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[ Upstream commitc4706c5058] The lockdep tool can report a circular lock dependency warning in the loop driver's AIO read/write path: ``` [ 6540.587728] kworker/u96:5/72779 is trying to acquire lock: [ 6540.593856] ff110001b5968440 (sb_writers#9){.+.+}-{0:0}, at: loop_process_work+0x11a/0xf70 [loop] [ 6540.603786] [ 6540.603786] but task is already holding lock: [ 6540.610291] ff110001b5968440 (sb_writers#9){.+.+}-{0:0}, at: loop_process_work+0x11a/0xf70 [loop] [ 6540.620210] [ 6540.620210] other info that might help us debug this: [ 6540.627499] Possible unsafe locking scenario: [ 6540.627499] [ 6540.634110] CPU0 [ 6540.636841] ---- [ 6540.639574] lock(sb_writers#9); [ 6540.643281] lock(sb_writers#9); [ 6540.646988] [ 6540.646988] *** DEADLOCK *** ``` This patch fixes the issue by using the AIO-specific helpers `kiocb_start_write()` and `kiocb_end_write()`. These functions are designed to be used with a `kiocb` and manage write sequencing correctly for asynchronous I/O without introducing the problematic lock dependency. The `kiocb` is already part of the `loop_cmd` struct, so this change also simplifies the completion function `lo_rw_aio_do_completion()` by using the `iocb` from the `cmd` struct directly, instead of retrieving the loop device from the request queue. Fixes:39d86db34e("loop: add file_start_write() and file_end_write()") Cc: Changhui Zhong <czhong@redhat.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20250716114808.3159657-1-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.