From cb1b813f0df60219063f2accd3b92a10f55aa741 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 8 Dec 2023 10:47:38 +0100
Subject: [PATCH] lock-util: make global lock return parameter to
 image_path_lock() optional

When adding unprivileged nspawn support we don't really want a global
lock file, since we cannot even access the dir they are stored in, hence
make the concept optional.

Some minor other modernizations.
---
 src/basic/lock-util.h       |  2 +-
 src/shared/discover-image.c | 46 ++++++++++++++++++++++---------------
 2 files changed, 29 insertions(+), 19 deletions(-)

diff --git a/src/basic/lock-util.h b/src/basic/lock-util.h
index 91b332f803c..8fb4757968c 100644
--- a/src/basic/lock-util.h
+++ b/src/basic/lock-util.h
@@ -17,7 +17,7 @@ static inline int make_lock_file(const char *p, int operation, LockFile *ret) {
 int make_lock_file_for(const char *p, int operation, LockFile *ret);
 void release_lock_file(LockFile *f);
 
-#define LOCK_FILE_INIT { .dir_fd = -EBADF, .fd = -EBADF }
+#define LOCK_FILE_INIT (LockFile) { .dir_fd = -EBADF, .fd = -EBADF }
 
 /* POSIX locks with the same interface as flock(). */
 int posix_lock(int fd, int operation);
diff --git a/src/shared/discover-image.c b/src/shared/discover-image.c
index 00d32a9c876..bef64a6b043 100644
--- a/src/shared/discover-image.c
+++ b/src/shared/discover-image.c
@@ -1295,7 +1295,12 @@ static void make_lock_dir(void) {
         (void) mkdir("/run/systemd/nspawn/locks", 0700);
 }
 
-int image_path_lock(const char *path, int operation, LockFile *global, LockFile *local) {
+int image_path_lock(
+                const char *path,
+                int operation,
+                LockFile *ret_global,
+                LockFile *ret_local) {
+
         _cleanup_free_ char *p = NULL;
         LockFile t = LOCK_FILE_INIT;
         struct stat st;
@@ -1303,8 +1308,7 @@ int image_path_lock(const char *path, int operation, LockFile *global, LockFile
         int r;
 
         assert(path);
-        assert(global);
-        assert(local);
+        assert(ret_local);
 
         /* Locks an image path. This actually creates two locks: one "local" one, next to the image path
          * itself, which might be shared via NFS. And another "global" one, in /run, that uses the
@@ -1326,7 +1330,9 @@ int image_path_lock(const char *path, int operation, LockFile *global, LockFile
         }
 
         if (getenv_bool("SYSTEMD_NSPAWN_LOCK") == 0) {
-                *local = *global = (LockFile) LOCK_FILE_INIT;
+                *ret_local = LOCK_FILE_INIT;
+                if (ret_global)
+                        *ret_global = LOCK_FILE_INIT;
                 return 0;
         }
 
@@ -1342,19 +1348,23 @@ int image_path_lock(const char *path, int operation, LockFile *global, LockFile
                 if (exclusive)
                         return -EBUSY;
 
-                *local = *global = (LockFile) LOCK_FILE_INIT;
+                *ret_local = LOCK_FILE_INIT;
+                if (ret_global)
+                        *ret_global = LOCK_FILE_INIT;
                 return 0;
         }
 
-        if (stat(path, &st) >= 0) {
-                if (S_ISBLK(st.st_mode))
-                        r = asprintf(&p, "/run/systemd/nspawn/locks/block-%u:%u", major(st.st_rdev), minor(st.st_rdev));
-                else if (S_ISDIR(st.st_mode) || S_ISREG(st.st_mode))
-                        r = asprintf(&p, "/run/systemd/nspawn/locks/inode-%lu:%lu", (unsigned long) st.st_dev, (unsigned long) st.st_ino);
-                else
-                        return -ENOTTY;
-                if (r < 0)
-                        return -ENOMEM;
+        if (ret_global) {
+                if (stat(path, &st) >= 0) {
+                        if (S_ISBLK(st.st_mode))
+                                r = asprintf(&p, "/run/systemd/nspawn/locks/block-%u:%u", major(st.st_rdev), minor(st.st_rdev));
+                        else if (S_ISDIR(st.st_mode) || S_ISREG(st.st_mode))
+                                r = asprintf(&p, "/run/systemd/nspawn/locks/inode-%lu:%lu", (unsigned long) st.st_dev, (unsigned long) st.st_ino);
+                        else
+                                return -ENOTTY;
+                        if (r < 0)
+                                return -ENOMEM;
+                }
         }
 
         /* For block devices we don't need the "local" lock, as the major/minor lock above should be
@@ -1372,15 +1382,15 @@ int image_path_lock(const char *path, int operation, LockFile *global, LockFile
         if (p) {
                 make_lock_dir();
 
-                r = make_lock_file(p, operation, global);
+                r = make_lock_file(p, operation, ret_global);
                 if (r < 0) {
                         release_lock_file(&t);
                         return r;
                 }
-        } else
-                *global = (LockFile) LOCK_FILE_INIT;
+        } else if (ret_global)
+                *ret_global = LOCK_FILE_INIT;
 
-        *local = t;
+        *ret_local = t;
         return 0;
 }
 
-- 
2.47.3