Merge tag 'erofs-for-6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs

Pull erofs updates from Gao Xiang:
 "In this cycle, large folios are now enabled in the iomap/fscache mode
  for uncompressed files first. In order to do that, we've also cleaned
  up better interfaces between erofs and fscache, which are acked by
  fscache/netfs folks and included in this pull request.

  Other than that, there are random fixes around erofs over fscache and
  crafted images by syzbot, minor cleanups and documentation updates.

  Summary:

   - Enable large folios for iomap/fscache mode

   - Avoid sysfs warning due to mounting twice with the same fsid and
     domain_id in fscache mode

   - Refine fscache interface among erofs, fscache, and cachefiles

   - Use kmap_local_page() only for metabuf

   - Fixes around crafted images found by syzbot

   - Minor cleanups and documentation updates"

* tag 'erofs-for-6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs:
  erofs: validate the extent length for uncompressed pclusters
  erofs: fix missing unmap if z_erofs_get_extent_compressedlen() fails
  erofs: Fix pcluster memleak when its block address is zero
  erofs: use kmap_local_page() only for erofs_bread()
  erofs: enable large folios for fscache mode
  erofs: support large folios for fscache mode
  erofs: switch to prepare_ondemand_read() in fscache mode
  fscache,cachefiles: add prepare_ondemand_read() callback
  erofs: clean up cached I/O strategies
  erofs: update documentation
  erofs: check the uniqueness of fsid in shared domain in advance
  erofs: enable large folios for iomap mode

1 files changed, 25 insertions, 13 deletions

diff --git a/Documentation/filesystems/erofs.rst b/Documentation/filesystems/erofs.rst
index 05e03d54af1a..067fd1670b1f 100644
--- a/Documentation/filesystems/erofs.rst
+++ b/Documentation/filesystems/erofs.rst
@@ -30,12 +30,18 @@ It is implemented to be a better choice for the following scenarios:
    especially for those embedded devices with limited memory and high-density
    hosts with numerous containers.
 
-Here is the main features of EROFS:
+Here are the main features of EROFS:
 
  - Little endian on-disk design;
 
- - 4KiB block size and 32-bit block addresses, therefore 16TiB address space
-   at most for now;
+ - Block-based distribution and file-based distribution over fscache are
+   supported;
+
+ - Support multiple devices to refer to external blobs, which can be used
+   for container images;
+
+ - 4KiB block size and 32-bit block addresses for each device, therefore
+   16TiB address space at most for now;
 
  - Two inode layouts for different requirements:
 
@@ -50,28 +56,31 @@ Here is the main features of EROFS:
    Metadata reserved      8 bytes       18 bytes
    =====================  ============  ======================================
 
- - Metadata and data could be mixed as an option;
-
- - Support extended attributes (xattrs) as an option;
+ - Support extended attributes as an option;
 
- - Support tailpacking data and xattr inline compared to byte-addressed
-   unaligned metadata or smaller block size alternatives;
-
- - Support POSIX.1e ACLs by using xattrs;
+ - Support POSIX.1e ACLs by using extended attributes;
 
  - Support transparent data compression as an option:
    LZ4 and MicroLZMA algorithms can be used on a per-file basis; In addition,
    inplace decompression is also supported to avoid bounce compressed buffers
    and page cache thrashing.
 
+ - Support chunk-based data deduplication and rolling-hash compressed data
+   deduplication;
+
+ - Support tailpacking inline compared to byte-addressed unaligned metadata
+   or smaller block size alternatives;
+
+ - Support merging tail-end data into a special inode as fragments.
+
+ - Support large folios for uncompressed files.
+
  - Support direct I/O on uncompressed files to avoid double caching for loop
    devices;
 
  - Support FSDAX on uncompressed images for secure containers and ramdisks in
    order to get rid of unnecessary page cache.
 
- - Support multiple devices for multi blob container images;
-
  - Support file-based on-demand loading with the Fscache infrastructure.
 
 The following git tree provides the file system user-space tools under
@@ -259,7 +268,7 @@ By the way, chunk-based files are all uncompressed for now.
 
 Data compression
 ----------------
-EROFS implements LZ4 fixed-sized output compression which generates fixed-sized
+EROFS implements fixed-sized output compression which generates fixed-sized
 compressed data blocks from variable-sized input in contrast to other existing
 fixed-sized input solutions. Relatively higher compression ratios can be gotten
 by using fixed-sized output compression since nowadays popular data compression
@@ -314,3 +323,6 @@ to understand its delta0 is constantly 1, as illustrated below::
 
 If another HEAD follows a HEAD lcluster, there is no room to record CBLKCNT,
 but it's easy to know the size of such pcluster is 1 lcluster as well.
+
+Since Linux v6.1, each pcluster can be used for multiple variable-sized extents,
+therefore it can be used for compressed data deduplication.