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Date:   Tue, 1 Oct 2019 00:52:57 -0700
From:   harshad shirwadkar <harshadshirwadkar@...il.com>
To:     Andreas Dilger <adilger@...ger.ca>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH v2 03/12] jbd2: fast commit setup and enable

Oops, I missed this, I'll handle this in V4. Thanks!

On Fri, Aug 9, 2019 at 1:02 PM Andreas Dilger <adilger@...ger.ca> wrote:
>
> On Aug 8, 2019, at 9:45 PM, Harshad Shirwadkar <harshadshirwadkar@...il.com> wrote:
> >
> > This patch allows file systems to turn fast commits on and thereby
> > restrict the normal journalling space to total journal blocks minus
> > JBD2_FAST_COMMIT_BLOCKS. Fast commits are not actually performed, just
> > the interface to turn fast commits on is opened.
> >
> > Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@...il.com>
> >
> > ---
> >
> > Changelog:
> >
> > V2: No changes since V1
> > ---
> > fs/ext4/super.c      |  3 ++-
> > fs/jbd2/journal.c    | 39 ++++++++++++++++++++++++++++++++-------
> > fs/ocfs2/journal.c   |  4 ++--
> > include/linux/jbd2.h |  2 +-
> > 4 files changed, 37 insertions(+), 11 deletions(-)
> >
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index e376ac040cce..81c3ec165822 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -4933,7 +4933,8 @@ static int ext4_load_journal(struct super_block *sb,
> >               if (save)
> >                       memcpy(save, ((char *) es) +
> >                              EXT4_S_ERR_START, EXT4_S_ERR_LEN);
> > -             err = jbd2_journal_load(journal);
> > +             err = jbd2_journal_load(journal,
> > +                                     test_opt2(sb, JOURNAL_FAST_COMMIT));
> >               if (save)
> >                       memcpy(((char *) es) + EXT4_S_ERR_START,
> >                              save, EXT4_S_ERR_LEN);
> > diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> > index 953990eb70a9..59ad709154a3 100644
> > --- a/fs/jbd2/journal.c
> > +++ b/fs/jbd2/journal.c
> > @@ -1159,12 +1159,15 @@ static journal_t *journal_init_common(struct block_device *bdev,
> >       journal->j_blk_offset = start;
> >       journal->j_maxlen = len;
> >       n = journal->j_blocksize / sizeof(journal_block_tag_t);
> > -     journal->j_wbufsize = n;
> > +     journal->j_wbufsize = n - JBD2_FAST_COMMIT_BLOCKS;
>
> The reservation of the JBD2_FAST_COMMIT_BLOCKS should only be done in
> the case of the FAST_COMMIT feature being enabled.  Otherwise it can
> hurt performance for filesystems where this feature is not enabled.
>
> Cheers, Andreas
>
> >       journal->j_wbuf = kmalloc_array(n, sizeof(struct buffer_head *),
> >                                       GFP_KERNEL);
> >       if (!journal->j_wbuf)
> >               goto err_cleanup;
> >
> > +     journal->j_fc_wbuf = &journal->j_wbuf[journal->j_wbufsize];
> > +     journal->j_fc_wbufsize = JBD2_FAST_COMMIT_BLOCKS;
> > +
> >       bh = getblk_unmovable(journal->j_dev, start, journal->j_blocksize);
> >       if (!bh) {
> >               pr_err("%s: Cannot get buffer for journal superblock\n",
> > @@ -1297,11 +1300,19 @@ static int journal_reset(journal_t *journal)
> >       }
> >
> >       journal->j_first = first;
> > -     journal->j_last = last;
> >
> > -     journal->j_head = first;
> > -     journal->j_tail = first;
> > -     journal->j_free = last - first;
> > +     if (jbd2_has_feature_fast_commit(journal)) {
> > +             journal->j_last_fc = last;
> > +             journal->j_last = last - JBD2_FAST_COMMIT_BLOCKS;
> > +             journal->j_first_fc = journal->j_last + 1;
> > +             journal->j_fc_off = 0;
> > +     } else {
> > +             journal->j_last = last;
> > +     }
> > +
> > +     journal->j_head = journal->j_first;
> > +     journal->j_tail = journal->j_first;
> > +     journal->j_free = journal->j_last - journal->j_first;
> >
> >       journal->j_tail_sequence = journal->j_transaction_sequence;
> >       journal->j_commit_sequence = journal->j_transaction_sequence - 1;
> > @@ -1626,9 +1637,17 @@ static int load_superblock(journal_t *journal)
> >       journal->j_tail_sequence = be32_to_cpu(sb->s_sequence);
> >       journal->j_tail = be32_to_cpu(sb->s_start);
> >       journal->j_first = be32_to_cpu(sb->s_first);
> > -     journal->j_last = be32_to_cpu(sb->s_maxlen);
> >       journal->j_errno = be32_to_cpu(sb->s_errno);
> >
> > +     if (jbd2_has_feature_fast_commit(journal)) {
> > +             journal->j_last_fc = be32_to_cpu(sb->s_maxlen);
> > +             journal->j_last = journal->j_last_fc - JBD2_FAST_COMMIT_BLOCKS;
> > +             journal->j_first_fc = journal->j_last + 1;
> > +             journal->j_fc_off = 0;
> > +     } else {
> > +             journal->j_last = be32_to_cpu(sb->s_maxlen);
> > +     }
> > +
> >       return 0;
> > }
> >
> > @@ -1641,7 +1660,7 @@ static int load_superblock(journal_t *journal)
> >  * a journal, read the journal from disk to initialise the in-memory
> >  * structures.
> >  */
> > -int jbd2_journal_load(journal_t *journal)
> > +int jbd2_journal_load(journal_t *journal, bool enable_fc)
> > {
> >       int err;
> >       journal_superblock_t *sb;
> > @@ -1684,6 +1703,12 @@ int jbd2_journal_load(journal_t *journal)
> >               return -EFSCORRUPTED;
> >       }
> >
> > +     if (enable_fc)
> > +             jbd2_journal_set_features(journal, 0, 0,
> > +                                       JBD2_FEATURE_INCOMPAT_FAST_COMMIT);
> > +     else
> > +             jbd2_journal_clear_features(journal, 0, 0,
> > +                                         JBD2_FEATURE_INCOMPAT_FAST_COMMIT);
> >       /* OK, we've finished with the dynamic journal bits:
> >        * reinitialise the dynamic contents of the superblock in memory
> >        * and reset them on disk. */
> > diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
> > index 930e3d388579..3b4d91b16e8e 100644
> > --- a/fs/ocfs2/journal.c
> > +++ b/fs/ocfs2/journal.c
> > @@ -1057,7 +1057,7 @@ int ocfs2_journal_load(struct ocfs2_journal *journal, int local, int replayed)
> >
> >       osb = journal->j_osb;
> >
> > -     status = jbd2_journal_load(journal->j_journal);
> > +     status = jbd2_journal_load(journal->j_journal, false);
> >       if (status < 0) {
> >               mlog(ML_ERROR, "Failed to load journal!\n");
> >               goto done;
> > @@ -1642,7 +1642,7 @@ static int ocfs2_replay_journal(struct ocfs2_super *osb,
> >               goto done;
> >       }
> >
> > -     status = jbd2_journal_load(journal);
> > +     status = jbd2_journal_load(journal, false);
> >       if (status < 0) {
> >               mlog_errno(status);
> >               if (!igrab(inode))
> > diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> > index 9a750b732241..153840b422cc 100644
> > --- a/include/linux/jbd2.h
> > +++ b/include/linux/jbd2.h
> > @@ -1476,7 +1476,7 @@ extern int         jbd2_journal_set_features
> >                  (journal_t *, unsigned long, unsigned long, unsigned long);
> > extern void      jbd2_journal_clear_features
> >                  (journal_t *, unsigned long, unsigned long, unsigned long);
> > -extern int      jbd2_journal_load       (journal_t *journal);
> > +extern int      jbd2_journal_load(journal_t *journal, bool enable_fc);
> > extern int       jbd2_journal_destroy    (journal_t *);
> > extern int       jbd2_journal_recover    (journal_t *journal);
> > extern int       jbd2_journal_wipe       (journal_t *, int);
> > --
> > 2.23.0.rc1.153.gdeed80330f-goog
> >
>
>
> Cheers, Andreas
>
>
>
>
>

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