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Shutemov" To: Yang Shi Cc: hughd@google.com, ziy@nvidia.com, kirill.shutemov@linux.intel.com, minchan@kernel.org, naoya.horiguchi@nec.com, wangyugui@e16-tech.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [v4 PATCH 1/2] mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split Message-ID: <20210527105214.jqbmyufsdtb5vdhm@box> References: <20210526201239.3351-1-shy828301@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210526201239.3351-1-shy828301@gmail.com> X-Rspamd-Queue-Id: 4F64EE000804 Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=shutemov-name.20150623.gappssmtp.com header.s=20150623 header.b=aim5QEUL; dmarc=none; spf=none (imf05.hostedemail.com: domain of kirill@shutemov.name has no SPF policy when checking 209.85.208.170) smtp.mailfrom=kirill@shutemov.name X-Rspamd-Server: rspam03 X-Stat-Signature: hc3zt9jbdgq36nt793fsjatztth8bpoh X-HE-Tag: 1622112722-998647 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 Wed, May 26, 2021 at 01:12:38PM -0700, Yang Shi wrote: > When debugging the bug reported by Wang Yugui [1], try_to_unmap() may > fail, but the first VM_BUG_ON_PAGE() just checks page_mapcount() however > it may miss the failure when head page is unmapped but other subpage is > mapped. Then the second DEBUG_VM BUG() that check total mapcount would > catch it. This may incur some confusion. And this is not a fatal issue, > so consolidate the two DEBUG_VM checks into one VM_WARN_ON_ONCE_PAGE(). > > [1] https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/ > > Reviewed-by: Zi Yan > Signed-off-by: Yang Shi For both patches: Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov