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Shutemov" , linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Hugh Dickins Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: BBD0110000F X-Stat-Signature: ahngnhdapqhsm9ghhmc7ewmjkuxhdosd X-HE-Tag: 1675372295-833356 X-HE-Meta: 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 JMEcT0FC 5hkGYB9ROyqM3ZynarXxHzAoGGrjJNK+i9Xe8uCiJS51rNo0uQ2wvsahhy6DyIqGVw+33Jj0bUmfsyAholdUSlbYR+ZcEF7M+IiM+poKxa2nJyMCJbjIcp/P/IbAGwYbL/tER3WTSgs+dFrFkisNrQekux85A3YSlRqoHSINtp2Possx9ZKm/jatRAY/DbcqLvjPLl8Hm1n+t/1UMAxGGyQXs9oWinEZRtCTDjs8UPrDYZppalzDTkjtn5Bq0Dm/e9bg0g7nbo+ZPJfFlXjDgb9QzoCJHBGy52Jaiq35zKGsNh7ZSpFzuXnwqaPAACAjOTvoa08ehJ3IyjvtyLRkPzI65JhsqwY3foiHkIZU+Tp5EhVh+IpFOnTZgeMLBHK30wehR2ujVmlq6u3s= X-Bogosity: Ham, tests=bogofilter, spamicity=0.001780, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Feb 2, 2023 at 12:04 PM Peter Xu wrote: > > On Wed, Feb 01, 2023 at 03:57:33PM -0800, Yang Shi wrote: > > > There's another problem where the current vma may not have uffd armed, > > > khugepaged may think it has nothing to do with uffd and moved on with > > > collapsing, but actually it's armed in another vma of either the current mm > > > or just another mm's. > > > > Out of curiosity, could you please elaborate how another vma armed > > with userfaultfd could have an impact on the vmas that are not armed? > > It's e.g. when >1 vmas mapped to the same shmem file on the same range, one > registered with uffd missing, others not. Then others can cause page cache > populated without generating message to the vma that got uffd missing mode > registered, so there'll be the same issue as when khugepaged accidentally > does thp collapsings. Thanks, Got it, thank you. > > -- > Peter Xu >