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![Mike Kravetz](/assets/img/avatar_default.png)
This reverts b43a999005
The reverted commit caused issues with migration and poisoning of anon
huge pages. The LTP move_pages12 test will cause an "unable to handle
kernel NULL pointer" BUG would occur with stack similar to:
RIP: 0010:down_write+0x1b/0x40
Call Trace:
migrate_pages+0x81f/0xb90
__ia32_compat_sys_migrate_pages+0x190/0x190
do_move_pages_to_node.isra.53.part.54+0x2a/0x50
kernel_move_pages+0x566/0x7b0
__x64_sys_move_pages+0x24/0x30
do_syscall_64+0x5b/0x180
entry_SYSCALL_64_after_hwframe+0x44/0xa9
The purpose of the reverted patch was to fix some long existing races
with huge pmd sharing. It used i_mmap_rwsem for this purpose with the
idea that this could also be used to address truncate/page fault races
with another patch. Further analysis has determined that i_mmap_rwsem
can not be used to address all these hugetlbfs synchronization issues.
Therefore, revert this patch while working an another approach to the
underlying issues.
Link: http://lkml.kernel.org/r/20190103235452.29335-2-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reported-by: Jan Stancek <jstancek@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Prakash Sangappa <prakash.sangappa@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
617 lines
16 KiB
C
617 lines
16 KiB
C
/*
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* mm/userfaultfd.c
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*
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* Copyright (C) 2015 Red Hat, Inc.
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*/
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#include <linux/mm.h>
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#include <linux/sched/signal.h>
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#include <linux/pagemap.h>
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#include <linux/rmap.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/userfaultfd_k.h>
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#include <linux/mmu_notifier.h>
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#include <linux/hugetlb.h>
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#include <linux/shmem_fs.h>
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#include <asm/tlbflush.h>
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#include "internal.h"
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static int mcopy_atomic_pte(struct mm_struct *dst_mm,
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pmd_t *dst_pmd,
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struct vm_area_struct *dst_vma,
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unsigned long dst_addr,
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unsigned long src_addr,
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struct page **pagep)
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{
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struct mem_cgroup *memcg;
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pte_t _dst_pte, *dst_pte;
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spinlock_t *ptl;
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void *page_kaddr;
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int ret;
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struct page *page;
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pgoff_t offset, max_off;
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struct inode *inode;
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if (!*pagep) {
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ret = -ENOMEM;
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page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
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if (!page)
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goto out;
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page_kaddr = kmap_atomic(page);
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ret = copy_from_user(page_kaddr,
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(const void __user *) src_addr,
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PAGE_SIZE);
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kunmap_atomic(page_kaddr);
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/* fallback to copy_from_user outside mmap_sem */
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if (unlikely(ret)) {
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ret = -ENOENT;
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*pagep = page;
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/* don't free the page */
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goto out;
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}
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} else {
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page = *pagep;
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*pagep = NULL;
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}
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/*
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* The memory barrier inside __SetPageUptodate makes sure that
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* preceeding stores to the page contents become visible before
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* the set_pte_at() write.
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*/
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__SetPageUptodate(page);
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ret = -ENOMEM;
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if (mem_cgroup_try_charge(page, dst_mm, GFP_KERNEL, &memcg, false))
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goto out_release;
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_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
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if (dst_vma->vm_flags & VM_WRITE)
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_dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
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dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
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if (dst_vma->vm_file) {
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/* the shmem MAP_PRIVATE case requires checking the i_size */
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inode = dst_vma->vm_file->f_inode;
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offset = linear_page_index(dst_vma, dst_addr);
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max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
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ret = -EFAULT;
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if (unlikely(offset >= max_off))
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goto out_release_uncharge_unlock;
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}
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ret = -EEXIST;
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if (!pte_none(*dst_pte))
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goto out_release_uncharge_unlock;
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inc_mm_counter(dst_mm, MM_ANONPAGES);
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page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
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mem_cgroup_commit_charge(page, memcg, false, false);
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lru_cache_add_active_or_unevictable(page, dst_vma);
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set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
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/* No need to invalidate - it was non-present before */
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update_mmu_cache(dst_vma, dst_addr, dst_pte);
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pte_unmap_unlock(dst_pte, ptl);
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ret = 0;
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out:
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return ret;
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out_release_uncharge_unlock:
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pte_unmap_unlock(dst_pte, ptl);
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mem_cgroup_cancel_charge(page, memcg, false);
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out_release:
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put_page(page);
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goto out;
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}
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static int mfill_zeropage_pte(struct mm_struct *dst_mm,
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pmd_t *dst_pmd,
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struct vm_area_struct *dst_vma,
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unsigned long dst_addr)
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{
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pte_t _dst_pte, *dst_pte;
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spinlock_t *ptl;
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int ret;
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pgoff_t offset, max_off;
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struct inode *inode;
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_dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
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dst_vma->vm_page_prot));
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dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
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if (dst_vma->vm_file) {
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/* the shmem MAP_PRIVATE case requires checking the i_size */
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inode = dst_vma->vm_file->f_inode;
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offset = linear_page_index(dst_vma, dst_addr);
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max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
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ret = -EFAULT;
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if (unlikely(offset >= max_off))
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goto out_unlock;
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}
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ret = -EEXIST;
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if (!pte_none(*dst_pte))
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goto out_unlock;
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set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
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/* No need to invalidate - it was non-present before */
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update_mmu_cache(dst_vma, dst_addr, dst_pte);
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ret = 0;
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out_unlock:
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pte_unmap_unlock(dst_pte, ptl);
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return ret;
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}
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static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
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{
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pgd_t *pgd;
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p4d_t *p4d;
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pud_t *pud;
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pgd = pgd_offset(mm, address);
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p4d = p4d_alloc(mm, pgd, address);
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if (!p4d)
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return NULL;
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pud = pud_alloc(mm, p4d, address);
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if (!pud)
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return NULL;
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/*
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* Note that we didn't run this because the pmd was
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* missing, the *pmd may be already established and in
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* turn it may also be a trans_huge_pmd.
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*/
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return pmd_alloc(mm, pud, address);
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}
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#ifdef CONFIG_HUGETLB_PAGE
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/*
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* __mcopy_atomic processing for HUGETLB vmas. Note that this routine is
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* called with mmap_sem held, it will release mmap_sem before returning.
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*/
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static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
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struct vm_area_struct *dst_vma,
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unsigned long dst_start,
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unsigned long src_start,
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unsigned long len,
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bool zeropage)
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{
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int vm_alloc_shared = dst_vma->vm_flags & VM_SHARED;
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int vm_shared = dst_vma->vm_flags & VM_SHARED;
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ssize_t err;
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pte_t *dst_pte;
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unsigned long src_addr, dst_addr;
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long copied;
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struct page *page;
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struct hstate *h;
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unsigned long vma_hpagesize;
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pgoff_t idx;
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u32 hash;
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struct address_space *mapping;
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/*
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* There is no default zero huge page for all huge page sizes as
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* supported by hugetlb. A PMD_SIZE huge pages may exist as used
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* by THP. Since we can not reliably insert a zero page, this
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* feature is not supported.
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*/
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if (zeropage) {
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up_read(&dst_mm->mmap_sem);
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return -EINVAL;
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}
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src_addr = src_start;
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dst_addr = dst_start;
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copied = 0;
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page = NULL;
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vma_hpagesize = vma_kernel_pagesize(dst_vma);
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/*
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* Validate alignment based on huge page size
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*/
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err = -EINVAL;
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if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
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goto out_unlock;
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retry:
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/*
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* On routine entry dst_vma is set. If we had to drop mmap_sem and
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* retry, dst_vma will be set to NULL and we must lookup again.
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*/
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if (!dst_vma) {
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err = -ENOENT;
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dst_vma = find_vma(dst_mm, dst_start);
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if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
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goto out_unlock;
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/*
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* Check the vma is registered in uffd, this is
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* required to enforce the VM_MAYWRITE check done at
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* uffd registration time.
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*/
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if (!dst_vma->vm_userfaultfd_ctx.ctx)
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goto out_unlock;
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if (dst_start < dst_vma->vm_start ||
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dst_start + len > dst_vma->vm_end)
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goto out_unlock;
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err = -EINVAL;
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if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
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goto out_unlock;
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vm_shared = dst_vma->vm_flags & VM_SHARED;
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}
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if (WARN_ON(dst_addr & (vma_hpagesize - 1) ||
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(len - copied) & (vma_hpagesize - 1)))
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goto out_unlock;
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/*
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* If not shared, ensure the dst_vma has a anon_vma.
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*/
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err = -ENOMEM;
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if (!vm_shared) {
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if (unlikely(anon_vma_prepare(dst_vma)))
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goto out_unlock;
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}
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h = hstate_vma(dst_vma);
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while (src_addr < src_start + len) {
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pte_t dst_pteval;
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BUG_ON(dst_addr >= dst_start + len);
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VM_BUG_ON(dst_addr & ~huge_page_mask(h));
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/*
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* Serialize via hugetlb_fault_mutex
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*/
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idx = linear_page_index(dst_vma, dst_addr);
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mapping = dst_vma->vm_file->f_mapping;
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hash = hugetlb_fault_mutex_hash(h, dst_mm, dst_vma, mapping,
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idx, dst_addr);
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mutex_lock(&hugetlb_fault_mutex_table[hash]);
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err = -ENOMEM;
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dst_pte = huge_pte_alloc(dst_mm, dst_addr, huge_page_size(h));
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if (!dst_pte) {
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mutex_unlock(&hugetlb_fault_mutex_table[hash]);
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goto out_unlock;
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}
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err = -EEXIST;
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dst_pteval = huge_ptep_get(dst_pte);
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if (!huge_pte_none(dst_pteval)) {
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mutex_unlock(&hugetlb_fault_mutex_table[hash]);
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goto out_unlock;
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}
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err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma,
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dst_addr, src_addr, &page);
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mutex_unlock(&hugetlb_fault_mutex_table[hash]);
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vm_alloc_shared = vm_shared;
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cond_resched();
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if (unlikely(err == -ENOENT)) {
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up_read(&dst_mm->mmap_sem);
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BUG_ON(!page);
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err = copy_huge_page_from_user(page,
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(const void __user *)src_addr,
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pages_per_huge_page(h), true);
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if (unlikely(err)) {
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err = -EFAULT;
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goto out;
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}
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down_read(&dst_mm->mmap_sem);
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dst_vma = NULL;
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goto retry;
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} else
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BUG_ON(page);
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if (!err) {
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dst_addr += vma_hpagesize;
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src_addr += vma_hpagesize;
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copied += vma_hpagesize;
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if (fatal_signal_pending(current))
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err = -EINTR;
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}
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if (err)
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break;
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}
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out_unlock:
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up_read(&dst_mm->mmap_sem);
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out:
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if (page) {
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/*
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* We encountered an error and are about to free a newly
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* allocated huge page.
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*
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* Reservation handling is very subtle, and is different for
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* private and shared mappings. See the routine
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* restore_reserve_on_error for details. Unfortunately, we
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* can not call restore_reserve_on_error now as it would
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* require holding mmap_sem.
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*
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* If a reservation for the page existed in the reservation
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* map of a private mapping, the map was modified to indicate
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* the reservation was consumed when the page was allocated.
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* We clear the PagePrivate flag now so that the global
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* reserve count will not be incremented in free_huge_page.
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* The reservation map will still indicate the reservation
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* was consumed and possibly prevent later page allocation.
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* This is better than leaking a global reservation. If no
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* reservation existed, it is still safe to clear PagePrivate
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* as no adjustments to reservation counts were made during
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* allocation.
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*
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* The reservation map for shared mappings indicates which
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* pages have reservations. When a huge page is allocated
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* for an address with a reservation, no change is made to
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* the reserve map. In this case PagePrivate will be set
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* to indicate that the global reservation count should be
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* incremented when the page is freed. This is the desired
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* behavior. However, when a huge page is allocated for an
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* address without a reservation a reservation entry is added
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* to the reservation map, and PagePrivate will not be set.
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* When the page is freed, the global reserve count will NOT
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* be incremented and it will appear as though we have leaked
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* reserved page. In this case, set PagePrivate so that the
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* global reserve count will be incremented to match the
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* reservation map entry which was created.
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*
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* Note that vm_alloc_shared is based on the flags of the vma
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* for which the page was originally allocated. dst_vma could
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* be different or NULL on error.
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*/
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if (vm_alloc_shared)
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SetPagePrivate(page);
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else
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ClearPagePrivate(page);
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put_page(page);
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}
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BUG_ON(copied < 0);
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BUG_ON(err > 0);
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BUG_ON(!copied && !err);
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return copied ? copied : err;
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}
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#else /* !CONFIG_HUGETLB_PAGE */
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/* fail at build time if gcc attempts to use this */
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extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
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struct vm_area_struct *dst_vma,
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unsigned long dst_start,
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unsigned long src_start,
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unsigned long len,
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bool zeropage);
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#endif /* CONFIG_HUGETLB_PAGE */
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static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
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pmd_t *dst_pmd,
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struct vm_area_struct *dst_vma,
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unsigned long dst_addr,
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unsigned long src_addr,
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struct page **page,
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bool zeropage)
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{
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ssize_t err;
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/*
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* The normal page fault path for a shmem will invoke the
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* fault, fill the hole in the file and COW it right away. The
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* result generates plain anonymous memory. So when we are
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* asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll
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* generate anonymous memory directly without actually filling
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* the hole. For the MAP_PRIVATE case the robustness check
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* only happens in the pagetable (to verify it's still none)
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* and not in the radix tree.
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*/
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if (!(dst_vma->vm_flags & VM_SHARED)) {
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if (!zeropage)
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err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
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dst_addr, src_addr, page);
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else
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err = mfill_zeropage_pte(dst_mm, dst_pmd,
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dst_vma, dst_addr);
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} else {
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if (!zeropage)
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err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd,
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dst_vma, dst_addr,
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src_addr, page);
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else
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err = shmem_mfill_zeropage_pte(dst_mm, dst_pmd,
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dst_vma, dst_addr);
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}
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return err;
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}
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static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
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unsigned long dst_start,
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unsigned long src_start,
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unsigned long len,
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bool zeropage,
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bool *mmap_changing)
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{
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struct vm_area_struct *dst_vma;
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ssize_t err;
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pmd_t *dst_pmd;
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unsigned long src_addr, dst_addr;
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long copied;
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struct page *page;
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/*
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* Sanitize the command parameters:
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*/
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BUG_ON(dst_start & ~PAGE_MASK);
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BUG_ON(len & ~PAGE_MASK);
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/* Does the address range wrap, or is the span zero-sized? */
|
|
BUG_ON(src_start + len <= src_start);
|
|
BUG_ON(dst_start + len <= dst_start);
|
|
|
|
src_addr = src_start;
|
|
dst_addr = dst_start;
|
|
copied = 0;
|
|
page = NULL;
|
|
retry:
|
|
down_read(&dst_mm->mmap_sem);
|
|
|
|
/*
|
|
* If memory mappings are changing because of non-cooperative
|
|
* operation (e.g. mremap) running in parallel, bail out and
|
|
* request the user to retry later
|
|
*/
|
|
err = -EAGAIN;
|
|
if (mmap_changing && READ_ONCE(*mmap_changing))
|
|
goto out_unlock;
|
|
|
|
/*
|
|
* Make sure the vma is not shared, that the dst range is
|
|
* both valid and fully within a single existing vma.
|
|
*/
|
|
err = -ENOENT;
|
|
dst_vma = find_vma(dst_mm, dst_start);
|
|
if (!dst_vma)
|
|
goto out_unlock;
|
|
/*
|
|
* Check the vma is registered in uffd, this is required to
|
|
* enforce the VM_MAYWRITE check done at uffd registration
|
|
* time.
|
|
*/
|
|
if (!dst_vma->vm_userfaultfd_ctx.ctx)
|
|
goto out_unlock;
|
|
|
|
if (dst_start < dst_vma->vm_start ||
|
|
dst_start + len > dst_vma->vm_end)
|
|
goto out_unlock;
|
|
|
|
err = -EINVAL;
|
|
/*
|
|
* shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
|
|
* it will overwrite vm_ops, so vma_is_anonymous must return false.
|
|
*/
|
|
if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
|
|
dst_vma->vm_flags & VM_SHARED))
|
|
goto out_unlock;
|
|
|
|
/*
|
|
* If this is a HUGETLB vma, pass off to appropriate routine
|
|
*/
|
|
if (is_vm_hugetlb_page(dst_vma))
|
|
return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
|
|
src_start, len, zeropage);
|
|
|
|
if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
|
|
goto out_unlock;
|
|
|
|
/*
|
|
* Ensure the dst_vma has a anon_vma or this page
|
|
* would get a NULL anon_vma when moved in the
|
|
* dst_vma.
|
|
*/
|
|
err = -ENOMEM;
|
|
if (!(dst_vma->vm_flags & VM_SHARED) &&
|
|
unlikely(anon_vma_prepare(dst_vma)))
|
|
goto out_unlock;
|
|
|
|
while (src_addr < src_start + len) {
|
|
pmd_t dst_pmdval;
|
|
|
|
BUG_ON(dst_addr >= dst_start + len);
|
|
|
|
dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
|
|
if (unlikely(!dst_pmd)) {
|
|
err = -ENOMEM;
|
|
break;
|
|
}
|
|
|
|
dst_pmdval = pmd_read_atomic(dst_pmd);
|
|
/*
|
|
* If the dst_pmd is mapped as THP don't
|
|
* override it and just be strict.
|
|
*/
|
|
if (unlikely(pmd_trans_huge(dst_pmdval))) {
|
|
err = -EEXIST;
|
|
break;
|
|
}
|
|
if (unlikely(pmd_none(dst_pmdval)) &&
|
|
unlikely(__pte_alloc(dst_mm, dst_pmd))) {
|
|
err = -ENOMEM;
|
|
break;
|
|
}
|
|
/* If an huge pmd materialized from under us fail */
|
|
if (unlikely(pmd_trans_huge(*dst_pmd))) {
|
|
err = -EFAULT;
|
|
break;
|
|
}
|
|
|
|
BUG_ON(pmd_none(*dst_pmd));
|
|
BUG_ON(pmd_trans_huge(*dst_pmd));
|
|
|
|
err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
|
|
src_addr, &page, zeropage);
|
|
cond_resched();
|
|
|
|
if (unlikely(err == -ENOENT)) {
|
|
void *page_kaddr;
|
|
|
|
up_read(&dst_mm->mmap_sem);
|
|
BUG_ON(!page);
|
|
|
|
page_kaddr = kmap(page);
|
|
err = copy_from_user(page_kaddr,
|
|
(const void __user *) src_addr,
|
|
PAGE_SIZE);
|
|
kunmap(page);
|
|
if (unlikely(err)) {
|
|
err = -EFAULT;
|
|
goto out;
|
|
}
|
|
goto retry;
|
|
} else
|
|
BUG_ON(page);
|
|
|
|
if (!err) {
|
|
dst_addr += PAGE_SIZE;
|
|
src_addr += PAGE_SIZE;
|
|
copied += PAGE_SIZE;
|
|
|
|
if (fatal_signal_pending(current))
|
|
err = -EINTR;
|
|
}
|
|
if (err)
|
|
break;
|
|
}
|
|
|
|
out_unlock:
|
|
up_read(&dst_mm->mmap_sem);
|
|
out:
|
|
if (page)
|
|
put_page(page);
|
|
BUG_ON(copied < 0);
|
|
BUG_ON(err > 0);
|
|
BUG_ON(!copied && !err);
|
|
return copied ? copied : err;
|
|
}
|
|
|
|
ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
|
|
unsigned long src_start, unsigned long len,
|
|
bool *mmap_changing)
|
|
{
|
|
return __mcopy_atomic(dst_mm, dst_start, src_start, len, false,
|
|
mmap_changing);
|
|
}
|
|
|
|
ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
|
|
unsigned long len, bool *mmap_changing)
|
|
{
|
|
return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing);
|
|
}
|