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Thu, 12 Nov 2026 04:16:54 -0800 (PST) Received: from milan ([2001:9b1:d5a0:a500::24b]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c504a618abesm330293966b.50.2026.11.12.04.16.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); 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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261110112546.261415-7-hao.ge@linux.dev> 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