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Jan Kara

2016-Nov-24 08:12 UTC

[Ocfs2-devel] [PATCH 0/7] quota: Use s_umount for quota on/off serialization

Hello,

this patch set changes quota code to use s_umount semaphore for serialization
of quota on/off operations among each other and with other quotactl and
quota writeback operations. So far we have used dedicated dqonoff_mutex but
that triggered lockdep warnings during fs freezing and also unnecessarily
serialized some quotactl operations.

Al, any objections to patch 1/7 exporting functionality to get superblock with
s_umount in exclusive mode? Alternatively I could add a wrapper around
get_super_thawed() in quota code to drop s_umount & get it in exclusive mode
and recheck that superblock didn't get unmounted / frozen but what I did
here
looked cleaner to me.

OCFS2 guys, it would be good if you could test ocfs2 quotas with this patch set
in some multi-node setup (I have tested just with a single node), especially
whether quota file recovery for other nodes still works as expected. Thanks.

If nobody objects, I'll push these changes through my tree to Linus.

								Honza

Jan Kara

2016-Nov-24 08:12 UTC

head link

[Ocfs2-devel] [PATCH 1/7] fs: Provide function to get superblock with exclusive s_umount

Quota code will need a variant of get_super_thawed() that returns
superblock with s_umount held in exclusive mode to serialize quota on
and quota off operations. Provide this functionality.

Signed-off-by: Jan Kara <jack at suse.cz>
---
 fs/super.c         | 80 ++++++++++++++++++++++++++++++++++++++++--------------
 include/linux/fs.h |  2 ++
 2 files changed, 62 insertions(+), 20 deletions(-)

diff --git a/fs/super.c b/fs/super.c
index c183835566c1..f7f724230e2b 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -558,6 +558,13 @@ void drop_super(struct super_block *sb)
 
 EXPORT_SYMBOL(drop_super);
 
+void drop_super_exclusive(struct super_block *sb)
+{
+	up_write(&sb->s_umount);
+	put_super(sb);
+}
+EXPORT_SYMBOL(drop_super_exclusive);
+
 /**
  *	iterate_supers - call function for all active superblocks
  *	@f: function to call
@@ -628,15 +635,7 @@ void iterate_supers_type(struct file_system_type *type,
 
 EXPORT_SYMBOL(iterate_supers_type);
 
-/**
- *	get_super - get the superblock of a device
- *	@bdev: device to get the superblock for
- *	
- *	Scans the superblock list and finds the superblock of the file system
- *	mounted on the device given. %NULL is returned if no match is found.
- */
-
-struct super_block *get_super(struct block_device *bdev)
+static struct super_block *__get_super(struct block_device *bdev, bool excl)
 {
 	struct super_block *sb;
 
@@ -651,11 +650,17 @@ struct super_block *get_super(struct block_device *bdev)
 		if (sb->s_bdev == bdev) {
 			sb->s_count++;
 			spin_unlock(&sb_lock);
-			down_read(&sb->s_umount);
+			if (!excl)
+				down_read(&sb->s_umount);
+			else
+				down_write(&sb->s_umount);
 			/* still alive? */
 			if (sb->s_root && (sb->s_flags & MS_BORN))
 				return sb;
-			up_read(&sb->s_umount);
+			if (!excl)
+				up_read(&sb->s_umount);
+			else
+				up_write(&sb->s_umount);
 			/* nope, got unmounted */
 			spin_lock(&sb_lock);
 			__put_super(sb);
@@ -666,32 +671,67 @@ struct super_block *get_super(struct block_device *bdev)
 	return NULL;
 }
 
-EXPORT_SYMBOL(get_super);
-
 /**
- *	get_super_thawed - get thawed superblock of a device
+ *	get_super - get the superblock of a device
  *	@bdev: device to get the superblock for
  *
  *	Scans the superblock list and finds the superblock of the file system
- *	mounted on the device. The superblock is returned once it is thawed
- *	(or immediately if it was not frozen). %NULL is returned if no match
- *	is found.
+ *	mounted on the device given. %NULL is returned if no match is found.
  */
-struct super_block *get_super_thawed(struct block_device *bdev)
+struct super_block *get_super(struct block_device *bdev)
+{
+	return __get_super(bdev, false);
+}
+EXPORT_SYMBOL(get_super);
+
+static struct super_block *__get_super_thawed(struct block_device *bdev,
+					      bool excl)
 {
 	while (1) {
-		struct super_block *s = get_super(bdev);
+		struct super_block *s = __get_super(bdev, excl);
 		if (!s || s->s_writers.frozen == SB_UNFROZEN)
 			return s;
-		up_read(&s->s_umount);
+		if (!excl)
+			up_read(&s->s_umount);
+		else
+			up_write(&s->s_umount);
 		wait_event(s->s_writers.wait_unfrozen,
 			   s->s_writers.frozen == SB_UNFROZEN);
 		put_super(s);
 	}
 }
+
+/**
+ *	get_super_thawed - get thawed superblock of a device
+ *	@bdev: device to get the superblock for
+ *
+ *	Scans the superblock list and finds the superblock of the file system
+ *	mounted on the device. The superblock is returned once it is thawed
+ *	(or immediately if it was not frozen). %NULL is returned if no match
+ *	is found.
+ */
+struct super_block *get_super_thawed(struct block_device *bdev)
+{
+	return __get_super_thawed(bdev, false);
+}
 EXPORT_SYMBOL(get_super_thawed);
 
 /**
+ *	get_super_exclusive_thawed - get thawed superblock of a device
+ *	@bdev: device to get the superblock for
+ *
+ *	Scans the superblock list and finds the superblock of the file system
+ *	mounted on the device. The superblock is returned once it is thawed
+ *	(or immediately if it was not frozen) and s_umount semaphore is held
+ *	in exclusive mode. %NULL is returned if no match is found.
+ */
+struct super_block *get_super_exclusive_thawed(struct block_device *bdev)
+{
+	return __get_super_thawed(bdev, true);
+}
+EXPORT_SYMBOL(get_super_exclusive_thawed);
+
+/**
  * get_active_super - get an active reference to the superblock of a device
  * @bdev: device to get the superblock for
  *
diff --git a/include/linux/fs.h b/include/linux/fs.h
index dc0478c07b2a..d04cfdefcd11 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2949,8 +2949,10 @@ extern void put_filesystem(struct file_system_type *fs);
 extern struct file_system_type *get_fs_type(const char *name);
 extern struct super_block *get_super(struct block_device *);
 extern struct super_block *get_super_thawed(struct block_device *);
+extern struct super_block *get_super_exclusive_thawed(struct block_device
*bdev);
 extern struct super_block *get_active_super(struct block_device *bdev);
 extern void drop_super(struct super_block *sb);
+extern void drop_super_exclusive(struct super_block *sb);
 extern void iterate_supers(void (*)(struct super_block *, void *), void *);
 extern void iterate_supers_type(struct file_system_type *,
 			        void (*)(struct super_block *, void *), void *);
-- 
2.6.6

Jan Kara

2016-Nov-24 08:12 UTC

head link

[Ocfs2-devel] [PATCH 2/7] quota: Hold s_umount in exclusive mode when enabling / disabling quotas

Currently we hold s_umount semaphore only in shared mode when enabling
or disabling quotas and use dqonoff_mutex for serializing quota state
changes on a filesystem and also quota state changes with other places
depending on current quota state. Using dedicated mutex for this causes
possible deadlocks during filesystem freezing (see following commit for
details) so we transition to using s_umount semaphore for the necessary
synchronization whose lock ordering is properly handled by the
filesystem freezing code. As a start grab s_umount in exclusive mode
when enabling / disabling quotas.

Signed-off-by: Jan Kara <jack at suse.cz>
---
 fs/quota/dquot.c | 11 +++++++++++
 fs/quota/quota.c | 15 +++++++++++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 1bfac28b7e7d..047afb966420 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -2107,6 +2107,10 @@ int dquot_disable(struct super_block *sb, int type,
unsigned int flags)
 	struct quota_info *dqopt = sb_dqopt(sb);
 	struct inode *toputinode[MAXQUOTAS];
 
+	/* s_umount should be held in exclusive mode */
+	if (WARN_ON_ONCE(down_read_trylock(&sb->s_umount)))
+		up_read(&sb->s_umount);
+
 	/* Cannot turn off usage accounting without turning off limits, or
 	 * suspend quotas and simultaneously turn quotas off. */
 	if ((flags & DQUOT_USAGE_ENABLED && !(flags &
DQUOT_LIMITS_ENABLED))
@@ -2371,6 +2375,10 @@ int dquot_resume(struct super_block *sb, int type)
 	int ret = 0, cnt;
 	unsigned int flags;
 
+	/* s_umount should be held in exclusive mode */
+	if (WARN_ON_ONCE(down_read_trylock(&sb->s_umount)))
+		up_read(&sb->s_umount);
+
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
 		if (type != -1 && cnt != type)
 			continue;
@@ -2430,6 +2438,9 @@ int dquot_enable(struct inode *inode, int type, int
format_id,
 
 	/* Just unsuspend quotas? */
 	BUG_ON(flags & DQUOT_SUSPENDED);
+	/* s_umount should be held in exclusive mode */
+	if (WARN_ON_ONCE(down_read_trylock(&sb->s_umount)))
+		up_read(&sb->s_umount);
 
 	if (!flags)
 		return 0;
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 2d445425aad7..790c61abc663 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -790,6 +790,12 @@ static int quotactl_cmd_write(int cmd)
 	return 1;
 }
 
+/* Return true if quotactl command is manipulating quota on/off state */
+static bool quotactl_cmd_onoff(int cmd)
+{
+	return (cmd == Q_QUOTAON) || (cmd == Q_QUOTAOFF);
+}
+
 #endif /* CONFIG_BLOCK */
 
 /*
@@ -809,7 +815,9 @@ static struct super_block *quotactl_block(const char __user
*special, int cmd)
 	putname(tmp);
 	if (IS_ERR(bdev))
 		return ERR_CAST(bdev);
-	if (quotactl_cmd_write(cmd))
+	if (quotactl_cmd_onoff(cmd))
+		sb = get_super_exclusive_thawed(bdev);
+	else if (quotactl_cmd_write(cmd))
 		sb = get_super_thawed(bdev);
 	else
 		sb = get_super(bdev);
@@ -872,7 +880,10 @@ SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char
__user *, special,
 
 	ret = do_quotactl(sb, type, cmds, id, addr, pathp);
 
-	drop_super(sb);
+	if (!quotactl_cmd_onoff(cmds))
+		drop_super(sb);
+	else
+		drop_super_exclusive(sb);
 out:
 	if (pathp && !IS_ERR(pathp))
 		path_put(pathp);
-- 
2.6.6

Jan Kara

2016-Nov-24 08:12 UTC

head link

[Ocfs2-devel] [PATCH 3/7] quota: Use s_umount protection for quota operations

Writeback quota is protected by s_umount semaphore held for reading
because every writeback must be protected by that lock (grabbed either
by the generic writeback code or by quotactl handler). Getting next
available ID in quota file, querying quota state, setting quota
information, getting quota format are all quotactl operations protected
by s_umount semaphore held for reading grabbed in quotactl handler.

This also fixes lockdep splat about possible deadlock during filesystem
freezing where sync_filesystem() is called with page-faults already
blocked but sync_filesystem() calls into dquot_writeback_dquots() which
grabs dqonoff_mutex which ranks above i_mutex (vfs_load_quota_inode()
grabs i_mutex under dqonoff_mutex) which clearly ranks below page fault
freeze protection (e.g. via mmap_sem dependencies). The reported problem
is not a real deadlock possibility since during quota on we check
whether filesystem freezing is not in progress but still it is good to
have this fixed.

Reported-by: Ted Tso <tytso at mit.edu>
Reported-by: Eric Whitney <enwlinux at gmail.com>
Signed-off-by: Jan Kara <jack at suse.cz>
---
 fs/quota/dquot.c | 39 ++++++++++-----------------------------
 fs/quota/quota.c |  6 +-----
 2 files changed, 11 insertions(+), 34 deletions(-)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 047afb966420..2a9dc3fb491c 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -617,7 +617,8 @@ int dquot_writeback_dquots(struct super_block *sb, int type)
 	int cnt;
 	int err, ret = 0;
 
-	mutex_lock(&dqopt->dqonoff_mutex);
+	WARN_ON_ONCE(!rwsem_is_locked(&sb->s_umount));
+
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
 		if (type != -1 && cnt != type)
 			continue;
@@ -653,7 +654,6 @@ int dquot_writeback_dquots(struct super_block *sb, int type)
 		    && info_dirty(&dqopt->info[cnt]))
 			sb->dq_op->write_info(sb, cnt);
 	dqstats_inc(DQST_SYNCS);
-	mutex_unlock(&dqopt->dqonoff_mutex);
 
 	return ret;
 }
@@ -683,7 +683,6 @@ int dquot_quota_sync(struct super_block *sb, int type)
 	 * Now when everything is written we can discard the pagecache so
 	 * that userspace sees the changes.
 	 */
-	mutex_lock(&dqopt->dqonoff_mutex);
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
 		if (type != -1 && cnt != type)
 			continue;
@@ -693,7 +692,6 @@ int dquot_quota_sync(struct super_block *sb, int type)
 		truncate_inode_pages(&dqopt->files[cnt]->i_data, 0);
 		inode_unlock(dqopt->files[cnt]);
 	}
-	mutex_unlock(&dqopt->dqonoff_mutex);
 
 	return 0;
 }
@@ -2050,21 +2048,13 @@ int dquot_get_next_id(struct super_block *sb, struct
kqid *qid)
 	struct quota_info *dqopt = sb_dqopt(sb);
 	int err;
 
-	mutex_lock(&dqopt->dqonoff_mutex);
-	if (!sb_has_quota_active(sb, qid->type)) {
-		err = -ESRCH;
-		goto out;
-	}
-	if (!dqopt->ops[qid->type]->get_next_id) {
-		err = -ENOSYS;
-		goto out;
-	}
+	if (!sb_has_quota_active(sb, qid->type))
+		return -ESRCH;
+	if (!dqopt->ops[qid->type]->get_next_id)
+		return -ENOSYS;
 	mutex_lock(&dqopt->dqio_mutex);
 	err = dqopt->ops[qid->type]->get_next_id(sb, qid);
 	mutex_unlock(&dqopt->dqio_mutex);
-out:
-	mutex_unlock(&dqopt->dqonoff_mutex);
-
 	return err;
 }
 EXPORT_SYMBOL(dquot_get_next_id);
@@ -2762,7 +2752,6 @@ int dquot_get_state(struct super_block *sb, struct
qc_state *state)
 	struct quota_info *dqopt = sb_dqopt(sb);
 	int type;
   
-	mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);
 	memset(state, 0, sizeof(*state));
 	for (type = 0; type < MAXQUOTAS; type++) {
 		if (!sb_has_quota_active(sb, type))
@@ -2784,7 +2773,6 @@ int dquot_get_state(struct super_block *sb, struct
qc_state *state)
 		tstate->nextents = 1;	/* We don't know... */
 		spin_unlock(&dq_data_lock);
 	}
-	mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
 	return 0;
 }
 EXPORT_SYMBOL(dquot_get_state);
@@ -2798,18 +2786,13 @@ int dquot_set_dqinfo(struct super_block *sb, int type,
struct qc_info *ii)
 	if ((ii->i_fieldmask & QC_WARNS_MASK) ||
 	    (ii->i_fieldmask & QC_RT_SPC_TIMER))
 		return -EINVAL;
-	mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);
-	if (!sb_has_quota_active(sb, type)) {
-		err = -ESRCH;
-		goto out;
-	}
+	if (!sb_has_quota_active(sb, type))
+		return -ESRCH;
 	mi = sb_dqopt(sb)->info + type;
 	if (ii->i_fieldmask & QC_FLAGS) {
 		if ((ii->i_flags & QCI_ROOT_SQUASH &&
-		     mi->dqi_format->qf_fmt_id != QFMT_VFS_OLD)) {
-			err = -EINVAL;
-			goto out;
-		}
+		     mi->dqi_format->qf_fmt_id != QFMT_VFS_OLD))
+			return -EINVAL;
 	}
 	spin_lock(&dq_data_lock);
 	if (ii->i_fieldmask & QC_SPC_TIMER)
@@ -2826,8 +2809,6 @@ int dquot_set_dqinfo(struct super_block *sb, int type,
struct qc_info *ii)
 	mark_info_dirty(sb, type);
 	/* Force write to disk */
 	sb->dq_op->write_info(sb, type);
-out:
-	mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
 	return err;
 }
 EXPORT_SYMBOL(dquot_set_dqinfo);
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 790c61abc663..0c8041688dcf 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -104,13 +104,9 @@ static int quota_getfmt(struct super_block *sb, int type,
void __user *addr)
 {
 	__u32 fmt;
 
-	mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);
-	if (!sb_has_quota_active(sb, type)) {
-		mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
+	if (!sb_has_quota_active(sb, type))
 		return -ESRCH;
-	}
 	fmt = sb_dqopt(sb)->info[type].dqi_format->qf_fmt_id;
-	mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
 	if (copy_to_user(addr, &fmt, sizeof(fmt)))
 		return -EFAULT;
 	return 0;
-- 
2.6.6

Jan Kara

2016-Nov-24 08:12 UTC

head link

[Ocfs2-devel] [PATCH 4/7] ocfs2: Protect periodic quota syncing with s_umount semaphore

New quota locking rules will require s_umount semaphore for all quota
scanning functions. Add is for periodic quota syncing.

Signed-off-by: Jan Kara <jack at suse.cz>
---
 fs/ocfs2/quota_global.c | 10 +++++++++-
 fs/ocfs2/super.c        |  1 -
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c
index 87e577a49b0d..cec495a921e3 100644
--- a/fs/ocfs2/quota_global.c
+++ b/fs/ocfs2/quota_global.c
@@ -634,7 +634,15 @@ static void qsync_work_fn(struct work_struct *work)
 						      dqi_sync_work.work);
 	struct super_block *sb = oinfo->dqi_gqinode->i_sb;
 
-	dquot_scan_active(sb, ocfs2_sync_dquot_helper, oinfo->dqi_type);
+	/*
+	 * We have to be careful here not to deadlock on s_umount as umount
+	 * disabling quotas may be in progress and it waits for this work to
+	 * complete. If trylock fails, we'll do the sync next time...
+	 */
+	if (down_read_trylock(&sb->s_umount)) {
+		dquot_scan_active(sb, ocfs2_sync_dquot_helper, oinfo->dqi_type);
+		up_read(&sb->s_umount);
+	}
 	schedule_delayed_work(&oinfo->dqi_sync_work,
 			      msecs_to_jiffies(oinfo->dqi_syncms));
 }
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index f56fe39fab04..5b9c0dfdb541 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -985,7 +985,6 @@ static void ocfs2_disable_quotas(struct ocfs2_super *osb)
 	for (type = 0; type < OCFS2_MAXQUOTAS; type++) {
 		if (!sb_has_quota_loaded(sb, type))
 			continue;
-		/* Cancel periodic syncing before we grab dqonoff_mutex */
 		oinfo = sb_dqinfo(sb, type)->dqi_priv;
 		cancel_delayed_work_sync(&oinfo->dqi_sync_work);
 		inode = igrab(sb->s_dquot.files[type]);
-- 
2.6.6

Jan Kara

2016-Nov-24 08:12 UTC

head link

[Ocfs2-devel] [PATCH 5/7] quota: Remove dqonoff_mutex from dquot_scan_active()

All callers of dquot_scan_active() now hold s_umount so we can rely on
that lock to protect us against quota state changes.

Signed-off-by: Jan Kara <jack at suse.cz>
---
 fs/quota/dquot.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 2a9dc3fb491c..d91aecc939c9 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -572,7 +572,8 @@ int dquot_scan_active(struct super_block *sb,
 	struct dquot *dquot, *old_dquot = NULL;
 	int ret = 0;
 
-	mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);
+	WARN_ON_ONCE(!rwsem_is_locked(&sb->s_umount));
+
 	spin_lock(&dq_list_lock);
 	list_for_each_entry(dquot, &inuse_list, dq_inuse) {
 		if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags))
@@ -603,7 +604,6 @@ int dquot_scan_active(struct super_block *sb,
 	spin_unlock(&dq_list_lock);
 out:
 	dqput(old_dquot);
-	mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
 	return ret;
 }
 EXPORT_SYMBOL(dquot_scan_active);
-- 
2.6.6

Jan Kara

2016-Nov-24 08:12 UTC

head link

[Ocfs2-devel] [PATCH 6/7] ocfs2: Use s_umount for quota recovery protection

Currently we use dqonoff_mutex to serialize quota recovery protection
and turning of quotas on / off. Use s_umount semaphore instead.

Signed-off-by: Jan Kara <jack at suse.cz>
---
 fs/ocfs2/quota_local.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/fs/ocfs2/quota_local.c b/fs/ocfs2/quota_local.c
index 8a54fd8a4fa5..32c5a40c1257 100644
--- a/fs/ocfs2/quota_local.c
+++ b/fs/ocfs2/quota_local.c
@@ -454,7 +454,7 @@ struct ocfs2_quota_recovery *ocfs2_begin_quota_recovery(
 /* Sync changes in local quota file into global quota file and
  * reinitialize local quota file.
  * The function expects local quota file to be already locked and
- * dqonoff_mutex locked. */
+ * s_umount locked in shared mode. */
 static int ocfs2_recover_local_quota_file(struct inode *lqinode,
 					  int type,
 					  struct ocfs2_quota_recovery *rec)
@@ -597,7 +597,7 @@ int ocfs2_finish_quota_recovery(struct ocfs2_super *osb,
 	printk(KERN_NOTICE "ocfs2: Finishing quota recovery on device (%s) for
"
 	       "slot %u\n", osb->dev_str, slot_num);
 
-	mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);
+	down_read(&sb->s_umount);
 	for (type = 0; type < OCFS2_MAXQUOTAS; type++) {
 		if (list_empty(&(rec->r_list[type])))
 			continue;
@@ -674,7 +674,7 @@ int ocfs2_finish_quota_recovery(struct ocfs2_super *osb,
 			break;
 	}
 out:
-	mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
+	up_read(&sb->s_umount);
 	kfree(rec);
 	return status;
 }
@@ -840,7 +840,10 @@ static int ocfs2_local_free_info(struct super_block *sb,
int type)
 	}
 	ocfs2_release_local_quota_bitmaps(&oinfo->dqi_chunk);
 
-	/* dqonoff_mutex protects us against racing with recovery thread... */
+	/*
+	 * s_umount held in exclusive mode protects us against racing with
+	 * recovery thread...
+	 */
 	if (oinfo->dqi_rec) {
 		ocfs2_free_quota_recovery(oinfo->dqi_rec);
 		mark_clean = 0;
-- 
2.6.6

Jan Kara

2016-Nov-24 08:12 UTC

head link

[Ocfs2-devel] [PATCH 7/7] quota: Remove dqonoff_mutex

The only places that were grabbing dqonoff_mutex are functions turning
quotas on and off and these are properly serialized using s_umount
semaphore. Remove dqonoff_mutex.

Signed-off-by: Jan Kara <jack at suse.cz>
---
 fs/quota/dquot.c      | 78 +++++++++++++++------------------------------------
 fs/super.c            |  1 -
 include/linux/quota.h |  1 -
 3 files changed, 23 insertions(+), 57 deletions(-)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index d91aecc939c9..0d9dccac39a8 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -119,8 +119,7 @@
  * spinlock to internal buffers before writing.
  *
  * Lock ordering (including related VFS locks) is the following:
- *   dqonoff_mutex > i_mutex > journal_lock > dquot->dq_lock >
dqio_mutex
- * dqonoff_mutex > i_mutex comes from dquot_quota_sync, dquot_enable, etc.
+ *   s_umount > i_mutex > journal_lock > dquot->dq_lock >
dqio_mutex
  */
 
 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dq_list_lock);
@@ -933,7 +932,7 @@ static int dqinit_needed(struct inode *inode, int type)
 	return 0;
 }
 
-/* This routine is guarded by dqonoff_mutex mutex */
+/* This routine is guarded by s_umount semaphore */
 static void add_dquot_ref(struct super_block *sb, int type)
 {
 	struct inode *inode, *old_inode = NULL;
@@ -2108,18 +2107,14 @@ int dquot_disable(struct super_block *sb, int type,
unsigned int flags)
 	    DQUOT_USAGE_ENABLED)))
 		return -EINVAL;
 
-	/* We need to serialize quota_off() for device */
-	mutex_lock(&dqopt->dqonoff_mutex);
-
 	/*
 	 * Skip everything if there's nothing to do. We have to do this because
 	 * sometimes we are called when fill_super() failed and calling
 	 * sync_fs() in such cases does no good.
 	 */
-	if (!sb_any_quota_loaded(sb)) {
-		mutex_unlock(&dqopt->dqonoff_mutex);
+	if (!sb_any_quota_loaded(sb))
 		return 0;
-	}
+
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
 		toputinode[cnt] = NULL;
 		if (type != -1 && cnt != type)
@@ -2173,7 +2168,6 @@ int dquot_disable(struct super_block *sb, int type,
unsigned int flags)
 		dqopt->info[cnt].dqi_bgrace = 0;
 		dqopt->ops[cnt] = NULL;
 	}
-	mutex_unlock(&dqopt->dqonoff_mutex);
 
 	/* Skip syncing and setting flags if quota files are hidden */
 	if (dqopt->flags & DQUOT_QUOTA_SYS_FILE)
@@ -2191,19 +2185,13 @@ int dquot_disable(struct super_block *sb, int type,
unsigned int flags)
 	 * changes done by userspace on the next quotaon() */
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
 		if (toputinode[cnt]) {
-			mutex_lock(&dqopt->dqonoff_mutex);
-			/* If quota was reenabled in the meantime, we have
-			 * nothing to do */
-			if (!sb_has_quota_loaded(sb, cnt)) {
-				inode_lock(toputinode[cnt]);
-				toputinode[cnt]->i_flags &= ~(S_IMMUTABLE |
+			WARN_ON_ONCE(sb_has_quota_loaded(sb, cnt));
+			inode_lock(toputinode[cnt]);
+			toputinode[cnt]->i_flags &= ~(S_IMMUTABLE |
 				  S_NOATIME | S_NOQUOTA);
-				truncate_inode_pages(&toputinode[cnt]->i_data,
-						     0);
-				inode_unlock(toputinode[cnt]);
-				mark_inode_dirty_sync(toputinode[cnt]);
-			}
-			mutex_unlock(&dqopt->dqonoff_mutex);
+			truncate_inode_pages(&toputinode[cnt]->i_data, 0);
+			inode_unlock(toputinode[cnt]);
+			mark_inode_dirty_sync(toputinode[cnt]);
 		}
 	if (sb->s_bdev)
 		invalidate_bdev(sb->s_bdev);
@@ -2275,6 +2263,10 @@ static int vfs_load_quota_inode(struct inode *inode, int
type, int format_id,
 		error = -EINVAL;
 		goto out_fmt;
 	}
+	if (sb_has_quota_loaded(sb, type)) {
+		error = -EBUSY;
+		goto out_fmt;
+	}
 
 	if (!(dqopt->flags & DQUOT_QUOTA_SYS_FILE)) {
 		/* As we bypass the pagecache we must now flush all the
@@ -2286,11 +2278,6 @@ static int vfs_load_quota_inode(struct inode *inode, int
type, int format_id,
 		sync_filesystem(sb);
 		invalidate_bdev(sb->s_bdev);
 	}
-	mutex_lock(&dqopt->dqonoff_mutex);
-	if (sb_has_quota_loaded(sb, type)) {
-		error = -EBUSY;
-		goto out_lock;
-	}
 
 	if (!(dqopt->flags & DQUOT_QUOTA_SYS_FILE)) {
 		/* We don't want quota and atime on quota files (deadlocks
@@ -2311,7 +2298,7 @@ static int vfs_load_quota_inode(struct inode *inode, int
type, int format_id,
 	error = -EIO;
 	dqopt->files[type] = igrab(inode);
 	if (!dqopt->files[type])
-		goto out_lock;
+		goto out_file_flags;
 	error = -EINVAL;
 	if (!fmt->qf_ops->check_quota_file(sb, type))
 		goto out_file_init;
@@ -2334,14 +2321,13 @@ static int vfs_load_quota_inode(struct inode *inode, int
type, int format_id,
 	spin_unlock(&dq_state_lock);
 
 	add_dquot_ref(sb, type);
-	mutex_unlock(&dqopt->dqonoff_mutex);
 
 	return 0;
 
 out_file_init:
 	dqopt->files[type] = NULL;
 	iput(inode);
-out_lock:
+out_file_flags:
 	if (oldflags != -1) {
 		inode_lock(inode);
 		/* Set the flags back (in the case of accidental quotaon()
@@ -2350,7 +2336,6 @@ static int vfs_load_quota_inode(struct inode *inode, int
type, int format_id,
 		inode->i_flags |= oldflags;
 		inode_unlock(inode);
 	}
-	mutex_unlock(&dqopt->dqonoff_mutex);
 out_fmt:
 	put_quota_format(fmt);
 
@@ -2372,12 +2357,9 @@ int dquot_resume(struct super_block *sb, int type)
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
 		if (type != -1 && cnt != type)
 			continue;
-
-		mutex_lock(&dqopt->dqonoff_mutex);
-		if (!sb_has_quota_suspended(sb, cnt)) {
-			mutex_unlock(&dqopt->dqonoff_mutex);
+		if (!sb_has_quota_suspended(sb, cnt))
 			continue;
-		}
+
 		inode = dqopt->files[cnt];
 		dqopt->files[cnt] = NULL;
 		spin_lock(&dq_state_lock);
@@ -2386,7 +2368,6 @@ int dquot_resume(struct super_block *sb, int type)
 							cnt);
 		dqopt->flags &= ~dquot_state_flag(DQUOT_STATE_FLAGS, cnt);
 		spin_unlock(&dq_state_lock);
-		mutex_unlock(&dqopt->dqonoff_mutex);
 
 		flags = dquot_generic_flag(flags, cnt);
 		ret = vfs_load_quota_inode(inode, cnt,
@@ -2422,7 +2403,6 @@ EXPORT_SYMBOL(dquot_quota_on);
 int dquot_enable(struct inode *inode, int type, int format_id,
 		 unsigned int flags)
 {
-	int ret = 0;
 	struct super_block *sb = inode->i_sb;
 	struct quota_info *dqopt = sb_dqopt(sb);
 
@@ -2436,28 +2416,16 @@ int dquot_enable(struct inode *inode, int type, int
format_id,
 		return 0;
 	/* Just updating flags needed? */
 	if (sb_has_quota_loaded(sb, type)) {
-		mutex_lock(&dqopt->dqonoff_mutex);
-		/* Now do a reliable test... */
-		if (!sb_has_quota_loaded(sb, type)) {
-			mutex_unlock(&dqopt->dqonoff_mutex);
-			goto load_quota;
-		}
 		if (flags & DQUOT_USAGE_ENABLED &&
-		    sb_has_quota_usage_enabled(sb, type)) {
-			ret = -EBUSY;
-			goto out_lock;
-		}
+		    sb_has_quota_usage_enabled(sb, type))
+			return -EBUSY;
 		if (flags & DQUOT_LIMITS_ENABLED &&
-		    sb_has_quota_limits_enabled(sb, type)) {
-			ret = -EBUSY;
-			goto out_lock;
-		}
+		    sb_has_quota_limits_enabled(sb, type))
+			return -EBUSY;
 		spin_lock(&dq_state_lock);
 		sb_dqopt(sb)->flags |= dquot_state_flag(flags, type);
 		spin_unlock(&dq_state_lock);
-out_lock:
-		mutex_unlock(&dqopt->dqonoff_mutex);
-		return ret;
+		return 0;
 	}
 
 load_quota:
diff --git a/fs/super.c b/fs/super.c
index f7f724230e2b..1709ed029a2c 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -244,7 +244,6 @@ static struct super_block *alloc_super(struct
file_system_type *type, int flags,
 	mutex_init(&s->s_vfs_rename_mutex);
 	lockdep_set_class(&s->s_vfs_rename_mutex,
&type->s_vfs_rename_key);
 	mutex_init(&s->s_dquot.dqio_mutex);
-	mutex_init(&s->s_dquot.dqonoff_mutex);
 	s->s_maxbytes = MAX_NON_LFS;
 	s->s_op = &default_op;
 	s->s_time_gran = 1000000000;
diff --git a/include/linux/quota.h b/include/linux/quota.h
index 55107a8ff887..b281d198ee5b 100644
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -520,7 +520,6 @@ static inline void quota_send_warning(struct kqid qid, dev_t
dev,
 struct quota_info {
 	unsigned int flags;			/* Flags for diskquotas on this device */
 	struct mutex dqio_mutex;		/* lock device while I/O in progress */
-	struct mutex dqonoff_mutex;		/* Serialize quotaon & quotaoff */
 	struct inode *files[MAXQUOTAS];		/* inodes of quotafiles */
 	struct mem_dqinfo info[MAXQUOTAS];	/* Information for each quota type */
 	const struct quota_format_ops *ops[MAXQUOTAS];	/* Operations for each type */
-- 
2.6.6

Eric Ren

2016-Nov-30 08:37 UTC

head link

[Ocfs2-devel] [PATCH 0/7] quota: Use s_umount for quota on/off serialization

Hello,

On 11/24/2016 04:12 PM, Jan Kara wrote:> Hello,
>
> this patch set changes quota code to use s_umount semaphore for
serialization
> of quota on/off operations among each other and with other quotactl and
> quota writeback operations. So far we have used dedicated dqonoff_mutex but
> that triggered lockdep warnings during fs freezing and also unnecessarily
> serialized some quotactl operations.
>
> Al, any objections to patch 1/7 exporting functionality to get superblock
with
> s_umount in exclusive mode? Alternatively I could add a wrapper around
> get_super_thawed() in quota code to drop s_umount & get it in exclusive
mode
> and recheck that superblock didn't get unmounted / frozen but what I
did here
> looked cleaner to me.
>
> OCFS2 guys, it would be good if you could test ocfs2 quotas with this patch
set
> in some multi-node setup (I have tested just with a single node),
especially
> whether quota file recovery for other nodes still works as expected.
Thanks.
With this patch set, the quota file recovery works well for ocfs2 on multiple
nodes.

Tested-by:    Eric Ren <zren at suse.com>

Thanks,
Eric>
> If nobody objects, I'll push these changes through my tree to Linus.
>
> 								Honza
> --
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>

Ocfs2 devel - Nov 2016 - [PATCH 7/7] quota: Remove dqonoff_mutex

[Ocfs2-devel] [PATCH 0/7] quota: Use s_umount for quota on/off serialization

[Ocfs2-devel] [PATCH 1/7] fs: Provide function to get superblock with exclusive s_umount

[Ocfs2-devel] [PATCH 2/7] quota: Hold s_umount in exclusive mode when enabling / disabling quotas

[Ocfs2-devel] [PATCH 3/7] quota: Use s_umount protection for quota operations

[Ocfs2-devel] [PATCH 4/7] ocfs2: Protect periodic quota syncing with s_umount semaphore

[Ocfs2-devel] [PATCH 5/7] quota: Remove dqonoff_mutex from dquot_scan_active()

[Ocfs2-devel] [PATCH 6/7] ocfs2: Use s_umount for quota recovery protection

[Ocfs2-devel] [PATCH 7/7] quota: Remove dqonoff_mutex

[Ocfs2-devel] [PATCH 0/7] quota: Use s_umount for quota on/off serialization