[PATCH v3 0/9] loop: Micro-refactoring set_loop() and add LOOP_CONFIGURE

[Xiaoming Ni]

LOOP_CONFIGURE is added to Linux 5.8

This allows userspace to completely setup a loop device with a single
ioctl, removing the in-between state where the device can be partially
configured - eg the loop device has a backing file associated with it,
but is reading from the wrong offset.

https://lwn.net/Articles/820408/
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3448914e8cc5

patch 1-8: To facilitate the addition of new functions, the code of set_loop() is micro-refactored.
	function                                             old     new   delta
	set_loop                                             760     716     -44
	------------------------------------------------------------------------------
	(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-44)             Total: -44 bytes

patch 9: add LOOP_CONFIGURE 
	Builders can use config to choose which algorithm to build into their busybox binary

---
v3: Fine-tuned based on review comments
  patch2: Rename local variables, use "loopdevno" instead of "i" in get_next_free_loop().
  patch7: Reduce indentation using guard statements in do_stat_and_mknod().
  patch9: Rename set_loop_configure_old() to set_loop_fd_and_status()
v2: http://lists.busybox.net/pipermail/busybox/2022-November/089990.html 
  changes in patch9:  add config for builder to select
v1: http://lists.busybox.net/pipermail/busybox/2022-November/089969.html
---
*** BLURB HERE ***

Xiaoming Ni (9):
  loop:refactor: extract subfunction open_file()
  loop:refactor: extract subfunction get_next_free_loop()
  loop:refactor: del close_and_try_next_loopN
  loop:refactor: extract subfunction set_loop_info()
  loop:refactor: extract subfunction set_loop_configure()
  loop:refactor: Use a structure to reduce parameters
  loop:refactor: Extract subfunction do_stat_and_mknod()
  loop:refactor: extract subfunction set_loop_dev()
  loop: Add LOOP_CONFIGURE ioctl

 libbb/Config.src |  22 ++++
 libbb/loop.c     | 292 ++++++++++++++++++++++++++++++-----------------
 2 files changed, 211 insertions(+), 103 deletions(-)

-- 
2.27.0