[PATCH v6 2/8] mm/shmem: Support memfile_notifier

[Chao Peng]

From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

Implement shmem as a memfile_notifier backing store. Essentially it
interacts with the memfile_notifier feature flags for userspace
access/page migration/page reclaiming and implements the necessary
memfile_backing_store callbacks.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
 include/linux/shmem_fs.h |   2 +
 mm/shmem.c               | 120 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 121 insertions(+), 1 deletion(-)

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index ab51d3cd39bd..a8e98bdd121e 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -9,6 +9,7 @@
 #include <linux/percpu_counter.h>
 #include <linux/xattr.h>
 #include <linux/fs_parser.h>
+#include <linux/memfile_notifier.h>
 
 /* inode in-kernel data */
 
@@ -25,6 +26,7 @@ struct shmem_inode_info {
        struct simple_xattrs    xattrs;         /* list of xattrs */
        atomic_t                stop_eviction;  /* hold when working on inode */
        struct timespec64       i_crtime;       /* file creation time */
+       struct memfile_node     memfile_node;   /* memfile node */
        struct inode            vfs_inode;
 };
 
diff --git a/mm/shmem.c b/mm/shmem.c
index 529c9ad3e926..f97ae328c87a 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -905,6 +905,24 @@ static struct folio *shmem_get_partial_folio(struct inode 
*inode, pgoff_t index)
        return page ? page_folio(page) : NULL;
 }
 
+static void notify_populate(struct inode *inode, pgoff_t start, pgoff_t end)
+{
+       struct shmem_inode_info *info = SHMEM_I(inode);
+
+       memfile_notifier_populate(&info->memfile_node, start, end);
+}
+
+static void notify_invalidate(struct inode *inode, struct folio *folio,
+                                  pgoff_t start, pgoff_t end)
+{
+       struct shmem_inode_info *info = SHMEM_I(inode);
+
+       start = max(start, folio->index);
+       end = min(end, folio->index + folio_nr_pages(folio));
+
+       memfile_notifier_invalidate(&info->memfile_node, start, end);
+}
+
 /*
  * Remove range of pages and swap entries from page cache, and free them.
  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
@@ -948,6 +966,8 @@ static void shmem_undo_range(struct inode *inode, loff_t 
lstart, loff_t lend,
                        }
                        index += folio_nr_pages(folio) - 1;
 
+                       notify_invalidate(inode, folio, start, end);
+
                        if (!unfalloc || !folio_test_uptodate(folio))
                                truncate_inode_folio(mapping, folio);
                        folio_unlock(folio);
@@ -1021,6 +1041,9 @@ static void shmem_undo_range(struct inode *inode, loff_t 
lstart, loff_t lend,
                                        index--;
                                        break;
                                }
+
+                               notify_invalidate(inode, folio, start, end);
+
                                VM_BUG_ON_FOLIO(folio_test_writeback(folio),
                                                folio);
                                truncate_inode_folio(mapping, folio);
@@ -1092,6 +1115,13 @@ static int shmem_setattr(struct user_namespace 
*mnt_userns,
                    (newsize > oldsize && (info->seals & F_SEAL_GROW)))
                        return -EPERM;
 
+               if (info->memfile_node.flags & MEMFILE_F_USER_INACCESSIBLE) {
+                       if(oldsize)
+                               return -EPERM;
+                       if (!PAGE_ALIGNED(newsize))
+                               return -EINVAL;
+               }
+
                if (newsize != oldsize) {
                        error = shmem_reacct_size(SHMEM_I(inode)->flags,
                                        oldsize, newsize);
@@ -1340,6 +1370,8 @@ static int shmem_writepage(struct page *page, struct 
writeback_control *wbc)
                goto redirty;
        if (!total_swap_pages)
                goto redirty;
+       if (info->memfile_node.flags & MEMFILE_F_UNRECLAIMABLE)
+               goto redirty;
 
        /*
         * Our capabilities prevent regular writeback or sync from ever calling
@@ -2234,6 +2266,9 @@ static int shmem_mmap(struct file *file, struct 
vm_area_struct *vma)
        if (ret)
                return ret;
 
+       if (info->memfile_node.flags & MEMFILE_F_USER_INACCESSIBLE)
+               return -EPERM;
+
        /* arm64 - allow memory tagging on RAM-based files */
        vma->vm_flags |= VM_MTE_ALLOWED;
 
@@ -2274,6 +2309,7 @@ static struct inode *shmem_get_inode(struct super_block 
*sb, const struct inode
                info->i_crtime = inode->i_mtime;
                INIT_LIST_HEAD(&info->shrinklist);
                INIT_LIST_HEAD(&info->swaplist);
+               memfile_node_init(&info->memfile_node);
                simple_xattrs_init(&info->xattrs);
                cache_no_acl(inode);
                mapping_set_large_folios(inode->i_mapping);
@@ -2442,6 +2478,8 @@ shmem_write_begin(struct file *file, struct address_space 
*mapping,
                if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
                        return -EPERM;
        }
+       if (unlikely(info->memfile_node.flags & MEMFILE_F_USER_INACCESSIBLE))
+               return -EPERM;
 
        ret = shmem_getpage(inode, index, pagep, SGP_WRITE);
 
@@ -2518,6 +2556,13 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, 
struct iov_iter *to)
                end_index = i_size >> PAGE_SHIFT;
                if (index > end_index)
                        break;
+
+               if (SHMEM_I(inode)->memfile_node.flags &
+                               MEMFILE_F_USER_INACCESSIBLE) {
+                       error = -EPERM;
+                       break;
+               }
+
                if (index == end_index) {
                        nr = i_size & ~PAGE_MASK;
                        if (nr <= offset)
@@ -2649,6 +2694,12 @@ static long shmem_fallocate(struct file *file, int mode, 
loff_t offset,
                        goto out;
                }
 
+               if ((info->memfile_node.flags & MEMFILE_F_USER_INACCESSIBLE) &&
+                   (!PAGE_ALIGNED(offset) || !PAGE_ALIGNED(len))) {
+                       error = -EINVAL;
+                       goto out;
+               }
+
                shmem_falloc.waitq = &shmem_falloc_waitq;
                shmem_falloc.start = (u64)unmap_start >> PAGE_SHIFT;
                shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
@@ -2768,6 +2819,7 @@ static long shmem_fallocate(struct file *file, int mode, 
loff_t offset,
        if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
                i_size_write(inode, offset + len);
        inode->i_ctime = current_time(inode);
+       notify_populate(inode, start, end);
 undone:
        spin_lock(&inode->i_lock);
        inode->i_private = NULL;
@@ -3754,6 +3806,20 @@ static int shmem_error_remove_page(struct address_space 
*mapping,
        return 0;
 }
 
+#ifdef CONFIG_MIGRATION
+static int shmem_migrate_page(struct address_space *mapping,
+                             struct page *newpage, struct page *page,
+                             enum migrate_mode mode)
+{
+       struct inode *inode = mapping->host;
+       struct shmem_inode_info *info = SHMEM_I(inode);
+
+       if (info->memfile_node.flags & MEMFILE_F_UNMOVABLE)
+               return -ENOTSUPP;
+       return migrate_page(mapping, newpage, page, mode);
+}
+#endif
+
 const struct address_space_operations shmem_aops = {
        .writepage      = shmem_writepage,
        .dirty_folio    = noop_dirty_folio,
@@ -3762,7 +3828,7 @@ const struct address_space_operations shmem_aops = {
        .write_end      = shmem_write_end,
 #endif
 #ifdef CONFIG_MIGRATION
-       .migratepage    = migrate_page,
+       .migratepage    = shmem_migrate_page,
 #endif
        .error_remove_page = shmem_error_remove_page,
 };
@@ -3879,6 +3945,54 @@ static struct file_system_type shmem_fs_type = {
        .fs_flags       = FS_USERNS_MOUNT,
 };
 
+#ifdef CONFIG_MEMFILE_NOTIFIER
+static struct memfile_node* shmem_lookup_memfile_node(struct file *file)
+{
+       struct inode *inode = file_inode(file);
+
+       if (!shmem_mapping(inode->i_mapping))
+               return NULL;
+
+       return  &SHMEM_I(inode)->memfile_node;
+}
+
+
+static int shmem_get_lock_pfn(struct file *file, pgoff_t offset, pfn_t *pfn,
+                             int *order)
+{
+       struct page *page;
+       int ret;
+
+       ret = shmem_getpage(file_inode(file), offset, &page, SGP_NOALLOC);
+       if (ret)
+               return ret;
+
+       *pfn = page_to_pfn_t(page);
+       *order = thp_order(compound_head(page));
+       return 0;
+}
+
+static void shmem_put_unlock_pfn(pfn_t pfn)
+{
+       struct page *page = pfn_t_to_page(pfn);
+
+       if (!page)
+               return;
+
+       VM_BUG_ON_PAGE(!PageLocked(page), page);
+
+       set_page_dirty(page);
+       unlock_page(page);
+       put_page(page);
+}
+
+static struct memfile_backing_store shmem_backing_store = {
+       .lookup_memfile_node = shmem_lookup_memfile_node,
+       .get_lock_pfn = shmem_get_lock_pfn,
+       .put_unlock_pfn = shmem_put_unlock_pfn,
+};
+#endif /* CONFIG_MEMFILE_NOTIFIER */
+
 int __init shmem_init(void)
 {
        int error;
@@ -3904,6 +4018,10 @@ int __init shmem_init(void)
        else
                shmem_huge = SHMEM_HUGE_NEVER; /* just in case it was patched */
 #endif
+
+#ifdef CONFIG_MEMFILE_NOTIFIER
+       memfile_register_backing_store(&shmem_backing_store);
+#endif
        return 0;
 
 out1:
-- 
2.25.1