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AJvYcCW4KC7JI4+Hq1R5bdCUQZCnS39kbZKsGdxWs28+PnMGk6sXi92sWlPWuhCYN2m8wJZU0p3cIEuiFA==@kvack.org X-Gm-Message-State: AOJu0YywV9RVPoHhZjB51Xyg5V3UiBHw7nthcJcb0Upvdjo2BLQFSm1r E07GAvD5rTPPRay9HGfdc6kke8n9vR66ha15sdGfNo5+wSjDgUGy4tcTvsEaUB0G9FIRCdTAusl 62Ifgulx24bjJGmjGpEtZZdpXCkNG6qc= X-Gm-Gg: AY/fxX7/DeHrqk6CwWlQrAkSf7aZDacr7lH8s3W5RP8mFV03aDNgscKLV58Mnc5zR96 wm4f72qsk1wUkcuYyhlfT2m9WuCGjoMfVyDV47O5+SAOwdWbPvagMsZyAD7bHMfa6g2Pj9bk+IE WNW9F3MmN1zpi0Kev3/LayC8YC1WWwwfqKLqr/a6cV8c4M1O4YTTH/tuqPDKb53oQbvWfVQiAAa L76gBGVMuMnHO02nw9HYdwRKvo/2mah99jYtAnPmonuZqOFe1bIytFBFyOw87dzMFRD5ytoUaMC Zp3SIRk= X-Google-Smtp-Source: AGHT+IGJvFDwoT5+R84Us2wOdELzTN8S3c6PUgRf9hT/zKx8b5q1OgRk0RWErpdB/opQupyeLAt4VEcLjgEF6Byjcpg= X-Received: by 2002:a17:907:985:b0:b83:3295:15d2 with SMTP id a640c23a62f3a-b8332956e52mr703338566b.30.1766821875590; Fri, 26 Dec 2025 23:51:15 -0800 (PST) MIME-Version: 1.0 References: <20251225094057.286954-1-wale.zhang.ftd@gmail.com> In-Reply-To: From: wale zhang Date: Sat, 27 Dec 2025 15:51:04 +0800 X-Gm-Features: AQt7F2rijk-P8LMsjT91azPRMPHyXbFD4DqPcrpAH0HjLoLruyYoTM-Bj-9sJ0w Message-ID: Subject: Re: [PATCH 1/1] mm,swapops: Fix compile error on set_pmd_migration_entry. To: Barry Song <21cnbao@gmail.com> Cc: akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, chrisl@kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 664C740009 X-Rspamd-Server: rspam04 X-Stat-Signature: 9khmupoaphocdc4efx7fkx6ikgy3fyx3 X-HE-Tag: 1766821877-291589 X-HE-Meta: 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 rRcn0up7 NRG1wIQz86gLcI6HNZgoaZECM5HtVl+WsYkLEGakW2ZKjaN2qeFD2Qp2sorrl0RpDiA6OFAuNxit/mr4z5Y8XY9LUQcXfMmV6DEFAE9darMDeEZo3ZAAdyX8tItYfq4ZfF7XBtWIBuR1257NEPe4qkrAtqQtDYIE+5LvDUTaRO+Q7KlS0PT5QJP4lHQrBKwMZ1ihnWBtU4jBzS3fT6Xba5VMT7wuQj9eUGF3zxxGM8rzeRNNZQ/CPrEmqwCFsaRGV/Es6LbPxtuXBgQX4b+qu0YG89rKH2zi8RuhUSZYePdTSkmwONAX1UbvEjFo5x8DqY0OnWvR/CNPE7/gD4JEALqVWzKE4KRa3uzTZFvaVDTn2YNFYaeYAeU9+1zcctYJ0f9+MQs3JkdbI75uYlJ2r6avrkFADbVM+YSw039+f1Xajg5awVmy+0oeB0ofGeTlHjylDRArtvLJ2BYBNbWBw1dhKcIkb59rgxC5I 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, Dec 27, 2025 at 2:43=E2=80=AFAM Barry Song <21cnbao@gmail.com> wrot= e: > > On Sat, Dec 27, 2025 at 12:46=E2=80=AFAM wale zhang wrote: > > > > On Thu, Dec 25, 2025 at 6:22=E2=80=AFPM Barry Song <21cnbao@gmail.com> = wrote: > > > > > > On Thu, Dec 25, 2025 at 10:41=E2=80=AFPM Wale Zhang wrote: > > > > > > > > ../include/linux/swapops.h: In function =E2=80=98set_pmd_migration_= entry=E2=80=99: > > > > ../include/linux/swapops.h:346:1: error: no return statement in fun= ction returning non-void [-Werror=3Dreturn-type] > > > > 346 | } > > > > | ^ > > > > cc1: some warnings being treated as errors > > > > > > > > Signed-off-by: Wale Zhang > > > > > > Sorry. NAK. > > > > > > This looks odd. We already have a BUILD_BUG(), so no fix is needed. > > > > > > we should already have: > > > ././include/linux/compiler_types.h:631:45: error: call to > > > =E2=80=98__compiletime_assert_907=E2=80=99 declared with attribute er= ror: BUILD_BUG > > > failed > > > 631 | _compiletime_assert(condition, msg, > > > __compiletime_assert_, __COUNTER__) > > > | ^ > > > ././include/linux/compiler_types.h:612:25: note: in definition of > > > macro =E2=80=98__compiletime_assert=E2=80=99 > > > 612 | prefix ## suffix(); > > > \ > > > | ^~~~~~ > > > > > > Do you actually see this being built? If so, please help identify why= it > > > gets built. > > > > Hello Barry, > > > > I compile the 6.19-rc2 for arm64 with -O0, this kind of error log will = appear. > > In file included from /home/wale/repo/linux/master/include/linux/leafop= s.h:11, > > from > > /home/wale/repo/linux/master/include/linux/userfaultfd_k.h:19, > > from /home/wale/repo/linux/master/include/linux/mm_inl= ine.h:10, > > from /home/wale/repo/linux/master/mm/internal.h:13, > > from /home/wale/repo/linux/master/mm/fadvise.c:24: > > /home/wale/repo/linux/master/include/linux/swapops.h: In function > > =E2=80=98set_pmd_migration_entry=E2=80=99: > > /home/wale/repo/linux/master/include/linux/swapops.h:346:1: error: no > > return statement in function returning non-void [-Werror=3Dreturn-type] > > 346 | } > > | ^ > > cc1: some warnings being treated as errors > > make[4]: *** [/home/wale/repo/linux/master/scripts/Makefile.build:287: > > mm/fadvise.o] Error 1 > > make[4]: *** Waiting for unfinished jobs.... > > > > There is an example on my > > github(https://github.com/wale-ftd/linux/commits/linux-6.12/) that > > used -O0 to compile the 6.12 kernel. If you're interested, you can > > check them out. > > This is not my question. The BUILD_BUG here means this code > should never be built. If it is built, then that indicates a bug. > So my question is: under what kernel configuration would this > code actually get built? Hello Barry, I'm very sorry for misunderstanding your meaning. For -O0, __OPTIMIZE__ isn't defined, so line 615 is hit. 595 #ifdef __OPTIMIZE__ 602 # define __compiletime_assert(condition, msg, prefix, suffix) = \ 612 prefix ## suffix(); 614 #else 615 # define __compiletime_assert(condition, msg, prefix, suffix) ((void)(condition)) 616 #endif Finally, set_pmd_migration_entry is defined as follow: static inline int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw= , struct page *page) { - BUILD_BUG(); + ((void)(0)); } > Thanks > Barry -- Thanks Wale