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I have encountered a NULL pointer dereference in throtl_schedule_pending_timer: [ 413.735396] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038 [ 413.735535] IP: [<ffffffff812ebbbf>] throtl_schedule_pending_timer+0x3f/0x210 [ 413.735643] PGD 22c8cf067 PUD 22cb34067 PMD 0 [ 413.735713] Oops: 0000 [#1] SMP ...... This is caused by the following case: blk_throtl_bio throtl_schedule_next_dispatch <= sq is top level one without parent throtl_schedule_pending_timer sq_to_tg(sq)->td->throtl_slice <= sq_to_tg(sq) returns NULL Fix it by using sq_to_td instead of sq_to_tg(sq)->td, which will always return a valid td. Fixes: 297e3d854784 ("blk-throttle: make throtl_slice tunable") Signed-off-by: Joseph Qi <qijiang.qj@alibaba-inc.com> Reviewed-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.