Lines Matching refs:journal
6 Introduced in ext3, the ext4 filesystem employs a journal to protect the
8 to 10,240,000 file system blocks (see man mke2fs(8) for more details on journal
12 cache, a record of the data being committed is also written to the journal. At
13 some later point in time, the journal code writes the transactions to their
16 crash during the second slow write, the journal can be replayed all the
18 gets written through the journal to the disk. The effect of this is to
23 through the journal. This means that file data blocks are /not/
26 option to control journal behavior. If ``data=journal``, all data and
27 metadata are written to disk through the journal. This is slower but
29 disk before the metadata are written to disk through the journal.
33 mode works by logging metadata blocks to the journal. In fast commit
42 The journal inode is typically inode 8. The first 68 bytes of the
43 journal inode are replicated in the ext4 superblock. The journal itself
53 The maximum size of a journal embedded in an ext4 filesystem is 2^32
59 Generally speaking, the journal has this format:
81 Optionally, an ext4 filesystem can be created with an external journal
82 device (as opposed to an internal journal, which uses a reserved inode).
84 zero and ``s_journal_uuid`` should be set. On the journal device there
86 The journal superblock will be in the next full block after the
108 Every block in the journal starts with a common 12-byte header
135 The journal block type can be any one of:
145 written through the journal during a transaction.
155 journal to skip writing blocks that were subsequently rewritten.
160 The super block for the journal is much simpler as compared to ext4's.
161 The key data kept within are size of the journal, and where to find the
164 The journal superblock is recorded as ``struct journal_superblock_s``,
178 - Static information describing the journal.
190 - Total number of blocks in this journal.
207 being zero does not imply that the journal is clean!
231 - 128-bit uuid for journal. This is compared against the copy in the ext4
236 - Number of file systems sharing this journal.
244 - Limit of journal blocks per transaction. (Not used?)
252 - Checksum algorithm used for the journal. See jbd2_checksum_type_ for
261 - Number of fast commit blocks in the journal.
279 The journal compat features are any combination of the following:
293 The journal incompat features are any combination of the following:
309 - This journal uses v2 of the checksum on-disk format. Each journal
312 journal. (JBD2_FEATURE_INCOMPAT_CSUM_V2)
314 - This journal uses v3 of the checksum on-disk format. This is the same as
315 v2, but the journal block tag size is fixed regardless of the size of
343 The descriptor block contains an array of journal block tags that
345 journal. Descriptor blocks are open-coded instead of being completely
368 journal feature and block tag flags are set.
370 If JBD2_FEATURE_INCOMPAT_CSUM_V3 is set, the journal block tag is
401 - Checksum of the journal UUID, the sequence number, and the data block.
417 The journal tag flags are any combination of the following:
436 If JBD2_FEATURE_INCOMPAT_CSUM_V3 is NOT set, the journal block tag
456 - Checksum of the journal UUID, the sequence number, and the data block.
501 - Checksum of the journal UUID + the descriptor block, with this field set
507 In general, the data blocks being written to disk through the journal
508 are written verbatim into the journal file after the descriptor block.
520 journal replay after the file block was written to disk will cause
523 **NOTE**: This mechanism is NOT used to express “this journal block is
524 superseded by this other journal block”, as the author (djwong)
573 - Checksum of the journal UUID + revocation block
579 completely written to the journal. Once this commit block reaches the
580 journal, the data stored with this transaction can be written to their
616 are set, the first ``__be32`` is the checksum of the journal UUID and
738 Checkpointing the journal ensures all transactions and their associated buffers
741 the filesystem including journal recovery, filesystem resizing, and freeing of
744 A journal checkpoint can be triggered from userspace via the ioctl
752 EXT4_IOC_CHECKPOINT_FLAG_ZEROOUT. These flags cause the journal blocks to be
753 discarded or zero-filled, respectively, after the journal checkpoint is