dissect-image: use backing_file stored in LoopDevice object to generate image name

Follow-up for e374439f4b8def786031ddbbd7dfdae3a335d4d2 (#24322).

This also simplify the logic of generating image name from image path.

6 files changed, 44 insertions, 52 deletions

diff --git a/src/core/namespace.c b/src/core/namespace.c
index 3fbf094851..468b27905e 100644
--- a/src/core/namespace.c
+++ b/src/core/namespace.c
@@ -2065,7 +2065,6 @@ int setup_namespace(
 
                 r = dissect_loop_device(
                                 loop_device,
-                                root_image,
                                 &verity,
                                 root_image_options,
                                 dissect_image_flags,
diff --git a/src/portable/portable.c b/src/portable/portable.c
index 9ac34ced6d..5d0a965db5 100644
--- a/src/portable/portable.c
+++ b/src/portable/portable.c
@@ -367,7 +367,6 @@ static int portable_extract_by_path(
 
                 r = dissect_loop_device(
                                 d,
-                                path,
                                 NULL, NULL,
                                 DISSECT_IMAGE_READ_ONLY |
                                 DISSECT_IMAGE_GENERIC_ROOT |
diff --git a/src/shared/discover-image.c b/src/shared/discover-image.c
index 6ddb279f0d..b3b59fc0bb 100644
--- a/src/shared/discover-image.c
+++ b/src/shared/discover-image.c
@@ -1198,7 +1198,6 @@ int image_read_metadata(Image *i) {
 
                 r = dissect_loop_device(
                                 d,
-                                i->path,
                                 NULL, NULL,
                                 DISSECT_IMAGE_GENERIC_ROOT |
                                 DISSECT_IMAGE_REQUIRE_ROOT |
diff --git a/src/shared/dissect-image.c b/src/shared/dissect-image.c
index dc7cf817f3..fce05bcfbd 100644
--- a/src/shared/dissect-image.c
+++ b/src/shared/dissect-image.c
@@ -193,7 +193,7 @@ static int make_partition_devname(
 
 int dissect_image(
                 int fd,
-                const char *original_path,
+                const char *image_path,
                 const VeritySettings *verity,
                 const MountOptions *mount_options,
                 uint64_t diskseq,
@@ -213,7 +213,7 @@ int dissect_image(
         _cleanup_(blkid_free_probep) blkid_probe b = NULL;
         _cleanup_free_ char *generic_node = NULL;
         sd_id128_t generic_uuid = SD_ID128_NULL;
-        const char *pttype = NULL, *sysname = NULL, *devname = NULL;
+        const char *pttype = NULL, *devname = NULL;
         blkid_partlist pl;
         int r, generic_nr = -1, n_partitions;
         struct stat st;
@@ -305,51 +305,45 @@ int dissect_image(
                 .has_init_system = -1,
         };
 
-        r = sd_device_get_sysname(d, &sysname);
-        if (r < 0)
-                return log_debug_errno(r, "Failed to get device sysname: %m");
-        if (original_path) {
-                _cleanup_free_ char *extracted_filename = NULL, *name_stripped = NULL;
-                r = path_extract_filename(original_path, &extracted_filename);
-                if (r < 0)
-                        return r;
-                r = raw_strip_suffixes(extracted_filename, &name_stripped);
-                if (r < 0)
-                        return r;
+        if (!image_path) {
+                const char *sysname;
 
-                free_and_replace(m->image_name, name_stripped);
-        } else if (startswith(sysname, "loop")) {
-                _cleanup_free_ char *extracted_filename = NULL, *name_stripped = NULL;
-                const char *full_path;
+                /* If image_path is not provided and the device is a loopback block device, then use the path
+                 * to the backing file. Note that the backing_file reference resolves symlinks, while for
+                 * sysext images we want the original path. */
 
-                /* Note that the backing_file reference resolves symlinks, while for sysext images we want the original path */
-                r = sd_device_get_sysattr_value(d, "loop/backing_file", &full_path);
+                r = sd_device_get_sysname(d, &sysname);
                 if (r < 0)
-                        log_debug_errno(r, "Failed to lookup image name via loop device backing file sysattr, ignoring: %m");
-                else {
-                        r = path_extract_filename(full_path, &extracted_filename);
-                        if (r < 0)
-                                return r;
-                        r = raw_strip_suffixes(extracted_filename, &name_stripped);
+                        return log_debug_errno(r, "Failed to get device sysname: %m");
+
+                if (startswith(sysname, "loop")) {
+                        r = sd_device_get_sysattr_value(d, "loop/backing_file", &image_path);
                         if (r < 0)
-                                return r;
+                                log_debug_errno(r, "Failed to lookup image name via loop device backing file sysattr, ignoring: %m");
                 }
+        }
 
-                free_and_replace(m->image_name, name_stripped);
-        } else {
-                r = free_and_strdup(&m->image_name, sysname);
+        if (image_path) {
+                _cleanup_free_ char *extracted_filename = NULL, *name_stripped = NULL;
+
+                r = path_extract_filename(image_path, &extracted_filename);
+                if (r < 0)
+                        return r;
+
+                r = raw_strip_suffixes(extracted_filename, &name_stripped);
                 if (r < 0)
                         return r;
+
+                if (!image_name_is_valid(name_stripped))
+                        log_debug("Image name %s is not valid, ignoring.", strna(name_stripped));
+                else
+                        m->image_name = TAKE_PTR(name_stripped);
         }
+
         r = sd_device_get_devname(d, &devname);
         if (r < 0)
                 return log_debug_errno(r, "Failed to get device devname: %m");
 
-        if (!image_name_is_valid(m->image_name)) {
-                log_debug("Image name %s is not valid, ignoring", strempty(m->image_name));
-                m->image_name = mfree(m->image_name);
-        }
-
         if ((!(flags & DISSECT_IMAGE_GPT_ONLY) &&
             (flags & DISSECT_IMAGE_GENERIC_ROOT)) ||
             (flags & DISSECT_IMAGE_NO_PARTITION_TABLE)) {
@@ -2827,7 +2821,7 @@ int dissect_loop_device_and_warn(
         if (!name)
                 name = ASSERT_PTR(loop->node);
 
-        r = dissect_loop_device(loop, name, verity, mount_options, flags, ret);
+        r = dissect_loop_device(loop, verity, mount_options, flags, ret);
         switch (r) {
 
         case -EOPNOTSUPP:
@@ -3093,7 +3087,6 @@ int verity_dissect_and_mount(
 
         r = dissect_loop_device(
                         loop_device,
-                        src,
                         &verity,
                         options,
                         dissect_image_flags,
@@ -3102,7 +3095,6 @@ int verity_dissect_and_mount(
         if (!verity.data_path && r == -ENOPKG)
                  r = dissect_loop_device(
                                 loop_device,
-                                src,
                                 &verity,
                                 options,
                                 dissect_image_flags | DISSECT_IMAGE_NO_PARTITION_TABLE,
diff --git a/src/shared/dissect-image.h b/src/shared/dissect-image.h
index cc0cf66180..c8d2e6de8f 100644
--- a/src/shared/dissect-image.h
+++ b/src/shared/dissect-image.h
@@ -253,10 +253,19 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(MountOptions*, mount_options_free_all);
 const char* mount_options_from_designator(const MountOptions *options, PartitionDesignator designator);
 
 int probe_filesystem(const char *node, char **ret_fstype);
-int dissect_image(int fd, const char *original_path, const VeritySettings *verity, const MountOptions *mount_options, uint64_t diskseq, uint64_t uevent_seqnum_not_before, usec_t timestamp_not_before, DissectImageFlags flags, DissectedImage **ret);
-static inline int dissect_loop_device(const LoopDevice *loop, const char *original_path, const VeritySettings *verity, const MountOptions *mount_options, DissectImageFlags flags, DissectedImage **ret) {
+int dissect_image(
+                int fd,
+                const char *image_path,
+                const VeritySettings *verity,
+                const MountOptions *mount_options,
+                uint64_t diskseq,
+                uint64_t uevent_seqnum_not_before,
+                usec_t timestamp_not_before,
+                DissectImageFlags flags,
+                DissectedImage **ret);
+static inline int dissect_loop_device(const LoopDevice *loop, const VeritySettings *verity, const MountOptions *mount_options, DissectImageFlags flags, DissectedImage **ret) {
         assert(loop);
-        return dissect_image(loop->fd, original_path, verity, mount_options, loop->diskseq, loop->uevent_seqnum_not_before, loop->timestamp_not_before, flags, ret);
+        return dissect_image(loop->fd, loop->backing_file, verity, mount_options, loop->diskseq, loop->uevent_seqnum_not_before, loop->timestamp_not_before, flags, ret);
 }
 int dissect_loop_device_and_warn(const char *name, const LoopDevice *loop, const VeritySettings *verity, const MountOptions *mount_options, DissectImageFlags flags, DissectedImage **ret);
 
diff --git a/src/test/test-loop-block.c b/src/test/test-loop-block.c
index 70d4aedb42..ee28ad4235 100644
--- a/src/test/test-loop-block.c
+++ b/src/test/test-loop-block.c
@@ -39,7 +39,6 @@ static void* thread_func(void *ptr) {
                 _cleanup_(loop_device_unrefp) LoopDevice *loop = NULL;
                 _cleanup_(umount_and_rmdir_and_freep) char *mounted = NULL;
                 _cleanup_(dissected_image_unrefp) DissectedImage *dissected = NULL;
-                _cleanup_free_ char *path = NULL;
 
                 if (now(CLOCK_MONOTONIC) >= end) {
                         log_notice("Time's up, exiting thread's loop");
@@ -59,12 +58,7 @@ static void* thread_func(void *ptr) {
 
                 log_notice("Acquired loop device %s, will mount on %s", loop->node, mounted);
 
-                r = fd_get_path(fd, &path);
-                if (r < 0)
-                        log_error_errno(r, "Failed to get path from fd: %m");
-                assert_se(r >= 0);
-
-                r = dissect_loop_device(loop, path, NULL, NULL, DISSECT_IMAGE_READ_ONLY, &dissected);
+                r = dissect_loop_device(loop, NULL, NULL, DISSECT_IMAGE_READ_ONLY, &dissected);
                 if (r < 0)
                         log_error_errno(r, "Failed dissect loopback device %s: %m", loop->node);
                 assert_se(r >= 0);
@@ -228,7 +222,7 @@ static int run(int argc, char *argv[]) {
         pthread_t threads[arg_n_threads];
         sd_id128_t id;
 
-        assert_se(dissect_loop_device(loop, p, NULL, NULL, 0, &dissected) >= 0);
+        assert_se(dissect_loop_device(loop, NULL, NULL, 0, &dissected) >= 0);
 
         assert_se(dissected->partitions[PARTITION_ESP].found);
         assert_se(dissected->partitions[PARTITION_ESP].node);
@@ -252,7 +246,7 @@ static int run(int argc, char *argv[]) {
         assert_se(make_filesystem(dissected->partitions[PARTITION_HOME].node, "ext4", "home", id, true) >= 0);
 
         dissected = dissected_image_unref(dissected);
-        assert_se(dissect_loop_device(loop, p, NULL, NULL, 0, &dissected) >= 0);
+        assert_se(dissect_loop_device(loop, NULL, NULL, 0, &dissected) >= 0);
 
         assert_se(mkdtemp_malloc(NULL, &mounted) >= 0);