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b=aPnNWxOLX/2EAdhnjyuRKA8Nlsexqz1WmC/7jqh3O2Y/BclABN7gji3LdeMw1mZvr p1oWXKpRZQt/1MJPul0JJdklevQ3499S+wL3QahdzkXn9C7HptYifJeMwPWkxu/M/X CF5WIfNUJdb2YnKmi22VDhdjfUFDRRPaP215rEqfLiQ2a77fZuzIC0ZOxwZ/bMvW9/ lJG966Anm0SlqegQ8xOrEnwaLn1jmIsdwsxejU3JWXi7FcPNBLg3GHfOQ/AWtHZH5P u4UDWWhC8pIyoGLEJjnE6LBQnI/q+uIvsJxJgfgYpIf8JoJNsHAa0AQ8JaHfinep/J ARw+kNEtYQmbg== Date: Tue, 22 Oct 2024 10:50:18 -0700 From: Namhyung Kim To: Andrii Nakryiko Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , LKML , bpf@vger.kernel.org, Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, Arnaldo Carvalho de Melo , Kees Cook Subject: Re: [PATCH bpf-next 1/2] bpf: Add open coded version of kmem_cache iterator Message-ID: References: <20241017080604.541872-1-namhyung@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 21DB81C0012 X-Stat-Signature: gtow8zqfkpucmdyrq8nzsqebtjhpxf68 X-HE-Tag: 1729619401-251631 X-HE-Meta: U2FsdGVkX18cHm1tuLt+TKr01dvYlH9V8n9/v8UI+Ag0O32IPj08CYQgqy8fyGW7guxiOC01DxUNI1a0yPFedWZ6oK6ab9dzanldLho31C9T7B2TIwHijbb9B4/x2TIQzxl9AQmKKrezXV7EcRc7F0/NmO9AC4+x7lL/GY6+iBwM4Z3jd66GR/CmpOCnKjKj7shkOrMBXJMT2c3qKH8E8PEu3iTDzQxCWFLEP/xMWSPpLJTBD7gJ+5ILiYrgcMhizjlAmDpHO+/qFr2+tsnY4GvamTwgEB0KgQRPSP6d5V7i0eDNhlyXzVsXFcLcmpriWg14321qN0w5u5biWhsIYtBJL4csafV7eiiAGnUMOkl2I1390oHKOLWiX4W8M91bVNkkEcpXTMBU3BzKsLGRqsSUcM/E3Ue87Wzm8ISFIkyJH+PxokmC0yQtTQr9yBw98FTq7tLYGz6C3L6E+Qt+/4RbOR4e4Vkxmk0KEsLdfO415JBVjbkk7grkh+mIgPNeD5K6P72Qub19jBuR+kgCoGyfbXMGuI4mKREolrrr7DiQTCTbbbaD28AWV8nTWrs2oGwT7WgUCbKXIVFOmV6Lfkz5Uog9msvQiJwh8VO6gDOsDp6bZ4rCJYkuRHo2D7HA7gSWkFIvZL/Vv5FG6yp2svGTTiqt7Y6m2KHWz0wJOK+eugH34/dH2cVkhC/7z9SCIQlGEqH3ZnwqsJfyWg+VKQDywsx1YlJ7+/az8mVkTQkZWLQk/zjon/Sp8xfp0KM6XFm+v1x8njCxY1WN6BPQBDzqP6ym2g7jypr1EXfwEPRJqwNXp5jVxN6W+pvEo1aXAlKonWEayVZH8yR/NMoRTzYDJCIBUd1JSrKYATjtj4ij4H3nI0pqi8qULS2UfYn2m3vMY9r/IY0PX+aLZL/4CLfFYVU28P9RrxxRVcXrA8pEeCPuhkegf+rOD0DsvRQPL9/XsW9duL68tj81ygp GCgpK/vL Ev278/80Ed/aHaFisc3ET4kL7JPzC7Dcw2Iqa2NQOHw1laOhEYBLag/yNfOtDyX7nlYMHthEB8WOxYfoaCFniLpfu5E0UpI64zneS49H6luC/SXmeRR/FYyobGDFcUvYCknXlYfJQ2gBfLhlinDK6u8jDmGDYNKIO2h2EuYZkb7v3Hl73Eo0U9VccB8cZajxk8Vcw5MgHGNwXZ728e4L8JVuf+S1kpb14+lvdR2mwz9m4jUi7pODNo0B6yn2Uw2rVF3Bo2Z5pdzz5vt8iUOZBb2eOXFNXJddABuxGW+aDNosatJXkRQt59yFenbJi3iiLadhU/WMAnOa6wgvHFYH3dgG9XlaYKlwEGaQl/RHlzm5RHEDiuKkWoG415E6qE7JQMpjjZRWDGemMe8b4FvICqGY6PN1Hsp7MZX7Q 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: List-Subscribe: List-Unsubscribe: Hello, On Mon, Oct 21, 2024 at 04:32:10PM -0700, Andrii Nakryiko wrote: > On Thu, Oct 17, 2024 at 1:06 AM Namhyung Kim wrote: > > > > Add a new open coded iterator for kmem_cache which can be called from a > > BPF program like below. It doesn't take any argument and traverses all > > kmem_cache entries. > > > > struct kmem_cache *pos; > > > > bpf_for_each(kmem_cache, pos) { > > ... > > } > > > > As it needs to grab slab_mutex, it should be called from sleepable BPF > > programs only. > > > > Signed-off-by: Namhyung Kim > > --- > > kernel/bpf/helpers.c | 3 ++ > > kernel/bpf/kmem_cache_iter.c | 87 ++++++++++++++++++++++++++++++++++++ > > 2 files changed, 90 insertions(+) > > > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > > index 073e6f04f4d765ff..d1dfa4f335577914 100644 > > --- a/kernel/bpf/helpers.c > > +++ b/kernel/bpf/helpers.c > > @@ -3111,6 +3111,9 @@ BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL) > > BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY) > > BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE) > > BTF_ID_FLAGS(func, bpf_get_kmem_cache) > > +BTF_ID_FLAGS(func, bpf_iter_kmem_cache_new, KF_ITER_NEW | KF_SLEEPABLE) > > +BTF_ID_FLAGS(func, bpf_iter_kmem_cache_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLEEPABLE) > > +BTF_ID_FLAGS(func, bpf_iter_kmem_cache_destroy, KF_ITER_DESTROY | KF_SLEEPABLE) > > I'm curious. Having bpf_iter_kmem_cache_{new,next,destroy} functions, > can we rewrite kmem_cache_iter_seq_next in terms of these ones, so > that we have less duplication of iteration logic? Or there will be > some locking concerns preventing this? (I haven't looked into the > actual logic much, sorry, lazy question) It should be fine with locking, I think there's a subtle difference between seq interface and the open coded iterator. But I'll think about how to reduce the duplication. Thanks for your review! Namhyung