superrob1500
/
mirror-linux
mirror of https://github.com/torvalds/linux
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

userfaultfd: introduce vm_uffd_ops->alloc_folio() 

and use it to refactor mfill_atomic_pte_zeroed_folio() and
mfill_atomic_pte_copy().

mfill_atomic_pte_zeroed_folio() and mfill_atomic_pte_copy() perform
almost identical actions:
* allocate a folio
* update folio contents (either copy from userspace of fill with zeros)
* update page tables with the new folio

Split a __mfill_atomic_pte() helper that handles both cases and uses newly
introduced vm_uffd_ops->alloc_folio() to allocate the folio.

Pass the ops structure from the callers to __mfill_atomic_pte() to later
allow using anon_uffd_ops for MAP_PRIVATE mappings of file-backed VMAs.

Note, that the new ops method is called alloc_folio() rather than
folio_alloc() to avoid clash with alloc_tag macro folio_alloc().

Link: https://lore.kernel.org/20260402041156.1377214-10-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: James Houghton <jthoughton@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrei Vagin <avagin@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Harry Yoo <harry.yoo@oracle.com>
Cc: Harry Yoo (Oracle) <harry@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nikita Kalyazin <kalyazin@amazon.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Carlier <devnexen@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
master
Mike Rapoport (Microsoft) 2026-04-02 07:11:50 +03:00 committed by Andrew Morton
parent dfc4d77182
commit ad9ac30813
2 changed files with 54 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/userfaultfd_k.h
View File

@ -94,6 +94,12 @@ struct vm_uffd_ops {
* The returned folio is locked and with reference held.
*/
struct folio *(*get_folio_noalloc)(struct inode *inode, pgoff_t pgoff);
/*
* Called during resolution of UFFDIO_COPY request.
* Should allocate and return a folio or NULL if allocation fails.
*/
struct folio *(*alloc_folio)(struct vm_area_struct *vma,
unsigned long addr);
};
/* A combined operation mode + behavior flags. */

92
mm/userfaultfd.c
View File

@ -42,8 +42,26 @@ static bool anon_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags)
return true;
}
static struct folio *anon_alloc_folio(struct vm_area_struct *vma,
unsigned long addr)
{
struct folio *folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma,
addr);
if (!folio)
return NULL;
if (mem_cgroup_charge(folio, vma->vm_mm, GFP_KERNEL)) {
folio_put(folio);
return NULL;
}
return folio;
}
static const struct vm_uffd_ops anon_uffd_ops = {
.can_userfault = anon_can_userfault,
.alloc_folio = anon_alloc_folio,
};
static const struct vm_uffd_ops *vma_uffd_ops(struct vm_area_struct *vma)
@ -456,7 +474,8 @@ static int mfill_copy_folio_retry(struct mfill_state *state, struct folio *folio
return 0;
}
static int mfill_atomic_pte_copy(struct mfill_state *state)
static int __mfill_atomic_pte(struct mfill_state *state,
const struct vm_uffd_ops *ops)
{
unsigned long dst_addr = state->dst_addr;
unsigned long src_addr = state->src_addr;
@ -464,16 +483,12 @@ static int mfill_atomic_pte_copy(struct mfill_state *state)
struct folio *folio;
int ret;
folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, state->vma, dst_addr);
folio = ops->alloc_folio(state->vma, state->dst_addr);
if (!folio)
return -ENOMEM;
ret = -ENOMEM;
if (mem_cgroup_charge(folio, state->vma->vm_mm, GFP_KERNEL))
goto out_release;
ret = mfill_copy_folio_locked(folio, src_addr);
if (unlikely(ret)) {
if (uffd_flags_mode_is(flags, MFILL_ATOMIC_COPY)) {
ret = mfill_copy_folio_locked(folio, src_addr);
/*
* Fallback to copy_from_user outside mmap_lock.
* If retry is successful, mfill_copy_folio_locked() returns
@ -481,9 +496,15 @@ static int mfill_atomic_pte_copy(struct mfill_state *state)
* If there was an error, we must mfill_put_vma() anyway and it
* will take care of unlocking if needed.
*/
ret = mfill_copy_folio_retry(state, folio);
if (ret)
goto out_release;
if (unlikely(ret)) {
ret = mfill_copy_folio_retry(state, folio);
if (ret)
goto err_folio_put;
}
} else if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) {
clear_user_highpage(&folio->page, state->dst_addr);
} else {
VM_WARN_ONCE(1, "Unknown UFFDIO operation, flags: %x", flags);
}
/*
@ -496,47 +517,30 @@ static int mfill_atomic_pte_copy(struct mfill_state *state)
ret = mfill_atomic_install_pte(state->pmd, state->vma, dst_addr,
&folio->page, true, flags);
if (ret)
goto out_release;
out:
return ret;
out_release:
goto err_folio_put;
return 0;
err_folio_put:
folio_put(folio);
/* Don't return -ENOENT so that our caller won't retry */
if (ret == -ENOENT)
ret = -EFAULT;
folio_put(folio);
goto out;
return ret;
}
static int mfill_atomic_pte_zeroed_folio(pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
unsigned long dst_addr)
static int mfill_atomic_pte_copy(struct mfill_state *state)
{
struct folio *folio;
int ret = -ENOMEM;
const struct vm_uffd_ops *ops = vma_uffd_ops(state->vma);
folio = vma_alloc_zeroed_movable_folio(dst_vma, dst_addr);
if (!folio)
return ret;
return __mfill_atomic_pte(state, ops);
}
if (mem_cgroup_charge(folio, dst_vma->vm_mm, GFP_KERNEL))
goto out_put;
static int mfill_atomic_pte_zeroed_folio(struct mfill_state *state)
{
const struct vm_uffd_ops *ops = vma_uffd_ops(state->vma);
/*
* The memory barrier inside __folio_mark_uptodate makes sure that
* zeroing out the folio become visible before mapping the page
* using set_pte_at(). See do_anonymous_page().
*/
__folio_mark_uptodate(folio);
ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
&folio->page, true, 0);
if (ret)
goto out_put;
return 0;
out_put:
folio_put(folio);
return ret;
return __mfill_atomic_pte(state, ops);
}
static int mfill_atomic_pte_zeropage(struct mfill_state *state)
@ -549,7 +553,7 @@ static int mfill_atomic_pte_zeropage(struct mfill_state *state)
int ret;
if (mm_forbids_zeropage(dst_vma->vm_mm))
return mfill_atomic_pte_zeroed_folio(dst_pmd, dst_vma, dst_addr);
return mfill_atomic_pte_zeroed_folio(state);
_dst_pte = pte_mkspecial(pfn_pte(zero_pfn(dst_addr),
dst_vma->vm_page_prot));