Prepare symlink caching for thread-safety

This doesn't actually change the external interfaces, so they are still
thread-unsafe, but it makes the code internally pass a pointer to a
local 'struct cache_def' around, so that the core code can be made
thread-safe.

The threaded index preloading will want to verify that the paths leading
up to a pathname are all real directories.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/symlinks.c b/symlinks.c
index 8dcd63261fff56e54c233224c6014b146d9bbeb3..08ad35330f38aeec17c11223fc4c145d573f6739 100644 (file)
--- a/symlinks.c
+++ b/symlinks.c
@@ -38,13 +38,13 @@ static struct cache_def {
        int flags;
        int track_flags;
        int prefix_len_stat_func;
-} cache;
+} default_cache;
 
-static inline void reset_lstat_cache(void)
+static inline void reset_lstat_cache(struct cache_def *cache)
 {
-       cache.path[0] = '\0';
-       cache.len = 0;
-       cache.flags = 0;
+       cache->path[0] = '\0';
+       cache->len = 0;
+       cache->flags = 0;
        /*
         * The track_flags and prefix_len_stat_func members is only
         * set by the safeguard rule inside lstat_cache()
@@ -70,23 +70,23 @@ static inline void reset_lstat_cache(void)
  * 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(const char *name, int len,
+static int lstat_cache(struct cache_def *cache, const char *name, int len,
                       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) {
+       if (cache->track_flags != track_flags ||
+           cache->prefix_len_stat_func != prefix_len_stat_func) {
                /*
                 * As a safeguard rule 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();
-               cache.track_flags = track_flags;
-               cache.prefix_len_stat_func = prefix_len_stat_func;
+               reset_lstat_cache(cache);
+               cache->track_flags = track_flags;
+               cache->prefix_len_stat_func = prefix_len_stat_func;
                match_len = last_slash = 0;
        } else {
                /*
@@ -94,10 +94,10 @@ static int lstat_cache(const char *name, int len,
                 * the 2 "excluding" path types.
                 */
                match_len = last_slash =
-                       longest_path_match(name, len, cache.path, cache.len,
+                       longest_path_match(name, len, cache->path, cache->len,
                                           &previous_slash);
-               match_flags = cache.flags & track_flags & (FL_NOENT|FL_SYMLINK);
-               if (match_flags && match_len == cache.len)
+               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
@@ -121,18 +121,18 @@ static int lstat_cache(const char *name, int len,
        max_len = len < PATH_MAX ? len : PATH_MAX;
        while (match_len < max_len) {
                do {
-                       cache.path[match_len] = name[match_len];
+                       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';
+               cache->path[last_slash] = '\0';
 
                if (last_slash <= prefix_len_stat_func)
-                       ret = stat(cache.path, &st);
+                       ret = stat(cache->path, &st);
                else
-                       ret = lstat(cache.path, &st);
+                       ret = lstat(cache->path, &st);
 
                if (ret) {
                        ret_flags = FL_LSTATERR;
@@ -156,9 +156,9 @@ static int lstat_cache(const char *name, int len,
         */
        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;
+               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) {
                /*
@@ -172,11 +172,11 @@ static int lstat_cache(const char *name, int len,
                 * 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;
+               cache->path[last_slash_dir] = '\0';
+               cache->len = last_slash_dir;
+               cache->flags = FL_DIR;
        } else {
-               reset_lstat_cache();
+               reset_lstat_cache(cache);
        }
        return ret_flags;
 }
@@ -188,16 +188,17 @@ static int lstat_cache(const char *name, int len,
 void invalidate_lstat_cache(const char *name, int len)
 {
        int match_len, previous_slash;
+       struct cache_def *cache = &default_cache;       /* FIXME */
 
-       match_len = longest_path_match(name, len, cache.path, cache.len,
+       match_len = longest_path_match(name, len, cache->path, cache->len,
                                       &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;
+               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();
+                       reset_lstat_cache(cache);
                }
        }
 }
@@ -207,7 +208,8 @@ void invalidate_lstat_cache(const char *name, int len)
  */
 void clear_lstat_cache(void)
 {
-       reset_lstat_cache();
+       struct cache_def *cache = &default_cache;       /* FIXME */
+       reset_lstat_cache(cache);
 }
 
 #define USE_ONLY_LSTAT  0
@@ -217,7 +219,8 @@ void clear_lstat_cache(void)
  */
 int has_symlink_leading_path(const char *name, int len)
 {
-       return lstat_cache(name, len,
+       struct cache_def *cache = &default_cache;       /* FIXME */
+       return lstat_cache(cache, name, len,
                           FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) &
                FL_SYMLINK;
 }
@@ -228,7 +231,8 @@ int has_symlink_leading_path(const char *name, int len)
  */
 int has_symlink_or_noent_leading_path(const char *name, int len)
 {
-       return lstat_cache(name, len,
+       struct cache_def *cache = &default_cache;       /* FIXME */
+       return lstat_cache(cache, name, len,
                           FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT) &
                (FL_SYMLINK|FL_NOENT);
 }
@@ -242,7 +246,8 @@ int has_symlink_or_noent_leading_path(const char *name, int len)
  */
 int has_dirs_only_path(const char *name, int len, int prefix_len)
 {
-       return lstat_cache(name, len,
+       struct cache_def *cache = &default_cache;       /* FIXME */
+       return lstat_cache(cache, name, len,
                           FL_DIR|FL_FULLPATH, prefix_len) &
                FL_DIR;
 }