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 none 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 | 87 ++++++++++++++++++++++++++++++++++++--------------------
unpack-trees.c | 4 +-
3 files changed, 59 insertions(+), 33 deletions(-)
diff --git a/cache.h b/cache.h
index 231c06d..11181aa 100644
--- a/cache.h
+++ b/cache.h
@@ -720,6 +720,7 @@ 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 b17e4b3..52b3b0e 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;
/* Returns the length (on a path component basis) of the longest
@@ -29,21 +30,23 @@ static inline int greatest_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 is can be indicated by the 'track_flags' argument.
@@ -55,22 +58,32 @@ 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 = greatest_match_lstat_cache(len, name);
- match_flags = cache.flags & track_flags & FL_SYMLINK;
- if (match_flags && match_len == cache.len)
- return match_flags;
- /*
- * If 'name' is a substring of the cache on a path component
- * basis, and a directory is cached, we can return
- * immediately.
- */
- match_flags = cache.flags & track_flags & FL_DIR;
- if (match_flags && match_len == 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 = greatest_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 'name' is a substring of the cache on a path
+ * component basis, and a directory is cached, we
+ * can return immediately.
+ */
+ match_flags = cache.flags & track_flags & FL_DIR;
+ if (match_flags && match_len == len)
+ return match_flags;
+ }
/* Okay, no match from the cache so far, so now we have to
* check the rest of the path components.
@@ -90,6 +103,8 @@ 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;
@@ -101,11 +116,11 @@ static int lstat_cache(int len, const char *name,
break;
}
- /* 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;
@@ -113,20 +128,20 @@ static int lstat_cache(int len, const char *name,
} else if (track_flags & FL_DIR &&
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 can not 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
+ * none existing directory and the track_flags says
+ * that we can not cache this fact, so the cache would
+ * then have been left empty in this case.
*
* But, if we is 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 none 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;
}
@@ -139,3 +154,13 @@ 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 54f301d..a3fd383 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;
@@ -584,7 +584,7 @@ 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)) {
--
1.6.0.2.GIT
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