* Dmitry Osipenko <digetx@xxxxxxxxx> [220725 15:14]: > 25.07.2022 21:49, Liam Howlett пишет: > > * Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> [220725 10:00]: > >> * 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/ > >> > > > > Dmitry, > > > > I am having a hard time reproducing this issue. What linux-next tag are > > you using? > > The next-20220722, like my trace log says. It has been broken for about > 2+ weeks in -next. For me the bug is triggered by loading KDE plasma on > NVIDIA Tegra tablet. I may try to reproduce it in Qemu if time will allow. Thanks. I don't have an NVIDIA Tegra tablet to test, but I did manage to find an issue with my 32b allocator. I was also able to get plasma running painfully slow in qemu armv7l with 1GB of ram. Unfortunately the maple tree has been dropped from linux-next for this merge window. I'll CC you on the allocator fix when I send it out to the linux-mm list and I will keep trying to replicate this exact crash. Regards, Liam
