Re:Re: [PATCH] mm/page_idle: call folio_test_lru() after folio_get()

[jiale yao]

Hi SJ,
Thanks for your review. I did take commit d6b8b02a27b3 as a reference.
Link: https://lore.kernel.org/20260525162256.8317-1-sj@xxxxxxxxxx

Thanks
Jiale










At 2026-07-23 08:42:49, "SJ Park" <sj@xxxxxxxxxx> wrote:
>On Wed, 22 Jul 2026 13:50:05 +0100 "Lorenzo Stoakes (ARM)" <ljs@xxxxxxxxxx> wrote:
>
>> Nooooo :) this is not how you send patches.
>> 
>> Also you should _reply_ to review comments, not just send another patch with no
>> reply. Comms is king.
>> 
>> Also - don't respin so quick. Wait a day.
>> 
>> Then send a v2, NOT in reply to anything.
>> 
>> Really best way is to use b4, docs at
>> https://b4.docs.kernel.org/en/latest/contributor/prep.html and etc.
>> 
>> But you can also do something like:
>> 
>> git format-patch -v2 HEAD~1
>> scripts/checkpatch.pl <patch filename>
>> scripts/get_maintainer.pl <patch filename>
>> git send-email --to="(andrew)" --cc="<list from get maintainers>" <patch filename>
>> 
>> 
>> On Wed, Jul 22, 2026 at 07:20:20PM +0800, jiale yao wrote:
>> > page_idle_get_folio() speculatively calls folio_test_lru() before
>> > folio_try_get(). The folio can get freed and reallocated to a tail page
>> > in the meantime. In that case, VM_BUG_ON_PGFLAGS() in
>> > const_folio_flags() can be triggered. Remove the speculative call.
>> >
>> > This is a sibling-path bug: damon_get_folio() was copied from this
>> > function with the same flawed pattern. Commit d6b8b02a27b3
>> > ("mm/damon/ops-common: call folio_test_lru() after folio_get()") fixed
>> > damon_get_folio(), but page_idle_get_folio() was left unfixed.
>
>I was actually thinking I should also do this, but I was again failed at
>managing my memory.  Thank you for doing this, Jiale!
>
>> > KCSAN
>> > (strict mode) confirms the data race on the folio flags:
>> >
>> >   BUG: KCSAN: data-race in ... / percpu_counter_add_batch
>> >     page_idle_get_folio+0x7a/0x2d0
>> >     page_idle_bitmap_read+0xc9/0x220
>> >
>> > Signed-off-by: Jiale Yao <yaojiale02@xxxxxxx>
>> > Reviewed-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
>
>> 
>> this should really be backported, so good to find the right commit to use as a Fixes: here.
>> 
>> Also then add Cc: <stable@xxxxxxxxxxxxxxx> so it gets send for backporting.
>> 
>> But _please_ wait a day before sending the v2 :)
>> 
>> > ---
>> 
>> Also in the v2 put a list of changes here (will not be included in commit msg)
>> with links to previous versions on lore.
>
>Assuming all the above nice suggestions from Lorenzo are accepted,
>
>Reviewed-by: SJ Park <sj@xxxxxxxxxx>
>
>
>Thanks,
>SJ
>
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