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-rw-r--r--Documentation/filesystems/ext4/journal.rst214
1 files changed, 107 insertions, 107 deletions
diff --git a/Documentation/filesystems/ext4/journal.rst b/Documentation/filesystems/ext4/journal.rst
index 5fad38860f17..a6bef5293a60 100644
--- a/Documentation/filesystems/ext4/journal.rst
+++ b/Documentation/filesystems/ext4/journal.rst
@@ -63,8 +63,8 @@ Generally speaking, the journal has this format:
:header-rows: 1
* - Superblock
- - descriptor\_block (data\_blocks or revocation\_block) [more data or
- revocations] commmit\_block
+ - descriptor_block (data_blocks or revocation_block) [more data or
+ revocations] commmit_block
- [more transactions...]
* -
- One transaction
@@ -93,8 +93,8 @@ superblock.
* - 1024 bytes of padding
- ext4 Superblock
- Journal Superblock
- - descriptor\_block (data\_blocks or revocation\_block) [more data or
- revocations] commmit\_block
+ - descriptor_block (data_blocks or revocation_block) [more data or
+ revocations] commmit_block
- [more transactions...]
* -
-
@@ -117,17 +117,17 @@ Every block in the journal starts with a common 12-byte header
- Name
- Description
* - 0x0
- - \_\_be32
- - h\_magic
+ - __be32
+ - h_magic
- jbd2 magic number, 0xC03B3998.
* - 0x4
- - \_\_be32
- - h\_blocktype
+ - __be32
+ - h_blocktype
- Description of what this block contains. See the jbd2_blocktype_ table
below.
* - 0x8
- - \_\_be32
- - h\_sequence
+ - __be32
+ - h_sequence
- The transaction ID that goes with this block.
.. _jbd2_blocktype:
@@ -177,99 +177,99 @@ which is 1024 bytes long:
-
- Static information describing the journal.
* - 0x0
- - journal\_header\_t (12 bytes)
- - s\_header
+ - journal_header_t (12 bytes)
+ - s_header
- Common header identifying this as a superblock.
* - 0xC
- - \_\_be32
- - s\_blocksize
+ - __be32
+ - s_blocksize
- Journal device block size.
* - 0x10
- - \_\_be32
- - s\_maxlen
+ - __be32
+ - s_maxlen
- Total number of blocks in this journal.
* - 0x14
- - \_\_be32
- - s\_first
+ - __be32
+ - s_first
- First block of log information.
* -
-
-
- Dynamic information describing the current state of the log.
* - 0x18
- - \_\_be32
- - s\_sequence
+ - __be32
+ - s_sequence
- First commit ID expected in log.
* - 0x1C
- - \_\_be32
- - s\_start
+ - __be32
+ - s_start
- Block number of the start of log. Contrary to the comments, this field
being zero does not imply that the journal is clean!
* - 0x20
- - \_\_be32
- - s\_errno
- - Error value, as set by jbd2\_journal\_abort().
+ - __be32
+ - s_errno
+ - Error value, as set by jbd2_journal_abort().
* -
-
-
- The remaining fields are only valid in a v2 superblock.
* - 0x24
- - \_\_be32
- - s\_feature\_compat;
+ - __be32
+ - s_feature_compat;
- Compatible feature set. See the table jbd2_compat_ below.
* - 0x28
- - \_\_be32
- - s\_feature\_incompat
+ - __be32
+ - s_feature_incompat
- Incompatible feature set. See the table jbd2_incompat_ below.
* - 0x2C
- - \_\_be32
- - s\_feature\_ro\_compat
+ - __be32
+ - s_feature_ro_compat
- Read-only compatible feature set. There aren't any of these currently.
* - 0x30
- - \_\_u8
- - s\_uuid[16]
+ - __u8
+ - s_uuid[16]
- 128-bit uuid for journal. This is compared against the copy in the ext4
super block at mount time.
* - 0x40
- - \_\_be32
- - s\_nr\_users
+ - __be32
+ - s_nr_users
- Number of file systems sharing this journal.
* - 0x44
- - \_\_be32
- - s\_dynsuper
+ - __be32
+ - s_dynsuper
- Location of dynamic super block copy. (Not used?)
* - 0x48
- - \_\_be32
- - s\_max\_transaction
+ - __be32
+ - s_max_transaction
- Limit of journal blocks per transaction. (Not used?)
* - 0x4C
- - \_\_be32
- - s\_max\_trans\_data
+ - __be32
+ - s_max_trans_data
- Limit of data blocks per transaction. (Not used?)
* - 0x50
- - \_\_u8
- - s\_checksum\_type
+ - __u8
+ - s_checksum_type
- Checksum algorithm used for the journal. See jbd2_checksum_type_ for
more info.
* - 0x51
- - \_\_u8[3]
- - s\_padding2
+ - __u8[3]
+ - s_padding2
-
* - 0x54
- - \_\_be32
- - s\_num\_fc\_blocks
+ - __be32
+ - s_num_fc_blocks
- Number of fast commit blocks in the journal.
* - 0x58
- - \_\_u32
- - s\_padding[42]
+ - __u32
+ - s_padding[42]
-
* - 0xFC
- - \_\_be32
- - s\_checksum
+ - __be32
+ - s_checksum
- Checksum of the entire superblock, with this field set to zero.
* - 0x100
- - \_\_u8
- - s\_users[16\*48]
+ - __u8
+ - s_users[16*48]
- ids of all file systems sharing the log. e2fsprogs/Linux don't allow
shared external journals, but I imagine Lustre (or ocfs2?), which use
the jbd2 code, might.
@@ -286,7 +286,7 @@ The journal compat features are any combination of the following:
- Description
* - 0x1
- Journal maintains checksums on the data blocks.
- (JBD2\_FEATURE\_COMPAT\_CHECKSUM)
+ (JBD2_FEATURE_COMPAT_CHECKSUM)
.. _jbd2_incompat:
@@ -299,23 +299,23 @@ The journal incompat features are any combination of the following:
* - Value
- Description
* - 0x1
- - Journal has block revocation records. (JBD2\_FEATURE\_INCOMPAT\_REVOKE)
+ - Journal has block revocation records. (JBD2_FEATURE_INCOMPAT_REVOKE)
* - 0x2
- Journal can deal with 64-bit block numbers.
- (JBD2\_FEATURE\_INCOMPAT\_64BIT)
+ (JBD2_FEATURE_INCOMPAT_64BIT)
* - 0x4
- - Journal commits asynchronously. (JBD2\_FEATURE\_INCOMPAT\_ASYNC\_COMMIT)
+ - Journal commits asynchronously. (JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)
* - 0x8
- This journal uses v2 of the checksum on-disk format. Each journal
metadata block gets its own checksum, and the block tags in the
descriptor table contain checksums for each of the data blocks in the
- journal. (JBD2\_FEATURE\_INCOMPAT\_CSUM\_V2)
+ journal. (JBD2_FEATURE_INCOMPAT_CSUM_V2)
* - 0x10
- This journal uses v3 of the checksum on-disk format. This is the same as
v2, but the journal block tag size is fixed regardless of the size of
- block numbers. (JBD2\_FEATURE\_INCOMPAT\_CSUM\_V3)
+ block numbers. (JBD2_FEATURE_INCOMPAT_CSUM_V3)
* - 0x20
- - Journal has fast commit blocks. (JBD2\_FEATURE\_INCOMPAT\_FAST\_COMMIT)
+ - Journal has fast commit blocks. (JBD2_FEATURE_INCOMPAT_FAST_COMMIT)
.. _jbd2_checksum_type:
@@ -355,11 +355,11 @@ Descriptor blocks consume at least 36 bytes, but use a full block:
- Name
- Descriptor
* - 0x0
- - journal\_header\_t
+ - journal_header_t
- (open coded)
- Common block header.
* - 0xC
- - struct journal\_block\_tag\_s
+ - struct journal_block_tag_s
- open coded array[]
- Enough tags either to fill up the block or to describe all the data
blocks that follow this descriptor block.
@@ -367,7 +367,7 @@ Descriptor blocks consume at least 36 bytes, but use a full block:
Journal block tags have any of the following formats, depending on which
journal feature and block tag flags are set.
-If JBD2\_FEATURE\_INCOMPAT\_CSUM\_V3 is set, the journal block tag is
+If JBD2_FEATURE_INCOMPAT_CSUM_V3 is set, the journal block tag is
defined as ``struct journal_block_tag3_s``, which looks like the
following. The size is 16 or 32 bytes.
@@ -380,24 +380,24 @@ following. The size is 16 or 32 bytes.
- Name
- Descriptor
* - 0x0
- - \_\_be32
- - t\_blocknr
+ - __be32
+ - t_blocknr
- Lower 32-bits of the location of where the corresponding data block
should end up on disk.
* - 0x4
- - \_\_be32
- - t\_flags
+ - __be32
+ - t_flags
- Flags that go with the descriptor. See the table jbd2_tag_flags_ for
more info.
* - 0x8
- - \_\_be32
- - t\_blocknr\_high
+ - __be32
+ - t_blocknr_high
- Upper 32-bits of the location of where the corresponding data block
- should end up on disk. This is zero if JBD2\_FEATURE\_INCOMPAT\_64BIT is
+ should end up on disk. This is zero if JBD2_FEATURE_INCOMPAT_64BIT is
not enabled.
* - 0xC
- - \_\_be32
- - t\_checksum
+ - __be32
+ - t_checksum
- Checksum of the journal UUID, the sequence number, and the data block.
* -
-
@@ -433,7 +433,7 @@ The journal tag flags are any combination of the following:
* - 0x8
- This is the last tag in this descriptor block.
-If JBD2\_FEATURE\_INCOMPAT\_CSUM\_V3 is NOT set, the journal block tag
+If JBD2_FEATURE_INCOMPAT_CSUM_V3 is NOT set, the journal block tag
is defined as ``struct journal_block_tag_s``, which looks like the
following. The size is 8, 12, 24, or 28 bytes:
@@ -446,18 +446,18 @@ following. The size is 8, 12, 24, or 28 bytes:
- Name
- Descriptor
* - 0x0
- - \_\_be32
- - t\_blocknr
+ - __be32
+ - t_blocknr
- Lower 32-bits of the location of where the corresponding data block
should end up on disk.
* - 0x4
- - \_\_be16
- - t\_checksum
+ - __be16
+ - t_checksum
- Checksum of the journal UUID, the sequence number, and the data block.
Note that only the lower 16 bits are stored.
* - 0x6
- - \_\_be16
- - t\_flags
+ - __be16
+ - t_flags
- Flags that go with the descriptor. See the table jbd2_tag_flags_ for
more info.
* -
@@ -466,8 +466,8 @@ following. The size is 8, 12, 24, or 28 bytes:
- This next field is only present if the super block indicates support for
64-bit block numbers.
* - 0x8
- - \_\_be32
- - t\_blocknr\_high
+ - __be32
+ - t_blocknr_high
- Upper 32-bits of the location of where the corresponding data block
should end up on disk.
* -
@@ -483,8 +483,8 @@ following. The size is 8, 12, 24, or 28 bytes:
``j_uuid`` field in ``struct journal_s``, but only tune2fs touches that
field.
-If JBD2\_FEATURE\_INCOMPAT\_CSUM\_V2 or
-JBD2\_FEATURE\_INCOMPAT\_CSUM\_V3 are set, the end of the block is a
+If JBD2_FEATURE_INCOMPAT_CSUM_V2 or
+JBD2_FEATURE_INCOMPAT_CSUM_V3 are set, the end of the block is a
``struct jbd2_journal_block_tail``, which looks like this:
.. list-table::
@@ -496,8 +496,8 @@ JBD2\_FEATURE\_INCOMPAT\_CSUM\_V3 are set, the end of the block is a
- Name
- Descriptor
* - 0x0
- - \_\_be32
- - t\_checksum
+ - __be32
+ - t_checksum
- Checksum of the journal UUID + the descriptor block, with this field set
to zero.
@@ -538,25 +538,25 @@ length, but use a full block:
- Name
- Description
* - 0x0
- - journal\_header\_t
- - r\_header
+ - journal_header_t
+ - r_header
- Common block header.
* - 0xC
- - \_\_be32
- - r\_count
+ - __be32
+ - r_count
- Number of bytes used in this block.
* - 0x10
- - \_\_be32 or \_\_be64
+ - __be32 or __be64
- blocks[0]
- Blocks to revoke.
-After r\_count is a linear array of block numbers that are effectively
+After r_count is a linear array of block numbers that are effectively
revoked by this transaction. The size of each block number is 8 bytes if
the superblock advertises 64-bit block number support, or 4 bytes
otherwise.
-If JBD2\_FEATURE\_INCOMPAT\_CSUM\_V2 or
-JBD2\_FEATURE\_INCOMPAT\_CSUM\_V3 are set, the end of the revocation
+If JBD2_FEATURE_INCOMPAT_CSUM_V2 or
+JBD2_FEATURE_INCOMPAT_CSUM_V3 are set, the end of the revocation
block is a ``struct jbd2_journal_revoke_tail``, which has this format:
.. list-table::
@@ -568,8 +568,8 @@ block is a ``struct jbd2_journal_revoke_tail``, which has this format:
- Name
- Description
* - 0x0
- - \_\_be32
- - r\_checksum
+ - __be32
+ - r_checksum
- Checksum of the journal UUID + revocation block
Commit Block
@@ -592,38 +592,38 @@ bytes long (but uses a full block):
- Name
- Descriptor
* - 0x0
- - journal\_header\_s
+ - journal_header_s
- (open coded)
- Common block header.
* - 0xC
- unsigned char
- - h\_chksum\_type
+ - h_chksum_type
- The type of checksum to use to verify the integrity of the data blocks
in the transaction. See jbd2_checksum_type_ for more info.
* - 0xD
- unsigned char
- - h\_chksum\_size
+ - h_chksum_size
- The number of bytes used by the checksum. Most likely 4.
* - 0xE
- unsigned char
- - h\_padding[2]
+ - h_padding[2]
-
* - 0x10
- - \_\_be32
- - h\_chksum[JBD2\_CHECKSUM\_BYTES]
+ - __be32
+ - h_chksum[JBD2_CHECKSUM_BYTES]
- 32 bytes of space to store checksums. If
- JBD2\_FEATURE\_INCOMPAT\_CSUM\_V2 or JBD2\_FEATURE\_INCOMPAT\_CSUM\_V3
+ JBD2_FEATURE_INCOMPAT_CSUM_V2 or JBD2_FEATURE_INCOMPAT_CSUM_V3
are set, the first ``__be32`` is the checksum of the journal UUID and
the entire commit block, with this field zeroed. If
- JBD2\_FEATURE\_COMPAT\_CHECKSUM is set, the first ``__be32`` is the
+ JBD2_FEATURE_COMPAT_CHECKSUM is set, the first ``__be32`` is the
crc32 of all the blocks already written to the transaction.
* - 0x30
- - \_\_be64
- - h\_commit\_sec
+ - __be64
+ - h_commit_sec
- The time that the transaction was committed, in seconds since the epoch.
* - 0x38
- - \_\_be32
- - h\_commit\_nsec
+ - __be32
+ - h_commit_nsec
- Nanoseconds component of the above timestamp.
Fast commits