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Merge branch 'kb/lstat-cache'

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* kb/lstat-cache:
  lstat_cache(): introduce clear_lstat_cache() function
  lstat_cache(): introduce invalidate_lstat_cache() function
  lstat_cache(): introduce has_dirs_only_path() function
  lstat_cache(): introduce has_symlink_or_noent_leading_path() function
  lstat_cache(): more cache effective symlink/directory detection
This commit is contained in:
Junio C Hamano 2009-01-25 17:13:34 -08:00
parent 9847a52432 bda6eb0da9
commit 0990e7aaaa
4 changed files with 248 additions and 77 deletions
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4
cache.h
View file

@ -721,6 +721,10 @@ 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 int has_dirs_only_path(int len, const char *name, int prefix_len);
extern void invalidate_lstat_cache(int len, const char *name);
extern void clear_lstat_cache(void);
extern struct alternate_object_database {
struct alternate_object_database *next;

34
entry.c
View file

@ -9,35 +9,25 @@ 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,
* and we set 'state->base_dir_len' below, such that
* we test the path components of the prefix with the
* stat() function instead of the lstat() function.
*/
if (has_dirs_only_path(len, buf, state->base_dir_len))
continue; /* ok, it is already a directory. */
/*
* We know stat_status == 0 means something exists
* there and this mkdir would fail, but that is an
* error codepath; we do not care, as we unlink and
* mkdir again in such a case.
* If this mkdir() would fail, it could be that there
* is already a symlink or something else exists
* there, therefore we then try to unlink it and try
* one more time to create the directory.
*/
if (mkdir(buf, 0777)) {
if (errno == EEXIST && state->force &&

283
symlinks.c
View file

@ -1,64 +1,241 @@
#include "cache.h"
struct pathname {
static struct cache_def {
char path[PATH_MAX + 1];
int len;
char path[PATH_MAX];
};
int flags;
int track_flags;
int prefix_len_stat_func;
} cache;
/* Return matching pathname prefix length, or zero if not matching */
static inline int match_pathname(int len, const char *name, struct pathname *match)
/*
* Returns the length (on a path component basis) of the longest
* common prefix match of 'name' and the cached path string.
*/
static inline int longest_match_lstat_cache(int len, const char *name,
int *previous_slash)
{
int match_len = match->len;
return (len > match_len &&
name[match_len] == '/' &&
!memcmp(name, match->path, match_len)) ? match_len : 0;
}
int max_len, match_len = 0, match_len_prev = 0, i = 0;
static inline void set_pathname(int len, const char *name, struct pathname *match)
{
if (len < PATH_MAX) {
match->len = len;
memcpy(match->path, name, len);
match->path[len] = 0;
}
}
int has_symlink_leading_path(int len, const char *name)
{
static struct pathname link, nonlink;
char path[PATH_MAX];
struct stat st;
char *sp;
int known_dir;
/*
* See if the last known symlink cache matches.
*/
if (match_pathname(len, name, &link))
return 1;
/*
* Get rid of the last known directory part
*/
known_dir = match_pathname(len, name, &nonlink);
while ((sp = strchr(name + known_dir + 1, '/')) != NULL) {
int thislen = sp - name ;
memcpy(path, name, thislen);
path[thislen] = 0;
if (lstat(path, &st))
return 0;
if (S_ISDIR(st.st_mode)) {
set_pathname(thislen, path, &nonlink);
known_dir = thislen;
continue;
max_len = len < cache.len ? len : cache.len;
while (i < max_len && name[i] == cache.path[i]) {
if (name[i] == '/') {
match_len_prev = match_len;
match_len = i;
}
if (S_ISLNK(st.st_mode)) {
set_pathname(thislen, path, &link);
return 1;
i++;
}
/* Is the cached path string a substring of 'name'? */
if (i == cache.len && cache.len < len && name[cache.len] == '/') {
match_len_prev = match_len;
match_len = cache.len;
/* Is 'name' a substring of the cached path string? */
} else if ((i == len && len < cache.len && cache.path[len] == '/') ||
(i == len && len == cache.len)) {
match_len_prev = match_len;
match_len = len;
}
*previous_slash = match_len_prev;
return match_len;
}
static inline void reset_lstat_cache(int track_flags, int prefix_len_stat_func)
{
cache.path[0] = '\0';
cache.len = 0;
cache.flags = 0;
cache.track_flags = track_flags;
cache.prefix_len_stat_func = prefix_len_stat_func;
}
#define FL_DIR (1 << 0)
#define FL_NOENT (1 << 1)
#define FL_SYMLINK (1 << 2)
#define FL_LSTATERR (1 << 3)
#define FL_ERR (1 << 4)
#define FL_FULLPATH (1 << 5)
/*
* Check if name 'name' of length 'len' has a symlink leading
* 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, which also can
* be used to indicate that we should check the full path.
*
* The 'prefix_len_stat_func' parameter can be used to set the length
* of the prefix, where the cache should use the stat() function
* instead of the lstat() function to test each path component.
*/
static int lstat_cache(int len, const char *name,
int track_flags, int prefix_len_stat_func)
{
int match_len, last_slash, last_slash_dir, previous_slash;
int match_flags, ret_flags, save_flags, max_len, ret;
struct stat st;
if (cache.track_flags != track_flags ||
cache.prefix_len_stat_func != prefix_len_stat_func) {
/*
* As a safeguard we clear the cache if the values of
* track_flags and/or prefix_len_stat_func does not
* match with the last supplied values.
*/
reset_lstat_cache(track_flags, prefix_len_stat_func);
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, &previous_slash);
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
* check the rest of the path components.
*/
ret_flags = FL_DIR;
last_slash_dir = last_slash;
max_len = len < PATH_MAX ? len : PATH_MAX;
while (match_len < max_len) {
do {
cache.path[match_len] = name[match_len];
match_len++;
} while (match_len < max_len && name[match_len] != '/');
if (match_len >= max_len && !(track_flags & FL_FULLPATH))
break;
last_slash = match_len;
cache.path[last_slash] = '\0';
if (last_slash <= prefix_len_stat_func)
ret = stat(cache.path, &st);
else
ret = lstat(cache.path, &st);
if (ret) {
ret_flags = FL_LSTATERR;
if (errno == ENOENT)
ret_flags |= FL_NOENT;
} else if (S_ISDIR(st.st_mode)) {
last_slash_dir = last_slash;
continue;
} else if (S_ISLNK(st.st_mode)) {
ret_flags = FL_SYMLINK;
} else {
ret_flags = FL_ERR;
}
break;
}
return 0;
/*
* 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_NOENT|FL_SYMLINK);
if (save_flags && last_slash > 0 && last_slash <= PATH_MAX) {
cache.path[last_slash] = '\0';
cache.len = last_slash;
cache.flags = save_flags;
} 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 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 or non-existing component).
*/
cache.path[last_slash_dir] = '\0';
cache.len = last_slash_dir;
cache.flags = FL_DIR;
} else {
reset_lstat_cache(track_flags, prefix_len_stat_func);
}
return ret_flags;
}
/*
* Invalidate the given 'name' from the cache, if 'name' matches
* completely with the cache.
*/
void invalidate_lstat_cache(int len, const char *name)
{
int match_len, previous_slash;
match_len = longest_match_lstat_cache(len, name, &previous_slash);
if (len == match_len) {
if ((cache.track_flags & FL_DIR) && previous_slash > 0) {
cache.path[previous_slash] = '\0';
cache.len = previous_slash;
cache.flags = FL_DIR;
} else
reset_lstat_cache(cache.track_flags,
cache.prefix_len_stat_func);
}
}
/*
* Completely clear the contents of the cache
*/
void clear_lstat_cache(void)
{
reset_lstat_cache(0, 0);
}
#define USE_ONLY_LSTAT 0
/*
* Return non-zero if path 'name' has a leading symlink component
*/
int has_symlink_leading_path(int len, const char *name)
{
return lstat_cache(len, name,
FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) &
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, USE_ONLY_LSTAT) &
(FL_SYMLINK|FL_NOENT);
}
/*
* Return non-zero if all path components of 'name' exists as a
* directory. If prefix_len > 0, we will test with the stat()
* function instead of the lstat() function for a prefix length of
* 'prefix_len', thus we then allow for symlinks in the prefix part as
* long as those points to real existing directories.
*/
int has_dirs_only_path(int len, const char *name, int prefix_len)
{
return lstat_cache(len, name,
FL_DIR|FL_FULLPATH, prefix_len) &
FL_DIR;
}

4
unpack-trees.c
View file

@ -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)) {