linux.git/Documentation/filesystems/ext4, branch v5.13

ext4: handle casefolding with encryption

2021-04-06T02:04:20+00:00

This adds support for encryption with casefolding.

Since the name on disk is case preserving, and also encrypted, we can no
longer just recompute the hash on the fly. Additionally, to avoid
leaking extra information from the hash of the unencrypted name, we use
siphash via an fscrypt v2 policy.

The hash is stored at the end of the directory entry for all entries
inside of an encrypted and casefolded directory apart from those that
deal with '.' and '..'. This way, the change is backwards compatible
with existing ext4 filesystems.

[ Changed to advertise this feature via the file:
  /sys/fs/ext4/features/encrypted_casefold -- TYT ]

Signed-off-by: Daniel Rosenberg 
Reviewed-by: Andreas Dilger 
Link: https://lore.kernel.org/r/20210319073414.1381041-2-drosen@google.com
Signed-off-by: Theodore Ts'o

ext4: add docs about fast commit idempotence

2020-12-17T18:30:44+00:00

Fast commit on-disk format is designed such that the replay of these
tags can be idempotent. This patch adds documentation in the code in
form of comments and in form kernel docs that describes these
characteristics. This patch also adds a TODO item needed to ensure
kernel fast commit replay idempotence.

Signed-off-by: Harshad Shirwadkar 
Link: https://lore.kernel.org/r/20201119232822.1860882-1-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o

ext4: describe fast_commit feature flags

2020-11-07T04:01:01+00:00

Fast commit feature has flags in the file system as well in JBD2. The
meaning of fast commit feature flags can get confusing. Update docs
and code to add more documentation about it.

Suggested-by: Jan Kara 
Signed-off-by: Harshad Shirwadkar 
Reviewed-by: Jan Kara 
Link: https://lore.kernel.org/r/20201106035911.1942128-2-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o

doc: update ext4 and journalling docs to include fast commit feature

2020-10-22T03:19:43+00:00

This patch adds necessary documentation for fast commits.

Signed-off-by: Harshad Shirwadkar 
Link: https://lore.kernel.org/r/20201015203802.3597742-2-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o

ext4: replace HTTP links with HTTPS ones

2020-08-06T05:01:57+00:00

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each file:
  If not .svg:
    For each line:
      If doesn't contain `\bxmlns\b`:
        For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
          If both the HTTP and HTTPS versions
          return 200 OK and serve the same content:
            Replace HTTP with HTTPS.

Signed-off-by: Alexander A. Klimov 
Link: https://lore.kernel.org/r/20200706190339.20709-1-grandmaster@al2klimov.de
Signed-off-by: Theodore Ts'o

fs/ext4: Disallow verity if inode is DAX

2020-05-29T02:09:47+00:00

Verity and DAX are incompatible.  Changing the DAX mode due to a verity
flag change is wrong without a corresponding address_space_operations
update.

Make the 2 options mutually exclusive by returning an error if DAX was
set first.

(Setting DAX is already disabled if Verity is set first.)

Reviewed-by: Jan Kara 
Signed-off-by: Ira Weiny 

Link: https://lore.kernel.org/r/20200528150003.828793-3-ira.weiny@intel.com
Signed-off-by: Theodore Ts'o

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

2019-09-21T20:37:39+00:00

Pull ext4 updates from Ted Ts'o:
 "Added new ext4 debugging ioctls to allow userspace to get information
  about the state of the extent status cache.

  Dropped workaround for pre-1970 dates which were encoded incorrectly
  in pre-4.4 kernels. Since both the kernel correctly generates, and
  e2fsck detects and fixes this issue for the past four years, it'e time
  to drop the workaround. (Also, it's not like files with dates in the
  distant past were all that common in the first place.)

  A lot of miscellaneous bug fixes and cleanups, including some ext4
  Documentation fixes. Also included are two minor bug fixes in
  fs/unicode"

* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (21 commits)
  unicode: make array 'token' static const, makes object smaller
  unicode: Move static keyword to the front of declarations
  ext4: add missing bigalloc documentation.
  ext4: fix kernel oops caused by spurious casefold flag
  ext4: fix integer overflow when calculating commit interval
  ext4: use percpu_counters for extent_status cache hits/misses
  ext4: fix potential use after free after remounting with noblock_validity
  jbd2: add missing tracepoint for reserved handle
  ext4: fix punch hole for inline_data file systems
  ext4: rework reserved cluster accounting when invalidating pages
  ext4: documentation fixes
  ext4: treat buffers with write errors as containing valid data
  ext4: fix warning inside ext4_convert_unwritten_extents_endio
  ext4: set error return correctly when ext4_htree_store_dirent fails
  ext4: drop legacy pre-1970 encoding workaround
  ext4: add new ioctl EXT4_IOC_GET_ES_CACHE
  ext4: add a new ioctl EXT4_IOC_GETSTATE
  ext4: add a new ioctl EXT4_IOC_CLEAR_ES_CACHE
  jbd2: flush_descriptor(): Do not decrease buffer head's ref count
  ext4: remove unnecessary error check
  ...

ext4: add missing bigalloc documentation.

2019-09-07T15:56:47+00:00

There was a broken link for bigalloc.  The page
https://ext4.wiki.kernel.org/index.php/Bigalloc was not migrated into
the current documentation sources.  This patch adds the contents of
that missing page into the section for Bigalloc itself.

Signed-off-by: Ayush Ranjan 
Link: https://lore.kernel.org/r/20190831154419.GA30357@fa19-cs241-404.cs.illinois.edu
Signed-off-by: Theodore Ts'o

ext4: documentation fixes

2019-08-23T03:18:33+00:00

This commit aims to fix the following issues in ext4 documentation:
- Flexible block group docs said that the aim was to group block
  metadata together instead of block group metadata.
- The documentation consistly uses "location" instead of "block number".
  It is easy to confuse location to be an absolute offset on disk. Added
  a line to clarify all location values are in terms of block numbers.
- Dirent2 docs said that the rec_len field is shortened instead of the
  name_len field.
- Typo in bg_checksum description.
- Inode size is 160 bytes now, and hence i_extra_isize is now 32.
- Cluster size formula was incorrect, it did not include the +10 to
  s_log_cluster_size value.
- Typo: there were two s_wtime_hi in the superblock struct.
- Superblock struct was outdated, added the new fields which were part
  of s_reserved earlier.
- Multiple mount protection seems to be implemented in fs/ext4/mmp.c.

Signed-off-by: Ayush Ranjan 
Signed-off-by: Theodore Ts'o 
Reviewed-by: Andreas Dilger

ext4: update on-disk format documentation for fs-verity

2019-08-13T02:33:51+00:00

Document the format of verity files on ext4, and the corresponding inode
and superblock flags.

Reviewed-by: Theodore Ts'o 
Signed-off-by: Eric Biggers