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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1763272025; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=pjcLQP3ZDHp6twNylqR3Sw+tWbznJ8lJtAsn5ePnKEo=; b=DtT6Z7uXom4E8gHoH5aRVV7uhRz+4iJZKjbUcvcqaHBHo+26utaCCY1mmA63nsd6erQBlZ r3ABG1tGumY/eSOk6yt/5vi2G8s00magS6+VSTzs+aLc8QrG801HH8cUxRSO6VWjFECZUS xgmLQ3KSVIooFIPi0ntq4tkJaICmLyU= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 2B5B060183; Sun, 16 Nov 2025 05:47:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 76BC3C4CEF1; Sun, 16 Nov 2025 05:47:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763272024; bh=VhOMKlmPNnj++jPAfsYIirLTiTxgnvzCapK9dNUeqh4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=f3PCgUrwougN1zKXC/ev3tHuCXsaagLLqRXl/9tu2Vy+Q5BYNo60sdkckcgpRRkRU QW4GB0Kd8l9K7CfxK6inwHkofGiAJW4FCHeX9iPcQVgo/2k1VUB/URuLhPJUhHeJMH XjA7bpDP3ojHGNPeh2+YxcLCr3gLbA6dhQUbSqLpXKPoR8yD9tLi8PcEySBcqGGArm 3AwRNFOA6U+wc6hui7nDl+xEkKE4EQKLe51hmRd2T41pI/OG+VIwz3wOT+ChDSUKpD Ze0N7ubs+fQL1k5c6JGtCaiVCWqdgSyrp78MXINMZtvweJweSkHQWElSAcwwUKdIY0 MZcJyLTcQl76Q== Date: Sun, 16 Nov 2025 07:46:56 +0200 From: Mike Rapoport To: Pasha Tatashin Cc: akpm@linux-foundation.org, bhe@redhat.com, jasonmiu@google.com, arnd@arndb.de, coxu@redhat.com, dave@vasilevsky.ca, ebiggers@google.com, graf@amazon.com, kees@kernel.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH v2 10/13] kho: Update FDT dynamically for subtree addition/removal Message-ID: References: <20251114190002.3311679-1-pasha.tatashin@soleen.com> <20251114190002.3311679-11-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: DD2AC180005 X-Stat-Signature: 1sxseep9wwjazak8qsfpogcquuxktah8 X-HE-Tag: 1763272025-167314 X-HE-Meta: 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 b8IeR7Zh iLepD1cd681rT3YuRH37CUk9gNakMZuEIWqQ49pI67EEDH0D4yw08zBjDbnRKqV1U7ZHWPZGySGj+e5vBbur+x3DFjh5YGCKKO2QsANdQzbeoBwRMt2hhL5asS/ZTXfWFYaVdkUD+p1laWmN3mToSkUb4fDlvtiikq87PuQUmiU2+j3kZCo1rILBBdkDB/3VLiv9pUQrKOkBYAGb2P3RmsnwR4nyL29TP4pDRrhfDw8ux9KFrFRTPfQyMoANxb92kq4PvW1DryYdqddo= 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: On Sat, Nov 15, 2025 at 09:51:07AM -0500, Pasha Tatashin wrote: > On Sat, Nov 15, 2025 at 4:40 AM Mike Rapoport wrote: > > > > On Fri, Nov 14, 2025 at 01:59:59PM -0500, Pasha Tatashin wrote: > > > - struct kho_sub_fdt *sub_fdt; > > > + phys_addr_t phys = virt_to_phys(fdt); > > > + void *root_fdt = kho_out.fdt; > > > + int err = -ENOMEM; > > > + int off, fdt_err; > > > > > > - sub_fdt = kmalloc(sizeof(*sub_fdt), GFP_KERNEL); > > > - if (!sub_fdt) > > > - return -ENOMEM; > > > + guard(mutex)(&kho_out.lock); > > > + > > > + fdt_err = fdt_open_into(root_fdt, root_fdt, PAGE_SIZE); > > > + if (fdt_err < 0) > > > + return err; > > > > > > - INIT_LIST_HEAD(&sub_fdt->l); > > > - sub_fdt->name = name; > > > - sub_fdt->fdt = fdt; > > > + off = fdt_add_subnode(root_fdt, 0, name); > > > > Why not > > fdt_err = fdt_add_subnode() > > > > as I asked in v1 review? > > > > Oh, I missed that, there is a slight difference between the two: > 'fdt_err' only contains FDT return value, i.e. error if negative. The > 'off' on the other hand in the happy path contains subnode offset, and > contains error only in the unhappy path. This is why I think it is a > little cleaner to keep different name, however, if you still prefer > re-using a single local variable for both, this is fix-up patch: > > diff --git a/kernel/liveupdate/kexec_handover.c > b/kernel/liveupdate/kexec_handover.c > index 224bdf5becb6..81f60ccb2dc7 100644 > --- a/kernel/liveupdate/kexec_handover.c > +++ b/kernel/liveupdate/kexec_handover.c > @@ -713,7 +713,7 @@ int kho_add_subtree(const char *name, void *fdt) > phys_addr_t phys = virt_to_phys(fdt); > void *root_fdt = kho_out.fdt; > int err = -ENOMEM; > - int off, fdt_err; > + int fdt_err; > > guard(mutex)(&kho_out.lock); > > @@ -721,14 +721,14 @@ int kho_add_subtree(const char *name, void *fdt) > if (fdt_err < 0) > return err; > > - off = fdt_add_subnode(root_fdt, 0, name); > - if (off < 0) { > - if (off == -FDT_ERR_EXISTS) > + fdt_err = fdt_add_subnode(root_fdt, 0, name); > + if (fdt_err < 0) { > + if (fdt_err == -FDT_ERR_EXISTS) > err = -EEXIST; > goto out_pack; > } > > - err = fdt_setprop(root_fdt, off, PROP_SUB_FDT, &phys, sizeof(phys)); > + err = fdt_setprop(root_fdt, fdt_err, PROP_SUB_FDT, &phys, sizeof(phys)); I missed 'off' here, never mind > if (err < 0) > goto out_pack; > -- Sincerely yours, Mike.