quota: quota core changes for quotaon on remount

Currently, we just turn quotas off on remount of filesystem to read-only
state.  The patch below adds necessary framework so that we can turn quotas
off on remount RO but we are able to automatically reenable them again when
filesystem is remounted to RW state.  All we need to do is to keep references
to inodes of quota files when remounting RO and using these references to
reenable quotas when remounting RW.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 78 insertions, 14 deletions

diff --git a/fs/dquot.c b/fs/dquot.c
index fc26d1097d3..dfba1623ccc 100644
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -1449,31 +1449,43 @@ static inline void set_enable_flags(struct quota_info *dqopt, int type)
 	switch (type) {
 		case USRQUOTA:
 			dqopt->flags |= DQUOT_USR_ENABLED;
+			dqopt->flags &= ~DQUOT_USR_SUSPENDED;
 			break;
 		case GRPQUOTA:
 			dqopt->flags |= DQUOT_GRP_ENABLED;
+			dqopt->flags &= ~DQUOT_GRP_SUSPENDED;
 			break;
 	}
 }
 
-static inline void reset_enable_flags(struct quota_info *dqopt, int type)
+static inline void reset_enable_flags(struct quota_info *dqopt, int type,
+				      int remount)
 {
 	switch (type) {
 		case USRQUOTA:
 			dqopt->flags &= ~DQUOT_USR_ENABLED;
+			if (remount)
+				dqopt->flags |= DQUOT_USR_SUSPENDED;
+			else
+				dqopt->flags &= ~DQUOT_USR_SUSPENDED;
 			break;
 		case GRPQUOTA:
 			dqopt->flags &= ~DQUOT_GRP_ENABLED;
+			if (remount)
+				dqopt->flags |= DQUOT_GRP_SUSPENDED;
+			else
+				dqopt->flags &= ~DQUOT_GRP_SUSPENDED;
 			break;
 	}
 }
 
+
 /*
  * Turn quota off on a device. type == -1 ==> quotaoff for all types (umount)
  */
-int vfs_quota_off(struct super_block *sb, int type)
+int vfs_quota_off(struct super_block *sb, int type, int remount)
 {
-	int cnt;
+	int cnt, ret = 0;
 	struct quota_info *dqopt = sb_dqopt(sb);
 	struct inode *toputinode[MAXQUOTAS];
 
@@ -1483,9 +1495,17 @@ int vfs_quota_off(struct super_block *sb, int type)
 		toputinode[cnt] = NULL;
 		if (type != -1 && cnt != type)
 			continue;
+		/* If we keep inodes of quota files after remount and quotaoff
+		 * is called, drop kept inodes. */
+		if (!remount && sb_has_quota_suspended(sb, cnt)) {
+			iput(dqopt->files[cnt]);
+			dqopt->files[cnt] = NULL;
+			reset_enable_flags(dqopt, cnt, 0);
+			continue;
+		}
 		if (!sb_has_quota_enabled(sb, cnt))
 			continue;
-		reset_enable_flags(dqopt, cnt);
+		reset_enable_flags(dqopt, cnt, remount);
 
 		/* Note: these are blocking operations */
 		drop_dquot_ref(sb, cnt);
@@ -1501,7 +1521,8 @@ int vfs_quota_off(struct super_block *sb, int type)
 		put_quota_format(dqopt->info[cnt].dqi_format);
 
 		toputinode[cnt] = dqopt->files[cnt];
-		dqopt->files[cnt] = NULL;
+		if (!remount)
+			dqopt->files[cnt] = NULL;
 		dqopt->info[cnt].dqi_flags = 0;
 		dqopt->info[cnt].dqi_igrace = 0;
 		dqopt->info[cnt].dqi_bgrace = 0;
@@ -1531,12 +1552,19 @@ int vfs_quota_off(struct super_block *sb, int type)
 				mutex_unlock(&toputinode[cnt]->i_mutex);
 				mark_inode_dirty(toputinode[cnt]);
 			}
-			iput(toputinode[cnt]);
 			mutex_unlock(&dqopt->dqonoff_mutex);
+			/* On remount RO, we keep the inode pointer so that we
+			 * can reenable quota on the subsequent remount RW.
+			 * But we have better not keep inode pointer when there
+			 * is pending delete on the quota file... */
+			if (!remount)
+				iput(toputinode[cnt]);
+			else if (!toputinode[cnt]->i_nlink)
+				ret = -EBUSY;
 		}
 	if (sb->s_bdev)
 		invalidate_bdev(sb->s_bdev);
-	return 0;
+	return ret;
 }
 
 /*
@@ -1574,7 +1602,8 @@ static int vfs_quota_on_inode(struct inode *inode, int type, int format_id)
 	invalidate_bdev(sb->s_bdev);
 	mutex_lock(&inode->i_mutex);
 	mutex_lock(&dqopt->dqonoff_mutex);
-	if (sb_has_quota_enabled(sb, type)) {
+	if (sb_has_quota_enabled(sb, type) ||
+			sb_has_quota_suspended(sb, type)) {
 		error = -EBUSY;
 		goto out_lock;
 	}
@@ -1597,6 +1626,7 @@ static int vfs_quota_on_inode(struct inode *inode, int type, int format_id)
 
 	dqopt->ops[type] = fmt->qf_ops;
 	dqopt->info[type].dqi_format = fmt;
+	dqopt->info[type].dqi_fmt_id = format_id;
 	INIT_LIST_HEAD(&dqopt->info[type].dqi_dirty_list);
 	mutex_lock(&dqopt->dqio_mutex);
 	if ((error = dqopt->ops[type]->read_file_info(sb, type)) < 0) {
@@ -1632,12 +1662,41 @@ out_fmt:
 	return error; 
 }
 
+/* Reenable quotas on remount RW */
+static int vfs_quota_on_remount(struct super_block *sb, int type)
+{
+	struct quota_info *dqopt = sb_dqopt(sb);
+	struct inode *inode;
+	int ret;
+
+	mutex_lock(&dqopt->dqonoff_mutex);
+	if (!sb_has_quota_suspended(sb, type)) {
+		mutex_unlock(&dqopt->dqonoff_mutex);
+		return 0;
+	}
+	BUG_ON(sb_has_quota_enabled(sb, type));
+
+	inode = dqopt->files[type];
+	dqopt->files[type] = NULL;
+	reset_enable_flags(dqopt, type, 0);
+	mutex_unlock(&dqopt->dqonoff_mutex);
+
+	ret = vfs_quota_on_inode(inode, type, dqopt->info[type].dqi_fmt_id);
+	iput(inode);
+
+	return ret;
+}
+
 /* Actual function called from quotactl() */
-int vfs_quota_on(struct super_block *sb, int type, int format_id, char *path)
+int vfs_quota_on(struct super_block *sb, int type, int format_id, char *path,
+		 int remount)
 {
 	struct nameidata nd;
 	int error;
 
+	if (remount)
+		return vfs_quota_on_remount(sb, type);
+
 	error = path_lookup(path, LOOKUP_FOLLOW, &nd);
 	if (error < 0)
 		return error;
diff --git a/fs/quota.c b/fs/quota.c
index 84f28dd7211..db1cc9f3c7a 100644
--- a/fs/quota.c
+++ b/fs/quota.c
@@ -69,7 +69,6 @@ static int generic_quotactl_valid(struct super_block *sb, int type, int cmd, qid
 	switch (cmd) {
 		case Q_GETFMT:
 		case Q_GETINFO:
-		case Q_QUOTAOFF:
 		case Q_SETINFO:
 		case Q_SETQUOTA:
 		case Q_GETQUOTA:
@@ -229,12 +228,12 @@ static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id, void
 
 			if (IS_ERR(pathname = getname(addr)))
 				return PTR_ERR(pathname);
-			ret = sb->s_qcop->quota_on(sb, type, id, pathname);
+			ret = sb->s_qcop->quota_on(sb, type, id, pathname, 0);
 			putname(pathname);
 			return ret;
 		}
 		case Q_QUOTAOFF:
-			return sb->s_qcop->quota_off(sb, type);
+			return sb->s_qcop->quota_off(sb, type, 0);
 
 		case Q_GETFMT: {
 			__u32 fmt;
diff --git a/fs/super.c b/fs/super.c
index 4798350b2bc..a5a4aca7e22 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -179,7 +179,7 @@ void deactivate_super(struct super_block *s)
 	if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
 		s->s_count -= S_BIAS-1;
 		spin_unlock(&sb_lock);
-		DQUOT_OFF(s);
+		DQUOT_OFF(s, 0);
 		down_write(&s->s_umount);
 		fs->kill_sb(s);
 		put_filesystem(fs);
@@ -608,6 +608,7 @@ retry:
 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 {
 	int retval;
+	int remount_rw;
 	
 #ifdef CONFIG_BLOCK
 	if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
@@ -625,8 +626,11 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 			mark_files_ro(sb);
 		else if (!fs_may_remount_ro(sb))
 			return -EBUSY;
-		DQUOT_OFF(sb);
+		retval = DQUOT_OFF(sb, 1);
+		if (retval < 0 && retval != -ENOSYS)
+			return -EBUSY;
 	}
+	remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
 
 	if (sb->s_op->remount_fs) {
 		lock_super(sb);
@@ -636,6 +640,8 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 			return retval;
 	}
 	sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
+	if (remount_rw)
+		DQUOT_ON_REMOUNT(sb);
 	return 0;
 }