On 2021/09/15 19:27, Greg KH wrote:
On Tue, Sep 14, 2021 at 08:54:02PM +0800, Yu Kuai wrote:If blk-throttle is enabled and io is issued before blk_throtl_register_queue() is done. Divide by zero crash will be triggered in tg_may_dispatch() because 'throtl_slice' is uninitialized. The problem is fixed in commit 75f4dca59694 ("block: call blk_register_queue earlier in device_add_disk") from mainline, however it's too hard to backport this patch due to lots of refactoring. Thus introduce a new flag QUEUE_FLAG_THROTL_INIT_DONE. It will be set after blk_throtl_register_queue() is done, and will be checked before applying any config. Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> --- block/blk-sysfs.c | 2 ++ block/blk-throttle.c | 41 +++++++++++++++++++++++++++++++++++++++-- include/linux/blkdev.h | 1 + 3 files changed, 42 insertions(+), 2 deletions(-)The commit you reference above is in 5.15-rc1. What about all of the other stable kernel releases newer than 4.19.y? You do not want to move to a newer release and have a regression.
All other kernel releases without this patch have the same issure, including v5.14.
And I would _REALLY_ like to take the identical commits that are upstream if at all possible. What is needed to backport instead of doing this one-off patch instead?
The function __device_add_disk() is quite different compared from 4.19.y to mainline, I haven't finish to collect that how many patches is needed yet, which is not easy to do...
When we take changes that are not upstream, almost always they are broken so we almost never want to do that.
I understand that, more proper fix should be calling blk_register_queue earlier in device_add_disk like the commit did. I'll try to do that and hope conflicts are not too much... Thanks, Kuai
thanks, greg k-h .
