diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/stable/sysfs-block | 3 | ||||
| -rw-r--r-- | Documentation/block/capability.rst | 10 | ||||
| -rw-r--r-- | Documentation/block/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/block/ublk.rst | 55 |
4 files changed, 48 insertions, 21 deletions
diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block index cd14ecb3c9a5..ac1e519272aa 100644 --- a/Documentation/ABI/stable/sysfs-block +++ b/Documentation/ABI/stable/sysfs-block @@ -432,7 +432,8 @@ Contact: linux-block@vger.kernel.org Description: [RW] This is the maximum number of kilobytes that the block layer will allow for a filesystem request. Must be smaller than - or equal to the maximum size allowed by the hardware. + or equal to the maximum size allowed by the hardware. Write 0 + to use default kernel settings. What: /sys/block/<disk>/queue/max_segment_size diff --git a/Documentation/block/capability.rst b/Documentation/block/capability.rst deleted file mode 100644 index 2ae7f064736a..000000000000 --- a/Documentation/block/capability.rst +++ /dev/null @@ -1,10 +0,0 @@ -=============================== -Generic Block Device Capability -=============================== - -This file documents the sysfs file ``block/<disk>/capability``. - -``capability`` is a bitfield, printed in hexadecimal, indicating which -capabilities a specific block device supports: - -.. kernel-doc:: include/linux/blkdev.h diff --git a/Documentation/block/index.rst b/Documentation/block/index.rst index c4c73db748a8..102953166429 100644 --- a/Documentation/block/index.rst +++ b/Documentation/block/index.rst @@ -10,7 +10,6 @@ Block bfq-iosched biovecs blk-mq - capability cmdline-partition data-integrity deadline-iosched diff --git a/Documentation/block/ublk.rst b/Documentation/block/ublk.rst index ba45c46cc0da..1713b2890abb 100644 --- a/Documentation/block/ublk.rst +++ b/Documentation/block/ublk.rst @@ -144,6 +144,43 @@ managing and controlling ublk devices with help of several control commands: For retrieving device info via ``ublksrv_ctrl_dev_info``. It is the server's responsibility to save IO target specific info in userspace. +- ``UBLK_CMD_GET_DEV_INFO2`` + Same purpose with ``UBLK_CMD_GET_DEV_INFO``, but ublk server has to + provide path of the char device of ``/dev/ublkc*`` for kernel to run + permission check, and this command is added for supporting unprivileged + ublk device, and introduced with ``UBLK_F_UNPRIVILEGED_DEV`` together. + Only the user owning the requested device can retrieve the device info. + + How to deal with userspace/kernel compatibility: + + 1) if kernel is capable of handling ``UBLK_F_UNPRIVILEGED_DEV`` + + If ublk server supports ``UBLK_F_UNPRIVILEGED_DEV``: + + ublk server should send ``UBLK_CMD_GET_DEV_INFO2``, given anytime + unprivileged application needs to query devices the current user owns, + when the application has no idea if ``UBLK_F_UNPRIVILEGED_DEV`` is set + given the capability info is stateless, and application should always + retrieve it via ``UBLK_CMD_GET_DEV_INFO2`` + + If ublk server doesn't support ``UBLK_F_UNPRIVILEGED_DEV``: + + ``UBLK_CMD_GET_DEV_INFO`` is always sent to kernel, and the feature of + UBLK_F_UNPRIVILEGED_DEV isn't available for user + + 2) if kernel isn't capable of handling ``UBLK_F_UNPRIVILEGED_DEV`` + + If ublk server supports ``UBLK_F_UNPRIVILEGED_DEV``: + + ``UBLK_CMD_GET_DEV_INFO2`` is tried first, and will be failed, then + ``UBLK_CMD_GET_DEV_INFO`` needs to be retried given + ``UBLK_F_UNPRIVILEGED_DEV`` can't be set + + If ublk server doesn't support ``UBLK_F_UNPRIVILEGED_DEV``: + + ``UBLK_CMD_GET_DEV_INFO`` is always sent to kernel, and the feature of + ``UBLK_F_UNPRIVILEGED_DEV`` isn't available for user + - ``UBLK_CMD_START_USER_RECOVERY`` This command is valid if ``UBLK_F_USER_RECOVERY`` feature is enabled. This @@ -180,6 +217,15 @@ managing and controlling ublk devices with help of several control commands: double-write since the driver may issue the same I/O request twice. It might be useful to a read-only FS or a VM backend. +Unprivileged ublk device is supported by passing ``UBLK_F_UNPRIVILEGED_DEV``. +Once the flag is set, all control commands can be sent by unprivileged +user. Except for command of ``UBLK_CMD_ADD_DEV``, permission check on +the specified char device(``/dev/ublkc*``) is done for all other control +commands by ublk driver, for doing that, path of the char device has to +be provided in these commands' payload from ublk server. With this way, +ublk device becomes container-ware, and device created in one container +can be controlled/accessed just inside this container. + Data plane ---------- @@ -254,15 +300,6 @@ with specified IO tag in the command data: Future development ================== -Container-aware ublk deivice ----------------------------- - -ublk driver doesn't handle any IO logic. Its function is well defined -for now and very limited userspace interfaces are needed, which is also -well defined too. It is possible to make ublk devices container-aware block -devices in future as Stefan Hajnoczi suggested [#stefan]_, by removing -ADMIN privilege. - Zero copy --------- |