mm: mmu_gather rework
Rework the existing mmu_gather infrastructure. The direct purpose of these patches was to allow preemptible mmu_gather, but even without that I think these patches provide an improvement to the status quo. The first 9 patches rework the mmu_gather infrastructure. For review purpose I've split them into generic and per-arch patches with the last of those a generic cleanup. The next patch provides generic RCU page-table freeing, and the followup is a patch converting s390 to use this. I've also got 4 patches from DaveM lined up (not included in this series) that uses this to implement gup_fast() for sparc64. Then there is one patch that extends the generic mmu_gather batching. After that follow the mm preemptibility patches, these make part of the mm a lot more preemptible. It converts i_mmap_lock and anon_vma->lock to mutexes which together with the mmu_gather rework makes mmu_gather preemptible as well. Making i_mmap_lock a mutex also enables a clean-up of the truncate code. This also allows for preemptible mmu_notifiers, something that XPMEM I think wants. Furthermore, it removes the new and universially detested unmap_mutex. This patch: Remove the first obstacle towards a fully preemptible mmu_gather. The current scheme assumes mmu_gather is always done with preemption disabled and uses per-cpu storage for the page batches. Change this to try and allocate a page for batching and in case of failure, use a small on-stack array to make some progress. Preemptible mmu_gather is desired in general and usable once i_mmap_lock becomes a mutex. Doing it before the mutex conversion saves us from having to rework the code by moving the mmu_gather bits inside the pte_lock. Also avoid flushing the tlb batches from under the pte lock, this is useful even without the i_mmap_lock conversion as it significantly reduces pte lock hold times. [akpm@linux-foundation.org: fix comment tpyo] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Miller <davem@davemloft.net> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Jeff Dike <jdike@addtoit.com> Cc: Richard Weinberger <richard@nod.at> Cc: Tony Luck <tony.luck@intel.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Hugh Dickins <hughd@google.com> Acked-by: Mel Gorman <mel@csn.ul.ie> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Namhyung Kim <namhyung@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
d05f3169c0
commit
d16dfc550f
10
fs/exec.c
10
fs/exec.c
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@ -600,7 +600,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
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unsigned long length = old_end - old_start;
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unsigned long new_start = old_start - shift;
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unsigned long new_end = old_end - shift;
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struct mmu_gather *tlb;
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struct mmu_gather tlb;
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BUG_ON(new_start > new_end);
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@ -626,12 +626,12 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
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return -ENOMEM;
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lru_add_drain();
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tlb = tlb_gather_mmu(mm, 0);
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tlb_gather_mmu(&tlb, mm, 0);
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if (new_end > old_start) {
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/*
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* when the old and new regions overlap clear from new_end.
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*/
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free_pgd_range(tlb, new_end, old_end, new_end,
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free_pgd_range(&tlb, new_end, old_end, new_end,
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vma->vm_next ? vma->vm_next->vm_start : 0);
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} else {
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/*
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@ -640,10 +640,10 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
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* have constraints on va-space that make this illegal (IA64) -
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* for the others its just a little faster.
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*/
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free_pgd_range(tlb, old_start, old_end, new_end,
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free_pgd_range(&tlb, old_start, old_end, new_end,
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vma->vm_next ? vma->vm_next->vm_start : 0);
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}
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tlb_finish_mmu(tlb, new_end, old_end);
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tlb_finish_mmu(&tlb, new_end, old_end);
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/*
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* Shrink the vma to just the new range. Always succeeds.
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@ -5,6 +5,8 @@
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* Copyright 2001 Red Hat, Inc.
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* Based on code from mm/memory.c Copyright Linus Torvalds and others.
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*
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* Copyright 2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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@ -22,51 +24,71 @@
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* and page free order so much..
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*/
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#ifdef CONFIG_SMP
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#ifdef ARCH_FREE_PTR_NR
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#define FREE_PTR_NR ARCH_FREE_PTR_NR
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#else
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#define FREE_PTE_NR 506
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#endif
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#define tlb_fast_mode(tlb) ((tlb)->nr == ~0U)
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#else
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#define FREE_PTE_NR 1
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#define tlb_fast_mode(tlb) 1
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#endif
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/*
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* If we can't allocate a page to make a big batch of page pointers
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* to work on, then just handle a few from the on-stack structure.
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*/
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#define MMU_GATHER_BUNDLE 8
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/* struct mmu_gather is an opaque type used by the mm code for passing around
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* any data needed by arch specific code for tlb_remove_page.
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*/
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struct mmu_gather {
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struct mm_struct *mm;
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unsigned int nr; /* set to ~0U means fast mode */
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unsigned int max; /* nr < max */
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unsigned int need_flush;/* Really unmapped some ptes? */
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unsigned int fullmm; /* non-zero means full mm flush */
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struct page * pages[FREE_PTE_NR];
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#ifdef HAVE_ARCH_MMU_GATHER
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struct arch_mmu_gather arch;
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#endif
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struct page **pages;
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struct page *local[MMU_GATHER_BUNDLE];
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};
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/* Users of the generic TLB shootdown code must declare this storage space. */
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DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
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static inline void __tlb_alloc_page(struct mmu_gather *tlb)
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{
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unsigned long addr = __get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
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if (addr) {
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tlb->pages = (void *)addr;
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tlb->max = PAGE_SIZE / sizeof(struct page *);
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}
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}
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/* tlb_gather_mmu
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* Return a pointer to an initialized struct mmu_gather.
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* Called to initialize an (on-stack) mmu_gather structure for page-table
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* tear-down from @mm. The @fullmm argument is used when @mm is without
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* users and we're going to destroy the full address space (exit/execve).
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*/
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static inline struct mmu_gather *
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tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush)
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static inline void
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tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm)
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{
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struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);
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tlb->mm = mm;
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/* Use fast mode if only one CPU is online */
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tlb->nr = num_online_cpus() > 1 ? 0U : ~0U;
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tlb->max = ARRAY_SIZE(tlb->local);
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tlb->pages = tlb->local;
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tlb->fullmm = full_mm_flush;
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if (num_online_cpus() > 1) {
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tlb->nr = 0;
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__tlb_alloc_page(tlb);
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} else /* Use fast mode if only one CPU is online */
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tlb->nr = ~0U;
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return tlb;
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tlb->fullmm = fullmm;
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#ifdef HAVE_ARCH_MMU_GATHER
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tlb->arch = ARCH_MMU_GATHER_INIT;
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#endif
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}
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static inline void
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tlb_flush_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
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tlb_flush_mmu(struct mmu_gather *tlb)
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{
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if (!tlb->need_flush)
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return;
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@ -75,6 +97,13 @@ tlb_flush_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
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if (!tlb_fast_mode(tlb)) {
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free_pages_and_swap_cache(tlb->pages, tlb->nr);
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tlb->nr = 0;
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/*
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* If we are using the local on-stack array of pages for MMU
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* gather, try allocating an off-stack array again as we have
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* recently freed pages.
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*/
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if (tlb->pages == tlb->local)
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__tlb_alloc_page(tlb);
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}
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}
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@ -85,29 +114,42 @@ tlb_flush_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
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static inline void
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tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
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{
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tlb_flush_mmu(tlb, start, end);
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tlb_flush_mmu(tlb);
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/* keep the page table cache within bounds */
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check_pgt_cache();
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put_cpu_var(mmu_gathers);
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if (tlb->pages != tlb->local)
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free_pages((unsigned long)tlb->pages, 0);
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}
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/* tlb_remove_page
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/* __tlb_remove_page
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* Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
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* handling the additional races in SMP caused by other CPUs caching valid
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* mappings in their TLBs.
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* mappings in their TLBs. Returns the number of free page slots left.
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* When out of page slots we must call tlb_flush_mmu().
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*/
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static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
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static inline int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
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{
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tlb->need_flush = 1;
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if (tlb_fast_mode(tlb)) {
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free_page_and_swap_cache(page);
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return;
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return 1; /* avoid calling tlb_flush_mmu() */
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}
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tlb->pages[tlb->nr++] = page;
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if (tlb->nr >= FREE_PTE_NR)
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tlb_flush_mmu(tlb, 0, 0);
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VM_BUG_ON(tlb->nr > tlb->max);
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return tlb->max - tlb->nr;
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}
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/* tlb_remove_page
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* Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when
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* required.
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*/
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static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
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{
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if (!__tlb_remove_page(tlb, page))
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tlb_flush_mmu(tlb);
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}
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/**
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@ -906,7 +906,7 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
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unsigned long size);
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unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
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unsigned long size, struct zap_details *);
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unsigned long unmap_vmas(struct mmu_gather **tlb,
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unsigned long unmap_vmas(struct mmu_gather *tlb,
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struct vm_area_struct *start_vma, unsigned long start_addr,
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unsigned long end_addr, unsigned long *nr_accounted,
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struct zap_details *);
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46
mm/memory.c
46
mm/memory.c
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@ -912,12 +912,13 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
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long *zap_work, struct zap_details *details)
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{
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struct mm_struct *mm = tlb->mm;
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int force_flush = 0;
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pte_t *pte;
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spinlock_t *ptl;
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int rss[NR_MM_COUNTERS];
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init_rss_vec(rss);
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again:
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pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
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arch_enter_lazy_mmu_mode();
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do {
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page_remove_rmap(page);
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if (unlikely(page_mapcount(page) < 0))
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print_bad_pte(vma, addr, ptent, page);
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tlb_remove_page(tlb, page);
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force_flush = !__tlb_remove_page(tlb, page);
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if (force_flush)
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break;
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continue;
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}
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/*
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arch_leave_lazy_mmu_mode();
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pte_unmap_unlock(pte - 1, ptl);
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/*
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* mmu_gather ran out of room to batch pages, we break out of
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* the PTE lock to avoid doing the potential expensive TLB invalidate
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* and page-free while holding it.
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*/
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if (force_flush) {
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force_flush = 0;
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tlb_flush_mmu(tlb);
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if (addr != end)
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goto again;
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}
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return addr;
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}
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* ensure that any thus-far unmapped pages are flushed before unmap_vmas()
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* drops the lock and schedules.
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*/
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unsigned long unmap_vmas(struct mmu_gather **tlbp,
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unsigned long unmap_vmas(struct mmu_gather *tlb,
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struct vm_area_struct *vma, unsigned long start_addr,
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unsigned long end_addr, unsigned long *nr_accounted,
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struct zap_details *details)
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{
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long zap_work = ZAP_BLOCK_SIZE;
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unsigned long tlb_start = 0; /* For tlb_finish_mmu */
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int tlb_start_valid = 0;
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unsigned long start = start_addr;
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spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
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int fullmm = (*tlbp)->fullmm;
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struct mm_struct *mm = vma->vm_mm;
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mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
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@ -1152,11 +1164,6 @@ unsigned long unmap_vmas(struct mmu_gather **tlbp,
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untrack_pfn_vma(vma, 0, 0);
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while (start != end) {
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if (!tlb_start_valid) {
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tlb_start = start;
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tlb_start_valid = 1;
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}
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if (unlikely(is_vm_hugetlb_page(vma))) {
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/*
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* It is undesirable to test vma->vm_file as it
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@ -1177,7 +1184,7 @@ unsigned long unmap_vmas(struct mmu_gather **tlbp,
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start = end;
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} else
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start = unmap_page_range(*tlbp, vma,
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start = unmap_page_range(tlb, vma,
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start, end, &zap_work, details);
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if (zap_work > 0) {
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@ -1185,19 +1192,13 @@ unsigned long unmap_vmas(struct mmu_gather **tlbp,
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break;
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}
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tlb_finish_mmu(*tlbp, tlb_start, start);
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if (need_resched() ||
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(i_mmap_lock && spin_needbreak(i_mmap_lock))) {
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if (i_mmap_lock) {
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*tlbp = NULL;
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if (i_mmap_lock)
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goto out;
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}
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cond_resched();
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}
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*tlbp = tlb_gather_mmu(vma->vm_mm, fullmm);
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tlb_start_valid = 0;
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zap_work = ZAP_BLOCK_SIZE;
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}
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}
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@ -1217,16 +1218,15 @@ unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
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unsigned long size, struct zap_details *details)
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{
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struct mm_struct *mm = vma->vm_mm;
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struct mmu_gather *tlb;
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struct mmu_gather tlb;
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unsigned long end = address + size;
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unsigned long nr_accounted = 0;
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lru_add_drain();
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tlb = tlb_gather_mmu(mm, 0);
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tlb_gather_mmu(&tlb, mm, 0);
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update_hiwater_rss(mm);
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end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
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if (tlb)
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tlb_finish_mmu(tlb, address, end);
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tlb_finish_mmu(&tlb, address, end);
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return end;
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}
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18
mm/mmap.c
18
mm/mmap.c
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@ -1903,17 +1903,17 @@ static void unmap_region(struct mm_struct *mm,
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unsigned long start, unsigned long end)
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{
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struct vm_area_struct *next = prev? prev->vm_next: mm->mmap;
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struct mmu_gather *tlb;
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struct mmu_gather tlb;
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unsigned long nr_accounted = 0;
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lru_add_drain();
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tlb = tlb_gather_mmu(mm, 0);
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tlb_gather_mmu(&tlb, mm, 0);
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update_hiwater_rss(mm);
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unmap_vmas(&tlb, vma, start, end, &nr_accounted, NULL);
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vm_unacct_memory(nr_accounted);
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free_pgtables(tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS,
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next? next->vm_start: 0);
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tlb_finish_mmu(tlb, start, end);
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free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
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next ? next->vm_start : 0);
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tlb_finish_mmu(&tlb, start, end);
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}
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/*
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@ -2255,7 +2255,7 @@ EXPORT_SYMBOL(do_brk);
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/* Release all mmaps. */
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void exit_mmap(struct mm_struct *mm)
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{
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struct mmu_gather *tlb;
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struct mmu_gather tlb;
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struct vm_area_struct *vma;
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unsigned long nr_accounted = 0;
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unsigned long end;
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@ -2280,14 +2280,14 @@ void exit_mmap(struct mm_struct *mm)
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lru_add_drain();
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flush_cache_mm(mm);
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tlb = tlb_gather_mmu(mm, 1);
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tlb_gather_mmu(&tlb, mm, 1);
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/* update_hiwater_rss(mm) here? but nobody should be looking */
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/* Use -1 here to ensure all VMAs in the mm are unmapped */
|
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end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
|
||||
vm_unacct_memory(nr_accounted);
|
||||
|
||||
free_pgtables(tlb, vma, FIRST_USER_ADDRESS, 0);
|
||||
tlb_finish_mmu(tlb, 0, end);
|
||||
free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0);
|
||||
tlb_finish_mmu(&tlb, 0, end);
|
||||
|
||||
/*
|
||||
* Walk the list again, actually closing and freeing it,
|
||||
|
|
Loading…
Reference in New Issue
Block a user