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Tue, 22 Apr 2025 14:09:13 +0800 From: Enze Li To: SeongJae Park Cc: akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org Subject: Re: [PATCH] mm/damon/core: Initialize sampling_addr in damon_new_region() In-Reply-To: <20250421165526.8517-1-sj@kernel.org> (SeongJae Park's message of "Mon, 21 Apr 2025 09:55:25 -0700") Message-ID: <87plh46gf1.fsf@kylinos.cn> References: <20250421165526.8517-1-sj@kernel.org> Date: Tue, 22 Apr 2025 14:09:09 +0800 MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: 19A771C0006 X-Stat-Signature: wtj94kju1abwo4sixadofgdny1ujhh7r X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1745302160-753622 X-HE-Meta: U2FsdGVkX196bFta9/tgLFp9XHwNykUtEqLAtxgPPe6zKCA0rdKuSHUsIXU6mVm+C6jVOoNw+Zc0Lgj6LzvdoI+PCL2QGXz9XpccShScWBZWDNsqlJiwy+XaqfonMBJ1MAXsLhwIf7oAa8fO/4o/GufJFFnHlQPNd9WROwkjYt4c9hbw/hS0+YpSSz5/Tw2CUoMwVkXib5ikRcoYAsXqGYh/3zWZ+EihhVT6ZDtc2b1Csx2Mjhck1BgechnfOQ9gA9G7yO1Ehvpv8w7anGQF0hj0Tb3h96a+za5MxdGKTmjk0T+DibRBgSEWaMsk0CUwmKZBy3zkyVjBEtS557oFmJl9rbgFHsOnakFdqHrKj3qdo6SkvbEyVihDPN1oyUcSP9nDLwv2xP9rxFH1yxzsFG2jl4XxLp1l7TwPzVEZNFF/1eMYYmMdo0e3kbcsgWTCmZE4hNwqfL35H4E19UG5+GizAqHv0crmQFTS/C3kHBnDwNu0a8yeuIl6VINdDd4qEgYckI3BAr9nCB19S9LkcTlIrvOgHPVMXnyIQ/LJWB9mXW5No5gCQf7DtUZKPoN5FeuhZnZ6fp1YdwFl3C+IgrOJ4hXad8ci0hSq+Pe5xotrgmIRHXmvXhpSuW2QAWFVFklG/eTF5OF0JgZR2EEzw4OVdu+VpGjHzBuFtu9FhFmwAm+tnG6GJ9wz7KzpazzaBLfMt4VFUTYFasT5DZYqzrqgcZx+bIUk8nm2xydw3MIZIyX0SzExEeBDGi6L7LcXSs0ii1FYzmOlQy+V6DnJAYOPxG54o0JC475EfJw4VVpdZGyeLLTzWld4ZTfso+K9qk2On88e86CJCJYy+DgxfLJA4u80l7koZzLh200sIywbKBPj7f86TzRMjvhzPdHBsVdbWv0/m1ib1/SIg4ammOThRe1kLr1kkxyuMVhjtqPLUjy0DnV+MJ2Wc+lEVhljXBXo/TJ7YlEY4bXZs4A WuPtdbnR QQwGwYUfKX2u/1DIJyH3wNaKKnavO6l+MAcNAkMzZiLZ7Pg8L6Bz7Gv871hnl154C8Ry5l6TN15KRh5o= 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: Hi SeongJae, Thanks for your review! When examining this function, I instinctively verified the initialization of all member variables. Personally, I'm quite partial to the practice of initializing all fields when creating an object - though I fully acknowledge that initializing sampling_addr may currently have no practical consequences. This patch serves purely as a preventive measure, so please don't hesitate to drop it if you consider it superfluous. Best Regards, Enze On Mon, Apr 21 2025 at 09:55:25 AM -0700, SeongJae Park wrote: > On Mon, 21 Apr 2025 11:39:19 +0800 Enze Li wrote: > >> Since sampling_addr is used across vaddr and paddr modules, initialize >> it in damon_new_region(). >> >> Signed-off-by: Enze Li >> --- >> mm/damon/core.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/mm/damon/core.c b/mm/damon/core.c >> index f0c1676f0599..d197a5e3901c 100644 >> --- a/mm/damon/core.c >> +++ b/mm/damon/core.c >> @@ -128,6 +128,7 @@ struct damon_region *damon_new_region(unsigned long start, unsigned long end) >> >> region->ar.start = start; >> region->ar.end = end; >> + region->sampling_addr = 0; >> region->nr_accesses = 0; >> region->nr_accesses_bp = 0; >> INIT_LIST_HEAD(®ion->list); > > I unfortunately cannot find why this is required. Is there a use case that > reads uninitialized sampling_addr or any problem that comes from the fact that > damon_new_regions() is not initializing the field? > > Only operations set implementations write and read damon_region->sampling_addr, > so I was thinking not initializing the field on the core layer is no problem. > I will be happy to be corrected if I'm missing something. > > > Thanks, > SJ > >> >> base-commit: 9d7a0577c9db35c4cc52db90bc415ea248446472 >> -- >> 2.43.0