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Fri, 04 Dec 2020 22:57:41 -0800 (PST) From: Nicholas Piggin To: linux-mm@kvack.org, Andrew Morton Cc: Nicholas Piggin , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Zefan Li , Jonathan Cameron , Christoph Hellwig , Christophe Leroy , Rick Edgecombe Subject: [PATCH v9 01/12] mm/vmalloc: fix vmalloc_to_page for huge vmap mappings Date: Sat, 5 Dec 2020 16:57:14 +1000 Message-Id: <20201205065725.1286370-2-npiggin@gmail.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20201205065725.1286370-1-npiggin@gmail.com> References: <20201205065725.1286370-1-npiggin@gmail.com> MIME-Version: 1.0 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: vmalloc_to_page returns NULL for addresses mapped by larger pages[*]. Whether or not a vmap is huge depends on the architecture details, alignments, boot options, etc., which the caller can not be expected to know. Therefore HUGE_VMAP is a regression for vmalloc_to_page. This change teaches vmalloc_to_page about larger pages, and returns the struct page that corresponds to the offset within the large page. This makes the API agnostic to mapping implementation details. [*] As explained by commit 029c54b095995 ("mm/vmalloc.c: huge-vmap: fail gracefully on unexpected huge vmap mappings") Signed-off-by: Nicholas Piggin --- mm/vmalloc.c | 41 ++++++++++++++++++++++++++--------------- 1 file changed, 26 insertions(+), 15 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 6ae491a8b210..f85124e88bdb 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -34,7 +34,7 @@ #include #include #include - +#include #include #include #include @@ -343,7 +343,9 @@ int is_vmalloc_or_module_addr(const void *x) } /* - * Walk a vmap address to the struct page it maps. + * Walk a vmap address to the struct page it maps. Huge vmap mappings will + * return the tail page that corresponds to the base page address, which + * matches small vmap mappings. */ struct page *vmalloc_to_page(const void *vmalloc_addr) { @@ -363,25 +365,33 @@ struct page *vmalloc_to_page(const void *vmalloc_addr) if (pgd_none(*pgd)) return NULL; + if (WARN_ON_ONCE(pgd_leaf(*pgd))) + return NULL; /* XXX: no allowance for huge pgd */ + if (WARN_ON_ONCE(pgd_bad(*pgd))) + return NULL; + p4d = p4d_offset(pgd, addr); if (p4d_none(*p4d)) return NULL; - pud = pud_offset(p4d, addr); + if (p4d_leaf(*p4d)) + return p4d_page(*p4d) + ((addr & ~P4D_MASK) >> PAGE_SHIFT); + if (WARN_ON_ONCE(p4d_bad(*p4d))) + return NULL; - /* - * Don't dereference bad PUD or PMD (below) entries. This will also - * identify huge mappings, which we may encounter on architectures - * that define CONFIG_HAVE_ARCH_HUGE_VMAP=y. Such regions will be - * identified as vmalloc addresses by is_vmalloc_addr(), but are - * not [unambiguously] associated with a struct page, so there is - * no correct value to return for them. - */ - WARN_ON_ONCE(pud_bad(*pud)); - if (pud_none(*pud) || pud_bad(*pud)) + pud = pud_offset(p4d, addr); + if (pud_none(*pud)) + return NULL; + if (pud_leaf(*pud)) + return pud_page(*pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); + if (WARN_ON_ONCE(pud_bad(*pud))) return NULL; + pmd = pmd_offset(pud, addr); - WARN_ON_ONCE(pmd_bad(*pmd)); - if (pmd_none(*pmd) || pmd_bad(*pmd)) + if (pmd_none(*pmd)) + return NULL; + if (pmd_leaf(*pmd)) + return pmd_page(*pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); + if (WARN_ON_ONCE(pmd_bad(*pmd))) return NULL; ptep = pte_offset_map(pmd, addr); @@ -389,6 +399,7 @@ struct page *vmalloc_to_page(const void *vmalloc_addr) if (pte_present(pte)) page = pte_page(pte); pte_unmap(ptep); + return page; } EXPORT_SYMBOL(vmalloc_to_page);