From 09c9306658f793f2cad1ed7856b55a7c4e758703 Mon Sep 17 00:00:00 2001 From: Kjetil Barvik Date: Sun, 18 Jan 2009 16:14:51 +0100 Subject: [PATCH] lstat_cache(): introduce has_symlink_or_noent_leading_path() function 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 Signed-off-by: Junio C Hamano --- 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 231c06d77..11181aa00 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 49fb4d8bc..c69556acf 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 54f301da6..a3fd383af 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)) { -- 2.26.2