From 08f57a31507274fd19c3fe207ffca21b3d1fcf74 Mon Sep 17 00:00:00 2001
From: Ryan Lahfa <ryan@lahfa.xyz>
Date: Fri, 21 Jun 2024 00:39:40 +0200
Subject: [PATCH] Linux 6.9 compat: fput for block device release

With new file-driven API, it is sufficient to `fput` the block device
handle to release it.

Signed-off-by: Ryan Lahfa <ryan@lahfa.xyz>
---
 config/kernel-blkdev.m4         | 24 +++++++++++++++++++++++-
 module/os/linux/zfs/vdev_disk.c |  2 ++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/config/kernel-blkdev.m4 b/config/kernel-blkdev.m4
index b3bc5739ad..88b2f69cc4 100644
--- a/config/kernel-blkdev.m4
+++ b/config/kernel-blkdev.m4
@@ -178,6 +178,20 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV_BDEV_RELEASE], [
 	])
 ])
 
+dnl #
+dnl # 6.9.x API change
+dnl # fput() replaces bdev_release()
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV_FPUT], [
+	ZFS_LINUX_TEST_SRC([fput], [
+		#include <linux/fs.h>
+		#include <linux/blkdev.h>
+	], [
+		struct file *f = NULL;
+		fput(f);
+	])
+])
+
 AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_PUT], [
 	AC_MSG_CHECKING([whether blkdev_put() exists])
 	ZFS_LINUX_TEST_RESULT([blkdev_put], [
@@ -197,7 +211,14 @@ AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_PUT], [
 				AC_DEFINE(HAVE_BDEV_RELEASE, 1,
 					[bdev_release() exists])
 			], [
-				ZFS_LINUX_TEST_ERROR([blkdev_put()])
+				ZFS_LINUX_TEST_RESULT([fput], [
+					AC_MSG_RESULT(yes)
+					AC_DEFINE(HAVE_BDEV_RELEASE_VIA_FPUT, 1,
+						[fput() can release a block device and exists]
+					)
+				], [
+					ZFS_LINUX_TEST_ERROR([blkdev_put()])
+				])
 			])
 		])
 	])
@@ -654,6 +675,7 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV], [
 	ZFS_AC_KERNEL_SRC_BLKDEV_PUT
 	ZFS_AC_KERNEL_SRC_BLKDEV_PUT_HOLDER
 	ZFS_AC_KERNEL_SRC_BLKDEV_BDEV_RELEASE
+	ZFS_AC_KERNEL_SRC_BLKDEV_FPUT
 	ZFS_AC_KERNEL_SRC_BLKDEV_REREAD_PART
 	ZFS_AC_KERNEL_SRC_BLKDEV_INVALIDATE_BDEV
 	ZFS_AC_KERNEL_SRC_BLKDEV_LOOKUP_BDEV
diff --git a/module/os/linux/zfs/vdev_disk.c b/module/os/linux/zfs/vdev_disk.c
index 9f5b526d72..da30dfad5a 100644
--- a/module/os/linux/zfs/vdev_disk.c
+++ b/module/os/linux/zfs/vdev_disk.c
@@ -263,6 +263,8 @@ vdev_blkdev_put(zfs_bdev_handle_t *bdh, spa_mode_t mode, void *holder)
 {
 #if defined(HAVE_BDEV_RELEASE)
 	return (bdev_release(bdh));
+#elif defined(HAVE_BDEV_RELEASE_VIA_FPUT)
+	return (fput(bdh));
 #elif defined(HAVE_BLKDEV_PUT_HOLDER)
 	return (blkdev_put(BDH_BDEV(bdh), holder));
 #else