->name;
- if (has_symlink_leading_path(ce_namelen(ce), ce->name))
+ if (has_symlink_or_noent_leading_path(ce_namelen(ce), ce->name))
return;
if (unlink(name))
return;
@@ -580,7 +580,7 @@ static int verify_absent(struct cache_entry *ce, const char *action,
if (o->index_only || o->reset || !o->update)
return 0;
- if (has_symlink_leading_path(ce_namelen(ce), ce->name))
+ if (has_symlink_or_noent_leading_path(ce_namelen(ce), ce->name))
return 0;
if (!lstat(ce->name, &st)) {
--
1.6.1.83.gd727f
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