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Tue, 02 Feb 2021 17:31:07 -0800 (PST) Received: from google.com ([2620:15c:211:201:1502:84f8:ffc3:45b]) by smtp.gmail.com with ESMTPSA id o20sm212189pgn.6.2021.02.02.17.31.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Feb 2021 17:31:06 -0800 (PST) Date: Tue, 2 Feb 2021 17:31:03 -0800 From: Minchan Kim To: Suren Baghdasaryan Cc: sumit.semwal@linaro.org, akpm@linux-foundation.org, hch@infradead.org, lmark@codeaurora.org, labbott@redhat.com, Brian.Starkey@arm.com, john.stultz@linaro.org, christian.koenig@amd.com, cgoldswo@codeaurora.org, orjan.eide@arm.com, robin.murphy@arm.com, jajones@nvidia.com, hridya@google.com, sspatil@google.com, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 1/2] mm: replace BUG_ON in vm_insert_page with a return of an error Message-ID: References: <20210203003134.2422308-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210203003134.2422308-1-surenb@google.com> 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 Tue, Feb 02, 2021 at 04:31:33PM -0800, Suren Baghdasaryan wrote: > Replace BUG_ON(vma->vm_flags & VM_PFNMAP) in vm_insert_page with > WARN_ON_ONCE and returning an error. This is to ensure users of the > vm_insert_page that set VM_PFNMAP are notified of the wrong flag usage > and get an indication of an error without panicing the kernel. > This will help identifying drivers that need to clear VM_PFNMAP before > using dmabuf system heap which is moving to use vm_insert_page. > > Suggested-by: Christoph Hellwig > Signed-off-by: Suren Baghdasaryan > --- > mm/memory.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/memory.c b/mm/memory.c > index feff48e1465a..e503c9801cd9 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1827,7 +1827,8 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, > return -EINVAL; > if (!(vma->vm_flags & VM_MIXEDMAP)) { > BUG_ON(mmap_read_trylock(vma->vm_mm)); Better to replace above BUG_ON with WARN_ON_ONCE, too?