From: Karel Zak <kzak@redhat.com>
Date: Tue, 30 Jun 2026 13:18:25 +0000 (+0200)
Subject: libblkid: add blkid_probe_open_device()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8b6ca6fef9e17c195167d3622808cb411132eadb;p=thirdparty%2Futil-linux.git

libblkid: add blkid_probe_open_device()

Add a convenience function that opens a device and assigns it to
the probe, using VFS operations if previously set. This enables
the composable pattern:

  blkid_new_probe()
  → blkid_probe_set_vfs()
  → blkid_probe_open_device()

Refactor blkid_new_probe_from_filename() to use it internally.

Addresses: https://github.com/util-linux/util-linux/issues/4308
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/libblkid/docs/libblkid-sections.txt b/libblkid/docs/libblkid-sections.txt
index 75b2b3a32..9a4ae2a54 100644
--- a/libblkid/docs/libblkid-sections.txt
+++ b/libblkid/docs/libblkid-sections.txt
@@ -61,6 +61,7 @@ blkid_probe_reset_buffers
 blkid_probe_reset_hints
 blkid_probe_set_device
 blkid_probe_set_hint
+blkid_probe_open_device
 blkid_probe_set_sectorsize
 blkid_probe_set_vfs
 blkid_probe_step_back
diff --git a/libblkid/src/blkid.h.in b/libblkid/src/blkid.h.in
index adfd3c3a6..ee85ef015 100644
--- a/libblkid/src/blkid.h.in
+++ b/libblkid/src/blkid.h.in
@@ -262,6 +262,10 @@ struct ul_vfs_ops {
 extern int blkid_probe_set_vfs(blkid_probe pr, const struct ul_vfs_ops *ops)
 			__ul_attribute__((nonnull(1)));
 
+extern int blkid_probe_open_device(blkid_probe pr, const char *filename,
+			int flags)
+			__ul_attribute__((nonnull));
+
 extern dev_t blkid_probe_get_devno(blkid_probe pr)
 			__ul_attribute__((nonnull));
 
diff --git a/libblkid/src/libblkid.sym b/libblkid/src/libblkid.sym
index cf520d9b7..55c4e23ac 100644
--- a/libblkid/src/libblkid.sym
+++ b/libblkid/src/libblkid.sym
@@ -194,5 +194,6 @@ BLKID_2_40 {
 
 BLKID_2_43 {
     blkid_evaluate_tag2;
+    blkid_probe_open_device;
     blkid_probe_set_vfs;
 } BLKID_2_40;
diff --git a/libblkid/src/probe.c b/libblkid/src/probe.c
index 6fa8ba563..7f4c2791d 100644
--- a/libblkid/src/probe.c
+++ b/libblkid/src/probe.c
@@ -205,60 +205,82 @@ blkid_probe blkid_clone_probe(blkid_probe parent)
 	return pr;
 }
 
-
-
 /**
- * blkid_new_probe_from_filename:
+ * blkid_probe_open_device:
+ * @pr: probe
  * @filename: device or regular file
+ * @flags: open(2) flags or 0 for default (O_RDONLY|O_CLOEXEC|O_NONBLOCK)
  *
- * This function is same as call open(filename), blkid_new_probe() and
- * blkid_probe_set_device(pr, fd, 0, 0).
+ * Opens the @filename and assigns it to the probe. This is equivalent to
+ * calling open() and blkid_probe_set_device(), but uses VFS operations
+ * if previously set by blkid_probe_set_vfs().
+ *
+ * This allows probe setup before the device is opened:
+ *
+ *   blkid_new_probe() → blkid_probe_set_vfs() → blkid_probe_open_device()
  *
  * The @filename is closed by blkid_free_probe() or by the
  * blkid_probe_set_device() call.
  *
- * Returns: a pointer to the newly allocated probe struct or NULL in case of
- * error.
+ * Since: 2.43
+ *
+ * Returns: 0 on success, or <0 in case of error.
  */
-blkid_probe blkid_new_probe_from_filename(const char *filename)
+int blkid_probe_open_device(blkid_probe pr, const char *filename, int flags)
 {
 	int fd;
-	blkid_probe pr = NULL;
 	struct stat sb;
 
-	/*
-	 * Check for hidden device-mapper devices (LVM internals, etc.)
-	 * before open() to avoid bumping the kernel open count.  A racing
-	 * DM_DEVICE_REMOVE would otherwise see EBUSY.
-	 *
-	 * Use sysfs_devno_is_dm_hidden() rather than _dm_private() so that
-	 * Stratis devices remain accessible to tools like mkfs.xfs that
-	 * need to probe device geometry.
-	 */
 	if (stat(filename, &sb) == 0 && S_ISBLK(sb.st_mode) &&
 	    sysfs_devno_is_dm_hidden(sb.st_rdev, NULL)) {
 		DBG(LOWPROBE, ul_debug("ignore hidden device mapper device"));
 		errno = EINVAL;
-		return NULL;
+		return -EINVAL;
 	}
 
-	fd = open(filename, O_RDONLY | O_CLOEXEC | O_NONBLOCK);
+	if (!flags)
+		flags = O_RDONLY | O_CLOEXEC | O_NONBLOCK;
+
+	fd = ul_vfs_open(pr->vfs, filename, flags, 0);
 	if (fd < 0)
-		return NULL;
+		return -errno;
+
+	if (blkid_probe_set_device(pr, fd, 0, 0)) {
+		ul_vfs_close(pr->vfs, fd);
+		return -errno ? -errno : -EINVAL;
+	}
+
+	pr->flags |= BLKID_FL_PRIVATE_FD;
+	return 0;
+}
+
+/**
+ * blkid_new_probe_from_filename:
+ * @filename: device or regular file
+ *
+ * This function is same as call open(filename), blkid_new_probe() and
+ * blkid_probe_set_device(pr, fd, 0, 0).
+ *
+ * The @filename is closed by blkid_free_probe() or by the
+ * blkid_probe_set_device() call.
+ *
+ * Returns: a pointer to the newly allocated probe struct or NULL in case of
+ * error.
+ */
+blkid_probe blkid_new_probe_from_filename(const char *filename)
+{
+	blkid_probe pr;
 
 	pr = blkid_new_probe();
 	if (!pr)
-		goto err;
+		return NULL;
 
-	if (blkid_probe_set_device(pr, fd, 0, 0))
-		goto err;
+	if (blkid_probe_open_device(pr, filename, 0)) {
+		blkid_free_probe(pr);
+		return NULL;
+	}
 
-	pr->flags |= BLKID_FL_PRIVATE_FD;
 	return pr;
-err:
-	close(fd);
-	blkid_free_probe(pr);
-	return NULL;
 }
 
 /**