Re: [PATCH v2] md/raid1: Fix stack memory use after return in raid1_reshape

[Wang Jinchao]

On 2025/6/12 19:58, Yu Kuai wrote:
> Hi,
>
> 在 2025/06/12 19:46, Wang Jinchao 写道:
> > On 2025/6/12 19:23, Yu Kuai wrote:
> > > Hi,
> > >
> > > 在 2025/06/12 17:55, Wang Jinchao 写道:
> > > > Now that we have the same information, I prefer patch-v1 before 
> > > > refactoring raid1_reshape,
> > > > because it’s really simple (only one line) and clearer to show the 
> > > > backup and restore logic.
> > > > Another reason is that v2 freezes the RAID longer than v1.
> > > > Would you like me to provide a v3 patch combining the v2 explanation 
> > > > with the v1 diff?
> > > > Thanks for your reviewing.
> > >
> > > I don't have preference here, feel free to do this.
> > >
> > > BTW, I feel raid1_reshape can be better coding with following：
> > >
> > > - covert r1bio_pool to use mempool_create_kmalloc_pool(use create
> > > instead of init to get rid of the werid assigment);
> > mempool_create_kmalloc_pool also calls init_waitqueue_head(&pool- 
> > >wait) internally, just like mempool_init.
>
> Please notice that creat will allocate memory for mempool, the list is
> no longer a stack value, the field bio_pool inside conf should also
> covert to a pointer.
>
> > So the issue only exists if newpool is allocated on the stack.
> > > - no need to reallocate pool_info;
> > > - convert raid1_info to use krealloc;
> > I think reallocating pool_info is only for backup and restore, similar 
> > to newpool.
>
> You can just change the old value directly, after everything is ready,
> with the first mempool change, pool_info is not needed for bio_pool.
> > > Welcome if you are willing to, otherwise I'll find myself sometime.
> > I'm a newcomer to RAID and can't quite catch up with it right now.
> > Maybe I can refactor it later, and I look forward to your guidance.
> > >
>
> No hurry, take you time :)
👍
You're right — now I understand the whole.
I'm willing to try refactoring raid1_reshape later.
> Thanks,
> Kuai