Merge tag 'erofs-for-5.5-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs

 - Metadata & data could be mixed by design;

 - 2 inode versions for different requirements:

                          v1            v2

                          compact (v1)  extended (v2)

   Inode metadata size:   32 bytes      64 bytes

   Max file size:         4 GB          16 EB (also limited by max. vol size)

   Max uids/gids:         65536         4294967296

   File creation time:    no            yes (64 + 32-bit timestamp)

   File change time:      no            yes (64 + 32-bit timestamp)

   Max hardlinks:         65536         4294967296

   Metadata reserved:     4 bytes       14 bytes

 - Support POSIX.1e ACLs by using xattrs;

 - Support transparent file compression as an option:

   LZ4 algorithm with 4 KB fixed-output compression for high performance;

   LZ4 algorithm with 4 KB fixed-sized output compression for high performance.

The following git tree provides the file system user-space tools under

development (ex, formatting tool mkfs.erofs):

may not. All metadatas can be now observed in two different spaces (views):

 1. Inode metadata space

    Each valid inode should be aligned with an inode slot, which is a fixed

    value (32 bytes) and designed to be kept in line with v1 inode size.

    value (32 bytes) and designed to be kept in line with compact inode size.

    Each inode can be directly found with the following formula:

         inode offset = meta_blkaddr * block_size + 32 * nid

                                                       |-> aligned with 4B

    Inode could be 32 or 64 bytes, which can be distinguished from a common

    field which all inode versions have -- i_advise:

    field which all inode versions have -- i_format:

        __________________               __________________

       |     i_advise     |             |     i_advise     |

       |     i_format     |             |     i_format     |

       |__________________|             |__________________|

       |        ...       |             |        ...       |

       |                  |             |                  |

                                        |__________________| 64 bytes

    Xattrs, extents, data inline are followed by the corresponding inode with

    proper alignes, and they could be optional for different data mappings,

    _currently_ there are totally 3 valid data mappings supported:

    proper alignment, and they could be optional for different data mappings.

    _currently_ total 4 valid data mappings are supported:

     1) flat file data without data inline (no extent);

     2) fixed-output size data compression (must have extents);

     3) flat file data with tail-end data inline (no extent);

     0  flat file data without data inline (no extent);

     1  fixed-sized output data compression (with non-compacted indexes);

     2  flat file data with tail packing data inline (no extent);

     3  fixed-sized output data compression (with compacted indexes, v5.3+).

    The size of the optional xattrs is indicated by i_xattr_count in inode

    header. Large xattrs or xattrs shared by many different files can be

Compression

-----------

Currently, EROFS supports 4KB fixed-output clustersize transparent file

compression, as illustrated below:

Currently, EROFS supports 4KB fixed-sized output transparent file compression,

as illustrated below:

         |---- Variant-Length Extent ----|-------- VLE --------|----- VLE -----

         clusterofs                      clusterofs            clusterofs

	struct listxattr_iter it;

	ret = init_inode_xattrs(d_inode(dentry));

	if (ret == -ENOATTR)

		return 0;

	if (ret)

		return ret;