From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 123/131] hugetlbfs: get unmapped area below TASK_UNMAPPED_BASE for hugetlbfs Date: Wed, 03 Jun 2020 16:03:34 -0700 Message-ID: <20200603230334.Lpv8ZBv0H%akpm@linux-foundation.org> References: <20200603155549.e041363450869eaae4c7f05b@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:47810 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726716AbgFCXIn (ORCPT ); Wed, 3 Jun 2020 19:08:43 -0400 In-Reply-To: <20200603155549.e041363450869eaae4c7f05b@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, cg.chen@huawei.com, chenjie6@huawei.com, hushijie3@huawei.com, linux-mm@kvack.org, lkp@intel.com, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, nixiaoming@huawei.com, torvalds@linux-foundation.org, wangkefeng.wang@huawei.com, will@kernel.org, yangerkun@huawei.com From: Shijie Hu Subject: hugetlbfs: get unmapped area below TASK_UNMAPPED_BASE for hugetlbfs In a 32-bit program, running on arm64 architecture. When the address space below mmap base is completely exhausted, shmat() for huge pages will return ENOMEM, but shmat() for normal pages can still success on no-legacy mode. This seems not fair. For normal pages, the calling trace of get_unmapped_area() is: => mm->get_unmapped_area() if on legacy mode, => arch_get_unmapped_area() => vm_unmapped_area() if on no-legacy mode, => arch_get_unmapped_area_topdown() => vm_unmapped_area() For huge pages, the calling trace of get_unmapped_area() is: => file->f_op->get_unmapped_area() => hugetlb_get_unmapped_area() => vm_unmapped_area() To solve this issue, we only need to make hugetlb_get_unmapped_area() take the same way as mm->get_unmapped_area(). Add *bottomup() and *topdown() for hugetlbfs, and check current mm->get_unmapped_area() to decide which one to use. If mm->get_unmapped_area is equal to arch_get_unmapped_area_topdown(), hugetlb_get_unmapped_area() calls topdown routine, otherwise calls bottomup routine. Link: http://lkml.kernel.org/r/20200518065338.113664-1-hushijie3@huawei.com Signed-off-by: Shijie Hu Signed-off-by: Mike Kravetz Reported-by: kbuild test robot Cc: Will Deacon Cc: Xiaoming Ni Cc: Kefeng Wang Cc: yangerkun Cc: ChenGang Cc: Chen Jie Signed-off-by: Andrew Morton --- fs/hugetlbfs/inode.c | 67 ++++++++++++++++++++++++++++++++++++----- 1 file changed, 59 insertions(+), 8 deletions(-) --- a/fs/hugetlbfs/inode.c~hugetlbfs-get-unmapped-area-below-task_unmapped_base-for-hugetlbfs +++ a/fs/hugetlbfs/inode.c @@ -38,6 +38,7 @@ #include #include +#include static const struct super_operations hugetlbfs_ops; static const struct address_space_operations hugetlbfs_aops; @@ -191,13 +192,60 @@ out: #ifndef HAVE_ARCH_HUGETLB_UNMAPPED_AREA static unsigned long +hugetlb_get_unmapped_area_bottomup(struct file *file, unsigned long addr, + unsigned long len, unsigned long pgoff, unsigned long flags) +{ + struct hstate *h = hstate_file(file); + struct vm_unmapped_area_info info; + + info.flags = 0; + info.length = len; + info.low_limit = current->mm->mmap_base; + info.high_limit = TASK_SIZE; + info.align_mask = PAGE_MASK & ~huge_page_mask(h); + info.align_offset = 0; + return vm_unmapped_area(&info); +} + +static unsigned long +hugetlb_get_unmapped_area_topdown(struct file *file, unsigned long addr, + unsigned long len, unsigned long pgoff, unsigned long flags) +{ + struct hstate *h = hstate_file(file); + struct vm_unmapped_area_info info; + + info.flags = VM_UNMAPPED_AREA_TOPDOWN; + info.length = len; + info.low_limit = max(PAGE_SIZE, mmap_min_addr); + info.high_limit = current->mm->mmap_base; + info.align_mask = PAGE_MASK & ~huge_page_mask(h); + info.align_offset = 0; + addr = vm_unmapped_area(&info); + + /* + * A failed mmap() very likely causes application failure, + * so fall back to the bottom-up function here. This scenario + * can happen with large stack limits and large mmap() + * allocations. + */ + if (unlikely(offset_in_page(addr))) { + VM_BUG_ON(addr != -ENOMEM); + info.flags = 0; + info.low_limit = current->mm->mmap_base; + info.high_limit = TASK_SIZE; + addr = vm_unmapped_area(&info); + } + + return addr; +} + +static unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { struct mm_struct *mm = current->mm; struct vm_area_struct *vma; struct hstate *h = hstate_file(file); - struct vm_unmapped_area_info info; if (len & ~huge_page_mask(h)) return -EINVAL; @@ -218,13 +266,16 @@ hugetlb_get_unmapped_area(struct file *f return addr; } - info.flags = 0; - info.length = len; - info.low_limit = TASK_UNMAPPED_BASE; - info.high_limit = TASK_SIZE; - info.align_mask = PAGE_MASK & ~huge_page_mask(h); - info.align_offset = 0; - return vm_unmapped_area(&info); + /* + * Use mm->get_unmapped_area value as a hint to use topdown routine. + * If architectures have special needs, they should define their own + * version of hugetlb_get_unmapped_area. + */ + if (mm->get_unmapped_area == arch_get_unmapped_area_topdown) + return hugetlb_get_unmapped_area_topdown(file, addr, len, + pgoff, flags); + return hugetlb_get_unmapped_area_bottomup(file, addr, len, + pgoff, flags); } #endif _