zonefs: prevent use of seq files as swap file

The sequential write constraint of sequential zone file prevent their
use as swap files. Only allow conventional zone files to be used as swap
files.

Fixes: 8dcc1a9 ("fs: New zonefs file system")
Cc: <[email protected]>
Reviewed-by: Johannes Thumshirn <[email protected]>
Signed-off-by: Damien Le Moal <[email protected]>

Author: damien-lemoal

fs/zonefs/super.c

@@ -165,6 +165,21 @@ static int zonefs_writepages(struct address_space *mapping,
 	return iomap_writepages(mapping, wbc, &wpc, &zonefs_writeback_ops);
 }
 
+static int zonefs_swap_activate(struct swap_info_struct *sis,
+				struct file *swap_file, sector_t *span)
+{
+	struct inode *inode = file_inode(swap_file);
+	struct zonefs_inode_info *zi = ZONEFS_I(inode);
+
+	if (zi->i_ztype != ZONEFS_ZTYPE_CNV) {
+		zonefs_err(inode->i_sb,
+			   "swap file: not a conventional zone file\n");
+		return -EINVAL;
+	}
+
+	return iomap_swapfile_activate(sis, swap_file, span, &zonefs_iomap_ops);
+}
+
 static const struct address_space_operations zonefs_file_aops = {
 	.readpage		= zonefs_readpage,
 	.readahead		= zonefs_readahead,
@@ -177,6 +192,7 @@ static const struct address_space_operations zonefs_file_aops = {
 	.is_partially_uptodate	= iomap_is_partially_uptodate,
 	.error_remove_page	= generic_error_remove_page,
 	.direct_IO		= noop_direct_IO,
+	.swap_activate		= zonefs_swap_activate,
 };
 
 static void zonefs_update_stats(struct inode *inode, loff_t new_isize)