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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: ep4mcnhh1xzqm7d1drrs8j8tqibhzcsw X-Rspamd-Queue-Id: 7323BC0012 X-Rspamd-Server: rspam11 X-Rspam-User: X-HE-Tag: 1751469945-742753 X-HE-Meta: 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 WbwJvNnv 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 02.07.25 15:01, Harry Yoo wrote: > On Wed, Jul 02, 2025 at 02:01:33PM +0200, David Hildenbrand wrote: >> On 02.07.25 13:54, Harry Yoo wrote: >>> On Mon, Jun 30, 2025 at 03:00:01PM +0200, David Hildenbrand wrote: >>>> Instead, let's use a page flag. As the page flag can result in >>>> false-positives, glue it to the page types for which we >>>> support/implement movable_ops page migration. >>>> >>>> The flag reused by PageMovableOps() might be sued by other pages, so >>>> warning in case it is set in page_has_movable_ops() might result in >>>> false-positive warnings. >>>> >>>> Reviewed-by: Zi Yan >>>> Signed-off-by: David Hildenbrand >>>> --- >>> >>> LGTM, >>> Reviewed-by: Harry Yoo >>> >>> With a question: is there any reason to change the page flag >>> operations to use atomic bit ops? >> >> As we have the page lock in there, it's complicated. I thought about this >> when writing that code, and was not able to convince myself that it is safe. >> >> But that was when I was prototyping and reshuffling patches, and we would >> still have code that would clear the flag. > >> Given that we only allow setting the flag, it might be okay to use the >> non-atomic variant as long as there can be nobody racing with us when >> modifying flags. Especially trying to lock the folio concurrently is the big >> problem. >> >> In isolate_movable_ops_page(), there is a comment about checking the flag >> before grabbing the page lock, so that should be handled. > > Right. > >> I'll have to check some other cases in balloon/zsmalloc code. > > Okay, it's totally fine to go with atomic version and then > switching back to non atomic ops when we're sure it's safe. > I'll definitely do the following: diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 8b23a74963feb..5f2b570735852 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -1145,9 +1145,11 @@ PAGEFLAG(Isolated, isolated, PF_ANY); * the flag might be used in other context for other pages. Always use * page_has_movable_ops() instead. */ -PAGEFLAG(MovableOps, movable_ops, PF_NO_TAIL); +TESTPAGEFLAG(MovableOps, movable_ops, PF_NO_TAIL); +SETPAGEFLAG(MovableOps, movable_ops, PF_NO_TAIL); #else /* !CONFIG_MIGRATION */ -PAGEFLAG_FALSE(MovableOps, movable_ops); +TESTPAGEFLAG_FALSE(MovableOps, movable_ops); +SETPAGEFLAG_NOOP(MovableOps, movable_ops); #endif /* CONFIG_MIGRATION */ /** Because the flag must not get cleared. There is no __SETPAGEFLAG_NOOP yet, unfortunately. -- Cheers, David / dhildenb