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Thu, 12 Nov 2026 04:16:53 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Thu, 12 Nov 2026 13:16:50 +0100 To: Hao Ge Cc: Uladzislau Rezki , Dev Jain , Suren Baghdasaryan , Andrew Morton , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Dennis Zhou , Tejun Heo , Christoph Lameter , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, Sashiko Subject: Re: [PATCH v4 6/9] mm/vmalloc: only flush the cache after the vmap succeeded Message-ID: References: <20261110112546.261415-1-hao.ge@linux.dev> <20261110112546.261415-7-hao.ge@linux.dev> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261110112546.261415-7-hao.ge@linux.dev> X-Stat-Signature: 3orb6qc7fq18es8b3ypc1uw4ury3x4dm X-Rspam-User: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 8C18C10000C X-HE-Tag: 1794485815-910714 X-HE-Meta: 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 1aNm1c5d 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, Nov 10, 2026 at 07:25:43PM +0800, Hao Ge wrote: > vmap_page_range() and __vmap_pages_range() call flush_cache_vmap() > before they even look at the error code. A failed mapping is never > used, so the flush is pointless at best. > > According to the Sashiko review it is worse than pointless on UML: > flush_cache_vmap() there is flush_tlb_kernel_range(), which syncs the > PTEs into the host OS. Flushing a half-installed mapping therefore > leaves host mappings behind for a range that was just freed again. > > Only flush when the mapping, and for vmap_page_range() also the KMSAN > metadata, is fully set up. > > Reported-by: Sashiko > Signed-off-by: Hao Ge > --- > mm/vmalloc.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 0565cbfe325c..3f98056f8c7e 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -369,10 +369,12 @@ int vmap_page_range(unsigned long addr, unsigned long end, > > err = vmap_range_noflush(addr, end, phys_addr, pgprot_nx(prot), > ioremap_max_page_shift); > - flush_cache_vmap(addr, end); > if (!err) > err = kmsan_ioremap_page_range(addr, end, phys_addr, prot, > ioremap_max_page_shift); > + if (!err) > + flush_cache_vmap(addr, end); > + > return err; > } > > @@ -758,7 +760,9 @@ static int __vmap_pages_range(unsigned long addr, unsigned long end, > int err; > > err = vmap_pages_range_noflush(addr, end, prot, pages, page_shift, gfp_mask); > - flush_cache_vmap(addr, end); > + if (!err) > + flush_cache_vmap(addr, end); > + > return err; > } > > -- > 2.25.1 > Like Suren noted, vmap_pages_range_batched() should be fixed also. -- Uladzislau Rezki