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Date: Fri, 9 Aug 2019 14:02:13 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Harshad Shirwadkar <harshadshirwadkar@...il.com>
Cc: linux-ext4@...r.kernel.org
Subject: Re: [PATCH v2 03/12] jbd2: fast commit setup and enable
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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