From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> Avoid allocating a new VMA when it a vma modification can occur. When a brk() can expand or contract a VMA, then the single store operation will only modify one index of the maple tree instead of causing a node to split or coalesce. This avoids unnecessary allocations/frees of maple tree nodes and VMAs. Move some limit & flag verifications out of the do_brk_flags() function to use only relevant checks in the code path of bkr() and vm_brk_flags(). Set the vma to check if it can expand in vm_brk_flags() if extra criteria are met. Drop userfaultfd from do_brk_flags() path and only use it in vm_brk_flags() path since that is the only place a munmap will happen. Link: https://lkml.kernel.org/r/20220504011345.662299-7-Liam.Howlett@xxxxxxxxxx Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: David Howells <dhowells@xxxxxxxxxx> Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> Cc: SeongJae Park <sj@xxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/mmap.c | 286 +++++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 228 insertions(+), 58 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 7d6b5bdbdd1d..784d38ee8d94 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -194,17 +194,40 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) return next; } -static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags, - struct list_head *uf); +/* + * check_brk_limits() - Use platform specific check of range & verify mlock + * limits. + * @addr: The address to check + * @len: The size of increase. + * + * Return: 0 on success. + */ +static int check_brk_limits(unsigned long addr, unsigned long len) +{ + unsigned long mapped_addr; + + mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED); + if (IS_ERR_VALUE(mapped_addr)) + return mapped_addr; + + return mlock_future_check(current->mm, current->mm->def_flags, len); +} +static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma, + unsigned long newbrk, unsigned long oldbrk, + struct list_head *uf); +static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *brkvma, + unsigned long addr, unsigned long request, + unsigned long flags); SYSCALL_DEFINE1(brk, unsigned long, brk) { unsigned long newbrk, oldbrk, origbrk; struct mm_struct *mm = current->mm; - struct vm_area_struct *next; + struct vm_area_struct *brkvma, *next = NULL; unsigned long min_brk; bool populate; bool downgraded = false; LIST_HEAD(uf); + MA_STATE(mas, &mm->mm_mt, 0, 0); if (mmap_write_lock_killable(mm)) return -EINTR; @@ -246,35 +269,52 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) /* * Always allow shrinking brk. - * __do_munmap() may downgrade mmap_lock to read. + * do_brk_munmap() may downgrade mmap_lock to read. */ if (brk <= mm->brk) { int ret; + /* Search one past newbrk */ + mas_set(&mas, newbrk); + brkvma = mas_find(&mas, oldbrk); + BUG_ON(brkvma == NULL); + if (brkvma->vm_start >= oldbrk) + goto out; /* mapping intersects with an existing non-brk vma. */ /* - * mm->brk must to be protected by write mmap_lock so update it - * before downgrading mmap_lock. When __do_munmap() fails, - * mm->brk will be restored from origbrk. + * mm->brk must be protected by write mmap_lock. + * do_brk_munmap() may downgrade the lock, so update it + * before calling do_brk_munmap(). */ mm->brk = brk; - ret = __do_munmap(mm, newbrk, oldbrk-newbrk, &uf, true); - if (ret < 0) { - mm->brk = origbrk; - goto out; - } else if (ret == 1) { + mas.last = oldbrk - 1; + ret = do_brk_munmap(&mas, brkvma, newbrk, oldbrk, &uf); + if (ret == 1) { downgraded = true; - } - goto success; + goto success; + } else if (!ret) + goto success; + + mm->brk = origbrk; + goto out; } - /* Check against existing mmap mappings. */ - next = find_vma(mm, oldbrk); + if (check_brk_limits(oldbrk, newbrk - oldbrk)) + goto out; + + /* + * Only check if the next VMA is within the stack_guard_gap of the + * expansion area + */ + mas_set(&mas, oldbrk); + next = mas_find(&mas, newbrk - 1 + PAGE_SIZE + stack_guard_gap); if (next && newbrk + PAGE_SIZE > vm_start_gap(next)) goto out; + brkvma = mas_prev(&mas, mm->start_brk); /* Ok, looks good - let it rip. */ - if (do_brk_flags(oldbrk, newbrk-oldbrk, 0, &uf) < 0) + if (do_brk_flags(&mas, brkvma, oldbrk, newbrk - oldbrk, 0) < 0) goto out; + mm->brk = brk; success: @@ -2791,38 +2831,113 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size, } /* - * this is really a simplified "do_mmap". it only handles - * anonymous maps. eventually we may be able to do some - * brk-specific accounting here. + * brk_munmap() - Unmap a parital vma. + * @mas: The maple tree state. + * @vma: The vma to be modified + * @newbrk: the start of the address to unmap + * @oldbrk: The end of the address to unmap + * @uf: The userfaultfd list_head + * + * Returns: 1 on success. + * unmaps a partial VMA mapping. Does not handle alignment, downgrades lock if + * possible. */ -static int do_brk_flags(unsigned long addr, unsigned long len, - unsigned long flags, struct list_head *uf) +static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma, + unsigned long newbrk, unsigned long oldbrk, + struct list_head *uf) { - struct mm_struct *mm = current->mm; - struct vm_area_struct *vma, *prev; - pgoff_t pgoff = addr >> PAGE_SHIFT; - int error; - unsigned long mapped_addr; - validate_mm_mt(mm); + struct mm_struct *mm = vma->vm_mm; + struct vm_area_struct unmap; + unsigned long unmap_pages; + int ret = 1; + + arch_unmap(mm, newbrk, oldbrk); + + if (likely((vma->vm_end < oldbrk) || + ((vma->vm_start == newbrk) && (vma->vm_end == oldbrk)))) { + /* remove entire mapping(s) */ + mas_set(mas, newbrk); + if (vma->vm_start != newbrk) + mas_reset(mas); /* cause a re-walk for the first overlap. */ + ret = __do_munmap(mm, newbrk, oldbrk - newbrk, uf, true); + goto munmap_full_vma; + } + + vma_init(&unmap, mm); + unmap.vm_start = newbrk; + unmap.vm_end = oldbrk; + ret = userfaultfd_unmap_prep(&unmap, newbrk, oldbrk, uf); + if (ret) + return ret; + ret = 1; - /* Until we need other flags, refuse anything except VM_EXEC. */ - if ((flags & (~VM_EXEC)) != 0) - return -EINVAL; - flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags; + /* Change the oldbrk of vma to the newbrk of the munmap area */ + vma_adjust_trans_huge(vma, vma->vm_start, newbrk, 0); + if (mas_preallocate(mas, vma, GFP_KERNEL)) + return -ENOMEM; - mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED); - if (IS_ERR_VALUE(mapped_addr)) - return mapped_addr; + if (vma->anon_vma) { + anon_vma_lock_write(vma->anon_vma); + anon_vma_interval_tree_pre_update_vma(vma); + } - error = mlock_future_check(mm, mm->def_flags, len); - if (error) - return error; + vma->vm_end = newbrk; + vma_init(&unmap, mm); + unmap.vm_start = newbrk; + unmap.vm_end = oldbrk; + if (vma->anon_vma) + vma_set_anonymous(&unmap); - /* Clear old maps, set up prev and uf */ - if (munmap_vma_range(mm, addr, len, &prev, uf)) - return -ENOMEM; + vma_mas_remove(&unmap, mas); + + vmacache_invalidate(vma->vm_mm); + if (vma->anon_vma) { + anon_vma_interval_tree_post_update_vma(vma); + anon_vma_unlock_write(vma->anon_vma); + } + + unmap_pages = vma_pages(&unmap); + if (vma->vm_flags & VM_LOCKED) + mm->locked_vm -= unmap_pages; + + mmap_write_downgrade(mm); + unmap_region(mm, &unmap, vma, newbrk, oldbrk); + /* Statistics */ + vm_stat_account(mm, vma->vm_flags, -unmap_pages); + if (vma->vm_flags & VM_ACCOUNT) + vm_unacct_memory(unmap_pages); + +munmap_full_vma: + validate_mm_mt(mm); + return ret; +} + +/* + * do_brk_flags() - Increase the brk vma if the flags match. + * @mas: The maple tree state. + * @addr: The start address + * @len: The length of the increase + * @vma: The vma, + * @flags: The VMA Flags + * + * Extend the brk VMA from addr to addr + len. If the VMA is NULL or the flags + * do not match then create a new anonymous VMA. Eventually we may be able to + * do some brk-specific accounting here. + */ +static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma, + unsigned long addr, unsigned long len, + unsigned long flags) +{ + struct mm_struct *mm = current->mm; + struct vm_area_struct *prev = NULL; + validate_mm_mt(mm); - /* Check against address space limits *after* clearing old maps... */ + + /* + * Check against address space limits by the changed size + * Note: This happens *after* clearing old mappings in some code paths. + */ + flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags; if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT)) return -ENOMEM; @@ -2832,30 +2947,56 @@ static int do_brk_flags(unsigned long addr, unsigned long len, if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT)) return -ENOMEM; - /* Can we just expand an old private anonymous mapping? */ - vma = vma_merge(mm, prev, addr, addr + len, flags, - NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX, NULL); - if (vma) - goto out; - /* - * create a vma struct for an anonymous mapping + * Expand the existing vma if possible; Note that singular lists do not + * occur after forking, so the expand will only happen on new VMAs. */ - vma = vm_area_alloc(mm); - if (!vma) { - vm_unacct_memory(len >> PAGE_SHIFT); - return -ENOMEM; + if (vma && + (!vma->anon_vma || list_is_singular(&vma->anon_vma_chain)) && + ((vma->vm_flags & ~VM_SOFTDIRTY) == flags)) { + mas->index = vma->vm_start; + mas->last = addr + len - 1; + vma_adjust_trans_huge(vma, addr, addr + len, 0); + if (vma->anon_vma) { + anon_vma_lock_write(vma->anon_vma); + anon_vma_interval_tree_pre_update_vma(vma); + } + vma->vm_end = addr + len; + vma->vm_flags |= VM_SOFTDIRTY; + if (mas_store_gfp(mas, vma, GFP_KERNEL)) + return -ENOMEM; + + if (vma->anon_vma) { + anon_vma_interval_tree_post_update_vma(vma); + anon_vma_unlock_write(vma->anon_vma); + } + khugepaged_enter_vma(vma, flags); + goto out; } + prev = vma; + + /* create a vma struct for an anonymous mapping */ + vma = vm_area_alloc(mm); + if (!vma) + goto vma_alloc_fail; vma_set_anonymous(vma); vma->vm_start = addr; vma->vm_end = addr + len; - vma->vm_pgoff = pgoff; + vma->vm_pgoff = addr >> PAGE_SHIFT; vma->vm_flags = flags; vma->vm_page_prot = vm_get_page_prot(flags); - if(vma_link(mm, vma, prev)) - goto no_vma_link; + mas_set_range(mas, vma->vm_start, addr + len - 1); + if ( mas_store_gfp(mas, vma, GFP_KERNEL)) + goto mas_store_fail; + mm->map_count++; + + if (!prev) + prev = mas_prev(mas, 0); + + __vma_link_list(mm, vma, prev); + mm->map_count++; out: perf_event_mmap(vma); mm->total_vm += len >> PAGE_SHIFT; @@ -2866,18 +3007,22 @@ static int do_brk_flags(unsigned long addr, unsigned long len, validate_mm_mt(mm); return 0; -no_vma_link: +mas_store_fail: vm_area_free(vma); +vma_alloc_fail: + vm_unacct_memory(len >> PAGE_SHIFT); return -ENOMEM; } int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags) { struct mm_struct *mm = current->mm; + struct vm_area_struct *vma = NULL; unsigned long len; int ret; bool populate; LIST_HEAD(uf); + MA_STATE(mas, &mm->mm_mt, addr, addr); len = PAGE_ALIGN(request); if (len < request) @@ -2888,13 +3033,38 @@ int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags) if (mmap_write_lock_killable(mm)) return -EINTR; - ret = do_brk_flags(addr, len, flags, &uf); + /* Until we need other flags, refuse anything except VM_EXEC. */ + if ((flags & (~VM_EXEC)) != 0) + return -EINVAL; + + ret = check_brk_limits(addr, len); + if (ret) + goto limits_failed; + + if (find_vma_intersection(mm, addr, addr + len)) + ret = do_munmap(mm, addr, len, &uf); + + if (ret) + goto munmap_failed; + + vma = mas_prev(&mas, 0); + if (!vma || vma->vm_end != addr || vma_policy(vma) || + !can_vma_merge_after(vma, flags, NULL, NULL, + addr >> PAGE_SHIFT,NULL_VM_UFFD_CTX, NULL)) + vma = NULL; + + ret = do_brk_flags(&mas, vma, addr, len, flags); populate = ((mm->def_flags & VM_LOCKED) != 0); mmap_write_unlock(mm); userfaultfd_unmap_complete(mm, &uf); if (populate && !ret) mm_populate(addr, len); return ret; + +munmap_failed: +limits_failed: + mmap_write_unlock(mm); + return ret; } EXPORT_SYMBOL(vm_brk_flags); -- 2.35.1
