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Tue, 13 Feb 2024 15:07:38 -0500 (EST) Message-ID: <457bde90-5ce7-4c60-9268-e5980ddf6cc0@efficios.com> Date: Tue, 13 Feb 2024 15:07:38 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 1/8] dax: alloc_dax() return ERR_PTR(-EOPNOTSUPP) for CONFIG_DAX=n Content-Language: en-US To: Dan Williams , Lukas Wunner Cc: Arnd Bergmann , Dave Chinner , linux-kernel@vger.kernel.org, Andrew Morton , Linus Torvalds , Vishal Verma , Dave Jiang , Matthew Wilcox , Russell King , linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-xfs@vger.kernel.org, dm-devel@lists.linux.dev, nvdimm@lists.linux.dev, linux-s390@vger.kernel.org References: <20240212163101.19614-1-mathieu.desnoyers@efficios.com> <20240212163101.19614-2-mathieu.desnoyers@efficios.com> <20240213063226.GA4740@wunner.de> <65cbbdfe19172_29b129476@dwillia2-mobl3.amr.corp.intel.com.notmuch> From: Mathieu Desnoyers In-Reply-To: <65cbbdfe19172_29b129476@dwillia2-mobl3.amr.corp.intel.com.notmuch> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 5A86640018 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: sufjwdyzfyrzapuq8p871dt9bz9pgddy X-HE-Tag: 1707854859-71733 X-HE-Meta: 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 TslJPtzO XWvR47EO0E/B6ti7FNntwBKWZEc++uQa89bvmaQ98R/L++mglsBMEif/emk+93+kz/HWNgHQFQ+fRePZ050M9InLhKqLYh02DtoRkSkZqf/EVT9sQVMLlNygkpT2dhXREUIb28hIltodQuUGByHKyb4W0SM2cvLLf7PHbov8Eb7b/7LaJ+TpShOXFUh5mRBs4THi7yWeYhjliM1yb5v161MUvNCel5WACy8EuH48hZWBBKNlLSIEpXtMdSDIkLHwIEusPhmwXxNxNovj45s/TG5/L3yT4bsmdGbdgHCqnBg5KDv2R/7IB8MupsLSji3+f6Ptm/5PWbWlOnL/bsHTUTzxI+w== 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 2024-02-13 14:07, Dan Williams wrote: > Lukas Wunner wrote: >> On Mon, Feb 12, 2024 at 11:30:54AM -0500, Mathieu Desnoyers wrote: >>> Change the return value from NULL to PTR_ERR(-EOPNOTSUPP) for >>> CONFIG_DAX=n to be consistent with the fact that CONFIG_DAX=y >>> never returns NULL. >> >> All the callers of alloc_dax() only check for IS_ERR(). >> >> Doesn't this result in a change of behavior in all the callers? >> Previously they'd ignore the NULL return value and continue, >> now they'll error out. >> >> Given that, seems dangerous to add a Fixes tag with a v4.0 commit >> and thus risk regressing all stable kernels. > > Oh, good catch, yes that Fixes tag should be: > > 4e4ced93794a dax: Move mandatory ->zero_page_range() check in alloc_dax() > > ...as that was the one that updated the alloc_dax() calling convention > without fixing up the CONFIG_DAX=n case. > > This is a pre-requisite for restoring DAX operation on ARM32. I'll change the Fixes tag in this commit to: Fixes: 4e4ced93794a ("dax: Move mandatory ->zero_page_range() check in alloc_dax()") for v6. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com