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Tue, 10 Mar 2026 11:40:49 -0700 (PDT) Date: Wed, 11 Mar 2026 02:40:36 +0800 From: Kuan-Wei Chiu To: Philipp Hahn Cc: amd-gfx@lists.freedesktop.org, apparmor@lists.ubuntu.com, bpf@vger.kernel.org, ceph-devel@vger.kernel.org, cocci@inria.fr, dm-devel@lists.linux.dev, dri-devel@lists.freedesktop.org, gfs2@lists.linux.dev, intel-gfx@lists.freedesktop.org, intel-wired-lan@lists.osuosl.org, iommu@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-block@vger.kernel.org, linux-bluetooth@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-cifs@vger.kernel.org, linux-clk@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-gpio@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org, linux-media@vger.kernel.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, linux-mtd@lists.infradead.org, linux-nfs@vger.kernel.org, linux-omap@vger.kernel.org, linux-phy@lists.infradead.org, linux-pm@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-sctp@vger.kernel.org, linux-security-module@vger.kernel.org, linux-sh@vger.kernel.org, linux-sound@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-trace-kernel@vger.kernel.org, linux-usb@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, ntfs3@lists.linux.dev, samba-technical@lists.samba.org, sched-ext@lists.linux.dev, target-devel@vger.kernel.org, tipc-discussion@lists.sourceforge.net, v9fs@lists.linux.dev Subject: Re: [PATCH 00/61] treewide: Use IS_ERR_OR_NULL over manual NULL check - refactor Message-ID: References: <20260310-b4-is_err_or_null-v1-0-bd63b656022d@avm.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260310-b4-is_err_or_null-v1-0-bd63b656022d@avm.de> X-Stat-Signature: 4om5jxj387n9uhmb8zd1nub6jbx8n178 X-Rspam-User: X-Rspamd-Queue-Id: 67B7B20013 X-Rspamd-Server: rspam12 X-HE-Tag: 1773168051-41169 X-HE-Meta: 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 NUPMpL0S 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Philipp, On Tue, Mar 10, 2026 at 12:48:26PM +0100, Philipp Hahn wrote: > While doing some static code analysis I stumbled over a common pattern, > where IS_ERR() is combined with a NULL check. For that there is > IS_ERR_OR_NULL(). > > I've written a Coccinelle patch to find and patch those instances. > The patches follow grouped by subsystem. > > Patches 55-58 may be dropped as they have a (minor?) semantic change: > They use WARN_ON() or WARN_ON_ONCE(), but only in the IS_ERR() path, not > for the NULL check. Iff it is okay to print the warning also for NULL, > then the patches can be applied. > > While generating the patch set `checkpatch` complained about mixing > [un]likely() with IS_ERR_OR_NULL(), which already uses likely() > internally. I found and fixed several locations, where that combination > has been used. Thanks for the patchset. However, I think we need a explanation for why switching to IS_ERR_OR_NULL() is an improvement over the existing code. IMHO, the necessity of IS_ERR_OR_NULL() often highlights a confusing or flawed API design. It usually implies that the caller is unsure whether a failure results in an error pointer or a NULL pointer. Rather than doing a treewide conversion of this pattern, I believe it would be much more meaningful to review these instances case-by-case and fix the underlying APIs or caller logic instead. Additionally, a treewide refactoring like this has the practical drawback of creating unnecessary merge conflicts when backporting to stable trees. Regards, Kuan-Wei