Avoid running lstat(2) on the same cache entry.
Aside from the lstat(2) done for work tree files, there are
quite many lstat(2) calls in refname dwimming codepath. This
patch is not about reducing them.
* It adds a new ce_flag, CE_UPTODATE, that is meant to mark the
cache entries that record a regular file blob that is up to
date in the work tree. If somebody later walks the index and
wants to see if the work tree has changes, they do not have
to be checked with lstat(2) again.
* fill_stat_cache_info() marks the cache entry it just added
with CE_UPTODATE. This has the effect of marking the paths
we write out of the index and lstat(2) immediately as "no
need to lstat -- we know it is up-to-date", from quite a lot
fo callers:
- git-apply --index
- git-update-index
- git-checkout-index
- git-add (uses add_file_to_index())
- git-commit (ditto)
- git-mv (ditto)
* refresh_cache_ent() also marks the cache entry that are clean
with CE_UPTODATE.
* write_index is changed not to write CE_UPTODATE out to the
index file, because CE_UPTODATE is meant to be transient only
in core. For the same reason, CE_UPDATE is not written to
prevent an accident from happening.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/diff.c b/diff.c
index 5b8afdc..d464fe3 100644
--- a/diff.c
+++ b/diff.c
@@ -1510,17 +1510,22 @@
if (pos < 0)
return 0;
ce = active_cache[pos];
- if ((lstat(name, &st) < 0) ||
- !S_ISREG(st.st_mode) || /* careful! */
- ce_match_stat(ce, &st, 0) ||
- hashcmp(sha1, ce->sha1))
- return 0;
- /* we return 1 only when we can stat, it is a regular file,
- * stat information matches, and sha1 recorded in the cache
- * matches. I.e. we know the file in the work tree really is
- * the same as the <name, sha1> pair.
+
+ /*
+ * This is not the sha1 we are looking for, or
+ * unreusable because it is not a regular file.
*/
- return 1;
+ if (hashcmp(sha1, ce->sha1) || !S_ISREG(ce->ce_mode))
+ return 0;
+
+ /*
+ * If ce matches the file in the work tree, we can reuse it.
+ */
+ if (ce_uptodate(ce) ||
+ (!lstat(name, &st) && !ce_match_stat(ce, &st, 0)))
+ return 1;
+
+ return 0;
}
static int populate_from_stdin(struct diff_filespec *s)
