X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=read-cache.c;h=c5474d49758b640f8942b1e3eb1a1c8f47c78ed8;hb=9470657ad0d0472e3e3c2e352334f60e7bd777c1;hp=780601f071a0f5ae35b6d379abdd935d79ca92e2;hpb=29e4d3635709778bcc808dbad0477efad82f8d7e;p=git.git

diff --git a/read-cache.c b/read-cache.c
index 780601f0..c5474d49 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -87,7 +87,7 @@ static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
 	return 0;
 }
 
-int ce_match_stat(struct cache_entry *ce, struct stat *st)
+static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
 {
 	unsigned int changed = 0;
 
@@ -143,6 +143,13 @@ int ce_match_stat(struct cache_entry *ce, struct stat *st)
 	if (ce->ce_size != htonl(st->st_size))
 		changed |= DATA_CHANGED;
 
+	return changed;
+}
+
+int ce_match_stat(struct cache_entry *ce, struct stat *st)
+{
+	unsigned int changed = ce_match_stat_basic(ce, st);
+
 	/*
 	 * Within 1 second of this sequence:
 	 * 	echo xyzzy >file && git-update-index --add file
@@ -594,6 +601,50 @@ static int ce_flush(SHA_CTX *context, int fd)
 	return 0;
 }
 
+static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
+{
+	/*
+	 * The only thing we care about in this function is to smudge the
+	 * falsely clean entry due to touch-update-touch race, so we leave
+	 * everything else as they are.  We are called for entries whose
+	 * ce_mtime match the index file mtime.
+	 */
+	struct stat st;
+
+	if (lstat(ce->name, &st) < 0)
+		return;
+	if (ce_match_stat_basic(ce, &st))
+		return;
+	if (ce_modified_check_fs(ce, &st)) {
+		/* This is "racily clean"; smudge it.  Note that this
+		 * is a tricky code.  At first glance, it may appear
+		 * that it can break with this sequence:
+		 *
+		 * $ echo xyzzy >frotz
+		 * $ git-update-index --add frotz
+		 * $ : >frotz
+		 * $ sleep 3
+		 * $ echo filfre >nitfol
+		 * $ git-update-index --add nitfol
+		 *
+		 * but it does not.  Whe the second update-index runs,
+		 * it notices that the entry "frotz" has the same timestamp
+		 * as index, and if we were to smudge it by resetting its
+		 * size to zero here, then the object name recorded
+		 * in index is the 6-byte file but the cached stat information
+		 * becomes zero --- which would then match what we would
+		 * obtain from the filesystem next time we stat("frotz"). 
+		 *
+		 * However, the second update-index, before calling
+		 * this function, notices that the cached size is 6
+		 * bytes and what is on the filesystem is an empty
+		 * file, and never calls us, so the cached size information
+		 * for "frotz" stays 6 which does not match the filesystem.
+		 */
+		ce->ce_size = htonl(0);
+	}
+}
+
 int write_cache(int newfd, struct cache_entry **cache, int entries)
 {
 	SHA_CTX c;
@@ -616,6 +667,9 @@ int write_cache(int newfd, struct cache_entry **cache, int entries)
 		struct cache_entry *ce = cache[i];
 		if (!ce->ce_mode)
 			continue;
+		if (index_file_timestamp &&
+		    index_file_timestamp <= ntohl(ce->ce_mtime.sec))
+			ce_smudge_racily_clean_entry(ce);
 		if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
 			return -1;
 	}