[PATCH v2 04/20] lock_ref_sha1_basic(): use raceproof_create_file()

[Michael Haggerty <mhagger@xxxxxxxxxxxx>]

Instead of coding the retry loop inline, use raceproof_create_file() to
make lock acquisition safe against directory creation/deletion races.

Signed-off-by: Michael Haggerty <mhagger@xxxxxxxxxxxx>
---
 refs/files-backend.c | 47 +++++++++++++++++++----------------------------
 1 file changed, 19 insertions(+), 28 deletions(-)

diff --git a/refs/files-backend.c b/refs/files-backend.c
index b569762..a549942 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1889,6 +1889,19 @@ static int remove_empty_directories(struct strbuf *path)
 	return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
 }
 
+struct create_reflock_data {
+	struct lock_file *lk;
+	int lflags;
+};
+
+static int create_reflock(const char *path, void *cb)
+{
+	struct create_reflock_data *data = cb;
+
+	return hold_lock_file_for_update(data->lk, path, data->lflags) < 0
+		? -1 : 0;
+}
+
 /*
  * Locks a ref returning the lock on success and NULL on failure.
  * On failure errno is set to something meaningful.
@@ -1906,10 +1919,9 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 	struct ref_lock *lock;
 	int last_errno = 0;
 	int type;
-	int lflags = 0;
 	int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
 	int resolve_flags = 0;
-	int attempts_remaining = 3;
+	struct create_reflock_data create_reflock_data = {NULL, 0};
 
 	assert(err);
 
@@ -1921,7 +1933,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 		resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
 	if (flags & REF_NODEREF) {
 		resolve_flags |= RESOLVE_REF_NO_RECURSE;
-		lflags |= LOCK_NO_DEREF;
+		create_reflock_data.lflags |= LOCK_NO_DEREF;
 	}
 
 	refname = resolve_ref_unsafe(refname, resolve_flags,
@@ -1980,35 +1992,14 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 	lock->orig_ref_name = xstrdup(orig_refname);
 	strbuf_git_path(&ref_file, "%s", refname);
 
- retry:
-	switch (safe_create_leading_directories_const(ref_file.buf)) {
-	case SCLD_OK:
-		break; /* success */
-	case SCLD_VANISHED:
-		if (--attempts_remaining > 0)
-			goto retry;
-		/* fall through */
-	default:
+	create_reflock_data.lk = lock->lk;
+
+	if (raceproof_create_file(ref_file.buf, create_reflock, &create_reflock_data)) {
 		last_errno = errno;
-		strbuf_addf(err, "unable to create directory for %s",
-			    ref_file.buf);
+		unable_to_lock_message(ref_file.buf, errno, err);
 		goto error_return;
 	}
 
-	if (hold_lock_file_for_update(lock->lk, ref_file.buf, lflags) < 0) {
-		last_errno = errno;
-		if (errno == ENOENT && --attempts_remaining > 0)
-			/*
-			 * Maybe somebody just deleted one of the
-			 * directories leading to ref_file.  Try
-			 * again:
-			 */
-			goto retry;
-		else {
-			unable_to_lock_message(ref_file.buf, errno, err);
-			goto error_return;
-		}
-	}
 	if (verify_lock(lock, old_sha1, mustexist, err)) {
 		last_errno = errno;
 		goto error_return;
-- 
2.7.0

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