From: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
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.
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
include/linux/shmem_fs.h | 11 +++++
mm/shmem.c | 110 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 121 insertions(+)
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index ff078e7..fdaac9d4 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -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
diff --git a/mm/shmem.c b/mm/shmem.c
index ad7813d..6e5fe90 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -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 <asm/uaccess.h>
#include <asm/pgtable.h>
@@ -2135,6 +2136,115 @@ bool shmem_mapping(struct address_space *mapping)
return mapping->host->i_sb->s_op == &shmem_ops;
}
+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;
--
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