From: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Subject: userfaultfd: shmem: add shmem_mfill_zeropage_pte for userfaultfd support shmem_mfill_zeropage_pte is the low level routine that implements the userfaultfd UFFDIO_ZEROPAGE command. Since for shmem mappings zero pages are always allocated and accounted, the new method is a slight extension of the existing shmem_mcopy_atomic_pte. Link: http://lkml.kernel.org/r/1497939652-16528-4-git-send-email-rppt@xxxxxxxxxxxxxxxxxx Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/shmem_fs.h | 6 +++ mm/shmem.c | 62 ++++++++++++++++++++++++++----------- 2 files changed, 51 insertions(+), 17 deletions(-) diff -puN include/linux/shmem_fs.h~userfaultfd-shmem-add-shmem_mfill_zeropage_pte-for-userfaultfd-support include/linux/shmem_fs.h --- a/include/linux/shmem_fs.h~userfaultfd-shmem-add-shmem_mfill_zeropage_pte-for-userfaultfd-support +++ a/include/linux/shmem_fs.h @@ -137,9 +137,15 @@ extern int shmem_mcopy_atomic_pte(struct unsigned long dst_addr, unsigned long src_addr, struct page **pagep); +extern int shmem_mfill_zeropage_pte(struct mm_struct *dst_mm, + pmd_t *dst_pmd, + struct vm_area_struct *dst_vma, + unsigned long dst_addr); #else #define shmem_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, dst_addr, \ src_addr, pagep) ({ BUG(); 0; }) +#define shmem_mfill_zeropage_pte(dst_mm, dst_pmd, dst_vma, \ + dst_addr) ({ BUG(); 0; }) #endif #endif diff -puN mm/shmem.c~userfaultfd-shmem-add-shmem_mfill_zeropage_pte-for-userfaultfd-support mm/shmem.c --- a/mm/shmem.c~userfaultfd-shmem-add-shmem_mfill_zeropage_pte-for-userfaultfd-support +++ a/mm/shmem.c @@ -2207,12 +2207,13 @@ bool shmem_mapping(struct address_space 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) +static int shmem_mfill_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, + bool zeropage, + struct page **pagep) { struct inode *inode = file_inode(dst_vma->vm_file); struct shmem_inode_info *info = SHMEM_I(inode); @@ -2235,17 +2236,22 @@ int shmem_mcopy_atomic_pte(struct mm_str if (!page) goto out_unacct_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; - shmem_inode_unacct_blocks(inode, 1); - /* don't free the page */ - return -EFAULT; + if (!zeropage) { /* mcopy_atomic */ + 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; + shmem_inode_unacct_blocks(inode, 1); + /* don't free the page */ + return -EFAULT; + } + } else { /* mfill_zeropage_atomic */ + clear_highpage(page); } } else { page = *pagep; @@ -2311,6 +2317,28 @@ out_unacct_blocks: goto out; } +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) +{ + return shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, + dst_addr, src_addr, false, pagep); +} + +int shmem_mfill_zeropage_pte(struct mm_struct *dst_mm, + pmd_t *dst_pmd, + struct vm_area_struct *dst_vma, + unsigned long dst_addr) +{ + struct page *page = NULL; + + return shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, + dst_addr, 0, true, &page); +} + #ifdef CONFIG_TMPFS static const struct inode_operations shmem_symlink_inode_operations; static const struct inode_operations shmem_short_symlink_operations; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
