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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kefeng Wang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ron Economos Subject: Re: [PATCH v2] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release() Date: Tue, 24 Feb 2026 18:54:40 -0800 Message-ID: <20260225025440.63897-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260225022853.2347732-1-ziy@nvidia.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: a8hfn67znd6yptrurpoh6f66q1wxnuzq X-Rspam-User: X-Rspamd-Queue-Id: 83EEE180002 X-Rspamd-Server: rspam01 X-HE-Tag: 1771988084-945003 X-HE-Meta: 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 eJowNXYQ +VoPuEGtoP9EnBS3aWvbVLgCoIdY/kqWznVgKPyiL2PDR9Hm5rAAPMJAICihZUz9wk3I+LZ2ZzMg2uF1mrlTQlxp4gTS+bYBNC0kA+RhUen4LmzWFe6c4oUs74Qt5tOsp5snMorHVf0z4LPBskImn7pOkFwycvn9xkupLju1Cx0riArRkuS7D4uHKuEImOOXZnwBhPe2bHKpcJLoCnLV6hw0EQzMaGCT043NhYeBTlxhXDzN56xTt88z3R0cKYiT2N09zIZdLzqgschDym2A9aNLDJIpqqYXdt7PiourzWGJAJ+OuBKYjbMHNBxh0PDH5em1QZcheRgX+jlMDGyKFOYbIy1bPkvCs1rU5ct31cslnk4VCBOCEpbdwfSsEjPsqEKYl Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 24 Feb 2026 21:28:52 -0500 Zi Yan wrote: > When CONFIG_DEBUG_VM is not set, VM_WARN_ON is a NOP. Putting any statement > with side effect inside it is incorrect. Collect all put_page_testzero() > results and check the sum using WARN instead after the loop. > > Fixes: 9bda131c6093 ("mm: cma: add cma_alloc_frozen{_compound}()") > Reported-by: Ron Economos > Closes: https://lore.kernel.org/all/1b17c38f-30d3-4bb4-a7e1-e74b19ada885@w6rz.net/ > Suggested-by: Kefeng Wang > Signed-off-by: Zi Yan > --- > >From V1: > - Collect all put_page_testzero() results and do a single WARN after the > loop. > > mm/cma.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/cma.c b/mm/cma.c > index 94b5da468a7d..ea540d3f473c 100644 > --- a/mm/cma.c > +++ b/mm/cma.c > @@ -1013,6 +1013,7 @@ bool cma_release(struct cma *cma, const struct page *pages, > unsigned long count) > { > struct cma_memrange *cmr; > + unsigned long ret = 0; > unsigned long i, pfn; > > cmr = find_cma_memrange(cma, pages, count); > @@ -1021,7 +1022,9 @@ bool cma_release(struct cma *cma, const struct page *pages, > > pfn = page_to_pfn(pages); > for (i = 0; i < count; i++, pfn++) > - VM_WARN_ON(!put_page_testzero(pfn_to_page(pfn))); > + ret += put_page_testzero(pfn_to_page(pfn)); So, 'ret' will be incremented when put_page_testzero() returns 'true', right? Shouldn't 'ret' be inceremented only when put_page_testzero() returns 'false'? > + > + WARN(ret, "%lu pages are still in use!\n", ret); This will trigger the warning even if CONFIG_DEBUG_VM is unset. I'm fine with the changed behavior, but I'm curious if that is the real intention of this revision. Thanks, SJ [...]