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[34.145.75.25]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-845a40ee417sm2715140b3a.40.2026.06.24.12.10.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2026 12:10:43 -0700 (PDT) Date: Wed, 24 Jun 2026 19:10:39 +0000 From: Samiullah Khawaja To: Pranjal Shrivastava Cc: Marek Szyprowski , Will Deacon , Jason Gunthorpe , Pasha Tatashin , Mike Rapoport , Pratyush Yadav , Alexander Graf , Robin Murphy , Kevin Tian , iommu@lists.linux.dev, kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Matlack , Andrew Morton , Vipin Sharma Subject: Re: [RFC PATCH 2/4] dma/pool: Add an API to check if DMA allocation is from pool Message-ID: References: <20260505002737.2213734-1-skhawaja@google.com> <20260505002737.2213734-3-skhawaja@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: On Mon, Jun 08, 2026 at 06:10:02PM +0000, Pranjal Shrivastava wrote: >On Tue, May 05, 2026 at 12:27:35AM +0000, Samiullah Khawaja wrote: >> DMA allocations can be done through DMA pools, add an API that can be >> used to check if an allocation is done from a pool. This will be used in >> the later commit during preservation of DMA allocation. >> >> Signed-off-by: Samiullah Khawaja >> --- >> include/linux/dma-map-ops.h | 1 + >> kernel/dma/pool.c | 13 +++++++++++++ >> 2 files changed, 14 insertions(+) >> >> diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h >> index 6a1832a73cad..6a0bc4ea2467 100644 >> --- a/include/linux/dma-map-ops.h >> +++ b/include/linux/dma-map-ops.h >> @@ -216,6 +216,7 @@ struct page *dma_alloc_from_pool(struct device *dev, size_t size, >> bool (*phys_addr_ok)(struct device *, phys_addr_t, size_t)); >> bool dma_free_from_pool(struct device *dev, void *start, size_t size); >> >> +bool dma_is_from_pool(struct device *dev, void *start, size_t size); >> int dma_direct_set_offset(struct device *dev, phys_addr_t cpu_start, >> dma_addr_t dma_start, u64 size); >> >> diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c >> index 2b2fbb709242..32ce4d6d7683 100644 >> --- a/kernel/dma/pool.c >> +++ b/kernel/dma/pool.c >> @@ -307,3 +307,16 @@ bool dma_free_from_pool(struct device *dev, void *start, size_t size) >> >> return false; >> } >> + >> +bool dma_is_from_pool(struct device *dev, void *start, size_t size) > >Do we need struct device here? It seems unused? > >Nit: we only ever pass 0 gfp_flags to dma_guess_pool, should we instead >name it: dma_is_from_atomic_pool() to be more accurate? dma_guess_pool() goes through all of them when passing 0, look at the prev logic inside it and how it is used by the dma_free_from_pool(). But you are right they are all atomic, but semantically we want to check whether it is part of any pool so lets keep it as is. WDYT? > >> +{ >> + struct gen_pool *pool = NULL; >> + >> + while ((pool = dma_guess_pool(pool, 0))) { >> + if (!gen_pool_has_addr(pool, (unsigned long)start, size)) >> + continue; >> + return true; >> + } > >Nit: The loop looks slightly ugly, can we have: > >struct gen_pool *pool; > >for (pool = dma_guess_pool(NULL, 0); pool != NULL; pool = dma_guess_pool(pool, 0)) { > if (gen_pool_has_addr(pool, (unsigned long)start, size)) > return true; >} It is a basically a copy dma_free_from_pool() without the free part, so keeping the style consistent. > >> + >> + return false; >> +} >> -- >> 2.54.0.545.g6539524ca2-goog >> > >Thanks, >Praan Thanks, Sami