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| author | Harshad Shirwadkar <harshadshirwadkar@gmail.com> | 2020-11-05 19:58:50 -0800 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2020-11-06 23:01:01 -0500 |
| commit | a44ad6835da52fdf4df2e482f45a167336555121 (patch) | |
| tree | 176af5bf4223b6e1a47b1817fa06fa439c3d0613 | |
| parent | 7067b2619017d51e71686ca9756b454de0e5826a (diff) | |
| download | powerpc-a44ad6835da52fdf4df2e482f45a167336555121.tar.gz | |
ext4: describe fast_commit feature flags
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 <jack@suse.cz>
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20201106035911.1942128-2-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
| -rw-r--r-- | Documentation/filesystems/ext4/journal.rst | 6 | ||||
| -rw-r--r-- | Documentation/filesystems/ext4/super.rst | 7 | ||||
| -rw-r--r-- | fs/ext4/ext4.h | 7 |
3 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/filesystems/ext4/journal.rst b/Documentation/filesystems/ext4/journal.rst index 805a1e9ea3a5b0..849d5b119eb8b0 100644 --- a/Documentation/filesystems/ext4/journal.rst +++ b/Documentation/filesystems/ext4/journal.rst @@ -256,6 +256,10 @@ which is 1024 bytes long: - s\_padding2 - * - 0x54 + - \_\_be32 + - s\_num\_fc\_blocks + - Number of fast commit blocks in the journal. + * - 0x58 - \_\_u32 - s\_padding[42] - @@ -310,6 +314,8 @@ The journal incompat features are any combination of the following: - 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) + * - 0x20 + - Journal has fast commit blocks. (JBD2\_FEATURE\_INCOMPAT\_FAST\_COMMIT) .. _jbd2_checksum_type: diff --git a/Documentation/filesystems/ext4/super.rst b/Documentation/filesystems/ext4/super.rst index 93e55d7c1d4055..2eb1ab20498dd4 100644 --- a/Documentation/filesystems/ext4/super.rst +++ b/Documentation/filesystems/ext4/super.rst @@ -596,6 +596,13 @@ following: - Sparse Super Block, v2. If this flag is set, the SB field s\_backup\_bgs points to the two block groups that contain backup superblocks (COMPAT\_SPARSE\_SUPER2). + * - 0x400 + - Fast commits supported. Although fast commits blocks are + backward incompatible, fast commit blocks are not always + present in the journal. If fast commit blocks are present in + the journal, JBD2 incompat feature + (JBD2\_FEATURE\_INCOMPAT\_FAST\_COMMIT) gets + set (COMPAT\_FAST\_COMMIT). .. _super_incompat: diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 45fcdbf538d119..d513553ceafa7f 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1863,6 +1863,13 @@ static inline bool ext4_verity_in_progress(struct inode *inode) #define EXT4_FEATURE_COMPAT_RESIZE_INODE 0x0010 #define EXT4_FEATURE_COMPAT_DIR_INDEX 0x0020 #define EXT4_FEATURE_COMPAT_SPARSE_SUPER2 0x0200 +/* + * The reason why "FAST_COMMIT" is a compat feature is that, FS becomes + * incompatible only if fast commit blocks are present in the FS. Since we + * clear the journal (and thus the fast commit blocks), we don't mark FS as + * incompatible. We also have a JBD2 incompat feature, which gets set when + * there are fast commit blocks present in the journal. + */ #define EXT4_FEATURE_COMPAT_FAST_COMMIT 0x0400 #define EXT4_FEATURE_COMPAT_STABLE_INODES 0x0800 |