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SubjectRe: [PATCH 2/2] ext4: fast commit may miss file actions
Makes sense. With this change, we don't really need
EXT4_MF_FC_COMMITTING flag anymore. So, we can drop it. But other than
that, this patch looks good.

Reviewed-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>

On Fri, Jan 7, 2022 at 4:13 AM Xin Yin <yinxin.x@bytedance.com> wrote:
>
> in the follow scenario:
> 1. jbd start transaction n
> 2. task A get new handle for transaction n+1
> 3. task A do some actions and add inode to FC_Q_MAIN fc_q
> 4. jbd complete transaction n and clear FC_Q_MAIN fc_q
> 5. task A call fsync
>
> fast commit will lost the file actions during a full commit.
>
> we should also add updates to staging queue during a full commit.
> and in ext4_fc_cleanup(), when reset a inode's fc track range, check
> it's i_sync_tid, if it bigger than current transaction tid, do not
> rest it, or we will lost the track range.
>
> Signed-off-by: Xin Yin <yinxin.x@bytedance.com>
> ---
> fs/ext4/fast_commit.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
> index 3673d4798af3..4cea92aec7c4 100644
> --- a/fs/ext4/fast_commit.c
> +++ b/fs/ext4/fast_commit.c
> @@ -365,7 +365,8 @@ static int ext4_fc_track_template(
> spin_lock(&sbi->s_fc_lock);
> if (list_empty(&EXT4_I(inode)->i_fc_list))
> list_add_tail(&EXT4_I(inode)->i_fc_list,
> - (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_COMMITTING)) ?
> + (sbi->s_journal->j_flags & JBD2_FULL_COMMIT_ONGOING ||
> + sbi->s_journal->j_flags & JBD2_FAST_COMMIT_ONGOING) ?
> &sbi->s_fc_q[FC_Q_STAGING] :
> &sbi->s_fc_q[FC_Q_MAIN]);
> spin_unlock(&sbi->s_fc_lock);
> @@ -418,7 +419,8 @@ static int __track_dentry_update(struct inode *inode, void *arg, bool update)
> node->fcd_name.len = dentry->d_name.len;
>
> spin_lock(&sbi->s_fc_lock);
> - if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_COMMITTING))
> + if (sbi->s_journal->j_flags & JBD2_FULL_COMMIT_ONGOING ||
> + sbi->s_journal->j_flags & JBD2_FAST_COMMIT_ONGOING)
> list_add_tail(&node->fcd_list,
> &sbi->s_fc_dentry_q[FC_Q_STAGING]);
> else
> @@ -1202,7 +1204,8 @@ static void ext4_fc_cleanup(journal_t *journal, int full, tid_t tid)
> list_del_init(&iter->i_fc_list);
> ext4_clear_inode_state(&iter->vfs_inode,
> EXT4_STATE_FC_COMMITTING);
> - ext4_fc_reset_inode(&iter->vfs_inode);
> + if (iter->i_sync_tid <= tid)
> + ext4_fc_reset_inode(&iter->vfs_inode);
> /* Make sure EXT4_STATE_FC_COMMITTING bit is clear */
> smp_mb();
> #if (BITS_PER_LONG < 64)
> --
> 2.20.1
>

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