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b=nv4/MaqF5xA2NXG/j2hRDkX5Yy2qSd+HYWjSA9aN1U1TQHUSsqKEPfOB272mlQsZd E6e6yuwSzEJmVMCRNqHyM+hrjNamWjNwEAkFiz0Z7Bb4NDOpgM0LyW4G4qhPewZZYK diPcsxDQqNFFi5s1tWJFTMiRWn1BiOkcug+ssiLhyHL5l/x0ce4pfgwYjlX47u58QH Jikc1Rc5fqLmol2qAwE/fvc4Fwm0ZK3A+AbimX4gbIuGvhRSZuba2LAslfBoqQCpIr JBHdRhkY7VqjRypsRJnDcadGJfYM4LPnUKoFploHb5NM5K1mPd/okks1GN/K9DqKY7 FlibPEnsFLfpA== From: SeongJae Park To: Aaron Yang Cc: SeongJae Park , linux-mm@kvack.org, damon@lists.linux.dev Subject: Re: [PATCH v2] mm/damon/paddr: initialize 'folio' variables to NULL for safety and clarity Date: Sun, 4 Jan 2026 15:07:33 -0800 Message-ID: <20260104230735.67401-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260104013255.16962-1-yangqixiao@inspur.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Stat-Signature: cyzg3afnxi6dbc854ro6qbo6shydnq39 X-Rspam-User: X-Rspamd-Queue-Id: 84DF9140013 X-HE-Tag: 1767568060-170743 X-HE-Meta: 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 3kqNdCUe zDjoRC2EdhGQiKJN1IVQfKhSfzvZ3+WlLtLDOb2ksdbZJTlCduGX9D32IYrbnafGB12DClgvi5TGVeTGzjb/mQL9O6NrxOPHK/NQbwce+vPaAfk6JI5mdaPq4o63RIl4G2jFtJqRL2W8BdOgxq0NYbq9ZTQlgdDZybVrmWqY2KNocdx9byatuXfHJBo0LknORc4Ioj/tC73vXz9nsJY02sHwoeN4/kZcgkVDOk8QwSpurRtTLNC9Q8lTj1ixJO0aeUG6k936OsDF/7aK6N+I5z2queHwFeDJPebQYqQjJ8MVQZeuNvKoSf1S76g== 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 Sun, 4 Jan 2026 09:32:55 +0800 Aaron Yang wrote: > In damon_pa_mark_accessed_or_deactivate(), damon_pa_pageout(), > damon_pa_migrate(), and damon_pa_stat(), the local variable 'folio' is > declared but not initialized. > > Initialize 'folio' to NULL to: > - Follow kernel convention: uninitialized pointers should be > explicitly NULL Technically speaking, this is required only if it avoids unsafe code such as use of the uninitialized pointers. Because zero-length DAMON region is not allowed, this is not the main reason of this change that we discussed on v1 of this patch [1]. > - Improve code readability and maintainability This is the main goal of this change. This change allows readers be able to know the function is safe, without have to know the fact that length DAMON regions is disallowed. > - Provide safe fallback (NULL assignment to s->last_applied is harmless > and callers check for NULL before dereference) > > Signed-off-by: Aaron Yang Because my above comments are for only clarifications of minor details: Reviewed-by: SeongJae Park > --- FYI, this is a good place to summarize changes you made from the previous version. For more details, please refer to the doc [2]. [1] https://lore.kernel.org/20251231055737.73325-1-yangqixiao@inspur.com [2] https://origin.kernel.org/doc/html/latest/process/submitting-patches.html#commentary Thanks, SJ [...]