From bbd3e064362e5057cc4799ba2e4d68c7593e490b Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 15 Oct 2015 14:10:48 +0200 Subject: [PATCH] block: add an API for Persistent Reservations This commits adds a driver API and ioctls for controlling Persistent Reservations s/genericly/generically/ 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_operations instead of adding the members directly to avoid bloating all instances of devices that will never support Persistent Reservations. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- Documentation/block/pr.txt | 119 +++++++++++++++++++++++++++++++++++++ block/ioctl.c | 103 ++++++++++++++++++++++++++++++++ include/linux/blkdev.h | 2 + include/linux/pr.h | 18 ++++++ include/uapi/linux/pr.h | 48 +++++++++++++++ 5 files changed, 290 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 000000000000..d3eb1ca65051 --- /dev/null +++ b/Documentation/block/pr.txt @@ -0,0 +1,119 @@ + +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. +For a more detailed reference please refer the the SCSI Primary +Commands 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 behaviors 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. + + +The following ioctl are supported: +---------------------------------- + +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_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. + + +3. IOC_PR_RELEASE + +This ioctl command releases the reservation specified by key and flags +and thus removes any access restriction implied by it. + + +4. 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 for the +reservation key new_key. + + +5. IOC_PR_PREEMPT_ABORT + +This ioctl command works like IOC_PR_PREEMPT except that it also aborts +any outstanding command sent over a connection identified by old_key. + +6. IOC_PR_CLEAR + +This ioctl command unregisters both key and any other reservation key +registered with the device and drops any existing reservation. + + +Flags +----- + +All the ioctls have a flag field. Currently only one flag is supported: + + - PR_FL_IGNORE_KEY + + Ignore the existing reservation key. This is commonly supported for + IOC_PR_REGISTER, and some implementation may support the flag for + IOC_PR_RESERVE. + +For all unknown flags the kernel will return -EOPNOTSUPP. diff --git a/block/ioctl.c b/block/ioctl.c index df62b47d2379..0918aed2d847 100644 --- a/block/ioctl.c +++ b/block/ioctl.c @@ -7,6 +7,7 @@ #include #include #include +#include #include static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user *arg) @@ -295,6 +296,96 @@ 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) +{ + const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops; + struct pr_registration reg; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + if (!ops || !ops->pr_register) + return -EOPNOTSUPP; + if (copy_from_user(®, arg, sizeof(reg))) + return -EFAULT; + + if (reg.flags & ~PR_FL_IGNORE_KEY) + return -EOPNOTSUPP; + return ops->pr_register(bdev, reg.old_key, reg.new_key, reg.flags); +} + +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 (!capable(CAP_SYS_ADMIN)) + return -EPERM; + if (!ops || !ops->pr_reserve) + return -EOPNOTSUPP; + if (copy_from_user(&rsv, arg, sizeof(rsv))) + return -EFAULT; + + if (rsv.flags & ~PR_FL_IGNORE_KEY) + return -EOPNOTSUPP; + return ops->pr_reserve(bdev, rsv.key, rsv.type, rsv.flags); +} + +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 (!capable(CAP_SYS_ADMIN)) + return -EPERM; + if (!ops || !ops->pr_release) + return -EOPNOTSUPP; + if (copy_from_user(&rsv, arg, sizeof(rsv))) + return -EFAULT; + + if (rsv.flags) + return -EOPNOTSUPP; + 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 (!capable(CAP_SYS_ADMIN)) + return -EPERM; + if (!ops || !ops->pr_preempt) + return -EOPNOTSUPP; + if (copy_from_user(&p, arg, sizeof(p))) + return -EFAULT; + + if (p.flags) + return -EOPNOTSUPP; + 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 (!capable(CAP_SYS_ADMIN)) + return -EPERM; + if (!ops || !ops->pr_clear) + return -EOPNOTSUPP; + if (copy_from_user(&c, arg, sizeof(c))) + return -EFAULT; + + if (c.flags) + return -EOPNOTSUPP; + 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 +568,18 @@ 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); + 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 19c2e947d4d1..fe25da05e823 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 */ @@ -1633,6 +1634,7 @@ 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 000000000000..65c01c10b335 --- /dev/null +++ b/include/linux/pr.h @@ -0,0 +1,18 @@ +#ifndef LINUX_PR_H +#define LINUX_PR_H + +#include + +struct pr_ops { + int (*pr_register)(struct block_device *bdev, u64 old_key, u64 new_key, + u32 flags); + int (*pr_reserve)(struct block_device *bdev, u64 key, + enum pr_type type, u32 flags); + 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 000000000000..57d7c0f916b6 --- /dev/null +++ b/include/uapi/linux/pr.h @@ -0,0 +1,48 @@ +#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 flags; +}; + +struct pr_registration { + __u64 old_key; + __u64 new_key; + __u32 flags; + __u32 __pad; +}; + +struct pr_preempt { + __u64 old_key; + __u64 new_key; + __u32 type; + __u32 flags; +}; + +struct pr_clear { + __u64 key; + __u32 flags; + __u32 __pad; +}; + +#define PR_FL_IGNORE_KEY (1 << 0) /* ignore existing key */ + +#define IOC_PR_REGISTER _IOW('p', 200, struct pr_registration) +#define IOC_PR_RESERVE _IOW('p', 201, struct pr_reservation) +#define IOC_PR_RELEASE _IOW('p', 202, struct pr_reservation) +#define IOC_PR_PREEMPT _IOW('p', 203, struct pr_preempt) +#define IOC_PR_PREEMPT_ABORT _IOW('p', 204, struct pr_preempt) +#define IOC_PR_CLEAR _IOW('p', 205, struct pr_clear) + +#endif /* _UAPI_PR_H */ -- 2.20.1