[PATCH] fs: fix schedule while atomic caused by gfp of erofs_allocpage

[Zhaoyang Huang]

On Tue, Jul 16, 2024 at 2:50 PM Gao Xiang <hsiangkao at linux.alibaba.com> wrote:
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>
>
> On 2024/7/16 14:46, Gao Xiang wrote:
> >
> >
> > On 2024/7/16 14:43, Zhaoyang Huang wrote:
> >> On Tue, Jul 16, 2024 at 2:20 PM Gao Xiang <hsiangkao at linux.alibaba.com> wrote:
> >>>
> >>>
> >>>
> >
> > ...
> >
> >>>>>
> >>>>> I don't see why it's an atomic context,
> >>>>> so this patch is incorrect.
> >>>> Sorry, I should provide more details. page_cache_ra_unbounded() will
> >>>> call filemap_invalidate_lock_shared(mapping) to ensure the integrity
> >>>> of page cache during readahead, which will disable preempt.
> >>>
> >>> Why a rwsem sleepable lock disable preemption?
> >> emm, that's the original design of down_read()
> >
> > No.
> >
> >>
> >>> context should be always non-atomic context, which is applied
> >>> to all kernel filesystems.
> >>   AFAICT, filemap_fault/read have added the folios of readahead to page
> >> cache which means the aops->readahead basically just need to map the
> >> block to this folios and then launch the bio. The erofs is a little
> >> bit different to others as it has to alloc_pages for decompression
> >> when doing this.
> >
> > Interesting.  The whole .readahead is sleepable, including
> > submit block I/Os to storage.
>
> Also, please don't imagine your stack trace if it's a non-upstream
> kernel.
ok, it should be caused by a vendor hook function of the android
system. sorry for interrupting by my stupid.
>
> >
> > Nacked-by: Gao Xiang <hsiangkao at linux.alibaba.com>
> >
> > Thanks,
> > Gao Xiang