On Sat 31-10-20 13:05:09, Harshad Shirwadkar wrote: > 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@xxxxxxx> > Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx> Looks good to me. Thanks! You can add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza > --- > Documentation/filesystems/ext4/journal.rst | 6 ++++++ > Documentation/filesystems/ext4/super.rst | 7 +++++++ > fs/ext4/ext4.h | 7 +++++++ > 3 files changed, 20 insertions(+) > > diff --git a/Documentation/filesystems/ext4/journal.rst b/Documentation/filesystems/ext4/journal.rst > index 805a1e9ea3a5..849d5b119eb8 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 93e55d7c1d40..2eb1ab20498d 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 2337e443fa30..12673f9ec880 100644 > --- a/fs/ext4/ext4.h > +++ b/fs/ext4/ext4.h > @@ -1875,6 +1875,13 @@ 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 > > -- > 2.29.1.341.ge80a0c044ae-goog > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
