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charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 12BBD16000A X-Stat-Signature: 5rh4fifq75fuidwibo5hmohgsa1xb5pb X-Rspam-User: X-HE-Tag: 1674748781-260115 X-HE-Meta: U2FsdGVkX19sUx0aWFaUMFw1NM5l/lnuJ5JKj070qN6qSTLQLcQdz58WKVd+xvUmo5f2qpobGzpMYBttKvHVpmggUTxbP+lpb84bpNhUcRGMGqhWAuJFz3pZU3BBmpVvT0I2qTUfEPpgMqcirWC00QQnl62y/cC7NZOHCn2o8h4Uop09zeP7jDxKeatpIqGmsFNorFIk3TS93vHpb94ohFohYDUt2sJRvrse6/6UEoDnV5JXTEYULysOtwNky6MWM7BWssa69KHFYI9rD4kQVnoFVgRfrTE+71/0vfRD4l5rwlLAY5nWYS4Cyu7RM6719l0JtAyQ91aNDGk3KLYK3J9xcOWHbbHbEbTeoDsKKTS6JjsMIaUwgXZInEh4vELpYokEhb+28VRdhroWWHP6Vvmx/Wk7gfUeoGI1E9L4TWQTItjeFteZeIu5UizJP/ogsfz4ra5dVwziwKtNUyFpa5azUq8YbF1fEXvyhEdGS+Ah9OimXQanAZE1Qh4ItYon1/rbXMNmikzG4iaO6Y0HCWWbvgxxkPt67Wl3gP1+668i7Gb75q2GBkwQMC7Hz58l9yh7B6Ez+Qqyme5ksSa15a8cnYLJY+S+D3lQEBOJ1J+0ox3ODjAaGq0lQraSu2J87U1YBZeakWsFLHGVQQr2AGLu7qQxy1+/4VojAKK8FTJjDF0txcsu9GyGi93bA7CY76Q3QwCaYD08W5TAC4qTCxPRdC+a5009DP9ahUFToSTL7D+w+LGmXZk6RDLRW/7+tMj/emcev8GbHYm/yTxGDA7wZqi+kXa7dWAdvKJsetjw6Fj66lQnGu5mQRH73lfULnYh6fVFxyXwjqrOdooXpZcr1812MPdfW7wR6DV/CEWmtv9N0PUDsyhSFsQbm9phSfncevpXV8I9wzFk5aPnNy6PDVAztLKynZhmrL+13tQvwFEoU+1CObQgIgXdOyueSAtBOfAqvata2fud/L2 k8igS0K5 NDhX51OrbeJkfV62+Osyc3MLNstpAM8EMDL43oJ7NTNmkNxrxe0UhyZem4VMr/RhpP+jb5DVJ3h6LMaLBZzWEb4Ing6LQcl7EFGnOxVZNFPKzPsM6rz5X3Yi5U3oh1IEGyt4B51SyFhL8ahW7JM48iNpsK9Gb1YSGk+HRMe+id6cgJP/UOTkBaJZ6hz+8FEPKl6bIMeZQzg/C9VeEkXXJqI+G2In+CJuUCOnALjmY7EEVNU0G2u9dlvPhWYBhuPxJTBiPElNZdQXzQXZasGaWierNmAOMJn9+htDYja/UyGBA7SK+s8wYYOyedX9UT0jUi/QUOPSV3lJMeBudiPlddv0FH+7Z6GMtWyloGwO4nlR3LQuuRTzl4fdUDZij0qtE6Muc 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: On Thu, Jan 26, 2023 at 3:52 AM Mel Gorman wrote: > > On Wed, Jan 25, 2023 at 05:34:49PM -0800, Andrew Morton wrote: > > On Wed, 25 Jan 2023 16:50:01 -0800 Suren Baghdasaryan wrote: > > > > > On Wed, Jan 25, 2023 at 4:22 PM Andrew Morton wrote: > > > > > > > > On Wed, 25 Jan 2023 15:35:48 -0800 Suren Baghdasaryan wrote: > > > > > > > > > Convert vma assignment in vm_area_dup() to a memcpy() to prevent compiler > > > > > errors when we add a const modifier to vma->vm_flags. > > > > > > > > > > ... > > > > > > > > > > --- a/kernel/fork.c > > > > > +++ b/kernel/fork.c > > > > > @@ -482,7 +482,7 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig) > > > > > * orig->shared.rb may be modified concurrently, but the clone > > > > > * will be reinitialized. > > > > > */ > > > > > - *new = data_race(*orig); > > > > > + memcpy(new, orig, sizeof(*new)); > > > > > > > > The data_race() removal is unchangelogged? > > > > > > True. I'll add a note in the changelog about that. Ideally I would > > > like to preserve it but I could not find a way to do that. > > > > > > > Perhaps Paul can comment? > > > > I wonder if KCSAN knows how to detect this race, given that it's now in > > a memcpy. I assume so. > > data_race() is just wrapping an expression around > __kcsan_[en|dis]able_current and ensuring the expression is evaluated once > and returning the correct type. I believe the following should be sufficient. Thanks for the suggestion, Mel! I'll try that. > > diff --git a/kernel/fork.c b/kernel/fork.c > index 9f7fe3541897..1b30ee568e02 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -472,7 +472,7 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig) > * orig->shared.rb may be modified concurrently, but the clone > * will be reinitialized. > */ > - *new = data_race(*orig); > + data_race(memcpy(new, orig, sizeof(*new))); > INIT_LIST_HEAD(&new->anon_vma_chain); > dup_anon_vma_name(orig, new); > } > > I don't see how memcpy could automagically figure out whether the memcpy > is prone to races or not in an arbitrary context. > > Assuming using data_race this way is ok then > > Acked-by: Mel Gorman Thanks! > > -- > Mel Gorman > SUSE Labs