make USE_NSEC work as expected

Since the filesystem ext4 is now defined as stable in Linux v2.6.28,
and ext4 supports nanonsecond resolution timestamps natively, it is
time to make USE_NSEC work as expected.

This will make racy git situations less likely to happen.  For 'git
checkout' this means it will be less likely that we have to open, read
the contents of the file into RAM, and check if file is really
modified or not.  The result sould be a litle less used CPU time, less
pagefaults and a litle faster program, at least for 'git checkout'.

Since the number of possible racy git situations would increase when
disks gets faster, this patch would be more and more helpfull as times
go by.  For a fast Solid State Disk, this patch should be helpfull.

Note that, when file operations starts to take less than 1 nanosecond,
one would again start to get more racy git situations.

For more info on racy git, see Documentation/technical/racy-git.txt
For more info on ext4, see http://kernelnewbies.org/Ext4

Signed-off-by: Kjetil Barvik <barvik@broadpark.no>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/cache.h b/cache.h
index 770d8bc..2badbfe 100644
--- a/cache.h
+++ b/cache.h
@@ -140,8 +140,8 @@ struct ondisk_cache_entry_extended {
 };
 
 struct cache_entry {
-	unsigned int ce_ctime;
-	unsigned int ce_mtime;
+	struct cache_time ce_ctime;
+	struct cache_time ce_mtime;
 	unsigned int ce_dev;
 	unsigned int ce_ino;
 	unsigned int ce_mode;
@@ -282,7 +282,7 @@ struct index_state {
 	struct cache_entry **cache;
 	unsigned int cache_nr, cache_alloc, cache_changed;
 	struct cache_tree *cache_tree;
-	time_t timestamp;
+	struct cache_time timestamp;
 	void *alloc;
 	unsigned name_hash_initialized : 1,
 		 initialized : 1;