Linux 6.9 compat: bdev handles are now struct file

bdev_open_by_path() is replaced by bdev_file_open_by_path(), which
returns a plain old struct file*. Release function is gone entirely; the
regular file release function fput() will take care of the bdev
specifics.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Sponsored-by: https://despairlabs.com/sponsor/
Closes #16027
Closes #16033

config/kernel-blkdev.m4

@@ -54,6 +54,26 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV_BDEV_OPEN_BY_PATH], [
 	])
 ])
 
+dnl #
+dnl # 6.9.x API change
+dnl # bdev_file_open_by_path() replaced bdev_open_by_path(),
+dnl # and returns struct file*
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_BDEV_FILE_OPEN_BY_PATH], [
+	ZFS_LINUX_TEST_SRC([bdev_file_open_by_path], [
+		#include <linux/fs.h>
+		#include <linux/blkdev.h>
+	], [
+		struct file *file __attribute__ ((unused)) = NULL;
+		const char *path = "path";
+		fmode_t mode = 0;
+		void *holder = NULL;
+		struct blk_holder_ops h;
+
+		file = bdev_file_open_by_path(path, mode, holder, &h);
+	])
+])
+
 AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_GET_BY_PATH], [
 	AC_MSG_CHECKING([whether blkdev_get_by_path() exists and takes 3 args])
 	ZFS_LINUX_TEST_RESULT([blkdev_get_by_path], [
@@ -73,7 +93,16 @@ AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_GET_BY_PATH], [
 					[bdev_open_by_path() exists])
 				AC_MSG_RESULT(yes)
 			], [
-				ZFS_LINUX_TEST_ERROR([blkdev_get_by_path()])
+				AC_MSG_RESULT(no)
+				AC_MSG_CHECKING([whether bdev_file_open_by_path() exists])
+				ZFS_LINUX_TEST_RESULT([bdev_file_open_by_path], [
+					AC_DEFINE(HAVE_BDEV_FILE_OPEN_BY_PATH, 1,
+						[bdev_file_open_by_path() exists])
+					AC_MSG_RESULT(yes)
+				], [
+					AC_MSG_RESULT(no)
+					ZFS_LINUX_TEST_ERROR([blkdev_get_by_path()])
+				])
 			])
 		])
 	])
@@ -149,10 +178,19 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV_BDEV_RELEASE], [
 	])
 ])
 
+dnl #
+dnl # 6.9.x API change
+dnl #
+dnl # bdev_release() now private, but because bdev_file_open_by_path() returns
+dnl # struct file*, we can just use fput(). So the blkdev_put test no longer
+dnl # fails if not found.
+dnl #
+
 AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_PUT], [
 	AC_MSG_CHECKING([whether blkdev_put() exists])
 	ZFS_LINUX_TEST_RESULT([blkdev_put], [
 		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_BLKDEV_PUT, 1, [blkdev_put() exists])
 	], [
 		AC_MSG_RESULT(no)
 		AC_MSG_CHECKING([whether blkdev_put() accepts void* as arg 2])
@@ -168,7 +206,7 @@ AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_PUT], [
 				AC_DEFINE(HAVE_BDEV_RELEASE, 1,
 					[bdev_release() exists])
 			], [
-				ZFS_LINUX_TEST_ERROR([blkdev_put()])
+				AC_MSG_RESULT(no)
 			])
 		])
 	])
@@ -697,6 +735,7 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV], [
 	ZFS_AC_KERNEL_SRC_BLKDEV_GET_BY_PATH
 	ZFS_AC_KERNEL_SRC_BLKDEV_GET_BY_PATH_4ARG
 	ZFS_AC_KERNEL_SRC_BLKDEV_BDEV_OPEN_BY_PATH
+	ZFS_AC_KERNEL_SRC_BDEV_FILE_OPEN_BY_PATH
 	ZFS_AC_KERNEL_SRC_BLKDEV_PUT
 	ZFS_AC_KERNEL_SRC_BLKDEV_PUT_HOLDER
 	ZFS_AC_KERNEL_SRC_BLKDEV_BDEV_RELEASE

module/os/linux/zfs/vdev_disk.c

@@ -45,15 +45,25 @@
 /*
  * Linux 6.8.x uses a bdev_handle as an instance/refcount for an underlying
  * block_device. Since it carries the block_device inside, its convenient to
- * just use the handle as a proxy. For pre-6.8, we just emulate this with
+ * just use the handle as a proxy.
- * a cast, since we don't need any of the other fields inside the handle.
+ *
+ * Linux 6.9.x uses a file for the same purpose.
+ *
+ * For pre-6.8, we just emulate this with a cast, since we don't need any of
+ * the other fields inside the handle.
  */
-#ifdef HAVE_BDEV_OPEN_BY_PATH
+#if defined(HAVE_BDEV_OPEN_BY_PATH)
 typedef struct bdev_handle zfs_bdev_handle_t;
 #define	BDH_BDEV(bdh)		((bdh)->bdev)
 #define	BDH_IS_ERR(bdh)		(IS_ERR(bdh))
 #define	BDH_PTR_ERR(bdh)	(PTR_ERR(bdh))
 #define	BDH_ERR_PTR(err)	(ERR_PTR(err))
+#elif defined(HAVE_BDEV_FILE_OPEN_BY_PATH)
+typedef struct file zfs_bdev_handle_t;
+#define	BDH_BDEV(bdh)		(file_bdev(bdh))
+#define	BDH_IS_ERR(bdh)		(IS_ERR(bdh))
+#define	BDH_PTR_ERR(bdh)	(PTR_ERR(bdh))
+#define	BDH_ERR_PTR(err)	(ERR_PTR(err))
 #else
 typedef void zfs_bdev_handle_t;
 #define	BDH_BDEV(bdh)		((struct block_device *)bdh)
@@ -242,7 +252,9 @@ vdev_blkdev_get_by_path(const char *path, spa_mode_t smode, void *holder)
 {
 	vdev_bdev_mode_t bmode = vdev_bdev_mode(smode);
 
-#if defined(HAVE_BDEV_OPEN_BY_PATH)
+#if defined(HAVE_BDEV_FILE_OPEN_BY_PATH)
+	return (bdev_file_open_by_path(path, bmode, holder, NULL));
+#elif defined(HAVE_BDEV_OPEN_BY_PATH)
 	return (bdev_open_by_path(path, bmode, holder, NULL));
 #elif defined(HAVE_BLKDEV_GET_BY_PATH_4ARG)
 	return (blkdev_get_by_path(path, bmode, holder, NULL));
@@ -258,8 +270,10 @@ vdev_blkdev_put(zfs_bdev_handle_t *bdh, spa_mode_t smode, void *holder)
 	return (bdev_release(bdh));
 #elif defined(HAVE_BLKDEV_PUT_HOLDER)
 	return (blkdev_put(BDH_BDEV(bdh), holder));
-#else
+#elif defined(HAVE_BLKDEV_PUT)
 	return (blkdev_put(BDH_BDEV(bdh), vdev_bdev_mode(smode)));
+#else
+	fput(bdh);
 #endif
 }