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b=PEoX88doD61Dy5rzbllW/FcIDDbOq4DAALPWfQIeJTitzhFY2rnYcoTHy0BiUFznO Nxxa6CD3mv9ZnfYYdheKxsLrCafA3LYDp3mvc9ybz1wpI8eydhTIYMP7+NyqkcqcMq tlq6cyrx73qwfvRaHno0ByQ30zCqG1kzrSha6zZhqfg4qxQNPwvbWrEMvlZRt5Fzi0 a9dg7hqmHoQ1llyDSRfJ8ygnA9rOwuo9fqZrnVbkoDCr54PClhxn/7A6iXqSqbQXp9 jkQBtAoJI5gIWbbRBgeo6uFprzmZpvR8qW2vN4dkJosfY5Kh9OMnW9rNtpx0b0KihZ 6FKLJWX/Dn76Q== Date: Tue, 15 Sep 2026 21:37:51 +0300 From: Mike Rapoport To: Heiko Carstens Cc: Vineeth Vijayan , Peter Oberparleiter , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Vlastimil Babka , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 06/13] s390/cmf: Use kmalloc() for the CMB area Message-ID: References: <20260910-s390-cio-ready-v2-0-e931086fdde1@kernel.org> <20260910-s390-cio-ready-v2-6-e931086fdde1@kernel.org> <20260914175952.14910Fc6-hca@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260914175952.14910Fc6-hca@linux.ibm.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 0224C40006 X-Stat-Signature: xpozf1nx5y6b9p8rf1ruxz3bhfxebecz X-Rspam-User: X-HE-Tag: 1789497477-826905 X-HE-Meta: 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 bWHA44dK LTd7/kcnHZdF4FdVCM4Ru9YI00+DdfxyL5Vin+GztkhgMRZcfZHbgTLBmjdzkE1ButjUaw8a0FJHDOkO2EDggJEfBudZo+oyuHapUTVfumI2EYSwnu3cbhEsG1XhPEdhgHREvwC45ZJMkhSG9XQwnsBiygFcePVxdBrQ5zJ5JfHYLPTtu8/GMUuYKYefu83bAoDzlmkgzEbV2tjVe24dnWN+nktkJVr3DneK3T/5/NKlSD5mSAHBOcjcpyNhoYkq68b4R Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 14, 2026 at 07:59:52PM +0200, Heiko Carstens wrote: > On Thu, Sep 10, 2026 at 02:00:08PM +0300, Mike Rapoport (Microsoft) wrote: > > alloc_cmb() allocates the channel measurement block area shared by > > devices using the basic channel measurement format. > ... > > The measurement block origin must be 32-byte aligned. Each CMB is > > 32 bytes, so kmalloc() provides the required alignment without rounding > > the allocation to a power-of-two number of pages. Reject an empty area > > before allocating it. > > > > Replace use of __get_free_pages() with kmalloc() and free_pages() with > > kfree(). > ... > > spin_unlock(&cmb_area.lock); > > - mem = (void *)__get_free_pages(GFP_KERNEL, get_order(size)); > > + mem = kmalloc(size, GFP_KERNEL); > > spin_lock(&cmb_area.lock); > > > > if (cmb_area.mem) { > > /* ok, another thread was faster */ > > - free_pages((unsigned long)mem, get_order(size)); > > + kfree(mem); > > } else if (!mem) { > > /* no luck */ > > ret = -ENOMEM; > > This is the only patch which made me raise an eyebrow, since the allocated > area is smaller. But it looks all good according to the architecture. > Since the allocation changed anyway, it might also make sense to switch to > kzalloc() and get rid of the subsequent memset() (not in the context of the > above diff). I suppose separate alloc and memset() are there to save a couple of cycles when another thread is the first to allocate, no idea how important this is though :) I can send a patch on top if you'd like. > But... I doubt it is worth it to send yet another version just for this. > > The whole series looks good to me. Vineeth, Peter, any thoughts? -- Sincerely yours, Mike.