Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

Pull ext4 updates from Ted Ts'o:

 - further restructure ext4 documentation

 - fix up ext4's delayed allocation for bigalloc file systems

 - fix up some syzbot-detected races in EXT4_IOC_MOVE_EXT,
   EXT4_IOC_SWAP_BOOT, and ext4_remount

 - ... and a few other miscellaneous bugs and optimizations.

* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (21 commits)
  ext4: fix use-after-free race in ext4_remount()'s error path
  ext4: cache NULL when both default_acl and acl are NULL
  docs: promote the ext4 data structures book to top level
  docs: move ext4 administrative docs to admin-guide/
  jbd2: fix use after free in jbd2_log_do_checkpoint()
  ext4: propagate error from dquot_initialize() in EXT4_IOC_FSSETXATTR
  ext4: fix setattr project check in fssetxattr ioctl
  docs: make ext4 readme tables readable
  docs: fix ext4 documentation table formatting problems
  docs: generate a separate ext4 pdf file from the documentation
  ext4: convert fault handler to use vm_fault_t type
  ext4: initialize retries variable in ext4_da_write_inline_data_begin()
  ext4: fix EXT4_IOC_SWAP_BOOT
  ext4: fix build error when DX_DEBUG is defined
  ext4: fix argument checking in EXT4_IOC_MOVE_EXT
  ext4: fix reserved cluster accounting at page invalidation time
  ext4: adjust reserved cluster count when removing extents
  ext4: reduce reserved cluster count by number of allocated clusters
  ext4: fix reserved cluster accounting at delayed write time
  ext4: add new pending reservation mechanism
  ...

1 files changed, 73 insertions, 0 deletions

diff --git a/Documentation/filesystems/ext4/checksums.rst b/Documentation/filesystems/ext4/checksums.rst
new file mode 100644
index 000000000000..5519e253810d
--- /dev/null
+++ b/Documentation/filesystems/ext4/checksums.rst
@@ -0,0 +1,73 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Checksums
+---------
+
+Starting in early 2012, metadata checksums were added to all major ext4
+and jbd2 data structures. The associated feature flag is metadata\_csum.
+The desired checksum algorithm is indicated in the superblock, though as
+of October 2012 the only supported algorithm is crc32c. Some data
+structures did not have space to fit a full 32-bit checksum, so only the
+lower 16 bits are stored. Enabling the 64bit feature increases the data
+structure size so that full 32-bit checksums can be stored for many data
+structures. However, existing 32-bit filesystems cannot be extended to
+enable 64bit mode, at least not without the experimental resize2fs
+patches to do so.
+
+Existing filesystems can have checksumming added by running
+``tune2fs -O metadata_csum`` against the underlying device. If tune2fs
+encounters directory blocks that lack sufficient empty space to add a
+checksum, it will request that you run ``e2fsck -D`` to have the
+directories rebuilt with checksums. This has the added benefit of
+removing slack space from the directory files and rebalancing the htree
+indexes. If you \_ignore\_ this step, your directories will not be
+protected by a checksum!
+
+The following table describes the data elements that go into each type
+of checksum. The checksum function is whatever the superblock describes
+(crc32c as of October 2013) unless noted otherwise.
+
+.. list-table::
+   :widths: 20 8 50
+   :header-rows: 1
+
+   * - Metadata
+     - Length
+     - Ingredients
+   * - Superblock
+     - \_\_le32
+     - The entire superblock up to the checksum field. The UUID lives inside
+       the superblock.
+   * - MMP
+     - \_\_le32
+     - UUID + the entire MMP block up to the checksum field.
+   * - Extended Attributes
+     - \_\_le32
+     - UUID + the entire extended attribute block. The checksum field is set to
+       zero.
+   * - Directory Entries
+     - \_\_le32
+     - UUID + inode number + inode generation + the directory block up to the
+       fake entry enclosing the checksum field.
+   * - HTREE Nodes
+     - \_\_le32
+     - UUID + inode number + inode generation + all valid extents + HTREE tail.
+       The checksum field is set to zero.
+   * - Extents
+     - \_\_le32
+     - UUID + inode number + inode generation + the entire extent block up to
+       the checksum field.
+   * - Bitmaps
+     - \_\_le32 or \_\_le16
+     - UUID + the entire bitmap. Checksums are stored in the group descriptor,
+       and truncated if the group descriptor size is 32 bytes (i.e. ^64bit)
+   * - Inodes
+     - \_\_le32
+     - UUID + inode number + inode generation + the entire inode. The checksum
+       field is set to zero. Each inode has its own checksum.
+   * - Group Descriptors
+     - \_\_le16
+     - If metadata\_csum, then UUID + group number + the entire descriptor;
+       else if gdt\_csum, then crc16(UUID + group number + the entire
+       descriptor). In all cases, only the lower 16 bits are stored.
+