Merge pull request #15836 from poettering/makefs-lock

lock whole block device file running makefs

src/basic/blockdev-util.c

@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 
+#include <sys/file.h>
 #include <unistd.h>
 
 #include "alloc-util.h"
@@ -29,6 +30,8 @@ int block_get_whole_disk(dev_t d, dev_t *ret) {
                 *ret = d;
                 return 0;
         }
+        if (errno != ENOENT)
+                return -errno;
 
         /* If it is a partition find the originating device */
         xsprintf_sys_block_path(p, "/partition", d);
@@ -185,3 +188,29 @@ int get_block_device_harder(const char *path, dev_t *ret) {
 
         return 1;
 }
+
+int lock_whole_block_device(dev_t devt, int operation) {
+        _cleanup_free_ char *whole_node = NULL;
+        _cleanup_close_ int lock_fd = -1;
+        dev_t whole_devt;
+        int r;
+
+        /* Let's get a BSD file lock on the whole block device, as per: https://systemd.io/BLOCK_DEVICE_LOCKING */
+
+        r = block_get_whole_disk(devt, &whole_devt);
+        if (r < 0)
+                return r;
+
+        r = device_path_make_major_minor(S_IFBLK, whole_devt, &whole_node);
+        if (r < 0)
+                return r;
+
+        lock_fd = open(whole_node, O_RDONLY|O_CLOEXEC|O_NONBLOCK);
+        if (lock_fd < 0)
+                return -errno;
+
+        if (flock(lock_fd, operation) < 0)
+                return -errno;
+
+        return TAKE_FD(lock_fd);
+}

src/basic/blockdev-util.h

@@ -18,3 +18,5 @@ int block_get_originating(dev_t d, dev_t *ret);
 int get_block_device(const char *path, dev_t *dev);
 
 int get_block_device_harder(const char *path, dev_t *dev);
+
+int lock_whole_block_device(dev_t devt, int operation);

src/cryptsetup/cryptsetup-generator.c

@@ -367,12 +367,12 @@ static int create_disk(
 
         if (tmp)
                 fprintf(f,
-                        "ExecStartPost=/sbin/mke2fs '/dev/mapper/%s'\n",
+                        "ExecStartPost=" ROOTLIBEXECDIR "/systemd-makefs ext2 '/dev/mapper/%s'\n",
                         name_escaped);
 
         if (swap)
                 fprintf(f,
-                        "ExecStartPost=/sbin/mkswap '/dev/mapper/%s'\n",
+                        "ExecStartPost=" ROOTLIBEXECDIR "/systemd-makefs swap '/dev/mapper/%s'\n",
                         name_escaped);
 
         if (keydev)

src/partition/makefs.c

@@ -7,7 +7,9 @@
 #include <unistd.h>
 
 #include "alloc-util.h"
+#include "blockdev-util.h"
 #include "dissect-image.h"
+#include "fd-util.h"
 #include "main-func.h"
 #include "process-util.h"
 #include "signal-util.h"
@@ -42,6 +44,7 @@ static int makefs(const char *type, const char *device) {
 
 static int run(int argc, char *argv[]) {
         _cleanup_free_ char *device = NULL, *type = NULL, *detected = NULL;
+        _cleanup_close_ int lock_fd = -1;
         struct stat st;
         int r;
 
@@ -54,28 +57,31 @@ static int run(int argc, char *argv[]) {
         /* type and device must be copied because makefs calls safe_fork, which clears argv[] */
         type = strdup(argv[1]);
         if (!type)
-                return -ENOMEM;
+                return log_oom();
 
         device = strdup(argv[2]);
         if (!device)
-                return -ENOMEM;
+                return log_oom();
 
         if (stat(device, &st) < 0)
                 return log_error_errno(errno, "Failed to stat \"%s\": %m", device);
 
-        if (!S_ISBLK(st.st_mode))
+        if (S_ISBLK(st.st_mode)) {
+                /* Lock the device so that udev doesn't interfere with our work */
+
+                lock_fd = lock_whole_block_device(st.st_rdev, LOCK_EX);
+                if (lock_fd < 0)
+                        return log_error_errno(lock_fd, "Failed to lock whole block device of \"%s\": %m", device);
+        } else
                 log_info("%s is not a block device.", device);
 
         r = probe_filesystem(device, &detected);
+        if (r == -EUCLEAN)
+                return log_error_errno(r, "Ambiguous results of probing for file system on \"%s\", refusing to proceed.", device);
         if (r < 0)
-                return log_warning_errno(r,
-                                         r == -EUCLEAN ?
-                                         "Cannot reliably determine probe \"%s\", refusing to proceed." :
-                                         "Failed to probe \"%s\": %m",
-                                         device);
-
+                return log_error_errno(r, "Failed to probe \"%s\": %m", device);
         if (detected) {
-                log_info("%s is not empty (type %s), exiting", device, detected);
+                log_info("'%s' is not empty (contains file system of type %s), exiting.", device, detected);
                 return 0;
         }
 

src/shared/dissect-image.c

@@ -75,10 +75,9 @@ int probe_filesystem(const char *node, char **ret_fstype) {
                 log_debug("No type detected on partition %s", node);
                 goto not_found;
         }
-        if (r == -2) {
-                log_debug("Results ambiguous for partition %s", node);
-                return -EUCLEAN;
-        }
+        if (r == -2)
+                return log_debug_errno(SYNTHETIC_ERRNO(EUCLEAN),
+                                       "Results ambiguous for partition %s", node);
         if (r != 0)
                 return errno_or_else(EIO);