* Dmitry Osipenko <digetx@xxxxxxxxx> [220723 11:01]: > 20.07.2022 05:17, Liam Howlett пишет: > > 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. > > > > Add a wraper for munmap for the brk case called do_brk_munmap(). > > > > Link: https://lkml.kernel.org/r/20220504011345.662299-7-Liam.Howlett@xxxxxxxxxx > > Link: https://lkml.kernel.org/r/20220621204632.3370049-23-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 | 239 ++++++++++++++++++++++++++++++++++++++++-------------- > > 1 file changed, 179 insertions(+), 60 deletions(-) > > > > diff --git a/mm/mmap.c b/mm/mmap.c > > index 02d2fd90af80..33b408653201 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: > > @@ -2805,38 +2845,55 @@ 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); > > - > > - /* 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; > > - > > - mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED); > > - if (IS_ERR_VALUE(mapped_addr)) > > - return mapped_addr; > > + struct mm_struct *mm = vma->vm_mm; > > + int ret; > > > > - error = mlock_future_check(mm, mm->def_flags, len); > > - if (error) > > - return error; > > + arch_unmap(mm, newbrk, oldbrk); > > + ret = __do_munmap(mm, newbrk, oldbrk - newbrk, uf, true); > > + validate_mm_mt(mm); > > + return ret; > > +} > > > > - /* Clear old maps, set up prev and uf */ > > - if (munmap_vma_range(mm, addr, len, &prev, uf)) > > - return -ENOMEM; > > +/* > > + * 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; > > > > - /* Check against address space limits *after* clearing old maps... */ > > + validate_mm_mt(mm); > > + /* > > + * 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; > > > > @@ -2846,30 +2903,56 @@ 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)) > > + goto mas_expand_failed; > > + > > + 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; > > @@ -2880,18 +2963,29 @@ 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; > > + > > +mas_expand_failed: > > + if (vma->anon_vma) { > > + anon_vma_interval_tree_post_update_vma(vma); > > + anon_vma_unlock_write(vma->anon_vma); > > + } > > 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) > > @@ -2902,13 +2996,38 @@ 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); > > > > Hello, > > I cannot complete booting into graphics environment on ARM32 because > do_brk_flags() now crashes with a BUG_ON() on a recent linux-next and > this patch should be the cause. Please take a look, thanks in advance. > > ------------[ cut here ]------------ > kernel BUG at lib/maple_tree.c:911! > Internal error: Oops - BUG: 0 [#1] SMP ARM > Modules linked in: > CPU: 1 PID: 692 Comm: kwin_x11 Not tainted > 5.19.0-rc7-next-20220722-00130-g1583ab12487b #21 > Hardware name: NVIDIA Tegra SoC (Flattened Device Tree) > PC is at mas_update_gap+0xac/0x1a8 > LR is at 0xcc343e00 > pc : [<c0747314>] lr : [<cc343e00>] psr: 60080013 > sp : f1299ac8 ip : 999b6000 fp : f1299ae4 > r10: c1062588 r9 : 00000023 r8 : 00000001 > r7 : 0000001f r6 : cc0ea6a8 r5 : 00000000 r4 : f1299f54 > r3 : 00000000 r2 : c25a2000 r1 : 999b6000 r0 : 00000000 > Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none > Control: 10c5387d Table: 0d28404a DAC: 00000051 > Register r0 information: NULL pointer > Register r1 information: non-paged memory > Register r2 information: slab mm_struct start c25a2000 pointer offset 0 > size 168 > Register r3 information: NULL pointer > Register r4 information: 2-page vmalloc region starting at 0xf1298000 > allocated at kernel_clone+0x64/0x43c > Register r5 information: NULL pointer > Register r6 information: slab maple_node start cc0ea600 pointer offset 168 > Register r7 information: non-paged memory > Register r8 information: non-paged memory > Register r9 information: non-paged memory > Register r10 information: non-slab/vmalloc memory > Register r11 information: 2-page vmalloc region starting at 0xf1298000 > allocated at kernel_clone+0x64/0x43c > Register r12 information: non-paged memory > Process kwin_x11 (pid: 692, stack limit = 0x976e11bf) > ... > Backtrace: > mas_update_gap from mas_wr_modify+0x1b4/0x1898 > r7:0000001f r6:00000000 r5:f1299e90 r4:f1299f54 > mas_wr_modify from mas_wr_store_entry+0x138/0x4d8 > r10:cd26febc r9:00000023 r8:f1299f54 r7:00000cc0 r6:cd21d600 r5:f1299f54 > r4:f1299e90 > mas_wr_store_entry from mas_store_gfp+0x64/0x154 > r9:00000023 r8:f1299f54 r7:00000cc0 r6:cd21d600 r5:cd26fea0 r4:f1299f54 > mas_store_gfp from do_brk_flags+0x21c/0x318 > r10:cd26febc r9:00000023 r8:f1299f54 r7:0097a000 r6:cd26fec4 r5:c25a2000 > r4:cd26fea0 > do_brk_flags from sys_brk+0x27c/0x3c8 > r10:c25a2038 r9:00957000 r8:00000000 r7:cd21d600 r6:0097a000 r5:00957000 > r4:c25a2000 > sys_brk from ret_fast_syscall+0x0/0x1c Thanks for the report. I'm trying to test this now in qemu. I have a few extra patches that have been sent to the linux-mm but have not made it into next as of today (next-20220725) [1] [2] [3]. I don't think they will make a difference but you can try them while I keep working on testing arm32 on this end. 1. https://lore.kernel.org/linux-mm/20220722160546.1478722-1-Liam.Howlett@xxxxxxxxxx/ 2. https://lore.kernel.org/linux-mm/20220721005828.379405-1-Liam.Howlett@xxxxxxxxxx/ 3. https://lore.kernel.org/linux-mm/20220721005237.377987-1-Liam.Howlett@xxxxxxxxxx/ Regards, Liam
