On 29.11.22 12:21, Kirill A. Shutemov wrote:

On Mon, Nov 28, 2022 at 06:06:32PM -0600, Michael Roth wrote:

quoted

On Tue, Oct 25, 2022 at 11:13:37PM +0800, Chao Peng wrote:

quoted

From: "Kirill A. Shutemov" <redacted>

<snip>

quoted

+static struct file *restrictedmem_file_create(struct file *memfd)
+{
+	struct restrictedmem_data *data;
+	struct address_space *mapping;
+	struct inode *inode;
+	struct file *file;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return ERR_PTR(-ENOMEM);
+
+	data->memfd = memfd;
+	mutex_init(&data->lock);
+	INIT_LIST_HEAD(&data->notifiers);
+
+	inode = alloc_anon_inode(restrictedmem_mnt->mnt_sb);
+	if (IS_ERR(inode)) {
+		kfree(data);
+		return ERR_CAST(inode);
+	}
+
+	inode->i_mode |= S_IFREG;
+	inode->i_op = &restrictedmem_iops;
+	inode->i_mapping->private_data = data;
+
+	file = alloc_file_pseudo(inode, restrictedmem_mnt,
+				 "restrictedmem", O_RDWR,
+				 &restrictedmem_fops);
+	if (IS_ERR(file)) {
+		iput(inode);
+		kfree(data);
+		return ERR_CAST(file);
+	}
+
+	file->f_flags |= O_LARGEFILE;
+
+	mapping = memfd->f_mapping;
+	mapping_set_unevictable(mapping);
+	mapping_set_gfp_mask(mapping,
+			     mapping_gfp_mask(mapping) & ~__GFP_MOVABLE);

Is this supposed to prevent migration of pages being used for
restrictedmem/shmem backend?

Yes, my bad. I expected it to prevent migration, but it is not true.

Maybe add a comment that these pages are not movable and we don't want 
to place them into movable pageblocks (including CMA and ZONE_MOVABLE). 
That's the primary purpose of the GFP mask here.

-- 
Thanks,

David / dhildenb