Re: [PATCH] block: avoild hang when bio_list is non-NULL in submit_bio_wait()

[Christoph Hellwig <hch@infradead.org>]

On Mon, Mar 02, 2026 at 10:51:03AM +0800, Jiucheng Xu via B4 Relay wrote:
> From: Jiucheng Xu <jiucheng.xu@amlogic.com>
> 
> When current->bio_list is non-NULL in submit_bio_wait(),
> submit_bio_noacct_nocheck appends bio to bio_list but skips IO
> submission, causing submit_bio_wait() to hang indefinitely.
> 
> Fix this by temporarily backup bio_list, setting bio_list to
> NULL before calling submit_bio(), then restoring bio_list
> after submit_bio() returns.

No.  Fix this by not doing something that is a bad idea.

> I've trimmed down the call stack, as follows:
> 
> f2fs_submit_read_io
>   submit_bio
>     mmc_blk_mq_recovery
>       z_erofs_endio
>         vm_map_ram

->bi_end_io code really should not be having random in_atomic()
checks that make it completely different, but even if they have
that need to use GFP_NOIO.