erofs: verify metadata accesses for file-backed mounts

erofs: verify metadata accesses for file-backed mounts

For file-backed mounts, metadata is fetched via the page cache of
backing inodes to avoid double caching and redundant copy ops out
of RO uptodate folios, which is used by Android APEXes, ComposeFS,
containerd.  However, rw_verify_area() was missing prior to
metadata accesses.

Similar to vfs_iocb_iter_read(), fix this by:
 - Enabling fanotify pre-content hooks on metadata accesses;
 - security_file_permission() for security modules.

Verified that fanotify pre-content hooks now works correctly.

Fixes: fb176750266a ("erofs: add file-backed mount support")
Acked-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Chunhai Guo <guochunhai@vivo.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>