Messages in this thread | | | Date | Mon, 25 Jul 2022 22:13:53 +0300 | Subject | Re: [PATCH v12 22/69] mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap() | From | Dmitry Osipenko <> |
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25.07.2022 21:49, Liam Howlett пишет: > * Liam R. Howlett <Liam.Howlett@Oracle.com> [220725 10:00]: >> * Dmitry Osipenko <digetx@gmail.com> [220723 11:01]: >>> 20.07.2022 05:17, Liam Howlett пишет: >>>> From: "Liam R. Howlett" <Liam.Howlett@Oracle.com> >>>> >>>> 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@oracle.com >>>> Link: https://lkml.kernel.org/r/20220621204632.3370049-23-Liam.Howlett@oracle.com >>>> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com> >>>> Cc: Catalin Marinas <catalin.marinas@arm.com> >>>> Cc: David Howells <dhowells@redhat.com> >>>> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> >>>> Cc: SeongJae Park <sj@kernel.org> >>>> Cc: Vlastimil Babka <vbabka@suse.cz> >>>> Cc: Will Deacon <will@kernel.org> >>>> Cc: Davidlohr Bueso <dave@stgolabs.net> >>>> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> >>>> --- >>>> 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@oracle.com/ >> 2. https://lore.kernel.org/linux-mm/20220721005828.379405-1-Liam.Howlett@oracle.com/ >> 3. https://lore.kernel.org/linux-mm/20220721005237.377987-1-Liam.Howlett@oracle.com/ >> > > 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.
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