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[95.203.22.87]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5be33d8a485sm45759e87.54.2026.10.13.09.39.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Oct 2026 09:39:03 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 13 Oct 2026 18:39:00 +0200 To: Suren Baghdasaryan , Hao Ge Cc: Hao Ge , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Andrew Morton , Dennis Zhou , Tejun Heo , Christoph Lameter , Uladzislau Rezki , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, Sashiko Subject: Re: [RFC PATCH 2/4] mm/vmalloc: undo partial mappings inside the mapping functions Message-ID: References: <20261009063619.112313-1-hao.ge@linux.dev> <20261009063619.112313-3-hao.ge@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Stat-Signature: j436meay7ub9c3rm1crifd3hgq76neo6 X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 05C974000D X-HE-Tag: 1791909545-317478 X-HE-Meta: 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 O/dWQ3nP 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Oct 13, 2026 at 03:23:14PM +0400, Suren Baghdasaryan wrote: > On Fri, Oct 9, 2026 at 10:36 AM Hao Ge wrote: > > > > __vmap_pages_range_noflush() and friends can install some PTEs before > > failing and leave them mapped, and the kernel callers do not agree on > > who cleans them up. pcpu_map_pages() and kmsan_ioremap_page_range() > > roll back what they mapped before the failure, while > > vm_module_tags_populate() and the __GFP_NOFAIL retry loop in > > __vmalloc_area_node() rely on the mapping functions cleaning up and > > do not call anything like vunmap_range() themselves. When the same > > range is mapped again, the attempt hits the leftovers and fails, with > > a BUG() in vmap_pte_range() for huge mappings and a warning on the > > small-page path. > > > > After discussing with Suren and Ulad, we decided to put the rollback > > into the entry points of the vmap API rather than into every low-level > > helper. __vmap_pages_range_noflush() undoes the whole range it was > > asked to map when it fails, and vmap_page_range() undoes its range > > for the ioremap-style mappings. > > > > The rollback is __vunmap_range_noflush(), it only clears the PTEs, > > no TLB flush, nothing has touched these mappings. > > vmap_pages_range_noflush() drops the KMSAN metadata when the data > > mapping fails, and an empty range bails out with -EINVAL now, which > > used to BUG_ON() on the small-page path and map nothing at all on > > the huge-page one. > > > > Reported-by: Sashiko > > Suggested-by: Uladyslau Rezki > > Signed-off-by: Hao Ge > > --- > > mm/vmalloc.c | 44 ++++++++++++++++++++++++++++++++------------ > > 1 file changed, 32 insertions(+), 12 deletions(-) > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index db669103dc66..e1b376f57dd2 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -363,6 +363,9 @@ int vmap_page_range(unsigned long addr, unsigned long end, > > if (!err) > > err = kmsan_ioremap_page_range(addr, end, phys_addr, prot, > > ioremap_max_page_shift); > > + if (err) > > + __vunmap_range_noflush(addr, end); > > + > > return err; > > } > > > > @@ -683,27 +686,35 @@ int __vmap_pages_range_noflush(unsigned long addr, unsigned long end, > > pgprot_t prot, struct page **pages, unsigned int page_shift) > > { > > unsigned int i, nr = (end - addr) >> PAGE_SHIFT; > > + unsigned long start = addr; > > + int err = 0; > > + > > + if (WARN_ON_ONCE(addr >= end)) > > + return -EINVAL; > > > > if (WARN_ON_ONCE(page_shift < PAGE_SHIFT)) > > return -EINVAL; > > > > if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) || > > - page_shift == PAGE_SHIFT) > > - return vmap_small_pages_range_noflush(addr, end, prot, pages); > > - > > - for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) { > > - int err; > > - > > - err = vmap_range_noflush(addr, addr + (1UL << page_shift), > > + page_shift == PAGE_SHIFT) { > > + err = vmap_small_pages_range_noflush(addr, end, prot, pages); > > + } else { > > + for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) { > > + err = vmap_range_noflush(addr, addr + (1UL << page_shift), > > page_to_phys(pages[i]), prot, > > page_shift); > > - if (err) > > - return err; > > + if (err) > > + break; > > > > - addr += 1UL << page_shift; > > + addr += 1UL << page_shift; > > + } > > } > > > > - return 0; > > + /* Undo the PTEs installed before the failure. */ > > + if (err) > > + __vunmap_range_noflush(start, end); > > Would it be too complicated to track how much was actually mapped and > unmap only that portion? > I think it is possible to vunmap the range which is already unmapped. i.e. in this case it is better to no to track anything as soon as a mapping failure is a corner case. Also it is more reliable without extra track logic. -- Uladzislau Rezki