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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 <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig
Jens Axboe
parent
d8e4bb8103
commit
bbd3e06436
119
Documentation/block/pr.txt
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119
Documentation/block/pr.txt
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@ -0,0 +1,119 @@
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Block layer support for Persistent Reservations
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===============================================
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The Linux kernel supports a user space interface for simplified
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Persistent Reservations which map to block devices that support
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these (like SCSI). Persistent Reservations allow restricting
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access to block devices to specific initiators in a shared storage
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setup.
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This document gives a general overview of the support ioctl commands.
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For a more detailed reference please refer the the SCSI Primary
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Commands standard, specifically the section on Reservations and the
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"PERSISTENT RESERVE IN" and "PERSISTENT RESERVE OUT" commands.
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All implementations are expected to ensure the reservations survive
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a power loss and cover all connections in a multi path environment.
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These behaviors are optional in SPC but will be automatically applied
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by Linux.
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The following types of reservations are supported:
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--------------------------------------------------
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- PR_WRITE_EXCLUSIVE
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Only the initiator that owns the reservation can write to the
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device. Any initiator can read from the device.
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- PR_EXCLUSIVE_ACCESS
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Only the initiator that owns the reservation can access the
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device.
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- PR_WRITE_EXCLUSIVE_REG_ONLY
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Only initiators with a registered key can write to the device,
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Any initiator can read from the device.
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- PR_EXCLUSIVE_ACCESS_REG_ONLY
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Only initiators with a registered key can access the device.
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- PR_WRITE_EXCLUSIVE_ALL_REGS
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Only initiators with a registered key can write to the device,
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Any initiator can read from the device.
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All initiators with a registered key are considered reservation
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holders.
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Please reference the SPC spec on the meaning of a reservation
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holder if you want to use this type.
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- PR_EXCLUSIVE_ACCESS_ALL_REGS
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Only initiators with a registered key can access the device.
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All initiators with a registered key are considered reservation
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holders.
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Please reference the SPC spec on the meaning of a reservation
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holder if you want to use this type.
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The following ioctl are supported:
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----------------------------------
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1. IOC_PR_REGISTER
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This ioctl command registers a new reservation if the new_key argument
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is non-null. If no existing reservation exists old_key must be zero,
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if an existing reservation should be replaced old_key must contain
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the old reservation key.
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If the new_key argument is 0 it unregisters the existing reservation passed
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in old_key.
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2. IOC_PR_RESERVE
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This ioctl command reserves the device and thus restricts access for other
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devices based on the type argument. The key argument must be the existing
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reservation key for the device as acquired by the IOC_PR_REGISTER,
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IOC_PR_REGISTER_IGNORE, IOC_PR_PREEMPT or IOC_PR_PREEMPT_ABORT commands.
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3. IOC_PR_RELEASE
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This ioctl command releases the reservation specified by key and flags
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and thus removes any access restriction implied by it.
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4. IOC_PR_PREEMPT
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This ioctl command releases the existing reservation referred to by
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old_key and replaces it with a a new reservation of type for the
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reservation key new_key.
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5. IOC_PR_PREEMPT_ABORT
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This ioctl command works like IOC_PR_PREEMPT except that it also aborts
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any outstanding command sent over a connection identified by old_key.
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6. IOC_PR_CLEAR
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This ioctl command unregisters both key and any other reservation key
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registered with the device and drops any existing reservation.
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Flags
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-----
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All the ioctls have a flag field. Currently only one flag is supported:
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- PR_FL_IGNORE_KEY
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Ignore the existing reservation key. This is commonly supported for
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IOC_PR_REGISTER, and some implementation may support the flag for
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IOC_PR_RESERVE.
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For all unknown flags the kernel will return -EOPNOTSUPP.
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103
block/ioctl.c
103
block/ioctl.c
@ -7,6 +7,7 @@
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#include <linux/backing-dev.h>
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#include <linux/fs.h>
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#include <linux/blktrace_api.h>
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#include <linux/pr.h>
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#include <asm/uaccess.h>
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static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user *arg)
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@ -295,6 +296,96 @@ int __blkdev_driver_ioctl(struct block_device *bdev, fmode_t mode,
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*/
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EXPORT_SYMBOL_GPL(__blkdev_driver_ioctl);
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static int blkdev_pr_register(struct block_device *bdev,
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struct pr_registration __user *arg)
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{
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const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
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struct pr_registration reg;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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if (!ops || !ops->pr_register)
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return -EOPNOTSUPP;
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if (copy_from_user(®, arg, sizeof(reg)))
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return -EFAULT;
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if (reg.flags & ~PR_FL_IGNORE_KEY)
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return -EOPNOTSUPP;
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return ops->pr_register(bdev, reg.old_key, reg.new_key, reg.flags);
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}
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static int blkdev_pr_reserve(struct block_device *bdev,
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struct pr_reservation __user *arg)
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{
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const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
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struct pr_reservation rsv;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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if (!ops || !ops->pr_reserve)
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return -EOPNOTSUPP;
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if (copy_from_user(&rsv, arg, sizeof(rsv)))
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return -EFAULT;
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if (rsv.flags & ~PR_FL_IGNORE_KEY)
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return -EOPNOTSUPP;
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return ops->pr_reserve(bdev, rsv.key, rsv.type, rsv.flags);
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}
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static int blkdev_pr_release(struct block_device *bdev,
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struct pr_reservation __user *arg)
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{
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const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
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struct pr_reservation rsv;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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if (!ops || !ops->pr_release)
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return -EOPNOTSUPP;
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if (copy_from_user(&rsv, arg, sizeof(rsv)))
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return -EFAULT;
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if (rsv.flags)
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return -EOPNOTSUPP;
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return ops->pr_release(bdev, rsv.key, rsv.type);
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}
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static int blkdev_pr_preempt(struct block_device *bdev,
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struct pr_preempt __user *arg, bool abort)
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{
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const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
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struct pr_preempt p;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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if (!ops || !ops->pr_preempt)
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return -EOPNOTSUPP;
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if (copy_from_user(&p, arg, sizeof(p)))
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return -EFAULT;
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if (p.flags)
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return -EOPNOTSUPP;
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return ops->pr_preempt(bdev, p.old_key, p.new_key, p.type, abort);
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}
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static int blkdev_pr_clear(struct block_device *bdev,
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struct pr_clear __user *arg)
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{
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const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
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struct pr_clear c;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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if (!ops || !ops->pr_clear)
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return -EOPNOTSUPP;
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if (copy_from_user(&c, arg, sizeof(c)))
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return -EFAULT;
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if (c.flags)
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return -EOPNOTSUPP;
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return ops->pr_clear(bdev, c.key);
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}
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/*
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* Is it an unrecognized ioctl? The correct returns are either
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* ENOTTY (final) or ENOIOCTLCMD ("I don't know this one, try a
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@ -477,6 +568,18 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
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case BLKTRACESETUP:
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case BLKTRACETEARDOWN:
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return blk_trace_ioctl(bdev, cmd, argp);
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case IOC_PR_REGISTER:
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return blkdev_pr_register(bdev, argp);
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case IOC_PR_RESERVE:
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return blkdev_pr_reserve(bdev, argp);
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case IOC_PR_RELEASE:
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return blkdev_pr_release(bdev, argp);
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case IOC_PR_PREEMPT:
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return blkdev_pr_preempt(bdev, argp, false);
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case IOC_PR_PREEMPT_ABORT:
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return blkdev_pr_preempt(bdev, argp, true);
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case IOC_PR_CLEAR:
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return blkdev_pr_clear(bdev, argp);
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default:
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return __blkdev_driver_ioctl(bdev, mode, cmd, arg);
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}
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@ -35,6 +35,7 @@ struct sg_io_hdr;
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struct bsg_job;
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struct blkcg_gq;
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struct blk_flush_queue;
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struct pr_ops;
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#define BLKDEV_MIN_RQ 4
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#define BLKDEV_MAX_RQ 128 /* Default maximum */
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@ -1633,6 +1634,7 @@ struct block_device_operations {
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/* this callback is with swap_lock and sometimes page table lock held */
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void (*swap_slot_free_notify) (struct block_device *, unsigned long);
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struct module *owner;
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const struct pr_ops *pr_ops;
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};
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extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,
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18
include/linux/pr.h
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18
include/linux/pr.h
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@ -0,0 +1,18 @@
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#ifndef LINUX_PR_H
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#define LINUX_PR_H
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#include <uapi/linux/pr.h>
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struct pr_ops {
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int (*pr_register)(struct block_device *bdev, u64 old_key, u64 new_key,
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u32 flags);
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int (*pr_reserve)(struct block_device *bdev, u64 key,
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enum pr_type type, u32 flags);
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int (*pr_release)(struct block_device *bdev, u64 key,
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enum pr_type type);
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int (*pr_preempt)(struct block_device *bdev, u64 old_key, u64 new_key,
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enum pr_type type, bool abort);
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int (*pr_clear)(struct block_device *bdev, u64 key);
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};
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#endif /* LINUX_PR_H */
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48
include/uapi/linux/pr.h
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48
include/uapi/linux/pr.h
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@ -0,0 +1,48 @@
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#ifndef _UAPI_PR_H
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#define _UAPI_PR_H
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enum pr_type {
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PR_WRITE_EXCLUSIVE = 1,
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PR_EXCLUSIVE_ACCESS = 2,
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PR_WRITE_EXCLUSIVE_REG_ONLY = 3,
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PR_EXCLUSIVE_ACCESS_REG_ONLY = 4,
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PR_WRITE_EXCLUSIVE_ALL_REGS = 5,
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PR_EXCLUSIVE_ACCESS_ALL_REGS = 6,
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};
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struct pr_reservation {
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__u64 key;
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__u32 type;
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__u32 flags;
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};
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struct pr_registration {
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__u64 old_key;
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__u64 new_key;
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__u32 flags;
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__u32 __pad;
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};
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struct pr_preempt {
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__u64 old_key;
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__u64 new_key;
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__u32 type;
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__u32 flags;
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};
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struct pr_clear {
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__u64 key;
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__u32 flags;
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__u32 __pad;
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};
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#define PR_FL_IGNORE_KEY (1 << 0) /* ignore existing key */
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#define IOC_PR_REGISTER _IOW('p', 200, struct pr_registration)
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#define IOC_PR_RESERVE _IOW('p', 201, struct pr_reservation)
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#define IOC_PR_RELEASE _IOW('p', 202, struct pr_reservation)
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#define IOC_PR_PREEMPT _IOW('p', 203, struct pr_preempt)
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#define IOC_PR_PREEMPT_ABORT _IOW('p', 204, struct pr_preempt)
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#define IOC_PR_CLEAR _IOW('p', 205, struct pr_clear)
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#endif /* _UAPI_PR_H */
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