OverlayFS already has comprehensive support for idmapped mounts through
its ovl_copyattr() function and proper mnt_idmap() handling throughout
the codebase. The infrastructure correctly maps UIDs/GIDs from idmapped
upper and lower layers.
However, the filesystem was missing the FS_ALLOW_IDMAP flag, which
caused mount_setattr() calls with MOUNT_ATTR_IDMAP to fail with -EINVAL.
This change enables idmapped mount support by adding the FS_ALLOW_IDMAP
flag to the overlayfs file_system_type, allowing containers and other
applications to use idmapped mounts with overlay filesystems.
Signed-off-by: Sohan Kunkerkar <sohank2602@xxxxxxxxx>
---
fs/overlayfs/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index e19940d64..c628f9179 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1516,7 +1516,7 @@ struct file_system_type ovl_fs_type = {
.name = "overlay",
.init_fs_context = ovl_init_fs_context,
.parameters = ovl_parameter_spec,
- .fs_flags = FS_USERNS_MOUNT,
+ .fs_flags = FS_USERNS_MOUNT | FS_ALLOW_IDMAP,
.kill_sb = kill_anon_super,
};
MODULE_ALIAS_FS("overlay");
--
2.50.1
