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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: k9nrbkupg331x3bpeyna5jxbbpgbfe91 X-Rspamd-Queue-Id: C0D5E4000F X-Rspamd-Server: rspam11 X-Rspam-User: X-HE-Tag: 1751453713-628685 X-HE-Meta: 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 ybW0zBaa yL26E0/nA52HQi6zMVm/JIdM84a3M3OHhf3eRxGHYawbj2XRE+SN+hHeMuxqq6ggz303/vmntorxycINqFsNGuoxjfsNvcCvx8KEBGxcD0Q5estyxRAb8aUYRck5/u/R4fAZmEXUtQn3P9tgqHeghWAM1/9TmJx2/z6Fl5I8yFPa8MAMPeij1fcIKC0IABZNww7W0 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 12:10, Sergey Senozhatsky wrote: > On (25/07/02 10:25), David Hildenbrand wrote: >> On 02.07.25 10:11, Sergey Senozhatsky wrote: >>> On (25/06/30 14:59), David Hildenbrand wrote: >>> [..] >>>> static int zs_page_migrate(struct page *newpage, struct page *page, >>>> @@ -1736,6 +1736,13 @@ static int zs_page_migrate(struct page *newpage, struct page *page, >>>> unsigned long old_obj, new_obj; >>>> unsigned int obj_idx; >>>> + /* >>>> + * TODO: nothing prevents a zspage from getting destroyed while >>>> + * isolated: we should disallow that and defer it. >>>> + */ >>> >>> Can you elaborate? >> >> We can only free a zspage in free_zspage() while the page is locked. >> >> After we isolated a zspage page for migration (under page lock!), we drop > ^^ a physical page? (IOW zspage chain page?) > >> the lock again, to retake the lock when trying to migrate it. >> >> That means, there is a window where a zspage can be freed although the page >> is isolated for migration. > > I see, thanks. Looks somewhat fragile. Is this a new thing? No, it's been like that forever. And I was surprised that only zsmalloc behaves that way -- balloon implements isolation as one would expect it (disallow freeing while isolated). > >> While we currently keep that working (as far as I can see), in the future we >> want to remove that support from the core. > > Maybe comment can more explicitly distinguish zspage isolation and > physical page (zspage chain) isolation? zspages can get isolated > for compaction (defragmentation), for instance, which is a different > form of isolation. Well, it's confusing, as we have MM compaction (-> migration) and apparently zs_compact. I'll try to clarify that we are talking about isolation for page migration purposes. -- Cheers, David / dhildenb