Commit 7d64ae3a authored by Axel Rasmussen's avatar Axel Rasmussen Committed by Linus Torvalds
Browse files

userfaultfd/shmem: modify shmem_mfill_atomic_pte to use install_pte() 

In a previous commit, we added the mfill_atomic_install_pte() helper.
This helper does the job of setting up PTEs for an existing page, to map
it into a given VMA.  It deals with both the anon and shmem cases, as well
as the shared and private cases.

In other words, shmem_mfill_atomic_pte() duplicates a case it already
handles.  So, expose it, and let shmem_mfill_atomic_pte() use it directly,
to reduce code duplication.

This requires that we refactor shmem_mfill_atomic_pte() a bit:

Instead of doing accounting (shmem_recalc_inode() et al) part-way through
the PTE setup, do it afterward.  This frees up mfill_atomic_install_pte()
from having to care about this accounting, and means we don't need to e.g.
shmem_uncharge() in the error path.

A side effect is this switches shmem_mfill_atomic_pte() to use
lru_cache_add_inactive_or_unevictable() instead of just lru_cache_add().
This wrapper does some extra accounting in an exceptional case, if
appropriate, so it's actually the more correct thing to use.

Link: https://lkml.kernel.org/r/20210503180737.2487560-7-axelrasmussen@google.com


Signed-off-by: default avatarAxel Rasmussen <axelrasmussen@google.com>
Reviewed-by: default avatarPeter Xu <peterx@redhat.com>
Acked-by: default avatarHugh Dickins <hughd@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Wang Qing <wangqing@vivo.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 964ab004

include/linux/userfaultfd_k.h

+5 −0
Original line number Diff line number Diff line
@@ -53,6 +53,11 @@ enum mcopy_atomic_mode { 
	MCOPY_ATOMIC_CONTINUE,

};



extern int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,

				    struct vm_area_struct *dst_vma,

				    unsigned long dst_addr, struct page *page,

				    bool newly_allocated, bool wp_copy);



extern ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,

			    unsigned long src_start, unsigned long len,

			    bool *mmap_changing, __u64 mode);

mm/shmem.c

+12 −46
Original line number Diff line number Diff line
@@ -2376,14 +2376,11 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, 
	struct address_space *mapping = inode->i_mapping;

	gfp_t gfp = mapping_gfp_mask(mapping);

	pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);

	spinlock_t *ptl;

	void *page_kaddr;

	struct page *page;

	pte_t _dst_pte, *dst_pte;

	int ret;

	pgoff_t max_off;



	ret = -ENOMEM;

	if (!shmem_inode_acct_block(inode, 1)) {

		/*

		 * We may have got a page, returned -ENOENT triggering a retry,
@@ -2394,10 +2391,11 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, 
			put_page(*pagep);

			*pagep = NULL;

		}

		goto out;

		return -ENOMEM;

	}



	if (!*pagep) {

		ret = -ENOMEM;

		page = shmem_alloc_page(gfp, info, pgoff);

		if (!page)

			goto out_unacct_blocks;
@@ -2412,9 +2410,9 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, 
			/* fallback to copy_from_user outside mmap_lock */

			if (unlikely(ret)) {

				*pagep = page;

				shmem_inode_unacct_blocks(inode, 1);

				ret = -ENOENT;

				/* don't free the page */

				return -ENOENT;

				goto out_unacct_blocks;

			}

		} else {		/* ZEROPAGE */

			clear_highpage(page);
@@ -2440,32 +2438,10 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, 
	if (ret)

		goto out_release;



	_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));

	else {

		/*

		 * We don't set the pte dirty if the vma has no

		 * VM_WRITE permission, so mark the page dirty or it

		 * could be freed from under us. We could do it

		 * unconditionally before unlock_page(), but doing it

		 * only if VM_WRITE is not set is faster.

		 */

		set_page_dirty(page);

	}



	dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);



	ret = -EFAULT;

	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);

	if (unlikely(pgoff >= max_off))

		goto out_release_unlock;



	ret = -EEXIST;

	if (!pte_none(*dst_pte))

		goto out_release_unlock;



	lru_cache_add(page);

	ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,

				       page, true, false);

	if (ret)

		goto out_delete_from_cache;



	spin_lock_irq(&info->lock);

	info->alloced++;
@@ -2473,27 +2449,17 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, 
	shmem_recalc_inode(inode);

	spin_unlock_irq(&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);

	pte_unmap_unlock(dst_pte, ptl);

	SetPageDirty(page);

	unlock_page(page);

	ret = 0;

out:

	return ret;

out_release_unlock:

	pte_unmap_unlock(dst_pte, ptl);

	ClearPageDirty(page);

	return 0;

out_delete_from_cache:

	delete_from_page_cache(page);

out_release:

	unlock_page(page);

	put_page(page);

out_unacct_blocks:

	shmem_inode_unacct_blocks(inode, 1);

	goto out;

	return ret;

}

#endif /* CONFIG_USERFAULTFD */

mm/userfaultfd.c

+6 −11
Original line number Diff line number Diff line
@@ -51,15 +51,10 @@ struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, 
/*

 * Install PTEs, to map dst_addr (within dst_vma) to page.

 *

 * This function handles MCOPY_ATOMIC_CONTINUE (which is always file-backed),

 * whether or not dst_vma is VM_SHARED. It also handles the more general

 * MCOPY_ATOMIC_NORMAL case, when dst_vma is *not* VM_SHARED (it may be file

 * backed, or not).

 *

 * Note that MCOPY_ATOMIC_NORMAL for a VM_SHARED dst_vma is handled by

 * shmem_mcopy_atomic_pte instead.

 * This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem

 * and anon, and for both shared and private VMAs.

 */

static int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,

int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,

			     struct vm_area_struct *dst_vma,

			     unsigned long dst_addr, struct page *page,

			     bool newly_allocated, bool wp_copy)