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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.1 (3.54.1-1.fc41) MIME-Version: 1.0 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 81B87140015 X-Stat-Signature: 3m1n5bxem3bgao5jbya7esw6sg4fy5ji X-Rspam-User: X-HE-Tag: 1736874728-186084 X-HE-Meta: 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 OA3ALK0O +1l6ZPTKsbHcB8gevGAz8EZ9I9HM5dRD6P1nHw67oKQCAlIWaN3oE1TXJ4902TB7ZR2QZ0/CQXFCa3TT7S0PbEqCNS8HlejlfhPBA8jELX7vI/c5qmNN6ao3QssWYo1A6F71duka/al/rWgymOb/GqdZz+/rwUAvFPQzs0IsjOTQElaGxGGd/wEdbs/cWtiuFLrLblNa/Miqqscodmt77d17Pb31Wp3NZgpp9JXomtPQ/3YgFjExr1tH/A29fmUPh0JhQ/CpSKYiq34E= 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 Tue, 2025-01-14 at 18:00 +0100, Michal Hocko wrote: > On Tue 14-01-25 11:51:18, Rik van Riel wrote: > > On Tue, 2025-01-14 at 17:46 +0100, Michal Hocko wrote: > > > On Tue 14-01-25 11:09:55, Johannes Weiner wrote: > > >=20 > > > > charge_memcg > > > > mem_cgroup_swapin_charge_folio > > > > __read_swap_cache_async > > > > swapin_readahead > > > > do_swap_page > > > > handle_mm_fault > > > > do_user_addr_fault > > > > exc_page_fault > > > > asm_exc_page_fault > > > > __get_user > > >=20 > > > All the way here and return the failure to futex_cleanup which > > > doesn't > > > retry __get_user on the failure AFAICS (exit_robust_list). But I > > > might > > > be missing something, it's been quite some time since I've looked > > > into > > > futex code. > >=20 > > Can you explain how -ENOMEM would get propagated down > > past the page fault handler? > >=20 > > This isn't get_user_pages(), which can just pass > > -ENOMEM on to the caller. > >=20 > > If there is code to pass -ENOMEM on past the page > > fault exception handler, I have not been able to > > find it. How does this work? >=20 > This might be me misunderstading get_user machinery but doesn't it > return a failure on PF handler returing ENOMEM? I believe __get_user simply does a memcpy, and ends up in the page fault handler. It does not access userspace explicitly like we do with functions like get_user_pages. --=20 All Rights Reversed.