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 aDR/oJTt JguGW+bcdQ4Q0qXqj+B5rfRgLEBOTLO7yfJb3Rcya2TVwpjq+3f89ylEtsqGXXmDzmInzD8l+1s+JWkTXL8VrtKLzr9aus6jXrqcthXczBF/wSBfLElcSbpxS3iOOAKcEIJ3QJL05tlt8zBsIO5ejEYF08xJxtvgB/lKrIiVcY5ki3XyyQt2s2CwO15mU+xzojkC+IPf3lBcRsZ+V5Qf/Ym3d3EWOE74lUyRmYY4L7fSKi0PNabrgPRu1mvlBkEjKR3BPmvMx3eWnzrDGF0QpGyI8em+XQRwgt7Bq8Y9FOwbTM/h653ClVPNZSQdrzuA4/7FHpyKouoq5YZgnppLkm9Lfe8a02a5Pkt1gJTxEI0TIW02D1+UX1ujNbWqCKApomb5b1sjSz2J6sXxDm87XbjasmdB0eyea/GUf90M34EXHUe8tsFDTvZRVPQzvtrZYLKUEtpGZnz0K+wo+5cK+LLz/0bqYkdlMXmc+ZVdHUNFNBXI= 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: --=_MailMate_0EC9C18B-0D3F-486C-A60A-FED27DD40C6D_= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On 14 Aug 2023, at 23:56, Huang, Ying wrote: > Kefeng Wang writes: > >> On 2023/8/4 10:42, Zi Yan wrote: >>> On 3 Aug 2023, at 21:45, Kefeng Wang wrote: >>> >>>> On 2023/8/3 20:30, Matthew Wilcox wrote: >>>>> On Thu, Aug 03, 2023 at 03:13:21PM +0800, Kefeng Wang wrote: >>>>>> >>>>>> >>>>>> On 2023/8/2 20:21, Matthew Wilcox wrote: >>>>>>> On Wed, Aug 02, 2023 at 05:53:43PM +0800, Kefeng Wang wrote: >>>>>>>> err =3D -EACCES; >>>>>>>> - if (page_mapcount(page) > 1 && !migrate_all) >>>>>>>> - goto out_putpage; >>>>>>>> + if (folio_estimated_sharers(folio) > 1 && !migrate_all) >>>>>>>> + goto out_putfolio; >>>>>>> >>>>>>> I do not think this is the correct change. Maybe leave this line= >>>>>>> alone. >>>>>> >>>>>> Ok, I am aware of the discussion about this in other mail, will no= t >>>>>> change it(also the next two patch about this function), or wait th= e >>>>>> new work of David. >>>>>>> >>>>>>>> - if (PageHuge(page)) { >>>>>>>> - if (PageHead(page)) { >>>>>>>> - isolated =3D isolate_hugetlb(page_folio(page), pagelist); >>>>>>>> + if (folio_test_hugetlb(folio)) { >>>>>>>> + if (folio_test_large(folio)) { >>>>>>> >>>>>>> This makes no sense when you read it. All hugetlb folios are lar= ge, >>>>>>> by definition. Think about what this code used to do, and what i= t >>>>>>> should be changed to. >>>>>> >>>>>> hugetlb folio is self large folio, will drop redundant check >>>>> >>>>> No, that's not the difference. Keep thinking about it. This is no= t >>>>> a mechanical translation! >>>> >>>> >>>> if (PageHuge(page)) // page must be a hugetlb page >>>> if (PageHead(page)) // page must be a head page, not tail >>>> isolate_hugetlb() // isolate the hugetlb page if head >>>> >>>> After using folio, >>>> >>>> if (folio_test_hugetlb(folio)) // only check folio is hugetlb or = not >>>> >>>> I don't check the page is head or not, since the follow_page could >>>> return a sub-page, so the check PageHead need be retained, right? >>> Right. It will prevent the kernel from trying to isolate the same >>> hugetlb page >>> twice when two pages are in the same hugetlb folio. But looking at th= e >>> code, if you try to isolate an already-isolated hugetlb folio, isolat= e_hugetlb() >>> would return false, no error would show up. But it changes err value >>> from -EACCES to -EBUSY and user will see a different page status than= before. >> >> >> When check man[1], the current -EACCES is not right, -EBUSY is not >> precise but more suitable for this scenario, >> >> -EACCES >> The page is mapped by multiple processes and can be move= d >> only if MPOL_MF_MOVE_ALL is specified. >> >> -EBUSY The page is currently busy and cannot be moved. Try aga= in >> later. This occurs if a page is undergoing I/O or anoth= er >> kernel subsystem is holding a reference to the page. >> -ENOENT >> The page is not present. >> >>> I wonder why we do not have follow_folio() and returns -ENOENT error >>> pointer >>> when addr points to a non head page. It would make this patch more fo= lio if >>> follow_folio() can be used in place of follow_page(). One caveat is t= hat >>> user will see -ENOENT instead of -EACCES after this change. >>> >> >> -ENOENT is ok, but maybe the man need to be updated too. >> >> >> = >> [1] https://man7.org/linux/man-pages/man2/move_pages.2.html >> > > I don't think -ENOENT is appropriate. IIUC, -ENOENT means no need to > migrate. Which isn't the case here apparently. Are you referring to a comment or the man page? The man page says -ENOENT means the page is not present. Or you think it also implies there is no need to migrate? If yes, we probably need to update the man page. -- Best Regards, Yan, Zi --=_MailMate_0EC9C18B-0D3F-486C-A60A-FED27DD40C6D_= Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQJDBAEBCgAtFiEE6rR4j8RuQ2XmaZol4n+egRQHKFQFAmTbglIPHHppeUBudmlk aWEuY29tAAoJEOJ/noEUByhUDIYP/3a4b8PzQJjFgyVU8iaAf/90DYBDr9hBR/5P bVSYld85O1U3OgRFoEvwC+3rzvJKsBA8p9ZgTNr1Veuw9G13Dc0zCEGakdoFAp5f X08QX1GXSToQCdnR4p0CdAFG33UOevV3nO+Yb1eUu96NPBg612E8ZRBJtI7Tue+P vaFNNBq3cUcFU+PcNIazSyznrgouUCLz50yoXQIIx2EdH3XKx+OG8qy59FBk2RWH 0w+Se3qDJsAkS3eKVE4h3G1vlWelXrFdLbw5EEyZFc4thp5wjZjGhM7OwY2sHmIp NfG9AcG6OQnWlNsBheSUEADG6T9e7/8L/t6YZakNnUTx8RycNAsshmcyTaS9eliU AnX/ONMdys2AhEK1TEeWKi6LvGAsjRJCDaNT5et8CbWPtlkqRl0LC0VXbo6DZi34 9w9degPH2JDjuNK5Cwee03LNOjoI13atIOTWVFmCLBJC+tkkZ4n2BgMs7k3tVWvI DaiXL9iusMYMNBrVmDy+tKdYFRrD1PlIU12spZH1V8kYYbited47L0x2ms1FxO7j bqK5a81LVm6KOz5g8/YBxpLUbUlW8VNadjwyaEE+ega2raAAGqMqYdGVt28eo8xM s3uieom8UhHo8liRts8Tg1iGHdaHjpv0H4ZE0yoXw49mEMhwkPar9EAFT0RFGbIZ jVLslrPp =cV7F -----END PGP SIGNATURE----- --=_MailMate_0EC9C18B-0D3F-486C-A60A-FED27DD40C6D_=--