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| author | Girish Shilamkar <girish@clusterfs.com> | 2008-01-29 07:58:27 +0300 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2008-01-29 07:58:27 +0300 |
| commit | 818d276ceb83aa9fdebb5e0a53188290312de987 (patch) | |
| tree | de3fb4ffadd72caea2876c5232ce76cd14b3646e /Documentation/filesystems/ext4.txt | |
| parent | 8e85fb3f305b24b79c6d9cb7a56d22b062335ad3 (diff) | |
| download | linux-818d276ceb83aa9fdebb5e0a53188290312de987.tar.xz | |
ext4: Add the journal checksum feature
The journal checksum feature adds two new flags i.e
JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT and JBD2_FEATURE_COMPAT_CHECKSUM.
JBD2_FEATURE_CHECKSUM flag indicates that the commit block contains the
checksum for the blocks described by the descriptor blocks.
Due to checksums, writing of the commit record no longer needs to be
synchronous. Now commit record can be sent to disk without waiting for
descriptor blocks to be written to disk. This behavior is controlled
using JBD2_FEATURE_ASYNC_COMMIT flag. Older kernels/e2fsck should not be
able to recover the journal with _ASYNC_COMMIT hence it is made
incompat.
The commit header has been extended to hold the checksum along with the
type of the checksum.
For recovery in pass scan checksums are verified to ensure the sanity
and completeness(in case of _ASYNC_COMMIT) of every transaction.
Signed-off-by: Andreas Dilger <adilger@clusterfs.com>
Signed-off-by: Girish Shilamkar <girish@clusterfs.com>
Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Diffstat (limited to 'Documentation/filesystems/ext4.txt')
| -rw-r--r-- | Documentation/filesystems/ext4.txt | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index 6a4adcae9f9a..4f329afe20ec 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -89,6 +89,16 @@ When mounting an ext4 filesystem, the following option are accepted: extents ext4 will use extents to address file data. The file system will no longer be mountable by ext3. +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=update Update the ext4 file system's journal to the current format. |