On Apr 8, 2020, at 3:55 PM, Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx> wrote:
>
> From: Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx>
>
> Define feature flags for fast commits and add routines to allow ext4 to
> initialize fast commits. Note that we allow 128 blocks to be used for
> fast commits. As of now, that's the default constant value.
>
> Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx>
> +static inline int ext4_should_fast_commit(struct super_block *sb)
> +{
> + if (!ext4_has_feature_fast_commit(sb))
> + return 0;
> + if (!test_opt2(sb, JOURNAL_FAST_COMMIT))
> + return 0;
> + if (test_opt(sb, QUOTA))
> + return 0;
> + return 1;
> +}
This function seems more complex than it should be. In this patch the
ext4_should_fast_commit() function is only called once during mount, but
in later patches it looks like it is called many times per file/inode.
Why not just check JOURNAL_FAST_COMMIT, and clear it at mount/remount
time if the other conditions prevent fast commits being used at all?
It seems that JOURNAL_FAST_COMMIT is only set if the FAST_COMMIT feature
is already in the superblock, so always doing both checks seems redundant.
Also, maybe I missed the discussion, but why does having quotas enabled
on the filesystem disable fast commits entirely? I see in patch 11/20
that EXT4_FC_REASON_QUOTA is a reason not to do fast commit on the quota
inodes themselves, which seems like a reasonable limitation if needed,
but the above check disables FC for any filesystem with quota, and I
can't find anywhere that this line is later removed in this series.
Cheers, Andreas
Attachment:
signature.asc
Description: Message signed with OpenPGP
