diff options
Diffstat (limited to 'Documentation/block/pr.txt')
| -rw-r--r-- | Documentation/block/pr.txt | 119 |
1 files changed, 0 insertions, 119 deletions
diff --git a/Documentation/block/pr.txt b/Documentation/block/pr.txt deleted file mode 100644 index ac9b8e70e64b..000000000000 --- a/Documentation/block/pr.txt +++ /dev/null @@ -1,119 +0,0 @@ - -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 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. |