On Tue, Jun 13, 2023 at 12:29 PM Andrew Price <anpr...@redhat.com> wrote:
> On 12/06/2023 17:33, Andreas Gruenbacher wrote:
> > So far, at mount time, gfs2 would take the freeze glock in shared mode
> > and then immediately drop it again, turning it into a cached glock that
> > can be reclaimed at any time. To freeze the filesystem cluster-wide,
> > the node initiating the freeze would take the freeze glock in exclusive
> > mode, which would cause the freeze glock's freeze_go_sync() callback to
> > run on each node. There, gfs2 would freeze the filesystem and schedule
> > gfs2_freeze_func() to run. gfs2_freeze_func() would re-acquire the
> > freeze glock in shared mode, thaw the filesystem, and drop the freeze
> > glock again. The initiating node would keep the freeze glock held in
> > exclusive mode. To thaw the filesystem, the initiating node would drop
> > the freeze glock again, which would allow gfs2_freeze_func() to resume
> > on all nodes, leaving the filesystem in the thawed state.
> >
> > It turns out that in freeze_go_sync(), we cannot reliably and safely
> > freeze the filesystem. This is primarily because the final unmount of a
> > filesystem takes a write lock on the s_umount rw semaphore before
> > calling into gfs2_put_super(), and freeze_go_sync() needs to call
> > freeze_super() which also takes a write lock on the same semaphore,
> > causing a deadlock. We could work around this by trying to take an
> > active reference on the super block first, which would prevent unmount
> > from running at the same time. But that can fail, and freeze_go_sync()
> > isn't actually allowed to fail.
> >
> > To get around this, this patch changes the freeze glock locking scheme
> > as follows:
> >
> > At mount time, each node takes the freeze glock in shared mode. To
> > freeze a filesystem, the initiating node first freezes the filesystem
> > locally and then drops and re-acquires the freeze glock in exclusive
> > mode. All other nodes notice that there is contention on the freeze
> > glock in their go_callback callbacks, and they schedule
> > gfs2_freeze_func() to run. There, they freeze the filesystem locally
> > and drop and re-acquire the freeze glock before re-thawing the
> > filesystem. This is happening outside of the glock state engine, so
> > there, we are allowed to fail.
> >
> > From a cluster point of view, taking and immediately dropping a glock is
> > indistinguishable from taking the glock and only dropping it upon
> > contention, so this new scheme is compatible with the old one.
>
> Nice!
>
> > Signed-off-by: Andreas Gruenbacher <agrue...@redhat.com>
> > ---
> > fs/gfs2/glops.c | 52 +++++--------
> > fs/gfs2/log.c | 2 -
> > fs/gfs2/ops_fstype.c | 5 +-
> > fs/gfs2/recovery.c | 24 +++---
> > fs/gfs2/super.c | 179 ++++++++++++++++++++++++++++++++++---------
> > fs/gfs2/super.h | 1 +
> > fs/gfs2/util.c | 32 +++-----
> > 7 files changed, 185 insertions(+), 110 deletions(-)
> >
> > diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
> > index 01d433ed6ce7..7c48c7afd6a4 100644
> > --- a/fs/gfs2/glops.c
> > +++ b/fs/gfs2/glops.c
> > @@ -561,47 +561,33 @@ static void inode_go_dump(struct seq_file *seq,
> > struct gfs2_glock *gl,
> > }
> >
> > /**
> > - * freeze_go_sync - promote/demote the freeze glock
> > + * freeze_go_callback - A cluster node is requesting a freeze
> > * @gl: the glock
> > + * @remote: true if this came from a different cluster node
> > */
> >
> > -static int freeze_go_sync(struct gfs2_glock *gl)
> > +static void freeze_go_callback(struct gfs2_glock *gl, bool remote)
> > {
> > - int error = 0;
> > struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
> > + struct super_block *sb = sdp->sd_vfs;
> > +
> > + if (!remote ||
> > + gl->gl_state != LM_ST_SHARED ||
> > + gl->gl_demote_state != LM_ST_UNLOCKED)
> > + return;
> >
> > /*
> > - * We need to check gl_state == LM_ST_SHARED here and not gl_req ==
> > - * LM_ST_EXCLUSIVE. That's because when any node does a freeze,
> > - * all the nodes should have the freeze glock in SH mode and they all
> > - * call do_xmote: One for EX and the others for UN. They ALL must
> > - * freeze locally, and they ALL must queue freeze work. The
> > freeze_work
> > - * calls freeze_func, which tries to reacquire the freeze glock in SH,
> > - * effectively waiting for the thaw on the node who holds it in EX.
> > - * Once thawed, the work func acquires the freeze glock in
> > - * SH and everybody goes back to thawed.
> > + * Try to get an active super block reference to prevent racing with
> > + * unmount (see trylock_super()). But note that unmount isn't the
> > only
> > + * place where a write lock on s_umount is taken, and we can fail here
> > + * because of things like remount as well.
> > */
> > - if (gl->gl_state == LM_ST_SHARED && !gfs2_withdrawn(sdp) &&
> > - !test_bit(SDF_NORECOVERY, &sdp->sd_flags)) {
> > - atomic_set(&sdp->sd_freeze_state, SFS_STARTING_FREEZE);
> > - error = freeze_super(sdp->sd_vfs);
> > - if (error) {
> > - fs_info(sdp, "GFS2: couldn't freeze filesystem: %d\n",
> > - error);
> > - if (gfs2_withdrawn(sdp)) {
> > - atomic_set(&sdp->sd_freeze_state,
> > SFS_UNFROZEN);
> > - return 0;
> > - }
> > - gfs2_assert_withdraw(sdp, 0);
> > - }
> > - queue_work(gfs2_freeze_wq, &sdp->sd_freeze_work);
> > - if (test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags))
> > - gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_FREEZE |
> > - GFS2_LFC_FREEZE_GO_SYNC);
> > - else /* read-only mounts */
> > - atomic_set(&sdp->sd_freeze_state, SFS_FROZEN);
> > + if (down_read_trylock(&sb->s_umount)) {
> > + atomic_inc(&sb->s_active);
> > + up_read(&sb->s_umount);
> > + if (!queue_work(gfs2_freeze_wq, &sdp->sd_freeze_work))
> > + deactivate_super(sb);
> > }
> > - return 0;
> > }
> >
> > /**
> > @@ -761,9 +747,9 @@ const struct gfs2_glock_operations gfs2_rgrp_glops = {
> > };
> >
> > const struct gfs2_glock_operations gfs2_freeze_glops = {
> > - .go_sync = freeze_go_sync,
> > .go_xmote_bh = freeze_go_xmote_bh,
> > .go_demote_ok = freeze_go_demote_ok,
> > + .go_callback = freeze_go_callback,
> > .go_type = LM_TYPE_NONDISK,
> > .go_flags = GLOF_NONDISK,
> > };
> > diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
> > index d750d1128bed..dca535311dee 100644
> > --- a/fs/gfs2/log.c
> > +++ b/fs/gfs2/log.c
> > @@ -1136,8 +1136,6 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct
> > gfs2_glock *gl, u32 flags)
> > if (flags & (GFS2_LOG_HEAD_FLUSH_SHUTDOWN |
> > GFS2_LOG_HEAD_FLUSH_FREEZE))
> > gfs2_log_shutdown(sdp);
> > - if (flags & GFS2_LOG_HEAD_FLUSH_FREEZE)
> > - atomic_set(&sdp->sd_freeze_state, SFS_FROZEN);
> > }
> >
> > out_end:
> > diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
> > index 12eedba45dbb..4ce5718719ac 100644
> > --- a/fs/gfs2/ops_fstype.c
> > +++ b/fs/gfs2/ops_fstype.c
> > @@ -1140,7 +1140,6 @@ static int gfs2_fill_super(struct super_block *sb,
> > struct fs_context *fc)
> > int silent = fc->sb_flags & SB_SILENT;
> > struct gfs2_sbd *sdp;
> > struct gfs2_holder mount_gh;
> > - struct gfs2_holder freeze_gh;
> > int error;
> >
> > sdp = init_sbd(sb);
> > @@ -1269,15 +1268,15 @@ static int gfs2_fill_super(struct super_block *sb,
> > struct fs_context *fc)
> > }
> > }
> >
> > - error = gfs2_freeze_lock_shared(sdp, &freeze_gh, 0);
> > + error = gfs2_freeze_lock_shared(sdp, &sdp->sd_freeze_gh, 0);
> > if (error)
> > goto fail_per_node;
> >
> > if (!sb_rdonly(sb))
> > error = gfs2_make_fs_rw(sdp);
> >
> > - gfs2_freeze_unlock(&freeze_gh);
> > if (error) {
> > + gfs2_freeze_unlock(&sdp->sd_freeze_gh);
> > if (sdp->sd_quotad_process)
> > kthread_stop(sdp->sd_quotad_process);
> > sdp->sd_quotad_process = NULL;
> > diff --git a/fs/gfs2/recovery.c b/fs/gfs2/recovery.c
> > index 61ef07da40b2..afeda936e2be 100644
> > --- a/fs/gfs2/recovery.c
> > +++ b/fs/gfs2/recovery.c
> > @@ -404,7 +404,7 @@ void gfs2_recover_func(struct work_struct *work)
> > struct gfs2_inode *ip = GFS2_I(jd->jd_inode);
> > struct gfs2_sbd *sdp = GFS2_SB(jd->jd_inode);
> > struct gfs2_log_header_host head;
> > - struct gfs2_holder j_gh, ji_gh, thaw_gh;
> > + struct gfs2_holder j_gh, ji_gh;
> > ktime_t t_start, t_jlck, t_jhd, t_tlck, t_rep;
> > int ro = 0;
> > unsigned int pass;
> > @@ -465,14 +465,14 @@ void gfs2_recover_func(struct work_struct *work)
> > ktime_ms_delta(t_jhd, t_jlck));
> >
> > if (!(head.lh_flags & GFS2_LOG_HEAD_UNMOUNT)) {
> > - fs_info(sdp, "jid=%u: Acquiring the freeze glock...\n",
> > - jd->jd_jid);
> > -
> > - /* Acquire a shared hold on the freeze glock */
> > + mutex_lock(&sdp->sd_freeze_mutex);
> >
> > - error = gfs2_freeze_lock_shared(sdp, &thaw_gh,
> > LM_FLAG_PRIORITY);
> > - if (error)
> > + if (atomic_read(&sdp->sd_freeze_state) != SFS_UNFROZEN) {
> > + mutex_unlock(&sdp->sd_freeze_mutex);
> > + fs_warn(sdp, "jid=%u: Can't replay: filesystem "
> > + "is frozen\n", jd->jd_jid);
> > goto fail_gunlock_ji;
> > + }
> >
> > if (test_bit(SDF_RORECOVERY, &sdp->sd_flags)) {
> > ro = 1;
> > @@ -496,7 +496,7 @@ void gfs2_recover_func(struct work_struct *work)
> > fs_warn(sdp, "jid=%u: Can't replay: read-only block "
> > "device\n", jd->jd_jid);
> > error = -EROFS;
> > - goto fail_gunlock_thaw;
> > + goto fail_gunlock_nofreeze;
> > }
> >
> > t_tlck = ktime_get();
> > @@ -514,7 +514,7 @@ void gfs2_recover_func(struct work_struct *work)
> > lops_after_scan(jd, error, pass);
> > if (error) {
> > up_read(&sdp->sd_log_flush_lock);
> > - goto fail_gunlock_thaw;
> > + goto fail_gunlock_nofreeze;
> > }
> > }
> >
> > @@ -522,7 +522,7 @@ void gfs2_recover_func(struct work_struct *work)
> > clean_journal(jd, &head);
> > up_read(&sdp->sd_log_flush_lock);
> >
> > - gfs2_freeze_unlock(&thaw_gh);
> > + mutex_unlock(&sdp->sd_freeze_mutex);
> > t_rep = ktime_get();
> > fs_info(sdp, "jid=%u: Journal replayed in %lldms
> > [jlck:%lldms, "
> > "jhead:%lldms, tlck:%lldms, replay:%lldms]\n",
> > @@ -543,8 +543,8 @@ void gfs2_recover_func(struct work_struct *work)
> > fs_info(sdp, "jid=%u: Done\n", jd->jd_jid);
> > goto done;
> >
> > -fail_gunlock_thaw:
> > - gfs2_freeze_unlock(&thaw_gh);
> > +fail_gunlock_nofreeze:
> > + mutex_unlock(&sdp->sd_freeze_mutex);
> > fail_gunlock_ji:
> > if (jlocked) {
> > gfs2_glock_dq_uninit(&ji_gh);
> > diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
> > index 5f3e699ae922..eb41ab32695a 100644
> > --- a/fs/gfs2/super.c
> > +++ b/fs/gfs2/super.c
> > @@ -332,7 +332,12 @@ static int gfs2_lock_fs_check_clean(struct gfs2_sbd
> > *sdp)
> > struct lfcc *lfcc;
> > LIST_HEAD(list);
> > struct gfs2_log_header_host lh;
> > - int error;
> > + int error, error2;
> > +
> > + /*
> > + * Grab all the journal glocks in SH mode. We are *probably* doing
> > + * that to prevent recovery.
> > + */
> >
> > list_for_each_entry(jd, &sdp->sd_jindex_list, jd_list) {
> > lfcc = kmalloc(sizeof(struct lfcc), GFP_KERNEL);
> > @@ -349,11 +354,13 @@ static int gfs2_lock_fs_check_clean(struct gfs2_sbd
> > *sdp)
> > list_add(&lfcc->list, &list);
> > }
> >
> > + gfs2_freeze_unlock(&sdp->sd_freeze_gh);
> > +
> > error = gfs2_glock_nq_init(sdp->sd_freeze_gl, LM_ST_EXCLUSIVE,
> > LM_FLAG_NOEXP | GL_NOPID,
> > &sdp->sd_freeze_gh);
> > if (error)
> > - goto out;
> > + goto relock_shared;
> >
> > list_for_each_entry(jd, &sdp->sd_jindex_list, jd_list) {
> > error = gfs2_jdesc_check(jd);
> > @@ -368,8 +375,14 @@ static int gfs2_lock_fs_check_clean(struct gfs2_sbd
> > *sdp)
> > }
> > }
> >
> > - if (error)
> > - gfs2_freeze_unlock(&sdp->sd_freeze_gh);
> > + if (!error)
> > + goto out; /* success */
> > +
> > + gfs2_freeze_unlock(&sdp->sd_freeze_gh);
> > +
> > +relock_shared:
> > + error2 = gfs2_freeze_lock_shared(sdp, &sdp->sd_freeze_gh, 0);
> > + gfs2_assert_withdraw(sdp, !error2);
> >
> > out:
> > while (!list_empty(&list)) {
> > @@ -615,6 +628,8 @@ static void gfs2_put_super(struct super_block *sb)
> >
> > /* Release stuff */
> >
> > + gfs2_freeze_unlock(&sdp->sd_freeze_gh);
> > +
> > iput(sdp->sd_jindex);
> > iput(sdp->sd_statfs_inode);
> > iput(sdp->sd_rindex);
> > @@ -669,31 +684,81 @@ static int gfs2_sync_fs(struct super_block *sb, int
> > wait)
> > return sdp->sd_log_error;
> > }
> >
> > -void gfs2_freeze_func(struct work_struct *work)
> > +static int gfs2_freeze_locally(struct gfs2_sbd *sdp)
> > {
> > - int error;
> > - struct gfs2_holder freeze_gh;
> > - struct gfs2_sbd *sdp = container_of(work, struct gfs2_sbd,
> > sd_freeze_work);
> > struct super_block *sb = sdp->sd_vfs;
> > + int error;
> >
> > - atomic_inc(&sb->s_active);
> > - error = gfs2_freeze_lock_shared(sdp, &freeze_gh, 0);
> > - if (error) {
> > - gfs2_assert_withdraw(sdp, 0);
> > - } else {
> > - atomic_set(&sdp->sd_freeze_state, SFS_UNFROZEN);
> > - error = thaw_super(sb);
> > - if (error) {
> > - fs_info(sdp, "GFS2: couldn't thaw filesystem: %d\n",
> > - error);
> > - gfs2_assert_withdraw(sdp, 0);
> > + atomic_set(&sdp->sd_freeze_state, SFS_STARTING_FREEZE);
> > +
> > + error = freeze_super(sb);
> > + if (error)
> > + goto fail;
> > +
> > + if (test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags)) {
> > + gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_FREEZE |
> > + GFS2_LFC_FREEZE_GO_SYNC);
> > + if (gfs2_withdrawn(sdp)) {
> > + thaw_super(sb);
> > + error = -EIO;
> > + goto fail;
> > }
> > - gfs2_freeze_unlock(&freeze_gh);
> > }
> > + return 0;
> > +
> > +fail:
> > + atomic_set(&sdp->sd_freeze_state, SFS_UNFROZEN);
> > + return error;
> > +}
> > +
> > +static int gfs2_do_thaw(struct gfs2_sbd *sdp)
> > +{
> > + struct super_block *sb = sdp->sd_vfs;
> > + int error;
> > +
> > + error = gfs2_freeze_lock_shared(sdp, &sdp->sd_freeze_gh, 0);
> > + if (error)
> > + goto fail;
> > + error = thaw_super(sb);
> > + if (!error)
> > + return 0;
> > +
> > +fail:
> > + fs_info(sdp, "GFS2: couldn't thaw filesystem: %d\n", error);
> > + gfs2_assert_withdraw(sdp, 0);
> > + return error;
> > +}
> > +
> > +void gfs2_freeze_func(struct work_struct *work)
> > +{
> > + struct gfs2_sbd *sdp = container_of(work, struct gfs2_sbd,
> > sd_freeze_work);
> > + struct super_block *sb = sdp->sd_vfs;
> > + int error;
> > +
> > + mutex_lock(&sdp->sd_freeze_mutex);
> > + error = -EBUSY;
> > + if (atomic_read(&sdp->sd_freeze_state) != SFS_UNFROZEN)
> > + goto out_unlock;
> > +
> > + error = gfs2_freeze_locally(sdp);
> > + if (error)
> > + goto out_unlock;
> > +
> > + gfs2_freeze_unlock(&sdp->sd_freeze_gh);
> > + atomic_set(&sdp->sd_freeze_state, SFS_FROZEN);
> > +
> > + error = gfs2_do_thaw(sdp);
> > + if (error)
> > + goto out;
> > +
> > + atomic_set(&sdp->sd_freeze_state, SFS_UNFROZEN);
> > +
> > +out_unlock:
> > + mutex_unlock(&sdp->sd_freeze_mutex);
> > deactivate_super(sb);
> > - clear_bit_unlock(SDF_FREEZE_INITIATOR, &sdp->sd_flags);
> > - wake_up_bit(&sdp->sd_flags, SDF_FREEZE_INITIATOR);
> > - return;
> > +out:
> > + if (error)
> > + fs_info(sdp, "GFS2: couldn't freeze filesystem: %d\n", error);
> > }
> >
> > /**
> > @@ -707,21 +772,27 @@ static int gfs2_freeze_super(struct super_block *sb)
> > struct gfs2_sbd *sdp = sb->s_fs_info;
> > int error;
> >
> > - mutex_lock(&sdp->sd_freeze_mutex);
> > - if (atomic_read(&sdp->sd_freeze_state) != SFS_UNFROZEN) {
> > - error = -EBUSY;
> > + if (!mutex_trylock(&sdp->sd_freeze_mutex))
> > + return -EBUSY;
> > + error = -EBUSY;
> > + if (atomic_read(&sdp->sd_freeze_state) != SFS_UNFROZEN)
> > goto out;
> > - }
> >
> > for (;;) {
> > - if (gfs2_withdrawn(sdp)) {
> > - error = -EINVAL;
> > + error = gfs2_freeze_locally(sdp);
> > + if (error) {
> > + fs_info(sdp, "GFS2: couldn't freeze filesystem: %d\n",
> > + error);
> > goto out;
> > }
> >
> > error = gfs2_lock_fs_check_clean(sdp);
> > if (!error)
> > - break;
> > + break; /* success */
> > +
> > + error = gfs2_do_thaw(sdp);
> > + if (error)
> > + goto out;
> >
> > if (error == -EBUSY)
> > fs_err(sdp, "waiting for recovery before freeze\n");
> > @@ -735,8 +806,12 @@ static int gfs2_freeze_super(struct super_block *sb)
> > fs_err(sdp, "retrying...\n");
> > msleep(1000);
> > }
> > - set_bit(SDF_FREEZE_INITIATOR, &sdp->sd_flags);
> > +
> > out:
> > + if (!error) {
> > + set_bit(SDF_FREEZE_INITIATOR, &sdp->sd_flags);
> > + atomic_set(&sdp->sd_freeze_state, SFS_FROZEN);
> > + }
> > mutex_unlock(&sdp->sd_freeze_mutex);
> > return error;
> > }
> > @@ -750,17 +825,47 @@ static int gfs2_freeze_super(struct super_block *sb)
> > static int gfs2_thaw_super(struct super_block *sb)
> > {
> > struct gfs2_sbd *sdp = sb->s_fs_info;
> > + int error;
> >
> > - mutex_lock(&sdp->sd_freeze_mutex);
> > - if (atomic_read(&sdp->sd_freeze_state) != SFS_FROZEN ||
> > - !gfs2_holder_initialized(&sdp->sd_freeze_gh)) {
> > - mutex_unlock(&sdp->sd_freeze_mutex);
> > - return -EINVAL;
> > + if (!mutex_trylock(&sdp->sd_freeze_mutex))
> > + return -EBUSY;
> > + error = -EINVAL;
> > + if (!test_bit(SDF_FREEZE_INITIATOR, &sdp->sd_flags))
> > + goto out;
> > +
> > + gfs2_freeze_unlock(&sdp->sd_freeze_gh);
> > +
> > + error = gfs2_do_thaw(sdp);
> > +
> > + if (!error) {
> > + clear_bit(SDF_FREEZE_INITIATOR, &sdp->sd_flags);
> > + atomic_set(&sdp->sd_freeze_state, SFS_UNFROZEN);
> > }
> > +out:
> > + mutex_unlock(&sdp->sd_freeze_mutex);
> > + return error;
> > +}
> > +
> > +void gfs2_thaw_freeze_initiator(struct super_block *sb)
> > +{
> > + struct gfs2_sbd *sdp = sb->s_fs_info;
> > +
> > + mutex_lock(&sdp->sd_freeze_mutex);
> > + if (!test_bit(SDF_FREEZE_INITIATOR, &sdp->sd_flags))
> > + goto out;
> >
> > gfs2_freeze_unlock(&sdp->sd_freeze_gh);
> > +#if 0
> > + int error;
> > + error = thaw_super(sb);
> > + if (error)
> > + fs_info(sdp, "GFS2: couldn't thaw filesystem: %d\n", error);
> > + clear_bit(SDF_FREEZE_INITIATOR, &sdp->sd_flags);
> > + atomic_set(&sdp->sd_freeze_state, SFS_UNFROZEN);
> > +#endif
>
> Can be removed.
Ah, of course, thanks.
Andreas
> Andy
>
> > +
> > +out:
> > mutex_unlock(&sdp->sd_freeze_mutex);
> > - return wait_on_bit(&sdp->sd_flags, SDF_FREEZE_INITIATOR,
> > TASK_INTERRUPTIBLE);
> > }
> >
> > /**
> > diff --git a/fs/gfs2/super.h b/fs/gfs2/super.h
> > index 58d13fd77aed..bba58629bc45 100644
> > --- a/fs/gfs2/super.h
> > +++ b/fs/gfs2/super.h
> > @@ -46,6 +46,7 @@ extern void gfs2_statfs_change_out(const struct
> > gfs2_statfs_change_host *sc,
> > extern void update_statfs(struct gfs2_sbd *sdp, struct buffer_head *m_bh);
> > extern int gfs2_statfs_sync(struct super_block *sb, int type);
> > extern void gfs2_freeze_func(struct work_struct *work);
> > +extern void gfs2_thaw_freeze_initiator(struct super_block *sb);
> >
> > extern void free_local_statfs_inodes(struct gfs2_sbd *sdp);
> > extern struct inode *find_local_statfs_inode(struct gfs2_sbd *sdp,
> > diff --git a/fs/gfs2/util.c b/fs/gfs2/util.c
> > index 1743caee5505..00494dffb47c 100644
> > --- a/fs/gfs2/util.c
> > +++ b/fs/gfs2/util.c
> > @@ -124,7 +124,6 @@ static void signal_our_withdraw(struct gfs2_sbd *sdp)
> > struct gfs2_inode *ip;
> > struct gfs2_glock *i_gl;
> > u64 no_formal_ino;
> > - int log_write_allowed = test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);
> > int ret = 0;
> > int tries;
> >
> > @@ -152,24 +151,18 @@ static void signal_our_withdraw(struct gfs2_sbd *sdp)
> > */
> > clear_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);
> > if (!sb_rdonly(sdp->sd_vfs)) {
> > - struct gfs2_holder freeze_gh;
> > -
> > - gfs2_holder_mark_uninitialized(&freeze_gh);
> > - if (sdp->sd_freeze_gl &&
> > - !gfs2_glock_is_locked_by_me(sdp->sd_freeze_gl)) {
> > - ret = gfs2_freeze_lock_shared(sdp, &freeze_gh,
> > - log_write_allowed ? 0 : LM_FLAG_TRY);
> > - if (ret == GLR_TRYFAILED)
> > - ret = 0;
> > - }
> > - if (!ret)
> > - gfs2_make_fs_ro(sdp);
> > + bool locked = mutex_trylock(&sdp->sd_freeze_mutex);
> > +
> > + gfs2_make_fs_ro(sdp);
> > +
> > + if (locked)
> > + mutex_unlock(&sdp->sd_freeze_mutex);
> > +
> > /*
> > * Dequeue any pending non-system glock holders that can no
> > * longer be granted because the file system is withdrawn.
> > */
> > gfs2_gl_dq_holders(sdp);
> > - gfs2_freeze_unlock(&freeze_gh);
> > }
> >
> > if (sdp->sd_lockstruct.ls_ops->lm_lock == NULL) { /* lock_nolock */
> > @@ -187,15 +180,8 @@ static void signal_our_withdraw(struct gfs2_sbd *sdp)
> > }
> > sdp->sd_jinode_gh.gh_flags |= GL_NOCACHE;
> > gfs2_glock_dq(&sdp->sd_jinode_gh);
> > - if (test_bit(SDF_FREEZE_INITIATOR, &sdp->sd_flags)) {
> > - /* Make sure gfs2_thaw_super works if partially-frozen */
> > - flush_work(&sdp->sd_freeze_work);
> > - atomic_set(&sdp->sd_freeze_state, SFS_FROZEN);
> > - thaw_super(sdp->sd_vfs);
> > - } else {
> > - wait_on_bit(&i_gl->gl_flags, GLF_DEMOTE,
> > - TASK_UNINTERRUPTIBLE);
> > - }
> > + gfs2_thaw_freeze_initiator(sdp->sd_vfs);
> > + wait_on_bit(&i_gl->gl_flags, GLF_DEMOTE, TASK_UNINTERRUPTIBLE);
> >
> > /*
> > * holder_uninit to force glock_put, to force dlm to let go
>
