commit - 664d62f9f2469ee2bc583ab0bbc90e56bf2d560e
commit + 3bf0e21f50b11c683f08a06c8ab362fe220adc2b
blob - b374606457024caef32ca71ee66bd3057552e4b1
blob + 2b43e7ed974e7ba95556eac4c0b718e3c5706bb3
--- gotadmin/gotadmin.c
+++ gotadmin/gotadmin.c
@@ -1236,6 +1236,7 @@ cmd_cleanup(int argc, char *argv[])
 	struct got_repository *repo = NULL;
 	int ch, dry_run = 0, npacked = 0, verbosity = 0;
 	int remove_lonely_packidx = 0, ignore_mtime = 0;
+	struct got_lockfile *lock = NULL;
 	struct got_cleanup_progress_arg cpa;
 	struct got_lonely_packidx_progress_arg lpa;
 	off_t loose_before, loose_after;
@@ -1306,6 +1307,10 @@ cmd_cleanup(int argc, char *argv[])
 		    "this implies that objects must not be deleted");
 		goto done;
 	}
+
+	error = got_repo_cleanup_prepare(repo, &lock);
+	if (error)
+		goto done;
 
 	if (remove_lonely_packidx) {
 		memset(&lpa, 0, sizeof(lpa));
@@ -1381,6 +1386,7 @@ cmd_cleanup(int argc, char *argv[])
 	}
 
 done:
+	got_repo_cleanup_complete(repo, lock);
 	if (repo)
 		got_repo_close(repo);
 	if (pack_fds) {
blob - 57bb3f85a90ec6fdf48dc338be1a61ccab5a133c
blob + 67ccceea225850c691fd8c0b8c3c4a6e397498dd
--- include/got_repository_admin.h
+++ include/got_repository_admin.h
@@ -14,6 +14,8 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+struct got_lockfile;
+
 /* A callback function which gets invoked with progress information to print. */
 typedef const struct got_error *(*got_pack_progress_cb)(void *arg,
     int ncolored, int nfound, int ntrees, off_t packfile_size, int ncommits,
@@ -68,6 +70,18 @@ got_repo_list_pack(FILE *packfile, struct got_object_i
     struct got_repository *repo, got_pack_list_cb list_cb, void *list_arg,
     got_cancel_cb cancel_cb, void *cancel_arg);
 
+/*
+ * Prepare for removing loose objects or redundant packfiles.
+ *
+ * These functions do the necessary locking in order to avoid
+ * concurrent operation to irremediably damage the repository.
+ */
+const struct got_error *
+got_repo_cleanup_prepare(struct got_repository *, struct got_lockfile **);
+
+const struct got_error *
+got_repo_cleanup_complete(struct got_repository *, struct got_lockfile *);
+
 /* A callback function which gets invoked with cleanup information to print. */
 typedef const struct got_error *(*got_cleanup_progress_cb)(void *arg,
     int nloose, int ncommits, int npurged, int nredundant);
blob - 8220c815a61bbe282585b0a67e7b39f74ad2a9a4
blob + f44259d099d9b70c547d238971a7cc147c4e209f
--- lib/got_lib_repository.h
+++ lib/got_lib_repository.h
@@ -134,6 +134,9 @@ struct got_repository {
 
 	/* Settings read from got.conf. */
 	struct got_gotconfig *gotconfig;
+
+	/* cleanup lockfile */
+	struct got_lockfile *cleanup_lock;
 };
 
 const struct got_error*got_repo_cache_object(struct got_repository *,
blob - e1a1870147bfefcb7e3caaaedf16d6b92e78a5c1
blob + e5276a2237daae080959cb6cfda569fa291cddbe
--- lib/lockfile.c
+++ lib/lockfile.c
@@ -55,11 +55,11 @@ got_lockfile_lock(struct got_lockfile **lf, const char
 	do {
 		if (dir_fd != -1) {
 			(*lf)->fd = openat(dir_fd, (*lf)->path,
-			    O_RDONLY | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
+			    O_RDWR | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
 			    GOT_DEFAULT_FILE_MODE);
 		} else {
 			(*lf)->fd = open((*lf)->path,
-			    O_RDONLY | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
+			    O_RDWR | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
 			    GOT_DEFAULT_FILE_MODE);
 		}
 		if ((*lf)->fd != -1)
blob - 213bc1e83451612e1e2ba0be6bf664e3f4f44050
blob + bb314c3843f03978714c781199f72d807aeb3881
--- lib/repository_admin.c
+++ lib/repository_admin.c
@@ -611,6 +611,42 @@ done:
 	if (packidx)
 		got_packidx_close(packidx);
 	return err;
+}
+
+const struct got_error *
+got_repo_cleanup_prepare(struct got_repository *repo,
+    struct got_lockfile **lk)
+{
+	const struct got_error *err;
+	char myname[HOST_NAME_MAX + 1];
+
+	if (gethostname(myname, sizeof(myname)) == -1)
+		return got_error_from_errno("gethostname");
+
+	err = got_lockfile_lock(lk, "gc.pid", got_repo_get_fd(repo));
+	if (err)
+		return err;
+
+	/*
+	 * Git uses these info to provide some verbiage when finds a
+	 * lock during `git gc --force' so don't try too hard to avoid
+	 * short writes and don't care if a race happens between the
+	 * lockfile creation and the write itself.
+	 */
+	if (dprintf((*lk)->fd, "%d %s", getpid(), myname) < 0)
+		return got_error_from_errno("dprintf");
+
+	return NULL;
+}
+
+const struct got_error *
+got_repo_cleanup_complete(struct got_repository *repo,
+    struct got_lockfile *lk)
+{
+	if (lk == NULL)
+		return NULL;
+
+	return got_lockfile_unlock(lk, got_repo_get_fd(repo));
 }
 
 static const struct got_error *
@@ -1417,21 +1453,6 @@ got_repo_purge_redundant_packfiles(struct got_reposito
 	if (idset)
 		got_object_idset_free(idset);
 	return err;
-}
-
-static const struct got_error *
-remove_packidx(int dir_fd, const char *relpath)
-{
-	const struct got_error *err, *unlock_err;
-	struct got_lockfile *lf;
-
-	err = got_lockfile_lock(&lf, relpath, dir_fd);
-	if (err)
-		return err;
-	if (unlinkat(dir_fd, relpath, 0) == -1)
-		err = got_error_from_errno("unlinkat");
-	unlock_err = got_lockfile_unlock(lf, dir_fd);
-	return err ? err : unlock_err;
 }
 
 const struct got_error *
@@ -1491,9 +1512,10 @@ got_repo_remove_lonely_packidx(struct got_repository *
 		}
 
 		if (!dry_run) {
-			err = remove_packidx(packdir_fd, dent->d_name);
-			if (err)
+			if (unlinkat(packdir_fd, dent->d_name, 0) == -1) {
+				err = got_error_from_errno("unlinkat");
 				goto done;
+			}
 		}
 		if (progress_cb) {
 			char *path;