Persistent Reservation API

Persistent Reservation API

[Christoph Hellwig]

This series adds support for a simplified persistent reservation API
to the block layer.  The intent is that both in-kernel and userspace
consumers can use the API instead of having to hand craft SCSI or NVMe
command through the various pass through interfaces.  It also adds
DM support as getting reservations through dm-multipath is a major
pain with the current scheme.

NVMe support currently isn't included as I don't have a multihost
NVMe setup to test on, but if I can find a volunteer to test it I'm
happy to write the code for it.

The ioctl API is documented in Documentation/block/pr.txt, but to
fully understand the concept you'll have to read up the SPC spec,
PRs are too complicated that trying to rephrase them into different
terminology is just going to create confusion.

I also have a set of simple test tools available at:

	git://git.infradead.org/users/hch/pr-tests.git

[PATCH 1/6] block: cleanup blkdev_ioctl

[Christoph Hellwig]

Split out helpers for all non-trivial ioctls to make this function simpler,
and also start passing around a pointer version of the argument, as that's
what most ioctl handlers actually need.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/ioctl.c | 227 ++++++++++++++++++++++++++++++++--------------------------
 1 file changed, 127 insertions(+), 100 deletions(-)

diff --git a/block/ioctl.c b/block/ioctl.c
index 8061eba..df62b47 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -193,10 +193,20 @@ int blkdev_reread_part(struct block_device *bdev)
 }
 EXPORT_SYMBOL(blkdev_reread_part);
 
-static int blk_ioctl_discard(struct block_device *bdev, uint64_t start,
-			     uint64_t len, int secure)
+static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
+		unsigned long arg, unsigned long flags)
 {
-	unsigned long flags = 0;
+	uint64_t range[2];
+	uint64_t start, len;
+
+	if (!(mode & FMODE_WRITE))
+		return -EBADF;
+
+	if (copy_from_user(range, (void __user *)arg, sizeof(range)))
+		return -EFAULT;
+
+	start = range[0];
+	len = range[1];
 
 	if (start & 511)
 		return -EINVAL;
@@ -207,14 +217,24 @@ static int blk_ioctl_discard(struct block_device *bdev, uint64_t start,
 
 	if (start + len > (i_size_read(bdev->bd_inode) >> 9))
 		return -EINVAL;
-	if (secure)
-		flags |= BLKDEV_DISCARD_SECURE;
 	return blkdev_issue_discard(bdev, start, len, GFP_KERNEL, flags);
 }
 
-static int blk_ioctl_zeroout(struct block_device *bdev, uint64_t start,
-			     uint64_t len)
+static int blk_ioctl_zeroout(struct block_device *bdev, fmode_t mode,
+		unsigned long arg)
 {
+	uint64_t range[2];
+	uint64_t start, len;
+
+	if (!(mode & FMODE_WRITE))
+		return -EBADF;
+
+	if (copy_from_user(range, (void __user *)arg, sizeof(range)))
+		return -EFAULT;
+
+	start = range[0];
+	len = range[1];
+
 	if (start & 511)
 		return -EINVAL;
 	if (len & 511)
@@ -295,89 +315,115 @@ static inline int is_unrecognized_ioctl(int ret)
 		ret == -ENOIOCTLCMD;
 }
 
-/*
- * always keep this in sync with compat_blkdev_ioctl()
- */
-int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
-			unsigned long arg)
+static int blkdev_flushbuf(struct block_device *bdev, fmode_t mode,
+		unsigned cmd, unsigned long arg)
 {
-	struct gendisk *disk = bdev->bd_disk;
-	struct backing_dev_info *bdi;
-	loff_t size;
-	int ret, n;
-	unsigned int max_sectors;
+	int ret;
 
-	switch(cmd) {
-	case BLKFLSBUF:
-		if (!capable(CAP_SYS_ADMIN))
-			return -EACCES;
-
-		ret = __blkdev_driver_ioctl(bdev, mode, cmd, arg);
-		if (!is_unrecognized_ioctl(ret))
-			return ret;
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
 
-		fsync_bdev(bdev);
-		invalidate_bdev(bdev);
-		return 0;
+	ret = __blkdev_driver_ioctl(bdev, mode, cmd, arg);
+	if (!is_unrecognized_ioctl(ret))
+		return ret;
 
-	case BLKROSET:
-		ret = __blkdev_driver_ioctl(bdev, mode, cmd, arg);
-		if (!is_unrecognized_ioctl(ret))
-			return ret;
-		if (!capable(CAP_SYS_ADMIN))
-			return -EACCES;
-		if (get_user(n, (int __user *)(arg)))
-			return -EFAULT;
-		set_device_ro(bdev, n);
-		return 0;
+	fsync_bdev(bdev);
+	invalidate_bdev(bdev);
+	return 0;
+}
 
-	case BLKDISCARD:
-	case BLKSECDISCARD: {
-		uint64_t range[2];
+static int blkdev_roset(struct block_device *bdev, fmode_t mode,
+		unsigned cmd, unsigned long arg)
+{
+	int ret, n;
 
-		if (!(mode & FMODE_WRITE))
-			return -EBADF;
+	ret = __blkdev_driver_ioctl(bdev, mode, cmd, arg);
+	if (!is_unrecognized_ioctl(ret))
+		return ret;
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+	if (get_user(n, (int __user *)arg))
+		return -EFAULT;
+	set_device_ro(bdev, n);
+	return 0;
+}
 
-		if (copy_from_user(range, (void __user *)arg, sizeof(range)))
-			return -EFAULT;
+static int blkdev_getgeo(struct block_device *bdev,
+		struct hd_geometry __user *argp)
+{
+	struct gendisk *disk = bdev->bd_disk;
+	struct hd_geometry geo;
+	int ret;
 
-		return blk_ioctl_discard(bdev, range[0], range[1],
-					 cmd == BLKSECDISCARD);
-	}
-	case BLKZEROOUT: {
-		uint64_t range[2];
+	if (!argp)
+		return -EINVAL;
+	if (!disk->fops->getgeo)
+		return -ENOTTY;
+
+	/*
+	 * We need to set the startsect first, the driver may
+	 * want to override it.
+	 */
+	memset(&geo, 0, sizeof(geo));
+	geo.start = get_start_sect(bdev);
+	ret = disk->fops->getgeo(bdev, &geo);
+	if (ret)
+		return ret;
+	if (copy_to_user(argp, &geo, sizeof(geo)))
+		return -EFAULT;
+	return 0;
+}
 
-		if (!(mode & FMODE_WRITE))
-			return -EBADF;
+/* set the logical block size */
+static int blkdev_bszset(struct block_device *bdev, fmode_t mode,
+		int __user *argp)
+{
+	int ret, n;
 
-		if (copy_from_user(range, (void __user *)arg, sizeof(range)))
-			return -EFAULT;
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+	if (!argp)
+		return -EINVAL;
+	if (get_user(n, argp))
+		return -EFAULT;
 
-		return blk_ioctl_zeroout(bdev, range[0], range[1]);
+	if (!(mode & FMODE_EXCL)) {
+		bdgrab(bdev);
+		if (blkdev_get(bdev, mode | FMODE_EXCL, &bdev) < 0)
+			return -EBUSY;
 	}
 
-	case HDIO_GETGEO: {
-		struct hd_geometry geo;
+	ret = set_blocksize(bdev, n);
+	if (!(mode & FMODE_EXCL))
+		blkdev_put(bdev, mode | FMODE_EXCL);
+	return ret;
+}
 
-		if (!arg)
-			return -EINVAL;
-		if (!disk->fops->getgeo)
-			return -ENOTTY;
-
-		/*
-		 * We need to set the startsect first, the driver may
-		 * want to override it.
-		 */
-		memset(&geo, 0, sizeof(geo));
-		geo.start = get_start_sect(bdev);
-		ret = disk->fops->getgeo(bdev, &geo);
-		if (ret)
-			return ret;
-		if (copy_to_user((struct hd_geometry __user *)arg, &geo,
-					sizeof(geo)))
-			return -EFAULT;
-		return 0;
-	}
+/*
+ * always keep this in sync with compat_blkdev_ioctl()
+ */
+int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
+			unsigned long arg)
+{
+	struct backing_dev_info *bdi;
+	void __user *argp = (void __user *)arg;
+	loff_t size;
+	unsigned int max_sectors;
+
+	switch (cmd) {
+	case BLKFLSBUF:
+		return blkdev_flushbuf(bdev, mode, cmd, arg);
+	case BLKROSET:
+		return blkdev_roset(bdev, mode, cmd, arg);
+	case BLKDISCARD:
+		return blk_ioctl_discard(bdev, mode, arg, 0);
+	case BLKSECDISCARD:
+		return blk_ioctl_discard(bdev, mode, arg,
+				BLKDEV_DISCARD_SECURE);
+	case BLKZEROOUT:
+		return blk_ioctl_zeroout(bdev, mode, arg);
+	case HDIO_GETGEO:
+		return blkdev_getgeo(bdev, argp);
 	case BLKRAGET:
 	case BLKFRAGET:
 		if (!arg)
@@ -414,28 +460,11 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
 		bdi->ra_pages = (arg * 512) / PAGE_CACHE_SIZE;
 		return 0;
 	case BLKBSZSET:
-		/* set the logical block size */
-		if (!capable(CAP_SYS_ADMIN))
-			return -EACCES;
-		if (!arg)
-			return -EINVAL;
-		if (get_user(n, (int __user *) arg))
-			return -EFAULT;
-		if (!(mode & FMODE_EXCL)) {
-			bdgrab(bdev);
-			if (blkdev_get(bdev, mode | FMODE_EXCL, &bdev) < 0)
-				return -EBUSY;
-		}
-		ret = set_blocksize(bdev, n);
-		if (!(mode & FMODE_EXCL))
-			blkdev_put(bdev, mode | FMODE_EXCL);
-		return ret;
+		return blkdev_bszset(bdev, mode, argp);
 	case BLKPG:
-		ret = blkpg_ioctl(bdev, (struct blkpg_ioctl_arg __user *) arg);
-		break;
+		return blkpg_ioctl(bdev, argp);
 	case BLKRRPART:
-		ret = blkdev_reread_part(bdev);
-		break;
+		return blkdev_reread_part(bdev);
 	case BLKGETSIZE:
 		size = i_size_read(bdev->bd_inode);
 		if ((size >> 9) > ~0UL)
@@ -447,11 +476,9 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
 	case BLKTRACESTOP:
 	case BLKTRACESETUP:
 	case BLKTRACETEARDOWN:
-		ret = blk_trace_ioctl(bdev, cmd, (char __user *) arg);
-		break;
+		return blk_trace_ioctl(bdev, cmd, argp);
 	default:
-		ret = __blkdev_driver_ioctl(bdev, mode, cmd, arg);
+		return __blkdev_driver_ioctl(bdev, mode, cmd, arg);
 	}
-	return ret;
 }
 EXPORT_SYMBOL_GPL(blkdev_ioctl);
-- 
1.9.1

Re: [PATCH 1/6] block: cleanup blkdev_ioctl

[Martin K. Petersen]

>>>>> "Christoph" == Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org> writes:

Christoph> Split out helpers for all non-trivial ioctls to make this
Christoph> function simpler, and also start passing around a pointer
Christoph> version of the argument, as that's what most ioctl handlers
Christoph> actually need.

Looks good.

Reviewed-by: Martin K. Petersen <martin.petersen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 2/6] block: add a API for persistent reservations

[Christoph Hellwig]

This commits adds a driver API and ioctls for controling persistent
reservations genericly at the block layer.  Persistent reservations
are supported by SCSI and NVMe and allow controlling who gets access
to a device in a shared storage setup.

Note that we add a pr_ops structure to struct block_device_operation
instead of adding the members directly to avoid bloating all instances
of devices that will never support persistent reservations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 Documentation/block/pr.txt | 107 +++++++++++++++++++++++++++++++++++++++++++++
 block/ioctl.c              |  85 +++++++++++++++++++++++++++++++++++
 include/linux/blkdev.h     |   2 +
 include/linux/pr.h         |  18 ++++++++
 include/uapi/linux/pr.h    |  45 +++++++++++++++++++
 5 files changed, 257 insertions(+)
 create mode 100644 Documentation/block/pr.txt
 create mode 100644 include/linux/pr.h
 create mode 100644 include/uapi/linux/pr.h

diff --git a/Documentation/block/pr.txt b/Documentation/block/pr.txt
new file mode 100644
index 0000000..1ced450
--- /dev/null
+++ b/Documentation/block/pr.txt
@@ -0,0 +1,107 @@
+
+Block layer support for Persistent reservations
+===============================================
+
+The Linux kernel supports a user space interface for simplified
+Persistent Reservations which map to block devices that support
+these (like SCSI). Persistent Reservations allow restricting
+access to block devices to specific initiators in a shared storage
+setup.
+
+This document gives a general overview of the support ioctl commands,
+but for a more detailed reference please refer the the SCSI Primary
+Command standard, specifically the section on Reservations and the
+"PERSISTENT RESERVE IN" and "PERSISTENT RESERVE OUT" commands.
+
+All implementations are expected to ensure the reservations survive
+a power loss and cover all connections in a multi path environment.
+These behavior are optional in SPC but will be automatically applied
+by Linux.
+
+The following types of reservations are supported:
+
+ - PR_WRITE_EXCLUSIVE
+
+	Only the initiator that owns the reservation can write to the
+	device.  Any initiator can read from the device.
+
+ - PR_EXCLUSIVE_ACCESS
+
+	Only the initiator that owns the reservation can access the
+	device.
+
+ - PR_WRITE_EXCLUSIVE_REG_ONLY
+
+	Only initiators with a registered key can write to the device,
+	Any initiator can read from the device.
+
+ - PR_EXCLUSIVE_ACCESS_REG_ONLY
+
+	Only initiators with a registered key can access the device.
+
+ - PR_WRITE_EXCLUSIVE_ALL_REGS
+
+	Only initiators with a registered key can write to the device,
+	Any initiator can read from the device.
+	All initiators with a registered key are considered reservation
+	holders.
+	Please reference the SPC spec on the meaning of a reservation
+	holder if you want to use this type. 
+
+ - PR_EXCLUSIVE_ACCESS_ALL_REGS
+
+	Only initiators with a registered key can access the device.
+	All initiators with a registered key are considered reservation
+	holders.
+	Please reference the SPC spec on the meaning of a reservation
+	holder if you want to use this type. 
+
+
+1. IOC_PR_REGISTER
+
+This ioctl command registers a new reservation if the new_key argument
+is non-null.  If no existing reservation exists old_key must be zero,
+if an existing reservation should be replaced old_key must contain
+the old reservation key.
+
+If the new_key argument is 0 it unregisters the existing reservation passed
+in old_key.
+
+
+2. IOC_PR_REGISTER_IGNORE
+
+This ioctl command registers a new reservations with the key passed in
+new_key, ignoring and replacing any existing previous reservation.  The
+old_key argument is ignored.
+
+
+3. IOC_PR_RESERVE
+
+This ioctl command reserves the device and thus restricts access for other
+devices based on the type argument.  The key argument must be the existing
+reservation key for the device as acquired by the IOC_PR_REGISTER,
+IOC_PR_REGISTER_IGNORE, IOC_PR_PREEMPT or IOC_PR_PREEMPT_ABORT commands.
+
+
+4. IOC_PR_RELEASE
+
+This ioctl command releases the reservation specified by key and flags
+and thus removes any access restriction implied by it.
+
+
+5. IOC_PR_PREEMPT
+
+This ioctl command releases the existing reservation referred to by
+old_key and replaces it with a a new reservation of type type for the
+reservation key new_key.
+
+
+6. IOC_PR_PREEMPT_ABORT
+
+This ioctl command work like IOC_PR_PREEMPT except that it also aborts
+any outstanding command sent over a connection identified by old_key.
+
+7. IOC_PR_CLEAR
+
+This ioctl command unregisters both key and any other reservation key
+registered with the device and drops any existing reservation.
diff --git a/block/ioctl.c b/block/ioctl.c
index df62b47..34d8c77 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -7,6 +7,7 @@
 #include <linux/backing-dev.h>
 #include <linux/fs.h>
 #include <linux/blktrace_api.h>
+#include <linux/pr.h>
 #include <asm/uaccess.h>
 
 static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user *arg)
@@ -295,6 +296,76 @@ int __blkdev_driver_ioctl(struct block_device *bdev, fmode_t mode,
  */
 EXPORT_SYMBOL_GPL(__blkdev_driver_ioctl);
 
+static int blkdev_pr_register(struct block_device *bdev,
+		struct pr_registration __user *arg, bool ignore)
+{
+	const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
+	struct pr_registration reg;
+
+	if (!ops || !ops->pr_register)
+		return -EOPNOTSUPP;
+	if (copy_from_user(&reg, arg, sizeof(reg)))
+		return -EFAULT;
+
+	return ops->pr_register(bdev, reg.old_key, reg.new_key, ignore);
+}
+
+static int blkdev_pr_reserve(struct block_device *bdev,
+		struct pr_reservation __user *arg)
+{
+	const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
+	struct pr_reservation rsv;
+
+	if (!ops || !ops->pr_reserve)
+		return -EOPNOTSUPP;
+	if (copy_from_user(&rsv, arg, sizeof(rsv)))
+		return -EFAULT;
+
+	return ops->pr_reserve(bdev, rsv.key, rsv.type);
+}
+
+static int blkdev_pr_release(struct block_device *bdev,
+		struct pr_reservation __user *arg)
+{
+	const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
+	struct pr_reservation rsv;
+
+	if (!ops || !ops->pr_release)
+		return -EOPNOTSUPP;
+	if (copy_from_user(&rsv, arg, sizeof(rsv)))
+		return -EFAULT;
+
+	return ops->pr_release(bdev, rsv.key, rsv.type);
+}
+
+static int blkdev_pr_preempt(struct block_device *bdev,
+		struct pr_preempt __user *arg, bool abort)
+{
+	const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
+	struct pr_preempt p;
+
+	if (!ops || !ops->pr_preempt)
+		return -EOPNOTSUPP;
+	if (copy_from_user(&p, arg, sizeof(p)))
+		return -EFAULT;
+
+	return ops->pr_preempt(bdev, p.old_key, p.new_key, p.type, abort);
+}
+
+static int blkdev_pr_clear(struct block_device *bdev,
+		struct pr_clear __user *arg)
+{
+	const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
+	struct pr_clear c;
+
+	if (!ops || !ops->pr_clear)
+		return -EOPNOTSUPP;
+	if (copy_from_user(&c, arg, sizeof(c)))
+		return -EFAULT;
+
+	return ops->pr_clear(bdev, c.key);
+}
+
 /*
  * Is it an unrecognized ioctl? The correct returns are either
  * ENOTTY (final) or ENOIOCTLCMD ("I don't know this one, try a
@@ -477,6 +548,20 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
 	case BLKTRACESETUP:
 	case BLKTRACETEARDOWN:
 		return blk_trace_ioctl(bdev, cmd, argp);
+	case IOC_PR_REGISTER:
+		return blkdev_pr_register(bdev, argp, false);
+	case IOC_PR_REGISTER_IGNORE:
+		return blkdev_pr_register(bdev, argp, true);
+	case IOC_PR_RESERVE:
+		return blkdev_pr_reserve(bdev, argp);
+	case IOC_PR_RELEASE:
+		return blkdev_pr_release(bdev, argp);
+	case IOC_PR_PREEMPT:
+		return blkdev_pr_preempt(bdev, argp, false);
+	case IOC_PR_PREEMPT_ABORT:
+		return blkdev_pr_preempt(bdev, argp, true);
+	case IOC_PR_CLEAR:
+		return blkdev_pr_clear(bdev, argp);
 	default:
 		return __blkdev_driver_ioctl(bdev, mode, cmd, arg);
 	}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 243f29e..a07eec93 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -35,6 +35,7 @@ struct sg_io_hdr;
 struct bsg_job;
 struct blkcg_gq;
 struct blk_flush_queue;
+struct pr_ops;
 
 #define BLKDEV_MIN_RQ	4
 #define BLKDEV_MAX_RQ	128	/* Default maximum */
@@ -1568,6 +1569,7 @@ struct block_device_operations {
 	/* this callback is with swap_lock and sometimes page table lock held */
 	void (*swap_slot_free_notify) (struct block_device *, unsigned long);
 	struct module *owner;
+	const struct pr_ops *pr_ops;
 };
 
 extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,
diff --git a/include/linux/pr.h b/include/linux/pr.h
new file mode 100644
index 0000000..a6f0496
--- /dev/null
+++ b/include/linux/pr.h
@@ -0,0 +1,18 @@
+#ifndef LINUX_PR_H
+#define LINUX_PR_H
+
+#include <uapi/linux/pr.h>
+
+struct pr_ops {
+	int (*pr_register)(struct block_device *bdev, u64 old_key, u64 new_key,
+			bool ignore);
+	int (*pr_reserve)(struct block_device *bdev, u64 key,
+			enum pr_type type);
+	int (*pr_release)(struct block_device *bdev, u64 key,
+			enum pr_type type);
+	int (*pr_preempt)(struct block_device *bdev, u64 old_key, u64 new_key,
+			enum pr_type type, bool abort);
+	int (*pr_clear)(struct block_device *bdev, u64 key);
+};
+
+#endif /* LINUX_PR_H */
diff --git a/include/uapi/linux/pr.h b/include/uapi/linux/pr.h
new file mode 100644
index 0000000..6014d14
--- /dev/null
+++ b/include/uapi/linux/pr.h
@@ -0,0 +1,45 @@
+#ifndef _UAPI_PR_H
+#define _UAPI_PR_H
+
+enum pr_type {
+	PR_WRITE_EXCLUSIVE		= 1,
+	PR_EXCLUSIVE_ACCESS		= 2,
+	PR_WRITE_EXCLUSIVE_REG_ONLY	= 3,
+	PR_EXCLUSIVE_ACCESS_REG_ONLY	= 4,
+	PR_WRITE_EXCLUSIVE_ALL_REGS	= 5,
+	PR_EXCLUSIVE_ACCESS_ALL_REGS	= 6,
+};
+
+struct pr_reservation {
+	__u64	key;
+	__u32	type;
+	__u32	__pad;
+};
+
+struct pr_registration {
+	__u64	old_key;
+	__u64	new_key;
+};
+
+struct pr_preempt {
+	__u64	old_key;
+	__u64	new_key;
+	__u32	type;
+	__u32	__pad;
+};
+
+struct pr_clear {
+	__u64	key;
+};
+
+#define IOC_PR_REGISTER		_IOW('p', 200, struct pr_registration)
+#define IOC_PR_REGISTER_IGNORE	_IOW('p', 201, struct pr_registration)
+
+#define IOC_PR_RESERVE		_IOW('p', 202, struct pr_reservation)
+#define IOC_PR_RELEASE		_IOW('p', 203, struct pr_reservation)
+
+#define IOC_PR_PREEMPT		_IOW('p', 204, struct pr_preempt)
+#define IOC_PR_PREEMPT_ABORT	_IOW('p', 205, struct pr_preempt)
+#define IOC_PR_CLEAR		_IOW('p', 206, struct pr_clear)
+
+#endif /* _UAPI_PR_H */
-- 
1.9.1

Re: [PATCH 2/6] block: add a API for persistent reservations

[Martin K. Petersen]

>>>>> "Christoph" == Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org> writes:

Happy to see a generic interface for this. I wish PR semantics were
simpler but the code looks good to me.

Reviewed-by: Martin K. Petersen <martin.petersen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 3/6] sd: implement the persisten reservation API

[Christoph Hellwig]

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/scsi/sd.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 160e44e..e9bc210 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -51,6 +51,7 @@
 #include <linux/async.h>
 #include <linux/slab.h>
 #include <linux/pm_runtime.h>
+#include <linux/pr.h>
 #include <asm/uaccess.h>
 #include <asm/unaligned.h>
 
@@ -1535,6 +1536,94 @@ static int sd_compat_ioctl(struct block_device *bdev, fmode_t mode,
 }
 #endif
 
+static char sd_pr_type(enum pr_type type)
+{
+	switch (type) {
+	case PR_WRITE_EXCLUSIVE:
+		return 0x01;
+	case PR_EXCLUSIVE_ACCESS:
+		return 0x03;
+	case PR_WRITE_EXCLUSIVE_REG_ONLY:
+		return 0x05;
+	case PR_EXCLUSIVE_ACCESS_REG_ONLY:
+		return 0x06;
+	case PR_WRITE_EXCLUSIVE_ALL_REGS:
+		return 0x07;
+	case PR_EXCLUSIVE_ACCESS_ALL_REGS:
+		return 0x08;
+	default:
+		return 0;
+	}
+};
+
+static int sd_pr_command(struct block_device *bdev, u8 sa,
+		u64 key, u64 sa_key, u8 type, u8 flags)
+{
+	struct scsi_device *sdev = scsi_disk(bdev->bd_disk)->device;
+	struct scsi_sense_hdr sshdr;
+	int result;
+	u8 cmd[16] = { 0, };
+	u8 data[24] = { 0, };
+
+	cmd[0] = PERSISTENT_RESERVE_OUT;
+	cmd[1] = sa;
+	cmd[2] = type;
+	put_unaligned_be32(sizeof(data), &cmd[5]);
+
+	put_unaligned_be64(key, &data[0]);
+	put_unaligned_be64(sa_key, &data[8]);
+	data[20] = flags;
+
+	result = scsi_execute_req(sdev, cmd, DMA_TO_DEVICE, &data, sizeof(data),
+			&sshdr, SD_TIMEOUT, SD_MAX_RETRIES, NULL);
+
+	if ((driver_byte(result) & DRIVER_SENSE) &&
+	    (scsi_sense_valid(&sshdr))) {
+		sdev_printk(KERN_INFO, sdev, "PR commad failed: %d\n", result);
+		scsi_print_sense_hdr(sdev, NULL, &sshdr);
+	}
+
+	return result;
+}
+
+static int sd_pr_register(struct block_device *bdev, u64 old_key, u64 new_key,
+		bool ignore)
+{
+	return sd_pr_command(bdev, ignore ? 0x06 : 0x00, old_key, new_key, 0,
+			     (1 << 0) /* APTPL */ |
+			     (1 << 2) /* ALL_TG_PT */);
+}
+
+static int sd_pr_reserve(struct block_device *bdev, u64 key, enum pr_type type)
+{
+	return sd_pr_command(bdev, 0x01, key, 0, sd_pr_type(type), 0);
+}
+
+static int sd_pr_release(struct block_device *bdev, u64 key, enum pr_type type)
+{
+	return sd_pr_command(bdev, 0x02, key, 0, sd_pr_type(type), 0);
+}
+
+static int sd_pr_preempt(struct block_device *bdev, u64 old_key, u64 new_key,
+		enum pr_type type, bool abort)
+{
+	return sd_pr_command(bdev, abort ? 0x05 : 0x04, old_key, new_key,
+			     sd_pr_type(type), 0);
+}
+
+static int sd_pr_clear(struct block_device *bdev, u64 key)
+{
+	return sd_pr_command(bdev, 0x03, key, 0, 0, 0);
+}
+
+static const struct pr_ops sd_pr_ops = {
+	.pr_register	= sd_pr_register,
+	.pr_reserve	= sd_pr_reserve,
+	.pr_release	= sd_pr_release,
+	.pr_preempt	= sd_pr_preempt,
+	.pr_clear	= sd_pr_clear,
+};
+
 static const struct block_device_operations sd_fops = {
 	.owner			= THIS_MODULE,
 	.open			= sd_open,
@@ -1547,6 +1636,7 @@ static const struct block_device_operations sd_fops = {
 	.check_events		= sd_check_events,
 	.revalidate_disk	= sd_revalidate_disk,
 	.unlock_native_capacity	= sd_unlock_native_capacity,
+	.pr_ops			= &sd_pr_ops,
 };
 
 /**
-- 
1.9.1

Re: [PATCH 3/6] sd: implement the persisten reservation API

[Martin K. Petersen]

>>>>> "Christoph" == Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org> writes:

Slightly more verbose patch description would be nice. Code looks OK.

Reviewed-by: Martin K. Petersen <martin.petersen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 4/6] dm: refactor ioctl handling

[Christoph Hellwig]

This moves the call to blkdev_ioctl and the argument checking to core code,
and only leaves a callout to find the block device to operate on it the
targets.  This will simplifies the code and will allow us to pass through
ioctl-like command using other methods in the next patch.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/dm-flakey.c        | 14 +++++++-------
 drivers/md/dm-linear.c        | 12 ++++++------
 drivers/md/dm-log-writes.c    | 11 +++++------
 drivers/md/dm-mpath.c         | 30 +++++++++++-------------------
 drivers/md/dm-switch.c        | 19 ++++++++-----------
 drivers/md/dm-verity.c        | 13 ++++++-------
 drivers/md/dm.c               | 12 +++++++++++-
 include/linux/device-mapper.h |  4 ++--
 8 files changed, 56 insertions(+), 59 deletions(-)

diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
index b257e46..ec4ebc8 100644
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -371,20 +371,20 @@ static void flakey_status(struct dm_target *ti, status_type_t type,
 	}
 }
 
-static int flakey_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg)
+static int flakey_ioctl(struct dm_target *ti, struct block_device **bdev,
+		fmode_t *mode)
 {
 	struct flakey_c *fc = ti->private;
-	struct dm_dev *dev = fc->dev;
-	int r = 0;
+
+	*bdev = fc->dev->bdev;
 
 	/*
 	 * Only pass ioctls through if the device sizes match exactly.
 	 */
 	if (fc->start ||
-	    ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
-		r = scsi_verify_blk_ioctl(NULL, cmd);
-
-	return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
+	    ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
+		return 1;
+	return 0;
 }
 
 static int flakey_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 53e848c..d897707 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -113,21 +113,21 @@ static void linear_status(struct dm_target *ti, status_type_t type,
 	}
 }
 
-static int linear_ioctl(struct dm_target *ti, unsigned int cmd,
-			unsigned long arg)
+static int linear_ioctl(struct dm_target *ti, struct block_device **bdev,
+		fmode_t *mode)
 {
 	struct linear_c *lc = (struct linear_c *) ti->private;
 	struct dm_dev *dev = lc->dev;
-	int r = 0;
+
+	*bdev = dev->bdev;
 
 	/*
 	 * Only pass ioctls through if the device sizes match exactly.
 	 */
 	if (lc->start ||
 	    ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
-		r = scsi_verify_blk_ioctl(NULL, cmd);
-
-	return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
+		return 1;
+	return 0;
 }
 
 static int linear_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
index ad1b049..811fc42 100644
--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c
@@ -712,20 +712,19 @@ static void log_writes_status(struct dm_target *ti, status_type_t type,
 	}
 }
 
-static int log_writes_ioctl(struct dm_target *ti, unsigned int cmd,
-			    unsigned long arg)
+static int log_writes_ioctl(struct dm_target *ti, struct block_device **bdev,
+		fmode_t *mode)
 {
 	struct log_writes_c *lc = ti->private;
 	struct dm_dev *dev = lc->dev;
-	int r = 0;
 
+	*bdev = dev->bdev;
 	/*
 	 * Only pass ioctls through if the device sizes match exactly.
 	 */
 	if (ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
-		r = scsi_verify_blk_ioctl(NULL, cmd);
-
-	return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
+		return 1;
+	return 0;
 }
 
 static int log_writes_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index eff7bdd..8670597 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -1548,18 +1548,14 @@ out:
 	return r;
 }
 
-static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
-			   unsigned long arg)
+static int multipath_ioctl(struct dm_target *ti,
+		struct block_device **bdev, fmode_t *mode)
 {
 	struct multipath *m = ti->private;
 	struct pgpath *pgpath;
-	struct block_device *bdev;
-	fmode_t mode;
 	unsigned long flags;
 	int r;
 
-	bdev = NULL;
-	mode = 0;
 	r = 0;
 
 	spin_lock_irqsave(&m->lock, flags);
@@ -1570,26 +1566,17 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
 	pgpath = m->current_pgpath;
 
 	if (pgpath) {
-		bdev = pgpath->path.dev->bdev;
-		mode = pgpath->path.dev->mode;
+		*bdev = pgpath->path.dev->bdev;
+		*mode = pgpath->path.dev->mode;
 	}
 
 	if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path))
 		r = -ENOTCONN;
-	else if (!bdev)
+	else if (!*bdev)
 		r = -EIO;
 
 	spin_unlock_irqrestore(&m->lock, flags);
 
-	/*
-	 * Only pass ioctls through if the device sizes match exactly.
-	 */
-	if (!bdev || ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT) {
-		int err = scsi_verify_blk_ioctl(NULL, cmd);
-		if (err)
-			r = err;
-	}
-
 	if (r == -ENOTCONN && !fatal_signal_pending(current)) {
 		spin_lock_irqsave(&m->lock, flags);
 		if (!m->current_pg) {
@@ -1602,7 +1589,12 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
 		dm_table_run_md_queue_async(m->ti->table);
 	}
 
-	return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
+	/*
+	 * Only pass ioctls through if the device sizes match exactly.
+	 */
+	if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
+		return 1;
+	return r;
 }
 
 static int multipath_iterate_devices(struct dm_target *ti,
diff --git a/drivers/md/dm-switch.c b/drivers/md/dm-switch.c
index 50fca46..37d27e9 100644
--- a/drivers/md/dm-switch.c
+++ b/drivers/md/dm-switch.c
@@ -511,27 +511,24 @@ static void switch_status(struct dm_target *ti, status_type_t type,
  *
  * Passthrough all ioctls to the path for sector 0
  */
-static int switch_ioctl(struct dm_target *ti, unsigned cmd,
-			unsigned long arg)
+static int switch_ioctl(struct dm_target *ti,
+		struct block_device **bdev, fmode_t *mode)
 {
 	struct switch_ctx *sctx = ti->private;
-	struct block_device *bdev;
-	fmode_t mode;
 	unsigned path_nr;
-	int r = 0;
 
 	path_nr = switch_get_path_nr(sctx, 0);
 
-	bdev = sctx->path_list[path_nr].dmdev->bdev;
-	mode = sctx->path_list[path_nr].dmdev->mode;
+	*bdev = sctx->path_list[path_nr].dmdev->bdev;
+	*mode = sctx->path_list[path_nr].dmdev->mode;
 
 	/*
 	 * Only pass ioctls through if the device sizes match exactly.
 	 */
-	if (ti->len + sctx->path_list[path_nr].start != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
-		r = scsi_verify_blk_ioctl(NULL, cmd);
-
-	return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
+	if (ti->len + sctx->path_list[path_nr].start !=
+	    i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
+		return 1;
+	return 0;
 }
 
 static int switch_iterate_devices(struct dm_target *ti,
diff --git a/drivers/md/dm-verity.c b/drivers/md/dm-verity.c
index bb9c6a0..bd20c41 100644
--- a/drivers/md/dm-verity.c
+++ b/drivers/md/dm-verity.c
@@ -634,18 +634,17 @@ static void verity_status(struct dm_target *ti, status_type_t type,
 	}
 }
 
-static int verity_ioctl(struct dm_target *ti, unsigned cmd,
-			unsigned long arg)
+static int verity_ioctl(struct dm_target *ti, struct block_device **bdev,
+		fmode_t *mode)
 {
 	struct dm_verity *v = ti->private;
-	int r = 0;
+
+	*bdev = v->data_dev->bdev;
 
 	if (v->data_start ||
 	    ti->len != i_size_read(v->data_dev->bdev->bd_inode) >> SECTOR_SHIFT)
-		r = scsi_verify_blk_ioctl(NULL, cmd);
-
-	return r ? : __blkdev_driver_ioctl(v->data_dev->bdev, v->data_dev->mode,
-				     cmd, arg);
+		return 1;
+	return 0;
 }
 
 static int verity_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index f331d88..c68eb91 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -584,7 +584,17 @@ retry:
 		goto out;
 	}
 
-	r = tgt->type->ioctl(tgt, cmd, arg);
+	r = tgt->type->ioctl(tgt, &bdev, &mode);
+	if (r < 0)
+		goto out;
+
+	if (r > 0) {
+		r = scsi_verify_blk_ioctl(NULL, cmd);
+		if (r)
+			goto out;
+	}
+
+	r =  __blkdev_driver_ioctl(bdev, mode, cmd, arg);
 
 out:
 	dm_put_live_table(md, srcu_idx);
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 51cc1de..9b73138 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -79,8 +79,8 @@ typedef void (*dm_status_fn) (struct dm_target *ti, status_type_t status_type,
 
 typedef int (*dm_message_fn) (struct dm_target *ti, unsigned argc, char **argv);
 
-typedef int (*dm_ioctl_fn) (struct dm_target *ti, unsigned int cmd,
-			    unsigned long arg);
+typedef int (*dm_ioctl_fn) (struct dm_target *ti,
+			    struct block_device **bdev, fmode_t *mode);
 
 typedef int (*dm_merge_fn) (struct dm_target *ti, struct bvec_merge_data *bvm,
 			    struct bio_vec *biovec, int max_size);
-- 
1.9.1

Re: [PATCH 4/6] dm: refactor ioctl handling

[Mike Snitzer]

On Tue, Aug 04 2015 at  3:11am -0400,
Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org> wrote:

> This moves the call to blkdev_ioctl and the argument checking to core code,
> and only leaves a callout to find the block device to operate on it the
> targets.  This will simplifies the code and will allow us to pass through
> ioctl-like command using other methods in the next patch.
> 
> Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
...
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index f331d88..c68eb91 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -584,7 +584,17 @@ retry:
>  		goto out;
>  	}
>  
> -	r = tgt->type->ioctl(tgt, cmd, arg);
> +	r = tgt->type->ioctl(tgt, &bdev, &mode);
> +	if (r < 0)
> +		goto out;
> +
> +	if (r > 0) {
> +		r = scsi_verify_blk_ioctl(NULL, cmd);
> +		if (r)
> +			goto out;
> +	}
> +
> +	r =  __blkdev_driver_ioctl(bdev, mode, cmd, arg);
>  
>  out:
>  	dm_put_live_table(md, srcu_idx);
> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index 51cc1de..9b73138 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -79,8 +79,8 @@ typedef void (*dm_status_fn) (struct dm_target *ti, status_type_t status_type,
>  
>  typedef int (*dm_message_fn) (struct dm_target *ti, unsigned argc, char **argv);
>  
> -typedef int (*dm_ioctl_fn) (struct dm_target *ti, unsigned int cmd,
> -			    unsigned long arg);
> +typedef int (*dm_ioctl_fn) (struct dm_target *ti,
> +			    struct block_device **bdev, fmode_t *mode);
>  
>  typedef int (*dm_merge_fn) (struct dm_target *ti, struct bvec_merge_data *bvm,
>  			    struct bio_vec *biovec, int max_size);

This should be renamed to dm_prepare_ioctl_fn and the targets' hook
would be .prepare_ioctl

Open to other names but if the targets no longer issue the ioctl there
is little point to call it .ioctl

Re: [PATCH 4/6] dm: refactor ioctl handling

[Christoph Hellwig]

On Tue, Aug 04, 2015 at 01:56:16PM -0400, Mike Snitzer wrote:
> This should be renamed to dm_prepare_ioctl_fn and the targets' hook
> would be .prepare_ioctl
> 
> Open to other names but if the targets no longer issue the ioctl there
> is little point to call it .ioctl

Sure.  I had ioctl_allowed first but that sounded so ugly that I
undid the renaming..

[PATCH 5/6] dm: split out a helper to find the ioctl target

[Christoph Hellwig]

We want to reuse this code for the persistent reservation handling,
so move it into a helper.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/dm.c | 50 ++++++++++++++++++++++++++++++++------------------
 1 file changed, 32 insertions(+), 18 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index c68eb91..8dfc760 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -556,18 +556,16 @@ static int dm_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
 	return dm_get_geometry(md, geo);
 }
 
-static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
-			unsigned int cmd, unsigned long arg)
+static int dm_get_ioctl_table(struct mapped_device *md,
+		struct dm_target **tgt, struct block_device **bdev,
+		fmode_t *mode, int *srcu_idx)
 {
-	struct mapped_device *md = bdev->bd_disk->private_data;
-	int srcu_idx;
 	struct dm_table *map;
-	struct dm_target *tgt;
-	int r = -ENOTTY;
+	int r;
 
 retry:
-	map = dm_get_live_table(md, &srcu_idx);
-
+	r = -ENOTTY;
+	map = dm_get_live_table(md, srcu_idx);
 	if (!map || !dm_table_get_size(map))
 		goto out;
 
@@ -575,8 +573,9 @@ retry:
 	if (dm_table_get_num_targets(map) != 1)
 		goto out;
 
-	tgt = dm_table_get_target(map, 0);
-	if (!tgt->type->ioctl)
+	*tgt = dm_table_get_target(map, 0);
+
+	if (!(*tgt)->type->ioctl)
 		goto out;
 
 	if (dm_suspended_md(md)) {
@@ -584,10 +583,32 @@ retry:
 		goto out;
 	}
 
-	r = tgt->type->ioctl(tgt, &bdev, &mode);
+	r = (*tgt)->type->ioctl(*tgt, bdev, mode);
 	if (r < 0)
 		goto out;
 
+	return r;
+
+out:
+	dm_put_live_table(md, *srcu_idx);
+	if (r == -ENOTCONN) {
+		msleep(10);
+		goto retry;
+	}
+	return r;
+}
+
+static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
+			unsigned int cmd, unsigned long arg)
+{
+	struct mapped_device *md = bdev->bd_disk->private_data;
+	struct dm_target *tgt;
+	int srcu_idx, r;
+
+	r = dm_get_ioctl_table(md, &tgt, &bdev, &mode, &srcu_idx);
+	if (r < 0)
+		return r;
+
 	if (r > 0) {
 		r = scsi_verify_blk_ioctl(NULL, cmd);
 		if (r)
@@ -595,15 +616,8 @@ retry:
 	}
 
 	r =  __blkdev_driver_ioctl(bdev, mode, cmd, arg);
-
 out:
 	dm_put_live_table(md, srcu_idx);
-
-	if (r == -ENOTCONN) {
-		msleep(10);
-		goto retry;
-	}
-
 	return r;
 }
 
-- 
1.9.1

Re: [PATCH 5/6] dm: split out a helper to find the ioctl target

[Mike Snitzer]

On Tue, Aug 04 2015 at  3:11am -0400,
Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org> wrote:

> We want to reuse this code for the persistent reservation handling,
> so move it into a helper.
> 
> Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
> ---
>  drivers/md/dm.c | 50 ++++++++++++++++++++++++++++++++------------------
>  1 file changed, 32 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index c68eb91..8dfc760 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -556,18 +556,16 @@ static int dm_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
>  	return dm_get_geometry(md, geo);
>  }
>  
> -static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
> -			unsigned int cmd, unsigned long arg)
> +static int dm_get_ioctl_table(struct mapped_device *md,
> +		struct dm_target **tgt, struct block_device **bdev,
> +		fmode_t *mode, int *srcu_idx)

Would prefer to see something like:

static int dm_get_live_table_for_ioctl(struct mapped_device *md, int *srcu_idx,
	     struct dm_target **tgt, struct block_device **bdev, fmode_t *mode)

Otherwise, looks good.

Re: [PATCH 5/6] dm: split out a helper to find the ioctl target

[Christoph Hellwig]

On Tue, Aug 04, 2015 at 02:05:59PM -0400, Mike Snitzer wrote:
> static int dm_get_live_table_for_ioctl(struct mapped_device *md, int *srcu_idx,
> 	     struct dm_target **tgt, struct block_device **bdev, fmode_t *mode)
> 
> Otherwise, looks good.

I'll update it.

[PATCH 6/6] dm: add support for passing through persistent reservations

[Christoph Hellwig]

This adds support to pass through persistent reservation requests
similar to the existing ioctl handling, and with the same limitations,
e.g. devices may only have a single target attached.

This is mostly intended for multipathing.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/dm.c | 122 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 8dfc760..3388fa6 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -24,6 +24,7 @@
 #include <linux/ktime.h>
 #include <linux/elevator.h> /* for rq_end_sector() */
 #include <linux/blk-mq.h>
+#include <linux/pr.h>
 
 #include <trace/events/block.h>
 
@@ -3670,11 +3671,132 @@ void dm_free_md_mempools(struct dm_md_mempools *pools)
 	kfree(pools);
 }
 
+static int dm_pr_register(struct block_device *bdev, u64 old_key, u64 new_key,
+		bool ignore)
+{
+	struct mapped_device *md = bdev->bd_disk->private_data;
+	const struct pr_ops *ops;
+	struct dm_target *tgt;
+	fmode_t mode;
+	int srcu_idx, r;
+
+	r = dm_get_ioctl_table(md, &tgt, &bdev, &mode, &srcu_idx);
+	if (r < 0)
+		return r;
+
+	ops = bdev->bd_disk->fops->pr_ops;
+	if (ops && ops->pr_register)
+		r = ops->pr_register(bdev, old_key, new_key, ignore);
+	else
+		r = -EOPNOTSUPP;
+
+	dm_put_live_table(md, srcu_idx);
+	return r;
+}
+
+static int dm_pr_reserve(struct block_device *bdev, u64 key, enum pr_type type)
+{
+	struct mapped_device *md = bdev->bd_disk->private_data;
+	const struct pr_ops *ops;
+	struct dm_target *tgt;
+	fmode_t mode;
+	int srcu_idx, r;
+
+	r = dm_get_ioctl_table(md, &tgt, &bdev, &mode, &srcu_idx);
+	if (r < 0)
+		return r;
+
+	ops = bdev->bd_disk->fops->pr_ops;
+	if (ops && ops->pr_reserve)
+		r = ops->pr_reserve(bdev, key, type);
+	else
+		r = -EOPNOTSUPP;
+
+	dm_put_live_table(md, srcu_idx);
+	return r;
+}
+
+static int dm_pr_release(struct block_device *bdev, u64 key, enum pr_type type)
+{
+	struct mapped_device *md = bdev->bd_disk->private_data;
+	const struct pr_ops *ops;
+	struct dm_target *tgt;
+	fmode_t mode;
+	int srcu_idx, r;
+
+	r = dm_get_ioctl_table(md, &tgt, &bdev, &mode, &srcu_idx);
+	if (r < 0)
+		return r;
+
+	ops = bdev->bd_disk->fops->pr_ops;
+	if (ops && ops->pr_release)
+		r = ops->pr_release(bdev, key, type);
+	else
+		r = -EOPNOTSUPP;
+
+	dm_put_live_table(md, srcu_idx);
+	return r;
+}
+
+static int dm_pr_preempt(struct block_device *bdev, u64 old_key, u64 new_key,
+		enum pr_type type, bool abort)
+{
+	struct mapped_device *md = bdev->bd_disk->private_data;
+	const struct pr_ops *ops;
+	struct dm_target *tgt;
+	fmode_t mode;
+	int srcu_idx, r;
+
+	r = dm_get_ioctl_table(md, &tgt, &bdev, &mode, &srcu_idx);
+	if (r < 0)
+		return r;
+
+	ops = bdev->bd_disk->fops->pr_ops;
+	if (ops && ops->pr_preempt)
+		r = ops->pr_preempt(bdev, old_key, new_key, type, abort);
+	else
+		r = -EOPNOTSUPP;
+
+	dm_put_live_table(md, srcu_idx);
+	return r;
+}
+
+static int dm_pr_clear(struct block_device *bdev, u64 key)
+{
+	struct mapped_device *md = bdev->bd_disk->private_data;
+	const struct pr_ops *ops;
+	struct dm_target *tgt;
+	fmode_t mode;
+	int srcu_idx, r;
+
+	r = dm_get_ioctl_table(md, &tgt, &bdev, &mode, &srcu_idx);
+	if (r < 0)
+		return r;
+
+	ops = bdev->bd_disk->fops->pr_ops;
+	if (ops && ops->pr_clear)
+		r = ops->pr_clear(bdev, key);
+	else
+		r = -EOPNOTSUPP;
+
+	dm_put_live_table(md, srcu_idx);
+	return r;
+}
+
+static const struct pr_ops dm_pr_ops = {
+	.pr_register	= dm_pr_register,
+	.pr_reserve	= dm_pr_reserve,
+	.pr_release	= dm_pr_release,
+	.pr_preempt	= dm_pr_preempt,
+	.pr_clear	= dm_pr_clear,
+};
+
 static const struct block_device_operations dm_blk_dops = {
 	.open = dm_blk_open,
 	.release = dm_blk_close,
 	.ioctl = dm_blk_ioctl,
 	.getgeo = dm_blk_getgeo,
+	.pr_ops = &dm_pr_ops,
 	.owner = THIS_MODULE
 };
 
-- 
1.9.1

Re: Persistent Reservation API

[Mike Snitzer]

On Tue, Aug 04 2015 at  3:11am -0400,
Christoph Hellwig <hch@lst.de> wrote:

> This series adds support for a simplified persistent reservation API
> to the block layer.  The intent is that both in-kernel and userspace
> consumers can use the API instead of having to hand craft SCSI or NVMe
> command through the various pass through interfaces.  It also adds
> DM support as getting reservations through dm-multipath is a major
> pain with the current scheme.

The DM changes need to go through linux-dm.git.  Once the block and SCSI
bits land I'll rebase accordingly.  That cross-maintainer logisitics
aside, I'll reply with feedback on the DM patches.

Re: Persistent Reservation API

[Christoph Hellwig]

On Tue, Aug 04, 2015 at 01:53:49PM -0400, Mike Snitzer wrote:
> The DM changes need to go through linux-dm.git.  Once the block and SCSI
> bits land I'll rebase accordingly.  That cross-maintainer logisitics
> aside, I'll reply with feedback on the DM patches.

That sounds fine to me, thanks!

Re: Persistent Reservation API

[Keith Busch]

On Tue, 4 Aug 2015, Christoph Hellwig wrote:
> NVMe support currently isn't included as I don't have a multihost
> NVMe setup to test on, but if I can find a volunteer to test it I'm
> happy to write the code for it.

Looks pretty good so far. I'd be happy to give try it out with NVMe
subsystems.

Re: Persistent Reservation API

[Christoph Hellwig]

On Tue, Aug 04, 2015 at 06:04:04PM +0000, Keith Busch wrote:
> On Tue, 4 Aug 2015, Christoph Hellwig wrote:
>> NVMe support currently isn't included as I don't have a multihost
>> NVMe setup to test on, but if I can find a volunteer to test it I'm
>> happy to write the code for it.
>
> Looks pretty good so far. I'd be happy to give try it out with NVMe
> subsystems.

Thanks, I'll prepare a version once I get a few free minutes.