From 4c27fe4c4c84f3afd504ecff2420cc1ad420d38e Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Wed, 22 Feb 2017 15:43:25 -0800 Subject: [PATCH] userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support shmem_mcopy_atomic_pte is the low level routine that implements the userfaultfd UFFDIO_COPY command. It is based on the existing mcopy_atomic_pte routine with modifications for shared memory pages. Link: http://lkml.kernel.org/r/20161216144821.5183-29-aarcange@redhat.com Signed-off-by: Mike Rapoport Signed-off-by: Andrea Arcangeli Cc: "Dr. David Alan Gilbert" Cc: Hillf Danton Cc: Michael Rapoport Cc: Mike Kravetz Cc: Pavel Emelyanov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/shmem_fs.h | 11 ++++ mm/shmem.c | 110 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 121 insertions(+) diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index ff078e7043b6..fdaac9d4d46d 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -124,4 +124,15 @@ static inline bool shmem_huge_enabled(struct vm_area_struct *vma) } #endif +#ifdef CONFIG_SHMEM +extern int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, + struct vm_area_struct *dst_vma, + unsigned long dst_addr, + unsigned long src_addr, + struct page **pagep); +#else +#define shmem_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, dst_addr, \ + src_addr, pagep) ({ BUG(); 0; }) +#endif + #endif diff --git a/mm/shmem.c b/mm/shmem.c index 7d52cd4b504d..14de2a9e5083 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -70,6 +70,7 @@ static struct vfsmount *shm_mnt; #include #include #include +#include #include #include @@ -2178,6 +2179,115 @@ bool shmem_mapping(struct address_space *mapping) return mapping->a_ops == &shmem_aops; } +int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm, + pmd_t *dst_pmd, + struct vm_area_struct *dst_vma, + unsigned long dst_addr, + unsigned long src_addr, + struct page **pagep) +{ + struct inode *inode = file_inode(dst_vma->vm_file); + struct shmem_inode_info *info = SHMEM_I(inode); + struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); + struct address_space *mapping = inode->i_mapping; + gfp_t gfp = mapping_gfp_mask(mapping); + pgoff_t pgoff = linear_page_index(dst_vma, dst_addr); + struct mem_cgroup *memcg; + spinlock_t *ptl; + void *page_kaddr; + struct page *page; + pte_t _dst_pte, *dst_pte; + int ret; + + if (!*pagep) { + ret = -ENOMEM; + if (shmem_acct_block(info->flags, 1)) + goto out; + if (sbinfo->max_blocks) { + if (percpu_counter_compare(&sbinfo->used_blocks, + sbinfo->max_blocks) >= 0) + goto out_unacct_blocks; + percpu_counter_inc(&sbinfo->used_blocks); + } + + page = shmem_alloc_page(gfp, info, pgoff); + if (!page) + goto out_dec_used_blocks; + + page_kaddr = kmap_atomic(page); + ret = copy_from_user(page_kaddr, (const void __user *)src_addr, + PAGE_SIZE); + kunmap_atomic(page_kaddr); + + /* fallback to copy_from_user outside mmap_sem */ + if (unlikely(ret)) { + *pagep = page; + /* don't free the page */ + return -EFAULT; + } + } else { + page = *pagep; + *pagep = NULL; + } + + ret = mem_cgroup_try_charge(page, dst_mm, gfp, &memcg, false); + if (ret) + goto out_release; + + ret = radix_tree_maybe_preload(gfp & GFP_RECLAIM_MASK); + if (!ret) { + ret = shmem_add_to_page_cache(page, mapping, pgoff, NULL); + radix_tree_preload_end(); + } + if (ret) + goto out_release_uncharge; + + mem_cgroup_commit_charge(page, memcg, false, false); + + _dst_pte = mk_pte(page, dst_vma->vm_page_prot); + if (dst_vma->vm_flags & VM_WRITE) + _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte)); + + ret = -EEXIST; + dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); + if (!pte_none(*dst_pte)) + goto out_release_uncharge_unlock; + + __SetPageUptodate(page); + + lru_cache_add_anon(page); + + spin_lock(&info->lock); + info->alloced++; + inode->i_blocks += BLOCKS_PER_PAGE; + shmem_recalc_inode(inode); + spin_unlock(&info->lock); + + inc_mm_counter(dst_mm, mm_counter_file(page)); + page_add_file_rmap(page, false); + set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); + + /* No need to invalidate - it was non-present before */ + update_mmu_cache(dst_vma, dst_addr, dst_pte); + unlock_page(page); + pte_unmap_unlock(dst_pte, ptl); + ret = 0; +out: + return ret; +out_release_uncharge_unlock: + pte_unmap_unlock(dst_pte, ptl); +out_release_uncharge: + mem_cgroup_cancel_charge(page, memcg, false); +out_release: + put_page(page); +out_dec_used_blocks: + if (sbinfo->max_blocks) + percpu_counter_add(&sbinfo->used_blocks, -1); +out_unacct_blocks: + shmem_unacct_blocks(info->flags, 1); + goto out; +} + #ifdef CONFIG_TMPFS static const struct inode_operations shmem_symlink_inode_operations; static const struct inode_operations shmem_short_symlink_operations;