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Howlett" Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, christophe.leroy@csgroup.eu, jeffxu@chromium.org, jeffxu@google.com, linux-kernel@vger.kernel.org, npiggin@gmail.com, oliver.sang@intel.com, pedro.falcato@gmail.com Subject: Re: [PATCH 1/4] mm: Add optional close() to struct vm_special_mapping In-Reply-To: References: <20240807124103.85644-1-mpe@ellerman.id.au> Date: Mon, 12 Aug 2024 18:22:44 +1000 Message-ID: <87jzgm8817.fsf@mail.lhotse> MIME-Version: 1.0 Content-Type: text/plain X-Rspam-User: X-Stat-Signature: pscfau45mnu3b8ofn4p6ixye8ceozrnm X-Rspamd-Queue-Id: 43A0810000A X-Rspamd-Server: rspam11 X-HE-Tag: 1723450967-407710 X-HE-Meta: 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 qDFX6klz 9JxiT3xvvze+qH1IrdU0FC9XcXYAwCBflH1FkAdEujhd6nDg6ZMXqD/i+J4tPMFt2Ml5OiMG5dSPO2Hrd71wcmnaaNDOMDbxmFaNObqxhzBINflWohvlucVtfjgtIK4aqp2LuRY+Hw1lkMuyA3rZfp+RFy3V6lMflUG/a6gNE+3m567Fb6eBY/PZ/Y0S4gfaPKCC6rRpHoY3HdanSgYXK+dUTM49bKGZmISZZu44HZqBe5g7+99OMBf2eMNZH296d+SgS39wN2I7JvD3I1IgoczME5N2YFfDvyU5b3wg+bnKhw6gLQTQt1SKaCFqcQLVX90CH4x+IulvB1IOTQitea/OC7bI9M58SjVjuQq7YzzshQSLU6XxZtuZHrsO4aP/FwwGZ 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: "Liam R. Howlett" writes: > * Michael Ellerman [240807 08:41]: >> Add an optional close() callback to struct vm_special_mapping. It will >> be used, by powerpc at least, to handle unmapping of the VDSO. >> >> Suggested-by: Linus Torvalds >> Signed-off-by: Michael Ellerman >> --- >> include/linux/mm_types.h | 2 ++ >> mm/mmap.c | 3 +++ >> 2 files changed, 5 insertions(+) >> >> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h >> index 485424979254..ef32d87a3adc 100644 >> --- a/include/linux/mm_types.h >> +++ b/include/linux/mm_types.h >> @@ -1313,6 +1313,8 @@ struct vm_special_mapping { >> >> int (*mremap)(const struct vm_special_mapping *sm, >> struct vm_area_struct *new_vma); > > nit: missing new line? Ack. >> + void (*close)(const struct vm_special_mapping *sm, >> + struct vm_area_struct *vma); >> }; >> >> enum tlb_flush_reason { >> diff --git a/mm/mmap.c b/mm/mmap.c >> index d0dfc85b209b..24bd6aa9155c 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -3624,6 +3624,9 @@ static vm_fault_t special_mapping_fault(struct vm_fault *vmf); >> */ > > The above comment should probably be expanded to explain what this is > about, or removed. I expanded it slightly, happy for others to wordsmith it further. >> static void special_mapping_close(struct vm_area_struct *vma) >> { >> + const struct vm_special_mapping *sm = vma->vm_private_data; >> + if (sm->close) >> + sm->close(sm, vma); > > Right now we have the same sort of situation for mremap calls on > special: we have a call to the specific vma mremap() function. > ... > So, are we missing an opportunity to avoid every arch having the same > implementation here (that will evolve into random bugs existing in some > archs for years before someone realises the cloned code wasn't fixed)? > Do we already have a fix in ppc for the size checking that doesn't exist > in the other archs in the case of mremap? I took this as more of a meta comment/rant :) Yes I agree the implementation should eventually be generic, but this series is just about moving the existing powerpc behaviour from arch_unmap() into this hook. cheers