Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/Documentation/filesystems/ext4/ondisk/about.rst b/Documentation/filesystems/ext4/about.rst
similarity index 100%
rename from Documentation/filesystems/ext4/ondisk/about.rst
rename to Documentation/filesystems/ext4/about.rst
diff --git a/Documentation/filesystems/ext4/ondisk/allocators.rst b/Documentation/filesystems/ext4/allocators.rst
similarity index 100%
rename from Documentation/filesystems/ext4/ondisk/allocators.rst
rename to Documentation/filesystems/ext4/allocators.rst
diff --git a/Documentation/filesystems/ext4/ondisk/attributes.rst b/Documentation/filesystems/ext4/attributes.rst
similarity index 98%
rename from Documentation/filesystems/ext4/ondisk/attributes.rst
rename to Documentation/filesystems/ext4/attributes.rst
index 0b01b67..54386a0 100644
--- a/Documentation/filesystems/ext4/ondisk/attributes.rst
+++ b/Documentation/filesystems/ext4/attributes.rst
@@ -30,7 +30,7 @@
``ext4_xattr_ibody_header`` that is 4 bytes long:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -47,7 +47,7 @@
``struct ext4_xattr_header``, which is 32 bytes long:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -92,7 +92,7 @@
Attributes stored inside an inode do not need be stored in sorted order.
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -157,7 +157,7 @@
the key name. Here is a map of name index values to key prefixes:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Name Index
diff --git a/Documentation/filesystems/ext4/bigalloc.rst b/Documentation/filesystems/ext4/bigalloc.rst
new file mode 100644
index 0000000..72075aa
--- /dev/null
+++ b/Documentation/filesystems/ext4/bigalloc.rst
@@ -0,0 +1,34 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Bigalloc
+--------
+
+At the moment, the default size of a block is 4KiB, which is a commonly
+supported page size on most MMU-capable hardware. This is fortunate, as
+ext4 code is not prepared to handle the case where the block size
+exceeds the page size. However, for a filesystem of mostly huge files,
+it is desirable to be able to allocate disk blocks in units of multiple
+blocks to reduce both fragmentation and metadata overhead. The
+bigalloc feature provides exactly this ability.
+
+The bigalloc feature (EXT4_FEATURE_RO_COMPAT_BIGALLOC) changes ext4 to
+use clustered allocation, so that each bit in the ext4 block allocation
+bitmap addresses a power of two number of blocks. For example, if the
+file system is mainly going to be storing large files in the 4-32
+megabyte range, it might make sense to set a cluster size of 1 megabyte.
+This means that each bit in the block allocation bitmap now addresses
+256 4k blocks. This shrinks the total size of the block allocation
+bitmaps for a 2T file system from 64 megabytes to 256 kilobytes. It also
+means that a block group addresses 32 gigabytes instead of 128 megabytes,
+also shrinking the amount of file system overhead for metadata.
+
+The administrator can set a block cluster size at mkfs time (which is
+stored in the s\_log\_cluster\_size field in the superblock); from then
+on, the block bitmaps track clusters, not individual blocks. This means
+that block groups can be several gigabytes in size (instead of just
+128MiB); however, the minimum allocation unit becomes a cluster, not a
+block, even for directories. TaoBao had a patchset to extend the “use
+units of clusters instead of blocks” to the extent tree, though it is
+not clear where those patches went-- they eventually morphed into
+“extent tree v2” but that code has not landed as of May 2015.
+
diff --git a/Documentation/filesystems/ext4/ondisk/bitmaps.rst b/Documentation/filesystems/ext4/bitmaps.rst
similarity index 100%
rename from Documentation/filesystems/ext4/ondisk/bitmaps.rst
rename to Documentation/filesystems/ext4/bitmaps.rst
diff --git a/Documentation/filesystems/ext4/ondisk/blockgroup.rst b/Documentation/filesystems/ext4/blockgroup.rst
similarity index 94%
rename from Documentation/filesystems/ext4/ondisk/blockgroup.rst
rename to Documentation/filesystems/ext4/blockgroup.rst
index baf888e..3da1566 100644
--- a/Documentation/filesystems/ext4/ondisk/blockgroup.rst
+++ b/Documentation/filesystems/ext4/blockgroup.rst
@@ -71,11 +71,11 @@
superblock, group descriptors, data block bitmaps for groups 0-3, inode
bitmaps for groups 0-3, inode tables for groups 0-3, and the remaining
space in group 0 is for file data. The effect of this is to group the
-block metadata close together for faster loading, and to enable large
-files to be continuous on disk. Backup copies of the superblock and
-group descriptors are always at the beginning of block groups, even if
-flex\_bg is enabled. The number of block groups that make up a flex\_bg
-is given by 2 ^ ``sb.s_log_groups_per_flex``.
+block group metadata close together for faster loading, and to enable
+large files to be continuous on disk. Backup copies of the superblock
+and group descriptors are always at the beginning of block groups, even
+if flex\_bg is enabled. The number of block groups that make up a
+flex\_bg is given by 2 ^ ``sb.s_log_groups_per_flex``.
Meta Block Groups
-----------------
diff --git a/Documentation/filesystems/ext4/ondisk/blockmap.rst b/Documentation/filesystems/ext4/blockmap.rst
similarity index 100%
rename from Documentation/filesystems/ext4/ondisk/blockmap.rst
rename to Documentation/filesystems/ext4/blockmap.rst
diff --git a/Documentation/filesystems/ext4/ondisk/blocks.rst b/Documentation/filesystems/ext4/blocks.rst
similarity index 93%
rename from Documentation/filesystems/ext4/ondisk/blocks.rst
rename to Documentation/filesystems/ext4/blocks.rst
index 73d4dc0..bd722ec 100644
--- a/Documentation/filesystems/ext4/ondisk/blocks.rst
+++ b/Documentation/filesystems/ext4/blocks.rst
@@ -10,7 +10,9 @@
4KiB. You may experience mounting problems if block size is greater than
page size (i.e. 64KiB blocks on a i386 which only has 4KiB memory
pages). By default a filesystem can contain 2^32 blocks; if the '64bit'
-feature is enabled, then a filesystem can have 2^64 blocks.
+feature is enabled, then a filesystem can have 2^64 blocks. The location
+of structures is stored in terms of the block number the structure lives
+in and not the absolute offset on disk.
For 32-bit filesystems, limits are as follows:
diff --git a/Documentation/filesystems/ext4/ondisk/checksums.rst b/Documentation/filesystems/ext4/checksums.rst
similarity index 99%
rename from Documentation/filesystems/ext4/ondisk/checksums.rst
rename to Documentation/filesystems/ext4/checksums.rst
index 9d6a793..5519e25 100644
--- a/Documentation/filesystems/ext4/ondisk/checksums.rst
+++ b/Documentation/filesystems/ext4/checksums.rst
@@ -28,7 +28,7 @@
(crc32c as of October 2013) unless noted otherwise.
.. list-table::
- :widths: 1 1 4
+ :widths: 20 8 50
:header-rows: 1
* - Metadata
diff --git a/Documentation/filesystems/ext4/ondisk/directory.rst b/Documentation/filesystems/ext4/directory.rst
similarity index 97%
rename from Documentation/filesystems/ext4/ondisk/directory.rst
rename to Documentation/filesystems/ext4/directory.rst
index 8fcba68..073940c 100644
--- a/Documentation/filesystems/ext4/ondisk/directory.rst
+++ b/Documentation/filesystems/ext4/directory.rst
@@ -34,7 +34,7 @@
``dirent.rec_len`` to know for sure.
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -59,14 +59,14 @@
- File name.
Since file names cannot be longer than 255 bytes, the new directory
-entry format shortens the rec\_len field and uses the space for a file
+entry format shortens the name\_len field and uses the space for a file
type flag, probably to avoid having to load every inode during directory
tree traversal. This format is ``ext4_dir_entry_2``, which is at most
263 bytes long, though on disk you'll need to reference
``dirent.rec_len`` to know for sure.
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -99,7 +99,7 @@
The directory file type is one of the following values:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -130,7 +130,7 @@
``struct ext4_dir_entry_tail``:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -212,7 +212,7 @@
of a data block:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -305,7 +305,7 @@
The directory hash is one of the following values:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -327,7 +327,7 @@
also the full length of a data block:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -375,7 +375,7 @@
long:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -405,7 +405,7 @@
The dx\_tail structure is 8 bytes long and looks like this:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
diff --git a/Documentation/filesystems/ext4/ondisk/dynamic.rst b/Documentation/filesystems/ext4/dynamic.rst
similarity index 100%
rename from Documentation/filesystems/ext4/ondisk/dynamic.rst
rename to Documentation/filesystems/ext4/dynamic.rst
diff --git a/Documentation/filesystems/ext4/ondisk/eainode.rst b/Documentation/filesystems/ext4/eainode.rst
similarity index 100%
rename from Documentation/filesystems/ext4/ondisk/eainode.rst
rename to Documentation/filesystems/ext4/eainode.rst
diff --git a/Documentation/filesystems/ext4/ext4.rst b/Documentation/filesystems/ext4/ext4.rst
deleted file mode 100644
index 9d4368d..0000000
--- a/Documentation/filesystems/ext4/ext4.rst
+++ /dev/null
@@ -1,613 +0,0 @@
-.. SPDX-License-Identifier: GPL-2.0
-
-========================
-General Information
-========================
-
-Ext4 is an advanced level of the ext3 filesystem which incorporates
-scalability and reliability enhancements for supporting large filesystems
-(64 bit) in keeping with increasing disk capacities and state-of-the-art
-feature requirements.
-
-Mailing list: linux-ext4@vger.kernel.org
-Web site: http://ext4.wiki.kernel.org
-
-
-Quick usage instructions
-========================
-
-Note: More extensive information for getting started with ext4 can be
-found at the ext4 wiki site at the URL:
-http://ext4.wiki.kernel.org/index.php/Ext4_Howto
-
- - The latest version of e2fsprogs can be found at:
-
- https://www.kernel.org/pub/linux/kernel/people/tytso/e2fsprogs/
-
- or
-
- http://sourceforge.net/project/showfiles.php?group_id=2406
-
- or grab the latest git repository from:
-
- https://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git
-
- - Create a new filesystem using the ext4 filesystem type:
-
- # mke2fs -t ext4 /dev/hda1
-
- Or to configure an existing ext3 filesystem to support extents:
-
- # tune2fs -O extents /dev/hda1
-
- If the filesystem was created with 128 byte inodes, it can be
- converted to use 256 byte for greater efficiency via:
-
- # tune2fs -I 256 /dev/hda1
-
- - Mounting:
-
- # mount -t ext4 /dev/hda1 /wherever
-
- - When comparing performance with other filesystems, it's always
- important to try multiple workloads; very often a subtle change in a
- workload parameter can completely change the ranking of which
- filesystems do well compared to others. When comparing versus ext3,
- note that ext4 enables write barriers by default, while ext3 does
- not enable write barriers by default. So it is useful to use
- explicitly specify whether barriers are enabled or not when via the
- '-o barriers=[0|1]' mount option for both ext3 and ext4 filesystems
- for a fair comparison. When tuning ext3 for best benchmark numbers,
- it is often worthwhile to try changing the data journaling mode; '-o
- data=writeback' can be faster for some workloads. (Note however that
- running mounted with data=writeback can potentially leave stale data
- exposed in recently written files in case of an unclean shutdown,
- which could be a security exposure in some situations.) Configuring
- the filesystem with a large journal can also be helpful for
- metadata-intensive workloads.
-
-Features
-========
-
-Currently Available
--------------------
-
-* ability to use filesystems > 16TB (e2fsprogs support not available yet)
-* extent format reduces metadata overhead (RAM, IO for access, transactions)
-* extent format more robust in face of on-disk corruption due to magics,
-* internal redundancy in tree
-* improved file allocation (multi-block alloc)
-* lift 32000 subdirectory limit imposed by i_links_count[1]
-* nsec timestamps for mtime, atime, ctime, create time
-* inode version field on disk (NFSv4, Lustre)
-* reduced e2fsck time via uninit_bg feature
-* journal checksumming for robustness, performance
-* persistent file preallocation (e.g for streaming media, databases)
-* ability to pack bitmaps and inode tables into larger virtual groups via the
- flex_bg feature
-* large file support
-* inode allocation using large virtual block groups via flex_bg
-* delayed allocation
-* large block (up to pagesize) support
-* efficient new ordered mode in JBD2 and ext4 (avoid using buffer head to force
- the ordering)
-
-[1] Filesystems with a block size of 1k may see a limit imposed by the
-directory hash tree having a maximum depth of two.
-
-Options
-=======
-
-When mounting an ext4 filesystem, the following option are accepted:
-(*) == default
-
-======================= =======================================================
-Mount Option Description
-======================= =======================================================
-ro Mount filesystem read only. Note that ext4 will
- replay the journal (and thus write to the
- partition) even when mounted "read only". The
- mount options "ro,noload" can be used to prevent
- writes to the filesystem.
-
-journal_checksum Enable checksumming of the journal transactions.
- This will allow the recovery code in e2fsck and the
- kernel to detect corruption in the kernel. It is a
- compatible change and will be ignored by older kernels.
-
-journal_async_commit Commit block can be written to disk without waiting
- for descriptor blocks. If enabled older kernels cannot
- mount the device. This will enable 'journal_checksum'
- internally.
-
-journal_path=path
-journal_dev=devnum When the external journal device's major/minor numbers
- have changed, these options allow the user to specify
- the new journal location. The journal device is
- identified through either its new major/minor numbers
- encoded in devnum, or via a path to the device.
-
-norecovery Don't load the journal on mounting. Note that
-noload if the filesystem was not unmounted cleanly,
- skipping the journal replay will lead to the
- filesystem containing inconsistencies that can
- lead to any number of problems.
-
-data=journal All data are committed into the journal prior to being
- written into the main file system. Enabling
- this mode will disable delayed allocation and
- O_DIRECT support.
-
-data=ordered (*) All data are forced directly out to the main file
- system prior to its metadata being committed to the
- journal.
-
-data=writeback Data ordering is not preserved, data may be written
- into the main file system after its metadata has been
- committed to the journal.
-
-commit=nrsec (*) Ext4 can be told to sync all its data and metadata
- every 'nrsec' seconds. The default value is 5 seconds.
- This means that if you lose your power, you will lose
- as much as the latest 5 seconds of work (your
- filesystem will not be damaged though, thanks to the
- journaling). This default value (or any low value)
- will hurt performance, but it's good for data-safety.
- Setting it to 0 will have the same effect as leaving
- it at the default (5 seconds).
- Setting it to very large values will improve
- performance.
-
-barrier=<0|1(*)> This enables/disables the use of write barriers in
-barrier(*) the jbd code. barrier=0 disables, barrier=1 enables.
-nobarrier This also requires an IO stack which can support
- barriers, and if jbd gets an error on a barrier
- write, it will disable again with a warning.
- Write barriers enforce proper on-disk ordering
- of journal commits, making volatile disk write caches
- safe to use, at some performance penalty. If
- your disks are battery-backed in one way or another,
- disabling barriers may safely improve performance.
- The mount options "barrier" and "nobarrier" can
- also be used to enable or disable barriers, for
- consistency with other ext4 mount options.
-
-inode_readahead_blks=n This tuning parameter controls the maximum
- number of inode table blocks that ext4's inode
- table readahead algorithm will pre-read into
- the buffer cache. The default value is 32 blocks.
-
-nouser_xattr Disables Extended User Attributes. See the
- attr(5) manual page for more information about
- extended attributes.
-
-noacl This option disables POSIX Access Control List
- support. If ACL support is enabled in the kernel
- configuration (CONFIG_EXT4_FS_POSIX_ACL), ACL is
- enabled by default on mount. See the acl(5) manual
- page for more information about acl.
-
-bsddf (*) Make 'df' act like BSD.
-minixdf Make 'df' act like Minix.
-
-debug Extra debugging information is sent to syslog.
-
-abort Simulate the effects of calling ext4_abort() for
- debugging purposes. This is normally used while
- remounting a filesystem which is already mounted.
-
-errors=remount-ro Remount the filesystem read-only on an error.
-errors=continue Keep going on a filesystem error.
-errors=panic Panic and halt the machine if an error occurs.
- (These mount options override the errors behavior
- specified in the superblock, which can be configured
- using tune2fs)
-
-data_err=ignore(*) Just print an error message if an error occurs
- in a file data buffer in ordered mode.
-data_err=abort Abort the journal if an error occurs in a file
- data buffer in ordered mode.
-
-grpid New objects have the group ID of their parent.
-bsdgroups
-
-nogrpid (*) New objects have the group ID of their creator.
-sysvgroups
-
-resgid=n The group ID which may use the reserved blocks.
-
-resuid=n The user ID which may use the reserved blocks.
-
-sb=n Use alternate superblock at this location.
-
-quota These options are ignored by the filesystem. They
-noquota are used only by quota tools to recognize volumes
-grpquota where quota should be turned on. See documentation
-usrquota in the quota-tools package for more details
- (http://sourceforge.net/projects/linuxquota).
-
-jqfmt=<quota type> These options tell filesystem details about quota
-usrjquota=<file> so that quota information can be properly updated
-grpjquota=<file> during journal replay. They replace the above
- quota options. See documentation in the quota-tools
- package for more details
- (http://sourceforge.net/projects/linuxquota).
-
-stripe=n Number of filesystem blocks that mballoc will try
- to use for allocation size and alignment. For RAID5/6
- systems this should be the number of data
- disks * RAID chunk size in file system blocks.
-
-delalloc (*) Defer block allocation until just before ext4
- writes out the block(s) in question. This
- allows ext4 to better allocation decisions
- more efficiently.
-nodelalloc Disable delayed allocation. Blocks are allocated
- when the data is copied from userspace to the
- page cache, either via the write(2) system call
- or when an mmap'ed page which was previously
- unallocated is written for the first time.
-
-max_batch_time=usec Maximum amount of time ext4 should wait for
- additional filesystem operations to be batch
- together with a synchronous write operation.
- Since a synchronous write operation is going to
- force a commit and then a wait for the I/O
- complete, it doesn't cost much, and can be a
- huge throughput win, we wait for a small amount
- of time to see if any other transactions can
- piggyback on the synchronous write. The
- algorithm used is designed to automatically tune
- for the speed of the disk, by measuring the
- amount of time (on average) that it takes to
- finish committing a transaction. Call this time
- the "commit time". If the time that the
- transaction has been running is less than the
- commit time, ext4 will try sleeping for the
- commit time to see if other operations will join
- the transaction. The commit time is capped by
- the max_batch_time, which defaults to 15000us
- (15ms). This optimization can be turned off
- entirely by setting max_batch_time to 0.
-
-min_batch_time=usec This parameter sets the commit time (as
- described above) to be at least min_batch_time.
- It defaults to zero microseconds. Increasing
- this parameter may improve the throughput of
- multi-threaded, synchronous workloads on very
- fast disks, at the cost of increasing latency.
-
-journal_ioprio=prio The I/O priority (from 0 to 7, where 0 is the
- highest priority) which should be used for I/O
- operations submitted by kjournald2 during a
- commit operation. This defaults to 3, which is
- a slightly higher priority than the default I/O
- priority.
-
-auto_da_alloc(*) Many broken applications don't use fsync() when
-noauto_da_alloc replacing existing files via patterns such as
- fd = open("foo.new")/write(fd,..)/close(fd)/
- rename("foo.new", "foo"), or worse yet,
- fd = open("foo", O_TRUNC)/write(fd,..)/close(fd).
- If auto_da_alloc is enabled, ext4 will detect
- the replace-via-rename and replace-via-truncate
- patterns and force that any delayed allocation
- blocks are allocated such that at the next
- journal commit, in the default data=ordered
- mode, the data blocks of the new file are forced
- to disk before the rename() operation is
- committed. This provides roughly the same level
- of guarantees as ext3, and avoids the
- "zero-length" problem that can happen when a
- system crashes before the delayed allocation
- blocks are forced to disk.
-
-noinit_itable Do not initialize any uninitialized inode table
- blocks in the background. This feature may be
- used by installation CD's so that the install
- process can complete as quickly as possible; the
- inode table initialization process would then be
- deferred until the next time the file system
- is unmounted.
-
-init_itable=n The lazy itable init code will wait n times the
- number of milliseconds it took to zero out the
- previous block group's inode table. This
- minimizes the impact on the system performance
- while file system's inode table is being initialized.
-
-discard Controls whether ext4 should issue discard/TRIM
-nodiscard(*) commands to the underlying block device when
- blocks are freed. This is useful for SSD devices
- and sparse/thinly-provisioned LUNs, but it is off
- by default until sufficient testing has been done.
-
-nouid32 Disables 32-bit UIDs and GIDs. This is for
- interoperability with older kernels which only
- store and expect 16-bit values.
-
-block_validity(*) These options enable or disable the in-kernel
-noblock_validity facility for tracking filesystem metadata blocks
- within internal data structures. This allows multi-
- block allocator and other routines to notice
- bugs or corrupted allocation bitmaps which cause
- blocks to be allocated which overlap with
- filesystem metadata blocks.
-
-dioread_lock Controls whether or not ext4 should use the DIO read
-dioread_nolock locking. If the dioread_nolock option is specified
- ext4 will allocate uninitialized extent before buffer
- write and convert the extent to initialized after IO
- completes. This approach allows ext4 code to avoid
- using inode mutex, which improves scalability on high
- speed storages. However this does not work with
- data journaling and dioread_nolock option will be
- ignored with kernel warning. Note that dioread_nolock
- code path is only used for extent-based files.
- Because of the restrictions this options comprises
- it is off by default (e.g. dioread_lock).
-
-max_dir_size_kb=n This limits the size of directories so that any
- attempt to expand them beyond the specified
- limit in kilobytes will cause an ENOSPC error.
- This is useful in memory constrained
- environments, where a very large directory can
- cause severe performance problems or even
- provoke the Out Of Memory killer. (For example,
- if there is only 512mb memory available, a 176mb
- directory may seriously cramp the system's style.)
-
-i_version Enable 64-bit inode version support. This option is
- off by default.
-
-dax Use direct access (no page cache). See
- Documentation/filesystems/dax.txt. Note that
- this option is incompatible with data=journal.
-======================= =======================================================
-
-Data Mode
-=========
-There are 3 different data modes:
-
-* writeback mode
-
- In data=writeback mode, ext4 does not journal data at all. This mode provides
- a similar level of journaling as that of XFS, JFS, and ReiserFS in its default
- mode - metadata journaling. A crash+recovery can cause incorrect data to
- appear in files which were written shortly before the crash. This mode will
- typically provide the best ext4 performance.
-
-* ordered mode
-
- In data=ordered mode, ext4 only officially journals metadata, but it logically
- groups metadata information related to data changes with the data blocks into
- a single unit called a transaction. When it's time to write the new metadata
- out to disk, the associated data blocks are written first. In general, this
- mode performs slightly slower than writeback but significantly faster than
- journal mode.
-
-* journal mode
-
- data=journal mode provides full data and metadata journaling. All new data is
- written to the journal first, and then to its final location. In the event of
- a crash, the journal can be replayed, bringing both data and metadata into a
- consistent state. This mode is the slowest except when data needs to be read
- from and written to disk at the same time where it outperforms all others
- modes. Enabling this mode will disable delayed allocation and O_DIRECT
- support.
-
-/proc entries
-=============
-
-Information about mounted ext4 file systems can be found in
-/proc/fs/ext4. Each mounted filesystem will have a directory in
-/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
-/proc/fs/ext4/dm-0). The files in each per-device directory are shown
-in table below.
-
-Files in /proc/fs/ext4/<devname>
-
-================ =======
- File Content
-================ =======
- mb_groups details of multiblock allocator buddy cache of free blocks
-================ =======
-
-/sys entries
-============
-
-Information about mounted ext4 file systems can be found in
-/sys/fs/ext4. Each mounted filesystem will have a directory in
-/sys/fs/ext4 based on its device name (i.e., /sys/fs/ext4/hdc or
-/sys/fs/ext4/dm-0). The files in each per-device directory are shown
-in table below.
-
-Files in /sys/fs/ext4/<devname>:
-
-(see also Documentation/ABI/testing/sysfs-fs-ext4)
-
-============================= =================================================
-File Content
-============================= =================================================
- delayed_allocation_blocks This file is read-only and shows the number of
- blocks that are dirty in the page cache, but
- which do not have their location in the
- filesystem allocated yet.
-
-inode_goal Tuning parameter which (if non-zero) controls
- the goal inode used by the inode allocator in
- preference to all other allocation heuristics.
- This is intended for debugging use only, and
- should be 0 on production systems.
-
-inode_readahead_blks Tuning parameter which controls the maximum
- number of inode table blocks that ext4's inode
- table readahead algorithm will pre-read into
- the buffer cache
-
-lifetime_write_kbytes This file is read-only and shows the number of
- kilobytes of data that have been written to this
- filesystem since it was created.
-
- max_writeback_mb_bump The maximum number of megabytes the writeback
- code will try to write out before move on to
- another inode.
-
- mb_group_prealloc The multiblock allocator will round up allocation
- requests to a multiple of this tuning parameter if
- the stripe size is not set in the ext4 superblock
-
- mb_max_to_scan The maximum number of extents the multiblock
- allocator will search to find the best extent
-
- mb_min_to_scan The minimum number of extents the multiblock
- allocator will search to find the best extent
-
- mb_order2_req Tuning parameter which controls the minimum size
- for requests (as a power of 2) where the buddy
- cache is used
-
- mb_stats Controls whether the multiblock allocator should
- collect statistics, which are shown during the
- unmount. 1 means to collect statistics, 0 means
- not to collect statistics
-
- mb_stream_req Files which have fewer blocks than this tunable
- parameter will have their blocks allocated out
- of a block group specific preallocation pool, so
- that small files are packed closely together.
- Each large file will have its blocks allocated
- out of its own unique preallocation pool.
-
- session_write_kbytes This file is read-only and shows the number of
- kilobytes of data that have been written to this
- filesystem since it was mounted.
-
- reserved_clusters This is RW file and contains number of reserved
- clusters in the file system which will be used
- in the specific situations to avoid costly
- zeroout, unexpected ENOSPC, or possible data
- loss. The default is 2% or 4096 clusters,
- whichever is smaller and this can be changed
- however it can never exceed number of clusters
- in the file system. If there is not enough space
- for the reserved space when mounting the file
- mount will _not_ fail.
-============================= =================================================
-
-Ioctls
-======
-
-There is some Ext4 specific functionality which can be accessed by applications
-through the system call interfaces. The list of all Ext4 specific ioctls are
-shown in the table below.
-
-Table of Ext4 specific ioctls
-
-============================= =================================================
-Ioctl Description
-============================= =================================================
- EXT4_IOC_GETFLAGS Get additional attributes associated with inode.
- The ioctl argument is an integer bitfield, with
- bit values described in ext4.h. This ioctl is an
- alias for FS_IOC_GETFLAGS.
-
- EXT4_IOC_SETFLAGS Set additional attributes associated with inode.
- The ioctl argument is an integer bitfield, with
- bit values described in ext4.h. This ioctl is an
- alias for FS_IOC_SETFLAGS.
-
- EXT4_IOC_GETVERSION
- EXT4_IOC_GETVERSION_OLD
- Get the inode i_generation number stored for
- each inode. The i_generation number is normally
- changed only when new inode is created and it is
- particularly useful for network filesystems. The
- '_OLD' version of this ioctl is an alias for
- FS_IOC_GETVERSION.
-
- EXT4_IOC_SETVERSION
- EXT4_IOC_SETVERSION_OLD
- Set the inode i_generation number stored for
- each inode. The '_OLD' version of this ioctl
- is an alias for FS_IOC_SETVERSION.
-
- EXT4_IOC_GROUP_EXTEND This ioctl has the same purpose as the resize
- mount option. It allows to resize filesystem
- to the end of the last existing block group,
- further resize has to be done with resize2fs,
- either online, or offline. The argument points
- to the unsigned logn number representing the
- filesystem new block count.
-
- EXT4_IOC_MOVE_EXT Move the block extents from orig_fd (the one
- this ioctl is pointing to) to the donor_fd (the
- one specified in move_extent structure passed
- as an argument to this ioctl). Then, exchange
- inode metadata between orig_fd and donor_fd.
- This is especially useful for online
- defragmentation, because the allocator has the
- opportunity to allocate moved blocks better,
- ideally into one contiguous extent.
-
- EXT4_IOC_GROUP_ADD Add a new group descriptor to an existing or
- new group descriptor block. The new group
- descriptor is described by ext4_new_group_input
- structure, which is passed as an argument to
- this ioctl. This is especially useful in
- conjunction with EXT4_IOC_GROUP_EXTEND,
- which allows online resize of the filesystem
- to the end of the last existing block group.
- Those two ioctls combined is used in userspace
- online resize tool (e.g. resize2fs).
-
- EXT4_IOC_MIGRATE This ioctl operates on the filesystem itself.
- It converts (migrates) ext3 indirect block mapped
- inode to ext4 extent mapped inode by walking
- through indirect block mapping of the original
- inode and converting contiguous block ranges
- into ext4 extents of the temporary inode. Then,
- inodes are swapped. This ioctl might help, when
- migrating from ext3 to ext4 filesystem, however
- suggestion is to create fresh ext4 filesystem
- and copy data from the backup. Note, that
- filesystem has to support extents for this ioctl
- to work.
-
- EXT4_IOC_ALLOC_DA_BLKS Force all of the delay allocated blocks to be
- allocated to preserve application-expected ext3
- behaviour. Note that this will also start
- triggering a write of the data blocks, but this
- behaviour may change in the future as it is
- not necessary and has been done this way only
- for sake of simplicity.
-
- EXT4_IOC_RESIZE_FS Resize the filesystem to a new size. The number
- of blocks of resized filesystem is passed in via
- 64 bit integer argument. The kernel allocates
- bitmaps and inode table, the userspace tool thus
- just passes the new number of blocks.
-
- EXT4_IOC_SWAP_BOOT Swap i_blocks and associated attributes
- (like i_blocks, i_size, i_flags, ...) from
- the specified inode with inode
- EXT4_BOOT_LOADER_INO (#5). This is typically
- used to store a boot loader in a secure part of
- the filesystem, where it can't be changed by a
- normal user by accident.
- The data blocks of the previous boot loader
- will be associated with the given inode.
-============================= =================================================
-
-References
-==========
-
-kernel source: <file:fs/ext4/>
- <file:fs/jbd2/>
-
-programs: http://e2fsprogs.sourceforge.net/
-
-useful links: http://fedoraproject.org/wiki/ext3-devel
- http://www.bullopensource.org/ext4/
- http://ext4.wiki.kernel.org/index.php/Main_Page
- http://fedoraproject.org/wiki/Features/Ext4
diff --git a/Documentation/filesystems/ext4/ondisk/globals.rst b/Documentation/filesystems/ext4/globals.rst
similarity index 100%
rename from Documentation/filesystems/ext4/ondisk/globals.rst
rename to Documentation/filesystems/ext4/globals.rst
diff --git a/Documentation/filesystems/ext4/ondisk/group_descr.rst b/Documentation/filesystems/ext4/group_descr.rst
similarity index 92%
rename from Documentation/filesystems/ext4/ondisk/group_descr.rst
rename to Documentation/filesystems/ext4/group_descr.rst
index 759827e..7ba6114 100644
--- a/Documentation/filesystems/ext4/ondisk/group_descr.rst
+++ b/Documentation/filesystems/ext4/group_descr.rst
@@ -43,7 +43,7 @@
The block group descriptor is laid out in ``struct ext4_group_desc``.
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -99,9 +99,12 @@
* - 0x1E
- \_\_le16
- bg\_checksum
- - Group descriptor checksum; crc16(sb\_uuid+group+desc) if the
- RO\_COMPAT\_GDT\_CSUM feature is set, or crc32c(sb\_uuid+group\_desc) &
- 0xFFFF if the RO\_COMPAT\_METADATA\_CSUM feature is set.
+ - Group descriptor checksum; crc16(sb\_uuid+group\_num+bg\_desc) if the
+ RO\_COMPAT\_GDT\_CSUM feature is set, or
+ crc32c(sb\_uuid+group\_num+bg\_desc) & 0xFFFF if the
+ RO\_COMPAT\_METADATA\_CSUM feature is set. The bg\_checksum
+ field in bg\_desc is skipped when calculating crc16 checksum,
+ and set to zero if crc32c checksum is used.
* -
-
-
@@ -157,7 +160,7 @@
Block group flags can be any combination of the following:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
diff --git a/Documentation/filesystems/ext4/ondisk/ifork.rst b/Documentation/filesystems/ext4/ifork.rst
similarity index 98%
rename from Documentation/filesystems/ext4/ondisk/ifork.rst
rename to Documentation/filesystems/ext4/ifork.rst
index 5dbe3b2..b9816d5 100644
--- a/Documentation/filesystems/ext4/ondisk/ifork.rst
+++ b/Documentation/filesystems/ext4/ifork.rst
@@ -68,7 +68,7 @@
which is 12 bytes long:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -104,7 +104,7 @@
recorded as ``struct ext4_extent_idx``, and are 12 bytes long:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -134,7 +134,7 @@
and are also 12 bytes long:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -174,7 +174,7 @@
``struct ext4_extent_tail`` is 4 bytes long:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
diff --git a/Documentation/filesystems/ext4/index.rst b/Documentation/filesystems/ext4/index.rst
index 7112160..705d813 100644
--- a/Documentation/filesystems/ext4/index.rst
+++ b/Documentation/filesystems/ext4/index.rst
@@ -1,17 +1,14 @@
.. SPDX-License-Identifier: GPL-2.0
-===============
-ext4 Filesystem
-===============
-
-General usage and on-disk artifacts writen by ext4. More documentation may
-be ported from the wiki as time permits. This should be considered the
-canonical source of information as the details here have been reviewed by
-the ext4 community.
+===================================
+ext4 Data Structures and Algorithms
+===================================
.. toctree::
- :maxdepth: 5
+ :maxdepth: 6
:numbered:
- ext4
- ondisk/index
+ about
+ overview
+ globals
+ dynamic
diff --git a/Documentation/filesystems/ext4/ondisk/inlinedata.rst b/Documentation/filesystems/ext4/inlinedata.rst
similarity index 100%
rename from Documentation/filesystems/ext4/ondisk/inlinedata.rst
rename to Documentation/filesystems/ext4/inlinedata.rst
diff --git a/Documentation/filesystems/ext4/ondisk/inodes.rst b/Documentation/filesystems/ext4/inodes.rst
similarity index 97%
rename from Documentation/filesystems/ext4/ondisk/inodes.rst
rename to Documentation/filesystems/ext4/inodes.rst
index 655ce89..a65baff 100644
--- a/Documentation/filesystems/ext4/ondisk/inodes.rst
+++ b/Documentation/filesystems/ext4/inodes.rst
@@ -29,8 +29,9 @@
The inode table entry is laid out in ``struct ext4_inode``.
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
+ :class: longtable
* - Offset
- Size
@@ -176,7 +177,7 @@
The ``i_mode`` value is a combination of the following flags:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -227,7 +228,7 @@
The ``i_flags`` field is a combination of these values:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -276,6 +277,8 @@
- This is a huge file (EXT4\_HUGE\_FILE\_FL).
* - 0x80000
- Inode uses extents (EXT4\_EXTENTS\_FL).
+ * - 0x100000
+ - Verity protected file (EXT4\_VERITY\_FL).
* - 0x200000
- Inode stores a large extended attribute value in its data blocks
(EXT4\_EA\_INODE\_FL).
@@ -298,9 +301,9 @@
- Reserved for ext4 library (EXT4\_RESERVED\_FL).
* -
- Aggregate flags:
- * - 0x4BDFFF
+ * - 0x705BDFFF
- User-visible flags.
- * - 0x4B80FF
+ * - 0x604BC0FF
- User-modifiable flags. Note that while EXT4\_JOURNAL\_DATA\_FL and
EXT4\_EXTENTS\_FL can be set with setattr, they are not in the kernel's
EXT4\_FL\_USER\_MODIFIABLE mask, since it needs to handle the setting of
@@ -314,7 +317,7 @@
Linux:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -331,7 +334,7 @@
Hurd:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -346,7 +349,7 @@
Masix:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -365,7 +368,7 @@
Linux:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -402,7 +405,7 @@
Hurd:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -433,7 +436,7 @@
Masix:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -469,8 +472,8 @@
having to upgrade all of the on-disk inodes. Access to fields beyond
EXT2\_GOOD\_OLD\_INODE\_SIZE should be verified to be within
``i_extra_isize``. By default, ext4 inode records are 256 bytes, and (as
-of October 2013) the inode structure is 156 bytes
-(``i_extra_isize = 28``). The extra space between the end of the inode
+of August 2019) the inode structure is 160 bytes
+(``i_extra_isize = 32``). The extra space between the end of the inode
structure and the end of the inode record can be used to store extended
attributes. Each inode record can be as large as the filesystem block
size, though this is not terribly efficient.
diff --git a/Documentation/filesystems/ext4/ondisk/journal.rst b/Documentation/filesystems/ext4/journal.rst
similarity index 97%
rename from Documentation/filesystems/ext4/ondisk/journal.rst
rename to Documentation/filesystems/ext4/journal.rst
index e7031af..ea613ee 100644
--- a/Documentation/filesystems/ext4/ondisk/journal.rst
+++ b/Documentation/filesystems/ext4/journal.rst
@@ -48,7 +48,7 @@
Generally speaking, the journal has this format:
.. list-table::
- :widths: 1 1 78
+ :widths: 16 48 16
:header-rows: 1
* - Superblock
@@ -76,7 +76,7 @@
superblock.
.. list-table::
- :widths: 1 1 1 1 76
+ :widths: 12 12 12 32 12
:header-rows: 1
* - 1024 bytes of padding
@@ -98,7 +98,7 @@
``struct journal_header_s``:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -124,7 +124,7 @@
The journal block type can be any one of:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -154,7 +154,7 @@
which is 1024 bytes long:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -264,7 +264,7 @@
The journal compat features are any combination of the following:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -278,7 +278,7 @@
The journal incompat features are any combination of the following:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -306,7 +306,7 @@
most likely choices.
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -330,7 +330,7 @@
Descriptor blocks consume at least 36 bytes, but use a full block:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -355,7 +355,7 @@
following. The size is 16 or 32 bytes.
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -400,7 +400,7 @@
The journal tag flags are any combination of the following:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -421,7 +421,7 @@
following. The size is 8, 12, 24, or 28 bytes:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -471,7 +471,7 @@
``struct jbd2_journal_block_tail``, which looks like this:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -513,7 +513,7 @@
length, but use a full block:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -543,7 +543,7 @@
block is a ``struct jbd2_journal_revoke_tail``, which has this format:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -567,7 +567,7 @@
bytes long (but uses a full block):
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
diff --git a/Documentation/filesystems/ext4/ondisk/mmp.rst b/Documentation/filesystems/ext4/mmp.rst
similarity index 98%
rename from Documentation/filesystems/ext4/ondisk/mmp.rst
rename to Documentation/filesystems/ext4/mmp.rst
index b7d7a31..2566098 100644
--- a/Documentation/filesystems/ext4/ondisk/mmp.rst
+++ b/Documentation/filesystems/ext4/mmp.rst
@@ -32,7 +32,7 @@
The MMP structure (``struct mmp_struct``) is as follows:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 12 20 40
:header-rows: 1
* - Offset
diff --git a/Documentation/filesystems/ext4/ondisk/bigalloc.rst b/Documentation/filesystems/ext4/ondisk/bigalloc.rst
deleted file mode 100644
index c6d8855..0000000
--- a/Documentation/filesystems/ext4/ondisk/bigalloc.rst
+++ /dev/null
@@ -1,22 +0,0 @@
-.. SPDX-License-Identifier: GPL-2.0
-
-Bigalloc
---------
-
-At the moment, the default size of a block is 4KiB, which is a commonly
-supported page size on most MMU-capable hardware. This is fortunate, as
-ext4 code is not prepared to handle the case where the block size
-exceeds the page size. However, for a filesystem of mostly huge files,
-it is desirable to be able to allocate disk blocks in units of multiple
-blocks to reduce both fragmentation and metadata overhead. The
-`bigalloc <Bigalloc>`__ feature provides exactly this ability. The
-administrator can set a block cluster size at mkfs time (which is stored
-in the s\_log\_cluster\_size field in the superblock); from then on, the
-block bitmaps track clusters, not individual blocks. This means that
-block groups can be several gigabytes in size (instead of just 128MiB);
-however, the minimum allocation unit becomes a cluster, not a block,
-even for directories. TaoBao had a patchset to extend the “use units of
-clusters instead of blocks” to the extent tree, though it is not clear
-where those patches went-- they eventually morphed into “extent tree v2”
-but that code has not landed as of May 2015.
-
diff --git a/Documentation/filesystems/ext4/ondisk/index.rst b/Documentation/filesystems/ext4/ondisk/index.rst
deleted file mode 100644
index f7d082c..0000000
--- a/Documentation/filesystems/ext4/ondisk/index.rst
+++ /dev/null
@@ -1,9 +0,0 @@
-.. SPDX-License-Identifier: GPL-2.0
-
-==============================
-Data Structures and Algorithms
-==============================
-.. include:: about.rst
-.. include:: overview.rst
-.. include:: globals.rst
-.. include:: dynamic.rst
diff --git a/Documentation/filesystems/ext4/ondisk/overview.rst b/Documentation/filesystems/ext4/overview.rst
similarity index 97%
rename from Documentation/filesystems/ext4/ondisk/overview.rst
rename to Documentation/filesystems/ext4/overview.rst
index cbab18b..123ebfd 100644
--- a/Documentation/filesystems/ext4/ondisk/overview.rst
+++ b/Documentation/filesystems/ext4/overview.rst
@@ -24,3 +24,4 @@
.. include:: bigalloc.rst
.. include:: inlinedata.rst
.. include:: eainode.rst
+.. include:: verity.rst
diff --git a/Documentation/filesystems/ext4/ondisk/special_inodes.rst b/Documentation/filesystems/ext4/special_inodes.rst
similarity index 97%
rename from Documentation/filesystems/ext4/ondisk/special_inodes.rst
rename to Documentation/filesystems/ext4/special_inodes.rst
index a82f70c..9061aab 100644
--- a/Documentation/filesystems/ext4/ondisk/special_inodes.rst
+++ b/Documentation/filesystems/ext4/special_inodes.rst
@@ -6,7 +6,7 @@
ext4 reserves some inode for special features, as follows:
.. list-table::
- :widths: 1 79
+ :widths: 6 70
:header-rows: 1
* - inode Number
diff --git a/Documentation/filesystems/ext4/ondisk/super.rst b/Documentation/filesystems/ext4/super.rst
similarity index 96%
rename from Documentation/filesystems/ext4/ondisk/super.rst
rename to Documentation/filesystems/ext4/super.rst
index 5f81dd8..93e55d7 100644
--- a/Documentation/filesystems/ext4/ondisk/super.rst
+++ b/Documentation/filesystems/ext4/super.rst
@@ -19,7 +19,7 @@
``struct ext4_super_block``:
.. list-table::
- :widths: 1 1 1 77
+ :widths: 8 8 24 40
:header-rows: 1
* - Offset
@@ -58,7 +58,7 @@
* - 0x1C
- \_\_le32
- s\_log\_cluster\_size
- - Cluster size is (2 ^ s\_log\_cluster\_size) blocks if bigalloc is
+ - Cluster size is 2 ^ (10 + s\_log\_cluster\_size) blocks if bigalloc is
enabled. Otherwise s\_log\_cluster\_size must equal s\_log\_block\_size.
* - 0x20
- \_\_le32
@@ -447,7 +447,7 @@
- Upper 8 bits of the s_wtime field.
* - 0x275
- \_\_u8
- - s\_wtime_hi
+ - s\_mtime_hi
- Upper 8 bits of the s_mtime field.
* - 0x276
- \_\_u8
@@ -466,12 +466,20 @@
- s\_last_error_time_hi
- Upper 8 bits of the s_last_error_time_hi field.
* - 0x27A
- - \_\_u8[2]
- - s\_pad
+ - \_\_u8
+ - s\_pad[2]
- Zero padding.
* - 0x27C
+ - \_\_le16
+ - s\_encoding
+ - Filename charset encoding.
+ * - 0x27E
+ - \_\_le16
+ - s\_encoding_flags
+ - Filename charset encoding flags.
+ * - 0x280
- \_\_le32
- - s\_reserved[96]
+ - s\_reserved[95]
- Padding to the end of the block.
* - 0x3FC
- \_\_le32
@@ -483,7 +491,7 @@
The superblock state is some combination of the following:
.. list-table::
- :widths: 1 79
+ :widths: 8 72
:header-rows: 1
* - Value
@@ -500,7 +508,7 @@
The superblock error policy is one of the following:
.. list-table::
- :widths: 1 79
+ :widths: 8 72
:header-rows: 1
* - Value
@@ -517,7 +525,7 @@
The filesystem creator is one of the following:
.. list-table::
- :widths: 1 79
+ :widths: 8 72
:header-rows: 1
* - Value
@@ -538,7 +546,7 @@
The superblock revision is one of the following:
.. list-table::
- :widths: 1 79
+ :widths: 8 72
:header-rows: 1
* - Value
@@ -556,7 +564,7 @@
following:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -595,7 +603,7 @@
following:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -617,7 +625,7 @@
* - 0x80
- Enable a filesystem size of 2^64 blocks (INCOMPAT\_64BIT).
* - 0x100
- - Multiple mount protection. Not implemented (INCOMPAT\_MMP).
+ - Multiple mount protection (INCOMPAT\_MMP).
* - 0x200
- Flexible block groups. See the earlier discussion of this feature
(INCOMPAT\_FLEX\_BG).
@@ -647,7 +655,7 @@
the following:
.. list-table::
- :widths: 1 79
+ :widths: 16 64
:header-rows: 1
* - Value
@@ -696,13 +704,15 @@
(RO\_COMPAT\_READONLY)
* - 0x2000
- Filesystem tracks project quotas. (RO\_COMPAT\_PROJECT)
+ * - 0x8000
+ - Verity inodes may be present on the filesystem. (RO\_COMPAT\_VERITY)
.. _super_def_hash:
The ``s_def_hash_version`` field is one of the following:
.. list-table::
- :widths: 1 79
+ :widths: 8 72
:header-rows: 1
* - Value
@@ -725,7 +735,7 @@
The ``s_default_mount_opts`` field is any combination of the following:
.. list-table::
- :widths: 1 79
+ :widths: 8 72
:header-rows: 1
* - Value
@@ -767,7 +777,7 @@
The ``s_flags`` field is any combination of the following:
.. list-table::
- :widths: 1 79
+ :widths: 8 72
:header-rows: 1
* - Value
@@ -784,7 +794,7 @@
The ``s_encrypt_algos`` list can contain any of the following:
.. list-table::
- :widths: 1 79
+ :widths: 8 72
:header-rows: 1
* - Value
diff --git a/Documentation/filesystems/ext4/verity.rst b/Documentation/filesystems/ext4/verity.rst
new file mode 100644
index 0000000..3e4c0ee
--- /dev/null
+++ b/Documentation/filesystems/ext4/verity.rst
@@ -0,0 +1,41 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Verity files
+------------
+
+ext4 supports fs-verity, which is a filesystem feature that provides
+Merkle tree based hashing for individual readonly files. Most of
+fs-verity is common to all filesystems that support it; see
+:ref:`Documentation/filesystems/fsverity.rst <fsverity>` for the
+fs-verity documentation. However, the on-disk layout of the verity
+metadata is filesystem-specific. On ext4, the verity metadata is
+stored after the end of the file data itself, in the following format:
+
+- Zero-padding to the next 65536-byte boundary. This padding need not
+ actually be allocated on-disk, i.e. it may be a hole.
+
+- The Merkle tree, as documented in
+ :ref:`Documentation/filesystems/fsverity.rst
+ <fsverity_merkle_tree>`, with the tree levels stored in order from
+ root to leaf, and the tree blocks within each level stored in their
+ natural order.
+
+- Zero-padding to the next filesystem block boundary.
+
+- The verity descriptor, as documented in
+ :ref:`Documentation/filesystems/fsverity.rst <fsverity_descriptor>`,
+ with optionally appended signature blob.
+
+- Zero-padding to the next offset that is 4 bytes before a filesystem
+ block boundary.
+
+- The size of the verity descriptor in bytes, as a 4-byte little
+ endian integer.
+
+Verity inodes have EXT4_VERITY_FL set, and they must use extents, i.e.
+EXT4_EXTENTS_FL must be set and EXT4_INLINE_DATA_FL must be clear.
+They can have EXT4_ENCRYPT_FL set, in which case the verity metadata
+is encrypted as well as the data itself.
+
+Verity files cannot have blocks allocated past the end of the verity
+metadata.