aufs: for v5.3-rc1, maintain i_readcount

By the commit,
	387e3746d01c 2019-06-19 locks: eliminate false positive
		conflicts for write lease
inode->i_readcount becomes common to CONFIG_IMA and CONFIG_FILE_LOCKING.
In aufs branch management, eg. re-setting the branch attribute RW to RO,
aufs has to maintain i_readcount too.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/branch.c

@@ -1205,6 +1205,7 @@ static int au_br_mod_files_ro(struct super_block *sb, aufs_bindex_t bindex)
 	unsigned char verbose, writer;
 	struct file *file, *hf, **array;
 	struct au_hfile *hfile;
+	struct inode *h_inode;
 
 	mnt_flags = au_mntflags(sb);
 	verbose = !!au_opt_test(mnt_flags, VERBOSE);
@@ -1275,8 +1276,12 @@ static int au_br_mod_files_ro(struct super_block *sb, aufs_bindex_t bindex)
 		hf->f_mode &= ~(FMODE_WRITE | FMODE_WRITER);
 		spin_unlock(&hf->f_lock);
 		if (writer) {
-			put_write_access(file_inode(hf));
+			h_inode = file_inode(hf);
+			put_write_access(h_inode);
 			__mnt_drop_write(hf->f_path.mnt);
+			if ((hf->f_mode & (FMODE_READ | FMODE_WRITE))
+			    == FMODE_READ)
+				i_readcount_inc(h_inode);
 		}
 	}