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Mon, 16 Mar 2026 12:31:58 -0700 (PDT) MIME-Version: 1.0 References: <20260314051632.17931-1-kanchanapsridhar2026@gmail.com> <20260314171150.fd6a80a8f51a5390144d20d6@linux-foundation.org> In-Reply-To: From: "Kanchana P. Sridhar" Date: Mon, 16 Mar 2026 12:31:46 -0700 X-Gm-Features: AaiRm50uHztc3hCRDyQop5B6Uy8frGI_0E3Rv6hXqHswNBPf-6R2AC5AIzYdFn0 Message-ID: Subject: Re: [PATCH 0/2] zswap pool per-CPU acomp_ctx simplifications To: Yosry Ahmed Cc: Andrew Morton , hannes@cmpxchg.org, nphamcs@gmail.com, chengming.zhou@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, herbert@gondor.apana.org.au, senozhatsky@chromium.org, "Kanchana P. Sridhar" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: ojmpo9g9msrja3wi4cjpdbxe9duwabkq X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: B719C4000C X-HE-Tag: 1773689519-237171 X-HE-Meta: U2FsdGVkX185QZcqMaqrpWltI7bMRApDpq9Lh5uQoXGjZyTDLB5YfY8ed0ax26xcm3ZkHBJ53eM/4MdWeHnDx/qAXH3v7BM5Rldilr1a2rE3MVravrYMJAn2XH/2ay0U8Rr48/vXca3U0bIAxc1X6NKxYWLZlGWK2LIODBT3KIImjh/bvMXjprr21/ECjg1i94jheDWmbvVRL+Zd0csDwAdnX4F2mnHpu/EtNeTqzCZuad+7awPg8Ba4dUQiIjvE7Ia3GzkUm2RIj27qA0bL+CMX/mD4hFUa/vT+FBfQ5Mcy9lq3BgEObo9fCNjCQE7CI8nf8Zfr8FU5c/mzaYK3wKRPgquPIuBVB9m9ZO29QA5O+gWC2nbxYR3o9RaOumpDw3Rc7wCKD1lSs+O1IIcobGlTXHHr4vV1S4YYbFiEsNWWIcqICN3+N13BuRz1e/aSOmNTnMdFifzigx2yzzDYb5ZtMsMvPJ35Ch1mhUS06EzVhePrLPuwYiqcs3yzqfeixgujTv0GIEYnr8P7n1JWPRA1/AD//yHWZPoCbCEDVqf2KP4iRm6hhAXr4mzu5L3yoNo4GAl177vj3Lvz3NAAuRGrRBm9kAe/dedT8A/4eVT0XSmK8jKS2YsM9i5t1PyxG5QmBVLvaHOTXv7c2PGzdTLQ0E4oXOoLNWLQAYWBc4oXnxNw6TWaAwKUEjMMjhOAtd/sYtoZTsmNzEntKRk+ELmXTMccw+2FMnnrGZ4yv/ya0ff6YDcJGO/MPdsfwnWWPx4/ikuVDRD42c0rLxxRtXWEC93vyK/+3V/G39u9nVW6RGQAPMtPmPnDf2Aqi76K2mwR17NtYPleRygWpxz6gBbMLo8Dd1C8vZuuBasn7gyAufJfT8x7cSW46DZN6rEnVZoBkEJjvbZNsXRpnB0fBI6Za6dLb/3+/FRfOVzXV6kA+3blx7pcxB2MGc7LRJyQfzYoGgFacMS21tYKk5z MnYXmvuu 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 16, 2026 at 12:24=E2=80=AFPM Yosry Ahmed wro= te: > > On Mon, Mar 16, 2026 at 12:21=E2=80=AFPM Kanchana P. Sridhar > wrote: > > > > On Mon, Mar 16, 2026 at 11:30=E2=80=AFAM Yosry Ahmed = wrote: > > > > > > > > > If the maintainers think future-proofing is beneficial, I would= need > > > > > > to handle the PTR_ERR(NULL) which would send a false success st= atus. > > > > > > If we don't think we need to handle a future NULL return from > > > > > > crypto_alloc_acomp_node(), then I don't think this change is ne= eded. > > > > > > We could leave it as IS_ERR(acomp_ctx->acomp). I would like to = get the > > > > > > maintainers' inputs on how to proceed. > > > > > > > > > > > > > > acomp_ctx->req =3D acomp_request_alloc(acomp_ctx->acomp); > > > > > > > > - if (!acomp_ctx->req) { > > > > > > > > + if (IS_ERR_OR_NULL(acomp_ctx->req)) { > > > > > > > Is this change necessary for acomp_request_alloc()? > > > > > > > This function strictly returns NULL on allocation failure, no= t an error > > > > > > > pointer. Changing this to IS_ERR_OR_NULL() obscures the actua= l API contract > > > > > > > without providing a functional benefit. > > > > > > > > > > > > As of now, acomp_request_alloc() returns a valid "req" or NULL = in case > > > > > > of an error. Same question as above. The only benefit would be = making > > > > > > the code more robust to handle changes in the acomp API in futu= re. > > > > > > > > > > For this one, do we need to do IS_ERR_OR_NULL() in acomp_ctx_deal= loc() > > > > > to begin with? If acomp_request_alloc() only returns NULL, maybe = that > > > > > should also be a NULL check? > > > > > > > > This one is debatable, since acomp_ctx_dealloc() is intended to > > > > replace zswap_cpu_comp_dead(), which has the IS_ERR_OR_NULL(). I th= ink > > > > replacing this with IS_NULL(req) makes sense, but would like to > > > > confirm with you if changing existing behavior is Ok. > > > > > > I think it's fine as long as acomp_request_alloc() never returns an > > > error. Maybe do it in a separate patch first, change IS_ERR_OR_NULL() > > > to a NULL check in zswap_cpu_comp_dead(), with the reasoning explaine= d > > > in the changelog, to avoid hiding that change within the bigger patch= . > > > > Sounds good. > > > > > > > > Actually looking at zswap_cpu_comp_dead(), is the IS_ERR_OR_NULL() > > > check on acomp_ctx also misleading? Should that also just be a NULL > > > check? > > > > Even a NULL check would be redundant in this case, per my > > understanding, because if the alloc_percpu() call in > > zswap_pool_create() had failed, pool creation would have failed. > > > > I think a NULL check on the acomp_ctx would still be a good idea, just > > in case, since this is all part of CPU hotplug. I agree, we don't need > > an IS_ERR() check on acomp_ctx. > > So I think we do one patch to convert both IS_ERR_OR_NULL() to NULL > checks, and then the current patch 1, right? Yes.