Merge branch 'mh/ref-races'

"git pack-refs" that races with new ref creation or deletion have
been susceptible to lossage of refs under right conditions, which
has been tightened up.

* mh/ref-races:
  for_each_ref: load all loose refs before packed refs
  get_packed_ref_cache: reload packed-refs file when it changes
  add a stat_validity struct
  Extract a struct stat_data from cache_entry
  packed_ref_cache: increment refcount when locked
  do_for_each_entry(): increment the packed refs cache refcount
  refs: manage lifetime of packed refs cache via reference counting
  refs: implement simple transactions for the packed-refs file
  refs: wrap the packed refs cache in a level of indirection
  pack_refs(): split creation of packed refs and entry writing
  repack_without_ref(): split list curation and entry writing

1 files changed, 53 insertions, 7 deletions

diff --git a/cache.h b/cache.h
index ec8240f62a..dd0fb33a15 100644
--- a/cache.h
+++ b/cache.h
@@ -119,15 +119,19 @@ struct cache_time {
 	unsigned int nsec;
 };
 
+struct stat_data {
+	struct cache_time sd_ctime;
+	struct cache_time sd_mtime;
+	unsigned int sd_dev;
+	unsigned int sd_ino;
+	unsigned int sd_uid;
+	unsigned int sd_gid;
+	unsigned int sd_size;
+};
+
 struct cache_entry {
-	struct cache_time ce_ctime;
-	struct cache_time ce_mtime;
-	unsigned int ce_dev;
-	unsigned int ce_ino;
+	struct stat_data ce_stat_data;
 	unsigned int ce_mode;
-	unsigned int ce_uid;
-	unsigned int ce_gid;
-	unsigned int ce_size;
 	unsigned int ce_flags;
 	unsigned int ce_namelen;
 	unsigned char sha1[20];
@@ -511,6 +515,21 @@ extern int limit_pathspec_to_literal(void);
 #define HASH_FORMAT_CHECK 2
 extern int index_fd(unsigned char *sha1, int fd, struct stat *st, enum object_type type, const char *path, unsigned flags);
 extern int index_path(unsigned char *sha1, const char *path, struct stat *st, unsigned flags);
+
+/*
+ * Record to sd the data from st that we use to check whether a file
+ * might have changed.
+ */
+extern void fill_stat_data(struct stat_data *sd, struct stat *st);
+
+/*
+ * Return 0 if st is consistent with a file not having been changed
+ * since sd was filled.  If there are differences, return a
+ * combination of MTIME_CHANGED, CTIME_CHANGED, OWNER_CHANGED,
+ * INODE_CHANGED, and DATA_CHANGED.
+ */
+extern int match_stat_data(const struct stat_data *sd, struct stat *st);
+
 extern void fill_stat_cache_info(struct cache_entry *ce, struct stat *st);
 
 #define REFRESH_REALLY		0x0001	/* ignore_valid */
@@ -1338,4 +1357,31 @@ int checkout_fast_forward(const unsigned char *from,
 
 int sane_execvp(const char *file, char *const argv[]);
 
+/*
+ * A struct to encapsulate the concept of whether a file has changed
+ * since we last checked it. This uses criteria similar to those used
+ * for the index.
+ */
+struct stat_validity {
+	struct stat_data *sd;
+};
+
+void stat_validity_clear(struct stat_validity *sv);
+
+/*
+ * Returns 1 if the path is a regular file (or a symlink to a regular
+ * file) and matches the saved stat_validity, 0 otherwise.  A missing
+ * or inaccessible file is considered a match if the struct was just
+ * initialized, or if the previous update found an inaccessible file.
+ */
+int stat_validity_check(struct stat_validity *sv, const char *path);
+
+/*
+ * Update the stat_validity from a file opened at descriptor fd. If
+ * the file is missing, inaccessible, or not a regular file, then
+ * future calls to stat_validity_check will match iff one of those
+ * conditions continues to be true.
+ */
+void stat_validity_update(struct stat_validity *sv, int fd);
+
 #endif /* CACHE_H */