gfs2: Implement SEEK_HOLE / SEEK_DATA via iomap

So far, lseek on gfs2 did not report holes.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

fs/gfs2/file.c

@@ -60,9 +60,7 @@ static loff_t gfs2_llseek(struct file *file, loff_t offset, int whence)
 	loff_t error;
 
 	switch (whence) {
-	case SEEK_END: /* These reference inode->i_size */
-	case SEEK_DATA:
-	case SEEK_HOLE:
+	case SEEK_END:
 		error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
 					   &i_gh);
 		if (!error) {
@@ -70,8 +68,21 @@ static loff_t gfs2_llseek(struct file *file, loff_t offset, int whence)
 			gfs2_glock_dq_uninit(&i_gh);
 		}
 		break;
+
+	case SEEK_DATA:
+		error = gfs2_seek_data(file, offset);
+		break;
+
+	case SEEK_HOLE:
+		error = gfs2_seek_hole(file, offset);
+		break;
+
 	case SEEK_CUR:
 	case SEEK_SET:
+		/*
+		 * These don't reference inode->i_size and don't depend on the
+		 * block mapping, so we don't need the glock.
+		 */
 		error = generic_file_llseek(file, offset, whence);
 		break;
 	default:

fs/gfs2/inode.c

@@ -2029,6 +2029,44 @@ static int gfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 	return ret;
 }
 
+loff_t gfs2_seek_data(struct file *file, loff_t offset)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_holder gh;
+	loff_t ret;
+
+	inode_lock_shared(inode);
+	ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
+	if (!ret)
+		ret = iomap_seek_data(inode, offset, &gfs2_iomap_ops);
+	gfs2_glock_dq_uninit(&gh);
+	inode_unlock_shared(inode);
+
+	if (ret < 0)
+		return ret;
+	return vfs_setpos(file, ret, inode->i_sb->s_maxbytes);
+}
+
+loff_t gfs2_seek_hole(struct file *file, loff_t offset)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_holder gh;
+	loff_t ret;
+
+	inode_lock_shared(inode);
+	ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
+	if (!ret)
+		ret = iomap_seek_hole(inode, offset, &gfs2_iomap_ops);
+	gfs2_glock_dq_uninit(&gh);
+	inode_unlock_shared(inode);
+
+	if (ret < 0)
+		return ret;
+	return vfs_setpos(file, ret, inode->i_sb->s_maxbytes);
+}
+
 const struct inode_operations gfs2_file_iops = {
 	.permission = gfs2_permission,
 	.setattr = gfs2_setattr,

fs/gfs2/inode.h

@@ -109,6 +109,8 @@ extern int gfs2_setattr_simple(struct inode *inode, struct iattr *attr);
 extern struct inode *gfs2_lookup_simple(struct inode *dip, const char *name);
 extern void gfs2_dinode_out(const struct gfs2_inode *ip, void *buf);
 extern int gfs2_open_common(struct inode *inode, struct file *file);
+extern loff_t gfs2_seek_data(struct file *file, loff_t offset);
+extern loff_t gfs2_seek_hole(struct file *file, loff_t offset);
 
 extern const struct inode_operations gfs2_file_iops;
 extern const struct inode_operations gfs2_dir_iops;