mirror of
https://github.com/torvalds/linux
synced 2024-09-06 18:01:05 +00:00
userfaultfd/shmem: support UFFDIO_CONTINUE for shmem
With this change, userspace can resolve a minor fault within a shmem-backed area with a UFFDIO_CONTINUE ioctl. The semantics for this match those for hugetlbfs - we look up the existing page in the page cache, and install a PTE for it. This commit introduces a new helper: mfill_atomic_install_pte. Why handle UFFDIO_CONTINUE for shmem in mm/userfaultfd.c, instead of in shmem.c? The existing userfault implementation only relies on shmem.c for VM_SHARED VMAs. However, minor fault handling / CONTINUE work just fine for !VM_SHARED VMAs as well. We'd prefer to handle CONTINUE for shmem in one place, regardless of shared/private (to reduce code duplication). Why add a new mfill_atomic_install_pte helper? A problem we have with continue is that shmem_mfill_atomic_pte() and mcopy_atomic_pte() are *close* to what we want, but not exactly. We do want to setup the PTEs in a CONTINUE operation, but we don't want to e.g. allocate a new page, charge it (e.g. to the shmem inode), manipulate various flags, etc. Also we have the problem stated above: shmem_mfill_atomic_pte() and mcopy_atomic_pte() both handle one-half of the problem (shared / private) continue cares about. So, introduce mcontinue_atomic_pte(), to handle all of the shmem continue cases. Introduce the helper so it doesn't duplicate code with mcopy_atomic_pte(). In a future commit, shmem_mfill_atomic_pte() will also be modified to use this new helper. However, since this is a bigger refactor, it seems most clear to do it as a separate change. Link: https://lkml.kernel.org/r/20210503180737.2487560-5-axelrasmussen@google.com Signed-off-by: Axel Rasmussen <axelrasmussen@google.com> Acked-by: Hugh Dickins <hughd@google.com> Acked-by: Peter Xu <peterx@redhat.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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
c949b097ef
commit
153132571f
172
mm/userfaultfd.c
172
mm/userfaultfd.c
|
@ -48,6 +48,83 @@ struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm,
|
|||
return dst_vma;
|
||||
}
|
||||
|
||||
/*
|
||||
* 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.
|
||||
*/
|
||||
static 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)
|
||||
{
|
||||
int ret;
|
||||
pte_t _dst_pte, *dst_pte;
|
||||
bool writable = dst_vma->vm_flags & VM_WRITE;
|
||||
bool vm_shared = dst_vma->vm_flags & VM_SHARED;
|
||||
bool page_in_cache = page->mapping;
|
||||
spinlock_t *ptl;
|
||||
struct inode *inode;
|
||||
pgoff_t offset, max_off;
|
||||
|
||||
_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
|
||||
if (page_in_cache && !vm_shared)
|
||||
writable = false;
|
||||
if (writable || !page_in_cache)
|
||||
_dst_pte = pte_mkdirty(_dst_pte);
|
||||
if (writable) {
|
||||
if (wp_copy)
|
||||
_dst_pte = pte_mkuffd_wp(_dst_pte);
|
||||
else
|
||||
_dst_pte = pte_mkwrite(_dst_pte);
|
||||
}
|
||||
|
||||
dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
|
||||
|
||||
if (vma_is_shmem(dst_vma)) {
|
||||
/* serialize against truncate with the page table lock */
|
||||
inode = dst_vma->vm_file->f_inode;
|
||||
offset = linear_page_index(dst_vma, dst_addr);
|
||||
max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
|
||||
ret = -EFAULT;
|
||||
if (unlikely(offset >= max_off))
|
||||
goto out_unlock;
|
||||
}
|
||||
|
||||
ret = -EEXIST;
|
||||
if (!pte_none(*dst_pte))
|
||||
goto out_unlock;
|
||||
|
||||
if (page_in_cache)
|
||||
page_add_file_rmap(page, false);
|
||||
else
|
||||
page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
|
||||
|
||||
/*
|
||||
* Must happen after rmap, as mm_counter() checks mapping (via
|
||||
* PageAnon()), which is set by __page_set_anon_rmap().
|
||||
*/
|
||||
inc_mm_counter(dst_mm, mm_counter(page));
|
||||
|
||||
if (newly_allocated)
|
||||
lru_cache_add_inactive_or_unevictable(page, dst_vma);
|
||||
|
||||
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);
|
||||
ret = 0;
|
||||
out_unlock:
|
||||
pte_unmap_unlock(dst_pte, ptl);
|
||||
return ret;
|
||||
}
|
||||
|
||||
static int mcopy_atomic_pte(struct mm_struct *dst_mm,
|
||||
pmd_t *dst_pmd,
|
||||
struct vm_area_struct *dst_vma,
|
||||
|
@ -56,13 +133,9 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
|
|||
struct page **pagep,
|
||||
bool wp_copy)
|
||||
{
|
||||
pte_t _dst_pte, *dst_pte;
|
||||
spinlock_t *ptl;
|
||||
void *page_kaddr;
|
||||
int ret;
|
||||
struct page *page;
|
||||
pgoff_t offset, max_off;
|
||||
struct inode *inode;
|
||||
|
||||
if (!*pagep) {
|
||||
ret = -ENOMEM;
|
||||
|
@ -99,43 +172,12 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
|
|||
if (mem_cgroup_charge(page, dst_mm, GFP_KERNEL))
|
||||
goto out_release;
|
||||
|
||||
_dst_pte = pte_mkdirty(mk_pte(page, dst_vma->vm_page_prot));
|
||||
if (dst_vma->vm_flags & VM_WRITE) {
|
||||
if (wp_copy)
|
||||
_dst_pte = pte_mkuffd_wp(_dst_pte);
|
||||
else
|
||||
_dst_pte = pte_mkwrite(_dst_pte);
|
||||
}
|
||||
|
||||
dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
|
||||
if (dst_vma->vm_file) {
|
||||
/* the shmem MAP_PRIVATE case requires checking the i_size */
|
||||
inode = dst_vma->vm_file->f_inode;
|
||||
offset = linear_page_index(dst_vma, dst_addr);
|
||||
max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
|
||||
ret = -EFAULT;
|
||||
if (unlikely(offset >= max_off))
|
||||
goto out_release_uncharge_unlock;
|
||||
}
|
||||
ret = -EEXIST;
|
||||
if (!pte_none(*dst_pte))
|
||||
goto out_release_uncharge_unlock;
|
||||
|
||||
inc_mm_counter(dst_mm, MM_ANONPAGES);
|
||||
page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
|
||||
lru_cache_add_inactive_or_unevictable(page, dst_vma);
|
||||
|
||||
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);
|
||||
ret = 0;
|
||||
ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
|
||||
page, true, wp_copy);
|
||||
if (ret)
|
||||
goto out_release;
|
||||
out:
|
||||
return ret;
|
||||
out_release_uncharge_unlock:
|
||||
pte_unmap_unlock(dst_pte, ptl);
|
||||
out_release:
|
||||
put_page(page);
|
||||
goto out;
|
||||
|
@ -176,6 +218,41 @@ static int mfill_zeropage_pte(struct mm_struct *dst_mm,
|
|||
return ret;
|
||||
}
|
||||
|
||||
/* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */
|
||||
static int mcontinue_atomic_pte(struct mm_struct *dst_mm,
|
||||
pmd_t *dst_pmd,
|
||||
struct vm_area_struct *dst_vma,
|
||||
unsigned long dst_addr,
|
||||
bool wp_copy)
|
||||
{
|
||||
struct inode *inode = file_inode(dst_vma->vm_file);
|
||||
pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
|
||||
struct page *page;
|
||||
int ret;
|
||||
|
||||
ret = shmem_getpage(inode, pgoff, &page, SGP_READ);
|
||||
if (ret)
|
||||
goto out;
|
||||
if (!page) {
|
||||
ret = -EFAULT;
|
||||
goto out;
|
||||
}
|
||||
|
||||
ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
|
||||
page, false, wp_copy);
|
||||
if (ret)
|
||||
goto out_release;
|
||||
|
||||
unlock_page(page);
|
||||
ret = 0;
|
||||
out:
|
||||
return ret;
|
||||
out_release:
|
||||
unlock_page(page);
|
||||
put_page(page);
|
||||
goto out;
|
||||
}
|
||||
|
||||
static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
|
||||
{
|
||||
pgd_t *pgd;
|
||||
|
@ -367,11 +444,16 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
|
|||
unsigned long dst_addr,
|
||||
unsigned long src_addr,
|
||||
struct page **page,
|
||||
bool zeropage,
|
||||
enum mcopy_atomic_mode mode,
|
||||
bool wp_copy)
|
||||
{
|
||||
ssize_t err;
|
||||
|
||||
if (mode == MCOPY_ATOMIC_CONTINUE) {
|
||||
return mcontinue_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
|
||||
wp_copy);
|
||||
}
|
||||
|
||||
/*
|
||||
* The normal page fault path for a shmem will invoke the
|
||||
* fault, fill the hole in the file and COW it right away. The
|
||||
|
@ -383,7 +465,7 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
|
|||
* and not in the radix tree.
|
||||
*/
|
||||
if (!(dst_vma->vm_flags & VM_SHARED)) {
|
||||
if (!zeropage)
|
||||
if (mode == MCOPY_ATOMIC_NORMAL)
|
||||
err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
|
||||
dst_addr, src_addr, page,
|
||||
wp_copy);
|
||||
|
@ -393,7 +475,8 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
|
|||
} else {
|
||||
VM_WARN_ON_ONCE(wp_copy);
|
||||
err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
|
||||
dst_addr, src_addr, zeropage,
|
||||
dst_addr, src_addr,
|
||||
mode != MCOPY_ATOMIC_NORMAL,
|
||||
page);
|
||||
}
|
||||
|
||||
|
@ -415,7 +498,6 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
|
|||
long copied;
|
||||
struct page *page;
|
||||
bool wp_copy;
|
||||
bool zeropage = (mcopy_mode == MCOPY_ATOMIC_ZEROPAGE);
|
||||
|
||||
/*
|
||||
* Sanitize the command parameters:
|
||||
|
@ -478,7 +560,7 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
|
|||
|
||||
if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
|
||||
goto out_unlock;
|
||||
if (mcopy_mode == MCOPY_ATOMIC_CONTINUE)
|
||||
if (!vma_is_shmem(dst_vma) && mcopy_mode == MCOPY_ATOMIC_CONTINUE)
|
||||
goto out_unlock;
|
||||
|
||||
/*
|
||||
|
@ -526,7 +608,7 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
|
|||
BUG_ON(pmd_trans_huge(*dst_pmd));
|
||||
|
||||
err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
|
||||
src_addr, &page, zeropage, wp_copy);
|
||||
src_addr, &page, mcopy_mode, wp_copy);
|
||||
cond_resched();
|
||||
|
||||
if (unlikely(err == -ENOENT)) {
|
||||
|
|
Loading…
Reference in a new issue