On Thu, Jan 21, 2021 at 08:49:33AM -0800, Darrick J. Wong wrote:
> On Thu, Jan 21, 2021 at 09:08:27AM -0600, Bill O'Donnell wrote:
> > On Wed, Jan 06, 2021 at 12:41:19PM -0500, Brian Foster wrote:
> > > xfs_log_sbcount() syncs the superblock specifically to accumulate
> > > the in-core percpu superblock counters and commit them to disk. This
> > > is required to maintain filesystem consistency across quiesce
> > > (freeze, read-only mount/remount) or unmount when lazy superblock
> > > accounting is enabled because individual transactions do not update
> > > the superblock directly.
> > >
> > > This mechanism works as expected for writable mounts, but
> > > xfs_log_sbcount() skips the update for read-only mounts. Read-only
> > > mounts otherwise still allow log recovery and write out an unmount
> > > record during log quiesce. If a read-only mount performs log
> > > recovery, it can modify the in-core superblock counters and write an
> > > unmount record when the filesystem unmounts without ever syncing the
> > > in-core counters. This leaves the filesystem with a clean log but in
> > > an inconsistent state with regard to lazy sb counters.
> > >
> > > Update xfs_log_sbcount() to use the same logic
> > > xfs_log_unmount_write() uses to determine when to write an unmount
> > > record. We can drop the freeze state check because the update is
> > > already allowed during the freezing process and no context calls
> > > this function on an already frozen fs. This ensures that lazy
> > > accounting is always synced before the log is cleaned. Refactor this
> > > logic into a new helper to distinguish between a writable filesystem
> > > and a writable log. Specifically, the log is writable unless the
> > > filesystem is mounted with the norecovery mount option, the
> > > underlying log device is read-only, or the filesystem is shutdown.
> > >
> > > Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> > > Reviewed-by: Gao Xiang <hsiangkao@xxxxxxxxxx>
> >
> > works for me.
> > Reviewed-by: Bill O'Donnell <billodo@xxxxxxxxxx>
>
> Does this also apply to the v3 series that Brian just sent?
I only used this patch 1/9, as that was all I was focusing on.
>
> --D
>
> >
> > > ---
> > > fs/xfs/xfs_log.c | 28 ++++++++++++++++++++--------
> > > fs/xfs/xfs_log.h | 1 +
> > > fs/xfs/xfs_mount.c | 3 +--
> > > 3 files changed, 22 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> > > index fa2d05e65ff1..b445e63cbc3c 100644
> > > --- a/fs/xfs/xfs_log.c
> > > +++ b/fs/xfs/xfs_log.c
> > > @@ -347,6 +347,25 @@ xlog_tic_add_region(xlog_ticket_t *tic, uint len, uint type)
> > > tic->t_res_num++;
> > > }
> > >
> > > +bool
> > > +xfs_log_writable(
> > > + struct xfs_mount *mp)
> > > +{
> > > + /*
> > > + * Never write to the log on norecovery mounts, if the block device is
> > > + * read-only, or if the filesystem is shutdown. Read-only mounts still
> > > + * allow internal writes for log recovery and unmount purposes, so don't
> > > + * restrict that case here.
> > > + */
> > > + if (mp->m_flags & XFS_MOUNT_NORECOVERY)
> > > + return false;
> > > + if (xfs_readonly_buftarg(mp->m_log->l_targ))
> > > + return false;
> > > + if (XFS_FORCED_SHUTDOWN(mp))
> > > + return false;
> > > + return true;
> > > +}
> > > +
> > > /*
> > > * Replenish the byte reservation required by moving the grant write head.
> > > */
> > > @@ -886,15 +905,8 @@ xfs_log_unmount_write(
> > > {
> > > struct xlog *log = mp->m_log;
> > >
> > > - /*
> > > - * Don't write out unmount record on norecovery mounts or ro devices.
> > > - * Or, if we are doing a forced umount (typically because of IO errors).
> > > - */
> > > - if (mp->m_flags & XFS_MOUNT_NORECOVERY ||
> > > - xfs_readonly_buftarg(log->l_targ)) {
> > > - ASSERT(mp->m_flags & XFS_MOUNT_RDONLY);
> > > + if (!xfs_log_writable(mp))
> > > return;
> > > - }
> > >
> > > xfs_log_force(mp, XFS_LOG_SYNC);
> > >
> > > diff --git a/fs/xfs/xfs_log.h b/fs/xfs/xfs_log.h
> > > index 58c3fcbec94a..98c913da7587 100644
> > > --- a/fs/xfs/xfs_log.h
> > > +++ b/fs/xfs/xfs_log.h
> > > @@ -127,6 +127,7 @@ int xfs_log_reserve(struct xfs_mount *mp,
> > > int xfs_log_regrant(struct xfs_mount *mp, struct xlog_ticket *tic);
> > > void xfs_log_unmount(struct xfs_mount *mp);
> > > int xfs_log_force_umount(struct xfs_mount *mp, int logerror);
> > > +bool xfs_log_writable(struct xfs_mount *mp);
> > >
> > > struct xlog_ticket *xfs_log_ticket_get(struct xlog_ticket *ticket);
> > > void xfs_log_ticket_put(struct xlog_ticket *ticket);
> > > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> > > index 7110507a2b6b..a62b8a574409 100644
> > > --- a/fs/xfs/xfs_mount.c
> > > +++ b/fs/xfs/xfs_mount.c
> > > @@ -1176,8 +1176,7 @@ xfs_fs_writable(
> > > int
> > > xfs_log_sbcount(xfs_mount_t *mp)
> > > {
> > > - /* allow this to proceed during the freeze sequence... */
> > > - if (!xfs_fs_writable(mp, SB_FREEZE_COMPLETE))
> > > + if (!xfs_log_writable(mp))
> > > return 0;
> > >
> > > /*
> > > --
> > > 2.26.2
> > >
> >
>
