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https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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Lorenzo Stoakes (ARM)
35dd856770
Careful handling is required for sparc32 which implements page tables as part of a shared backing page. To support this, a custom __tlb_remove_table() function is required, as specified by CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE. This allows __pte_free_tlb() and __pmd_free_tlb() to specify which page table level is being freed, which is transmitted to __tlb_remove_table() through setting the lowest bit of the page table to 1 for a PMD and 0 for a PTE (the page tables are 256-byte aligned so this is safe to do). Next, since the page table freeing is done via RCU callback, and thus might be executed in softirq context, update the spin locks to IRQ save/restore. Then, in __tlb_remove_table(), figure out whether to free a PMD page table via free_pmd_fast() or a PTE via the newly introduced __pte_free() function, using the lower bit encoded in __pte_free_tlb() or __pmd_free_tlb() to determine which to call. As part of this change use this spin lock rather than mm->page_table_lock for all shared page table exclusion, as RCU freeing means that page tables can be freed from soft IRQ context so both don't have an mm and also mm->page_table_lock is not IRQ-safe. Note that the specification of CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE disables CONFIG_PT_RECLAIM for sparc32, which mirrors sparc64. This forms part of an overall effort to switch every architecture to this mode, and with it complete, means every architecture now supports CONFIG_MMU_GATHER_RCU_TABLE_FREE. Link: https://lore.kernel.org/20260925-rcu-pagetable-freeing-v5-10-31e91065fea4@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Kiryl Shutsemau (Meta) <kas@kernel.org> Tested-by: Lance Yang <lance.yang@linux.dev> Acked-by: Lance Yang <lance.yang@linux.dev> Cc: David Hildenbrand <david@kernel.org> Cc: Zi Yan <ziy@nvidia.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Liam R. Howlett <liam@infradead.org> Cc: Nico Pache <nico.pache@linux.dev> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Usama Arif <usama.arif@linux.dev> Cc: Guo Ren <guoren@kernel.org> Cc: Brian Cain <bcain@kernel.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Dinh Nguyen <dinguyen@kernel.org> Cc: Simon Schuster <schuster.simon@siemens-energy.com> Cc: Jonas Bonn <jonas@southpole.se> Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi> Cc: Stafford Horne <shorne@gmail.com> Cc: Rich Felker <dalias@libc.org> Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> Cc: Paul Walmsley <pjw@kernel.org> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Alexandre Ghiti <alex@ghiti.fr> Cc: Russell King <linux@armlinux.org.uk> Cc: Vineet Gupta <vgupta@kernel.org> Cc: Michal Simek <monstr@monstr.eu> Cc: Chris Zankel <chris@zankel.net> Cc: Max Filippov <jcmvbkbc@gmail.com> Cc: Will Deacon <will@kernel.org> Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: David S. Miller <davem@davemloft.net> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Richard Henderson <richard.henderson@linaro.org> Cc: Matt Turner <mattst88@gmail.com> Cc: Magnus Lindholm <linmag7@gmail.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Huacai Chen <chenhuacai@kernel.org> Cc: WANG Xuerui <kernel@xen0n.name> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: James Bottomley <james.bottomley@hansenpartnership.com> Cc: Helge Deller <deller@gmx.de> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Christophe Leroy <chleroy@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Richard Weinberger <richard@nod.at> Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com> Cc: Johannes Berg <johannes@sipsolutions.net> Cc: Thomas Gleixner <tglx@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Vlastimil Babka <vbabka@kernel.org> Cc: Mike Rapoport <rppt@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Peter Xu <peterx@redhat.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: Shakeel Butt <shakeel.butt@linux.dev> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Hugh Dickins <hughd@google.com> Cc: Qi Zheng <qi.zheng@linux.dev>