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>tirimbino
Christoph Hellwig
9 years ago
committed by
Jens Axboe
parent
d8e4bb8103
commit
bbd3e06436
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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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@ -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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@ -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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