drbd/0015-compat-block-use-the-holder-as-indication-for-exclus.patch

From 3b9fcc2cfaa32766724f371cc2054e057adbc425 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Moritz=20=22WanzenBug=22=20Wanzenb=C3=B6ck?=
 <moritz.wanzenboeck@linbit.com>
Date: Mon, 11 Sep 2023 13:36:07 +0200
Subject: [PATCH 15/20] compat: block: use the holder as indication for
 exclusive opens

See also upstream Linux kernel commit
2736e8eeb0cc ("block: use the holder as indication for exclusive opens")
Original message:

The current interface for exclusive opens is rather confusing as it
requires both the FMODE_EXCL flag and a holder.  Remove the need to pass
FMODE_EXCL and just key off the exclusive open off a non-NULL holder.

For blkdev_put this requires adding the holder argument, which provides
better debug checking that only the holder actually releases the hold,
but at the same time allows removing the now superfluous mode argument.
---
 .../cocci/blkdev_put__no_has_holder.cocci     | 38 +++++++++++++++++++
 drbd/drbd-kernel-compat/gen_patch_names.c     |  3 ++
 .../tests/blkdev_put_has_holder.c             | 17 +++++++++
 drbd/drbd_nl.c                                | 28 ++++++++------
 4 files changed, 75 insertions(+), 11 deletions(-)
 create mode 100644 drbd/drbd-kernel-compat/cocci/blkdev_put__no_has_holder.cocci
 create mode 100644 drbd/drbd-kernel-compat/tests/blkdev_put_has_holder.c

diff --git a/drbd/drbd-kernel-compat/cocci/blkdev_put__no_has_holder.cocci b/drbd/drbd-kernel-compat/cocci/blkdev_put__no_has_holder.cocci
new file mode 100644
index 000000000000..c903bc2d529c
--- /dev/null
+++ b/drbd/drbd-kernel-compat/cocci/blkdev_put__no_has_holder.cocci
@@ -0,0 +1,38 @@
+@@
+expression path, mode;
+@@
+  blkdev_get_by_path(
+  	path,
+- 	mode,
++ 	mode | FMODE_EXCL,
+  	...
+  )
+
+@@
+expression bdev, holder;
+@@
+  blkdev_put(
+  	bdev,
+- 	holder
++ 	FMODE_READ | FMODE_WRITE | FMODE_EXCL
+  )
+
+@@
+identifier device, bdev, holder, do_bd_unlink;
+@@
+  void close_backing_dev(
+  	struct drbd_device *device,
+  	struct block_device *bdev,
+-  	void *holder,
+  	bool do_bd_unlink
+  ) { ... }
+
+@@
+expression device, bdev, holder, do_bd_unlink;
+@@
+  close_backing_dev(
+  	device,
+  	bdev,
+- 	holder,
+  	do_bd_unlink
+  )
diff --git a/drbd/drbd-kernel-compat/gen_patch_names.c b/drbd/drbd-kernel-compat/gen_patch_names.c
index 6e4f06d9a3a7..4761c1ef7d0c 100644
--- a/drbd/drbd-kernel-compat/gen_patch_names.c
+++ b/drbd/drbd-kernel-compat/gen_patch_names.c
@@ -562,6 +562,9 @@ int main(int argc, char **argv)
 	patch(1, "block_device_operations_open", true, false,
 	      COMPAT_BLOCK_DEVICE_OPERATIONS_OPEN_TAKES_GENDISK, "takes_gendisk");
 
+	patch(1, "blkdev_put", true, false,
+	      COMPAT_BLKDEV_PUT_HAS_HOLDER, "has_holder");
+
 /* #define BLKDEV_ISSUE_ZEROOUT_EXPORTED */
 /* #define BLKDEV_ZERO_NOUNMAP */
 
diff --git a/drbd/drbd-kernel-compat/tests/blkdev_put_has_holder.c b/drbd/drbd-kernel-compat/tests/blkdev_put_has_holder.c
new file mode 100644
index 000000000000..d5f0c5dd0355
--- /dev/null
+++ b/drbd/drbd-kernel-compat/tests/blkdev_put_has_holder.c
@@ -0,0 +1,17 @@
+/* { "version": "v6.5-rc1", "commit": "ae220766d87cd6799dbf918fea10613ae14c0654", "comment": "block: remove the unused mode argument to ->release", "author": "Christoph Hellwig <hch@lst.de>", "date": "Thu Jun 8 13:02:37 2023 +0200" } */
+#include <linux/blkdev.h>
+
+#ifndef __same_type
+# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
+#endif
+
+void foo_blkdev_put(struct block_device *bdev, void *holder)
+{
+}
+
+
+void foo(void)
+{
+	BUILD_BUG_ON(!(__same_type(&blkdev_put, &foo_blkdev_put)));
+}
+
diff --git a/drbd/drbd_nl.c b/drbd/drbd_nl.c
index b7e9e43312f9..8c968cf252ca 100644
--- a/drbd/drbd_nl.c
+++ b/drbd/drbd_nl.c
@@ -2536,13 +2536,13 @@ bool want_bitmap(struct drbd_peer_device *peer_device)
 }
 
 static void close_backing_dev(struct drbd_device *device, struct block_device *bdev,
-	bool do_bd_unlink)
+	void *holder, bool do_bd_unlink)
 {
 	if (!bdev)
 		return;
 	if (do_bd_unlink)
 		bd_unlink_disk_holder(bdev, device->vdisk);
-	blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+	blkdev_put(bdev, holder);
 }
 
 void drbd_backing_dev_free(struct drbd_device *device, struct drbd_backing_dev *ldev)
@@ -2552,8 +2552,11 @@ void drbd_backing_dev_free(struct drbd_device *device, struct drbd_backing_dev *
 
 	drbd_dax_close(ldev);
 
-	close_backing_dev(device, ldev->md_bdev, ldev->md_bdev != ldev->backing_bdev);
-	close_backing_dev(device, ldev->backing_bdev, true);
+	close_backing_dev(device,
+			  ldev->md_bdev,
+			  ldev->md.meta_dev_idx < 0 ? (void *)device : (void *)drbd_m_holder,
+			  ldev->md_bdev != ldev->backing_bdev);
+	close_backing_dev(device, ldev->backing_bdev, device, true);
 
 	kfree(ldev->disk_conf);
 	kfree(ldev);
@@ -2563,7 +2566,7 @@ static struct block_device *open_backing_dev(struct drbd_device *device,
 		const char *bdev_path, void *claim_ptr)
 {
 	struct block_device *bdev = blkdev_get_by_path(bdev_path,
-				  FMODE_READ | FMODE_WRITE | FMODE_EXCL,
+				  FMODE_READ | FMODE_WRITE,
 				  claim_ptr, NULL);
 	if (IS_ERR(bdev)) {
 		drbd_err(device, "open(\"%s\") failed with %ld\n",
@@ -2588,6 +2591,7 @@ static int open_backing_devices(struct drbd_device *device,
 		struct drbd_backing_dev *nbc)
 {
 	struct block_device *bdev;
+	void *meta_claim_ptr;
 	int err;
 
 	bdev = open_backing_dev(device, new_disk_conf->backing_dev, device);
@@ -2597,12 +2601,17 @@ static int open_backing_devices(struct drbd_device *device,
 	err = link_backing_dev(device, new_disk_conf->backing_dev, bdev);
 	if (err) {
 		/* close without unlinking; otherwise error path will try to unlink */
-		close_backing_dev(device, bdev, false);
+		close_backing_dev(device, bdev, device, false);
 		return ERR_OPEN_DISK;
 	}
 
 	nbc->backing_bdev = bdev;
 
+	/* meta_claim_ptr: device, if claimed exclusively; shared drbd_m_holder,
+	 * if potentially shared with other drbd minors
+	 */
+	meta_claim_ptr = (new_disk_conf->meta_dev_idx < 0) ?
+		(void *)device : (void *)drbd_m_holder;
 	/*
 	 * meta_dev_idx >= 0: external fixed size, possibly multiple
 	 * drbd sharing one meta device.  TODO in that case, paranoia
@@ -2611,10 +2620,7 @@ static int open_backing_devices(struct drbd_device *device,
 	 * should check it for you already; but if you don't, or
 	 * someone fooled it, we need to double check here)
 	 */
-	bdev = open_backing_dev(device, new_disk_conf->meta_dev,
-		/* claim ptr: device, if claimed exclusively; shared drbd_m_holder,
-		 * if potentially shared with other drbd minors */
-			(new_disk_conf->meta_dev_idx < 0) ? (void*)device : (void*)drbd_m_holder);
+	bdev = open_backing_dev(device, new_disk_conf->meta_dev, meta_claim_ptr);
 	if (IS_ERR(bdev))
 		return ERR_OPEN_MD_DISK;
 
@@ -2624,7 +2630,7 @@ static int open_backing_devices(struct drbd_device *device,
 		err = link_backing_dev(device, new_disk_conf->meta_dev, bdev);
 		if (err) {
 			/* close without unlinking; otherwise error path will try to unlink */
-			close_backing_dev(device, bdev, false);
+			close_backing_dev(device, bdev, meta_claim_ptr, false);
 			return ERR_OPEN_MD_DISK;
 		}
 	}
-- 
2.35.3