Commit c498232812a34925fe280bd16938ba7ecf2cd6cc

Carlos Martín Nieto 2011-07-23T12:09:51

refs: don't stat so much In reference_read we stat a file and then call futils which stats it again. Use git_futils_readbuffer_updated to avoid the extra stat call. This introduces another parameter which is used to tell the caller whether the file was read or not. Modify the callers to take advantage of this new feature. This change removes ~140 stat calls from the test suite. Signed-off-by: Carlos Martín Nieto <cmn@elego.de>

diff --git a/src/refs.c b/src/refs.c
index 8022c2b..3d560f9 100644
--- a/src/refs.c
+++ b/src/refs.c
@@ -59,7 +59,7 @@ static uint32_t reftable_hash(const void *key, int hash_id)
 
 static void reference_free(git_reference *reference);
 static int reference_create(git_reference **ref_out, git_repository *repo, const char *name, git_rtype type);
-static int reference_read(git_fbuffer *file_content, time_t *mtime, const char *repo_path, const char *ref_name);
+static int reference_read(git_fbuffer *file_content, time_t *mtime, const char *repo_path, const char *ref_name, int *updated);
 
 /* loose refs */
 static int loose_parse_symbolic(git_reference *ref, git_fbuffer *file_content);
@@ -150,23 +150,16 @@ cleanup:
 	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to create reference");
 }
 
-static int reference_read(git_fbuffer *file_content, time_t *mtime, const char *repo_path, const char *ref_name)
+static int reference_read(git_fbuffer *file_content, time_t *mtime, const char *repo_path, const char *ref_name, int *updated)
 {
-	struct stat st;
 	char path[GIT_PATH_MAX];
 
+	assert(file_content && repo_path && ref_name);
+
 	/* Determine the full path of the file */
 	git_path_join(path, repo_path, ref_name);
 
-	if (p_stat(path, &st) < 0 || S_ISDIR(st.st_mode))
-		return git__throw(GIT_ENOTFOUND,
-			"Cannot read reference file '%s'", ref_name);
-
-	if (mtime)
-		*mtime = st.st_mtime;
-
-	if (file_content)
-		return git_futils_readbuffer(file_content, path);
+	return git_futils_readbuffer_updated(file_content, path, mtime, updated);
 
 	return GIT_SUCCESS;
 }
@@ -179,24 +172,26 @@ static int reference_read(git_fbuffer *file_content, time_t *mtime, const char *
  *****************************************/
 static int loose_update(git_reference *ref)
 {
-	int error;
-	time_t ref_time;
+	int error, updated;
 	git_fbuffer ref_file = GIT_FBUFFER_INIT;
 
 	if (ref->type & GIT_REF_PACKED)
 		return packed_load(ref->owner);
 
-	error = reference_read(NULL, &ref_time, ref->owner->path_repository, ref->name);
+/*	error = reference_read(NULL, &ref_time, ref->owner->path_repository, ref->name);
 	if (error < GIT_SUCCESS)
 		goto cleanup;
 
 	if (ref_time == ref->mtime)
 		return GIT_SUCCESS;
-
-	error = reference_read(&ref_file, &ref->mtime, ref->owner->path_repository, ref->name);
+*/
+	error = reference_read(&ref_file, &ref->mtime, ref->owner->path_repository, ref->name, &updated);
 	if (error < GIT_SUCCESS)
 		goto cleanup;
 
+	if (!updated)
+		goto cleanup;
+
 	if (ref->type == GIT_REF_SYMBOLIC)
 		error = loose_parse_symbolic(ref, &ref_file);
 	else if (ref->type == GIT_REF_OID)
@@ -205,9 +200,9 @@ static int loose_update(git_reference *ref)
 		error = git__throw(GIT_EOBJCORRUPTED,
 			"Invalid reference type (%d) for loose reference", ref->type);
 
-	git_futils_freebuffer(&ref_file);
 
 cleanup:
+	git_futils_freebuffer(&ref_file);
 	if (error != GIT_SUCCESS) {
 		reference_free(ref);
 		git_hashtable_remove(ref->owner->references.loose_cache, ref->name);
@@ -311,11 +306,11 @@ static int loose_lookup(
 	int error = GIT_SUCCESS;
 	git_fbuffer ref_file = GIT_FBUFFER_INIT;
 	git_reference *ref = NULL;
-	time_t ref_time;
+	time_t ref_time = 0;
 
 	*ref_out = NULL;
 
-	error = reference_read(&ref_file, &ref_time, repo->path_repository, name);
+	error = reference_read(&ref_file, &ref_time, repo->path_repository, name, NULL);
 	if (error < GIT_SUCCESS)
 		goto cleanup;
 
@@ -500,53 +495,49 @@ cleanup:
 
 static int packed_load(git_repository *repo)
 {
-	int error = GIT_SUCCESS;
+	int error = GIT_SUCCESS, updated;
 	git_fbuffer packfile = GIT_FBUFFER_INIT;
 	const char *buffer_start, *buffer_end;
 	git_refcache *ref_cache = &repo->references;
 
-	/* already loaded */
-	if (repo->references.packfile != NULL) {
-		time_t packed_time;
-
-		/* check if we can read the time of the index;
-		 * if we can read it and it matches the time of the
-		 * index we had previously loaded, we don't need to do
-		 * anything else.
-		 *
-		 * if we cannot load the time (e.g. the packfile
-		 * has disappeared) or the time is different, we
-		 * have to reload the packfile */
-
-		if (!reference_read(NULL, &packed_time, repo->path_repository, GIT_PACKEDREFS_FILE) &&
-			packed_time == ref_cache->packfile_time)
-			return GIT_SUCCESS;
-
-		git_hashtable_clear(repo->references.packfile);
-	} else {
+	/* First we make sure we have allocated the hash table */
+	if (ref_cache->packfile == NULL) {
 		ref_cache->packfile = git_hashtable_alloc(
 			default_table_size,
 			reftable_hash,
 			(git_hash_keyeq_ptr)strcmp);
 
-		if (ref_cache->packfile == NULL)
-			return GIT_ENOMEM;
+		if (ref_cache->packfile == NULL) {
+			error = GIT_ENOMEM;
+			goto cleanup;
+		}
 	}
 
-	/* read the packfile from disk;
-	 * store its modification time to check for future reloads */
-	error = reference_read(
-			&packfile,
-			&ref_cache->packfile_time,
-			repo->path_repository,
-			GIT_PACKEDREFS_FILE);
+	error = reference_read(&packfile, &ref_cache->packfile_time,
+						   repo->path_repository, GIT_PACKEDREFS_FILE, &updated);
 
-	/* there is no packfile on disk; that's ok */
-	if (error == GIT_ENOTFOUND)
+	/*
+	 * If we couldn't find the file, we need to clear the table and
+	 * return. On any other error, we return that error. If everything
+	 * went fine and the file wasn't updated, then there's nothing new
+	 * for us here, so just return. Anything else means we need to
+	 * refresh the packed refs.
+	 */
+	if (error == GIT_ENOTFOUND) {
+		git_hashtable_clear(ref_cache->packfile);
 		return GIT_SUCCESS;
+	} else if (error < GIT_SUCCESS) {
+		return git__rethrow(error, "Failed to read packed refs");
+	} else if (!updated) {
+		return GIT_SUCCESS;
+	}
 
-	if (error < GIT_SUCCESS)
-		goto cleanup;
+	/*
+	 * At this point, we want to refresh the packed refs. We already
+	 * have the contents in our buffer.
+	 */
+
+	git_hashtable_clear(ref_cache->packfile);
 
 	buffer_start = (const char *)packfile.data;
 	buffer_end = (const char *)(buffer_start) + packfile.len;
@@ -1624,6 +1615,7 @@ int git_repository__refcache_init(git_refcache *refs)
 
 	/* packfile loaded lazily */
 	refs->packfile = NULL;
+	refs->packfile_time = 0;
 
 	return (refs->loose_cache) ? GIT_SUCCESS : GIT_ENOMEM;
 }