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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 <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mike Rapoport 2017-02-22 15:43:25 -08:00 committed by Linus Torvalds
parent ba6907db6d
commit 4c27fe4c4c
2 changed files with 121 additions and 0 deletions
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11
include/linux/shmem_fs.h
View File

@ -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

110
mm/shmem.c
View File

@ -70,6 +70,7 @@ static struct vfsmount *shm_mnt;
#include <linux/syscalls.h>
#include <linux/fcntl.h>
#include <uapi/linux/memfd.h>
#include <linux/rmap.h>
#include <linux/uaccess.h>
#include <asm/pgtable.h>
@ -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;