This series introduces a new ioctl that makes it possible to atomically configure a loop device. Previously, if you wanted to set parameters such as the offset on a loop device, this required calling LOOP_SET_FD to set the backing file, and then LOOP_SET_STATUS to set the offset. However, in between these two calls, the loop device is available and would accept requests, which is generally not desirable. There are also performance benefits with combining these two ioctls into one, which are described in more detail in the last change in the series. Note that this series depends on "loop: Call loop_config_discard() only after new config is applied." [0], which I sent as a separate patch as it fixes an unrelated bug. [0]: https://lkml.org/lkml/2020/3/31/755 --- v2: - Addressed review comments from Bart van Assche: -- Use SECTOR_SHIFT constant -- Renamed loop_set_from_status() to loop_set_status_from_info() -- Added kerneldoc for loop_set_status_from_info() -- Removed dots in patch subject lines - Addressed review comments from Christoph Hellwig: -- Added missing padding in struct loop_fd_and_status -- Cleaned up some __user pointer handling in lo_ioctl -- Pass in a stack-initialized loop_info64 for the legacy LOOP_SET_FD case Martijn Coenen (5): loop: Refactor size calculation loop: Factor out configuring loop from status loop: Move loop_set_status_from_info() and friends up loop: rework lo_ioctl() __user argument casting loop: Add LOOP_SET_FD_AND_STATUS ioctl drivers/block/loop.c | 327 ++++++++++++++++++++++---------------- include/uapi/linux/loop.h | 7 + 2 files changed, 201 insertions(+), 133 deletions(-) -- 2.26.2.303.gf8c07b1a785-goog
