On Mon, 3 May 2021, Axel Rasmussen wrote:
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.
Signed-off-by: Axel Rasmussen axelrasmussen@google.com
Acked-by: Hugh Dickins hughd@google.com
And thanks for doing those late mcopy->mfill renamings, I think those represent Andrea's intent better.
As far as I'm concerned, this series is now ripe for picking into mmotm (bearing in mind the dependencies you noted in 00/10): thank you Axel.
include/linux/userfaultfd_k.h | 5 +++ mm/shmem.c | 58 ++++++++--------------------------- mm/userfaultfd.c | 17 ++++------ 3 files changed, 23 insertions(+), 57 deletions(-)
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 794d1538b8ba..331d2ccf0bcc 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -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); diff --git a/mm/shmem.c b/mm/shmem.c index e361f1d81c8d..2e9f56c83489 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2378,14 +2378,11 @@ 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,
@@ -2396,10 +2393,11 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, put_page(*pagep); *pagep = NULL; }
goto out;
return -ENOMEM;if (!*pagep) {
ret = -ENOMEM;@@ -2414,9 +2412,9 @@ 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; }@@ -2442,32 +2440,10 @@ 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++; @@ -2475,27 +2451,17 @@ 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 */ diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index d1ac73a0d2a9..5508f7d9e2dc 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -51,18 +51,13 @@ 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,
struct vm_area_struct *dst_vma,unsigned long dst_addr, struct page *page,bool newly_allocated, bool wp_copy)+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; -- 2.31.1.527.g47e6f16901-goog