Subject: Re: [RFC/PATCH 0/1] cygwin: Remove the Win32 l/stat() functions

From: Ramsay Jones <[email-masked]>
Date: Sun, 30 Jun 2013 18:28:40 +0100

Ramsay Jones wrote:
> Michael Haggerty wrote:
>> On 06/27/2013 12:35 AM, Jeff King wrote:
> [ ... ]
>>> I think Michael's assessment above is missing one thing.
>>
>> Peff is absolutely right; for some unknown reason I was thinking of the
>> consistency check as having been already fixed.
> 
> Well, the "cygwin: Remove the Win32 l/stat() functions" patch *does* fix
> the problem. :-D It's just a pity we can't use it on performance grounds. :(
> 
>>> [...#ifdef out consistency check on cygwin when lock is held...]
>>
>> Yes, this would work.
>>
>> But, taking a step back, I think it is a bad idea to have an unreliable
>> stat() masquerading as a real stat().  If we want to allow the use of an
>> unreliable stat for certain purposes, let's have two stat() interfaces:
>>
>> * the true stat() (in this case I guess cygwin's slow-but-correct
>> implementation)
>>
>> * some fast_but_maybe_unreliable_stat(), which would map to stat() on
>> most platforms but might map to the Windows stat() on cygwin when so
>> configured.
>>
>> By default the true stat() would always be used.  It should have to be a
>> conscious decision, taken only in specific, vetted scenarios, to use the
>> unreliable stat.
> 
> You have just described my second patch! :D

Unfortunately, I have not had any time to work on the patch this weekend.
However, despite the patch being a bit rough around the edges, I decided
to send it out (see below) to get some early feedback.

Note that it passes the t3210, t3211, t5500, t3200, t3301, t7606 and t1301
tests, but I have not run the full test suite.

Comments welcome.

ATB,
Ramsay Jones

-- >8 --
Subject: [PATCH] cygwin: Add fast_[l]stat() functions

Signed-off-by: Ramsay Jones <[email-masked]>
---
 builtin/apply.c        |  6 +++---
 builtin/commit.c       |  2 +-
 builtin/ls-files.c     |  2 +-
 builtin/rm.c           |  2 +-
 builtin/update-index.c |  2 +-
 check-racy.c           |  2 +-
 compat/cygwin.c        | 12 ------------
 compat/cygwin.h        | 10 +++-------
 diff-lib.c             |  2 +-
 diff.c                 |  2 +-
 entry.c                |  4 ++--
 git-compat-util.h      | 13 +++++++++++--
 help.c                 |  5 +----
 path.c                 |  9 +--------
 preload-index.c        |  2 +-
 read-cache.c           |  6 +++---
 unpack-trees.c         |  8 ++++----
 17 files changed, 36 insertions(+), 53 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 0e9b631..ca26caa 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3253,7 +3253,7 @@ static int load_current(struct image *image, struct patch *patch)
 	if (pos < 0)
 		return error(_("%s: does not exist in index"), name);
 	ce = active_cache[pos];
-	if (lstat(name, &st)) {
+	if (fast_lstat(name, &st)) {
 		if (errno != ENOENT)
 			return error(_("%s: %s"), name, strerror(errno));
 		if (checkout_target(ce, &st))
@@ -3396,7 +3396,7 @@ static int check_preimage(struct patch *patch, struct cache_entry **ce, struct s
 	if (previous) {
 		st_mode = previous->new_mode;
 	} else if (!cached) {
-		stat_ret = lstat(old_name, st);
+		stat_ret = fast_lstat(old_name, st);
 		if (stat_ret && errno != ENOENT)
 			return error(_("%s: %s"), old_name, strerror(errno));
 	}
@@ -3850,7 +3850,7 @@ static void add_index_file(const char *path, unsigned mode, void *buf, unsigned
 			die(_("corrupt patch for subproject %s"), path);
 	} else {
 		if (!cached) {
-			if (lstat(path, &st) < 0)
+			if (fast_lstat(path, &st) < 0)
 				die_errno(_("unable to stat newly created file '%s'"),
 					  path);
 			fill_stat_cache_info(ce, &st);
diff --git a/builtin/commit.c b/builtin/commit.c
index 6b693c1..1d208c6 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -231,7 +231,7 @@ static void add_remove_files(struct string_list *list)
 		if (p->util)
 			continue;
 
-		if (!lstat(p->string, &st)) {
+		if (!fast_lstat(p->string, &st)) {
 			if (add_to_cache(p->string, &st, 0))
 				die(_("updating files failed"));
 		} else
diff --git a/builtin/ls-files.c b/builtin/ls-files.c
index 08d9786..db66a0e 100644
--- a/builtin/ls-files.c
+++ b/builtin/ls-files.c
@@ -251,7 +251,7 @@ static void show_files(struct dir_struct *dir)
 				continue;
 			if (ce_skip_worktree(ce))
 				continue;
-			err = lstat(ce->name, &st);
+			err = fast_lstat(ce->name, &st);
 			if (show_deleted && err)
 				show_ce_entry(tag_removed, ce);
 			if (show_modified && ce_modified(ce, &st, 0))
diff --git a/builtin/rm.c b/builtin/rm.c
index 06025a2..4b783e7 100644
--- a/builtin/rm.c
+++ b/builtin/rm.c
@@ -143,7 +143,7 @@ static int check_local_mod(unsigned char *head, int index_only)
 		}
 		ce = active_cache[pos];
 
-		if (lstat(ce->name, &st) < 0) {
+		if (fast_lstat(ce->name, &st) < 0) {
 			if (errno != ENOENT && errno != ENOTDIR)
 				warning("'%s': %s", ce->name, strerror(errno));
 			/* It already vanished from the working tree */
diff --git a/builtin/update-index.c b/builtin/update-index.c
index 5c7762e..4790e4c 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -206,7 +206,7 @@ static int process_path(const char *path)
 	 * First things first: get the stat information, to decide
 	 * what to do about the pathname!
 	 */
-	if (lstat(path, &st) < 0)
+	if (fast_lstat(path, &st) < 0)
 		return process_lstat_error(path, errno);
 
 	if (S_ISDIR(st.st_mode))
diff --git a/check-racy.c b/check-racy.c
index 00d92a1..6124355 100644
--- a/check-racy.c
+++ b/check-racy.c
@@ -11,7 +11,7 @@ int main(int ac, char **av)
 		struct cache_entry *ce = active_cache[i];
 		struct stat st;
 
-		if (lstat(ce->name, &st)) {
+		if (fast_lstat(ce->name, &st)) {
 			error("lstat(%s): %s", ce->name, strerror(errno));
 			continue;
 		}
diff --git a/compat/cygwin.c b/compat/cygwin.c
index 91ce5d4..f07cbd3 100644
--- a/compat/cygwin.c
+++ b/compat/cygwin.c
@@ -6,18 +6,6 @@
 #include "../git-compat-util.h"
 #include "../cache.h" /* to read configuration */
 
-/*
- * Return POSIX permission bits, regardless of core.ignorecygwinfstricks
- */
-int cygwin_get_st_mode_bits(const char *path, int *mode)
-{
-	struct stat st;
-	if (lstat(path, &st) < 0)
-		return -1;
-	*mode = st.st_mode;
-	return 0;
-}
-
 static inline void filetime_to_timespec(const FILETIME *ft, struct timespec *ts)
 {
 	long long winTime = ((long long)ft->dwHighDateTime << 32) +
diff --git a/compat/cygwin.h b/compat/cygwin.h
index c04965a..8299f58 100644
--- a/compat/cygwin.h
+++ b/compat/cygwin.h
@@ -4,11 +4,7 @@
 typedef int (*stat_fn_t)(const char*, struct stat*);
 extern stat_fn_t cygwin_stat_fn;
 extern stat_fn_t cygwin_lstat_fn;
-int cygwin_get_st_mode_bits(const char *path, int *mode);
 
-#define get_st_mode_bits(p,m) cygwin_get_st_mode_bits((p),(m))
-#ifndef CYGWIN_C
-/* cygwin.c needs the original lstat() */
-#define stat(path, buf) (*cygwin_stat_fn)(path, buf)
-#define lstat(path, buf) (*cygwin_lstat_fn)(path, buf)
-#endif
+#define fast_stat(path, buf) (*cygwin_stat_fn)(path, buf)
+#define fast_lstat(path, buf) (*cygwin_lstat_fn)(path, buf)
+#define GIT_FAST_STAT
diff --git a/diff-lib.c b/diff-lib.c
index b6f4b21..401dab6 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -27,7 +27,7 @@
  */
 static int check_removed(const struct cache_entry *ce, struct stat *st)
 {
-	if (lstat(ce->name, st) < 0) {
+	if (fast_lstat(ce->name, st) < 0) {
 		if (errno != ENOENT && errno != ENOTDIR)
 			return -1;
 		return 1;
diff --git a/diff.c b/diff.c
index 208094f..212d3ff 100644
--- a/diff.c
+++ b/diff.c
@@ -2642,7 +2642,7 @@ static int reuse_worktree_file(const char *name, const unsigned char *sha1, int
 	 * 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)))
+	    (!fast_lstat(name, &st) && !ce_match_stat(ce, &st, 0)))
 		return 1;
 
 	return 0;
diff --git a/entry.c b/entry.c
index d7c131d..4d2ac73 100644
--- a/entry.c
+++ b/entry.c
@@ -210,7 +210,7 @@ static int write_entry(struct cache_entry *ce, char *path, const struct checkout
 finish:
 	if (state->refresh_cache) {
 		if (!fstat_done)
-			lstat(ce->name, &st);
+			fast_lstat(ce->name, &st);
 		fill_stat_cache_info(ce, &st);
 	}
 	return 0;
@@ -230,7 +230,7 @@ static int check_path(const char *path, int len, struct stat *st, int skiplen)
 		errno = ENOENT;
 		return -1;
 	}
-	return lstat(path, st);
+	return fast_lstat(path, st);
 }
 
 int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *topath)
diff --git a/git-compat-util.h b/git-compat-util.h
index ff193f4..7997bdb 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -129,8 +129,6 @@
 #include <poll.h>
 #endif
 
-extern int get_st_mode_bits(const char *path, int *mode);
-
 #if defined(__MINGW32__)
 /* pull in Windows compatibility stuff */
 #include "compat/mingw.h"
@@ -179,6 +177,17 @@ typedef unsigned long uintptr_t;
 #endif
 #endif
 
+#ifndef GIT_FAST_STAT
+static inline int fast_stat(const char *path, struct stat *st)
+{
+	return stat(path, st);
+}
+static inline int fast_lstat(const char *path, struct stat *st)
+{
+	return lstat(path, st);
+}
+#endif
+
 /* used on Mac OS X */
 #ifdef PRECOMPOSE_UNICODE
 #include "compat/precompose_utf8.h"
diff --git a/help.c b/help.c
index 08c54ef..f068925 100644
--- a/help.c
+++ b/help.c
@@ -107,10 +107,7 @@ static int is_executable(const char *name)
 	    !S_ISREG(st.st_mode))
 		return 0;
 
-#if defined(GIT_WINDOWS_NATIVE) || defined(__CYGWIN__)
-#if defined(__CYGWIN__)
-if ((st.st_mode & S_IXUSR) == 0)
-#endif
+#if defined(GIT_WINDOWS_NATIVE)
 {	/* cannot trust the executable bit, peek into the file instead */
 	char buf[3] = { 0 };
 	int n;
diff --git a/path.c b/path.c
index 7f3324a..3d244d3 100644
--- a/path.c
+++ b/path.c
@@ -5,13 +5,7 @@
 #include "strbuf.h"
 #include "string-list.h"
 
-#ifndef get_st_mode_bits
-/*
- * The replacement lstat(2) we use on Cygwin is incomplete and
- * may return wrong permission bits. Most of the time we do not care,
- * but the callsites of this wrapper do care.
- */
-int get_st_mode_bits(const char *path, int *mode)
+static int get_st_mode_bits(const char *path, int *mode)
 {
 	struct stat st;
 	if (lstat(path, &st) < 0)
@@ -19,7 +13,6 @@ int get_st_mode_bits(const char *path, int *mode)
 	*mode = st.st_mode;
 	return 0;
 }
-#endif
 
 static char bad_path[] = "/bad-path/";
 
diff --git a/preload-index.c b/preload-index.c
index 49cb08d..1bece91 100644
--- a/preload-index.c
+++ b/preload-index.c
@@ -57,7 +57,7 @@ static void *preload_thread(void *_data)
 			continue;
 		if (threaded_has_symlink_leading_path(&cache, ce->name, ce_namelen(ce)))
 			continue;
-		if (lstat(ce->name, &st))
+		if (fast_lstat(ce->name, &st))
 			continue;
 		if (ie_match_stat(index, ce, &st, CE_MATCH_RACY_IS_DIRTY))
 			continue;
diff --git a/read-cache.c b/read-cache.c
index d5201f9..ed33d9e 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -689,7 +689,7 @@ int add_to_index(struct index_state *istate, const char *path, struct stat *st,
 int add_file_to_index(struct index_state *istate, const char *path, int flags)
 {
 	struct stat st;
-	if (lstat(path, &st))
+	if (fast_lstat(path, &st))
 		die_errno("unable to stat '%s'", path);
 	return add_to_index(istate, path, &st, flags);
 }
@@ -1049,7 +1049,7 @@ static struct cache_entry *refresh_cache_ent(struct index_state *istate,
 		return ce;
 	}
 
-	if (lstat(ce->name, &st) < 0) {
+	if (fast_lstat(ce->name, &st) < 0) {
 		if (err)
 			*err = errno;
 		return NULL;
@@ -1635,7 +1635,7 @@ static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
 	 */
 	struct stat st;
 
-	if (lstat(ce->name, &st) < 0)
+	if (fast_lstat(ce->name, &st) < 0)
 		return;
 	if (ce_match_stat_basic(ce, &st))
 		return;
diff --git a/unpack-trees.c b/unpack-trees.c
index b27f2a6..1fe9b63 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -1215,7 +1215,7 @@ static int verify_uptodate_1(const struct cache_entry *ce,
 	else if (o->reset || ce_uptodate(ce))
 		return 0;
 
-	if (!lstat(ce->name, &st)) {
+	if (!fast_lstat(ce->name, &st)) {
 		int flags = CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE;
 		unsigned changed = ie_match_stat(o->src_index, ce, &st, flags);
 		if (!changed)
@@ -1432,13 +1432,13 @@ static int verify_absent_1(const struct cache_entry *ce,
 		char path[PATH_MAX + 1];
 		memcpy(path, ce->name, len);
 		path[len] = 0;
-		if (lstat(path, &st))
+		if (fast_lstat(path, &st))
 			return error("cannot stat '%s': %s", path,
 					strerror(errno));
 
 		return check_ok_to_remove(path, len, DT_UNKNOWN, NULL, &st,
 				error_type, o);
-	} else if (lstat(ce->name, &st)) {
+	} else if (fast_lstat(ce->name, &st)) {
 		if (errno != ENOENT)
 			return error("cannot stat '%s': %s", ce->name,
 				     strerror(errno));
@@ -1852,7 +1852,7 @@ int oneway_merge(const struct cache_entry * const *src,
 		int update = 0;
 		if (o->reset && o->update && !ce_uptodate(old) && !ce_skip_worktree(old)) {
 			struct stat st;
-			if (lstat(old->name, &st) ||
+			if (fast_lstat(old->name, &st) ||
 			    ie_match_stat(o->src_index, old, &st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE))
 				update |= CE_UPDATE;
 		}
-- 
1.8.3