quota: special case Q_SYNC without device name

The Q_SYNC command can be called without the path to a device, in which case
it iterates over all superblocks.  Special case this variant directly in
sys_quotactl so that the other code always gets a superblock and doesn't
need to deal with this case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 27 insertions, 13 deletions

diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index dcf7db91fc95..9fde5cd84f8d 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -124,10 +124,17 @@ void sync_quota_sb(struct super_block *sb, int type)
 }
 #endif
 
-static void sync_dquots(int type)
+static int quota_sync_all(int type)
 {
         struct super_block *sb;
         int cnt;
+        int ret;
+
+        if (type >= MAXQUOTAS)
+                return -EINVAL;
+        ret = security_quotactl(Q_SYNC, type, 0, NULL);
+        if (ret)
+                return ret;
 
         spin_lock(&sb_lock);
 restart:
@@ -157,6 +164,8 @@ restart:
                         goto restart;
         }
         spin_unlock(&sb_lock);
+
+        return 0;
 }
 
 static int quota_quotaon(struct super_block *sb, int type, int cmd, qid_t id,
@@ -322,12 +331,9 @@ static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id,
         case Q_SETQUOTA:
                 return quota_setquota(sb, type, id, addr);
         case Q_SYNC:
-                if (sb) {
-                        if (!sb->s_qcop->quota_sync)
-                                return -ENOSYS;
-                        sync_quota_sb(sb, type);
-                } else
-                        sync_dquots(type);
+                if (!sb->s_qcop->quota_sync)
+                        return -ENOSYS;
+                sync_quota_sb(sb, type);
                 return 0;
         case Q_XQUOTAON:
         case Q_XQUOTAOFF:
@@ -392,18 +398,26 @@ SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
         cmds = cmd >> SUBCMDSHIFT;
         type = cmd & SUBCMDMASK;
 
-        if (cmds != Q_SYNC || special) {
-                sb = quotactl_block(special);
-                if (IS_ERR(sb))
-                        return PTR_ERR(sb);
+        /*
+         * As a special case Q_SYNC can be called without a specific device.
+         * It will iterate all superblocks that have quota enabled and call
+         * the sync action on each of them.
+         */
+        if (!special) {
+                if (cmds == Q_SYNC)
+                        return quota_sync_all(type);
+                return -ENODEV;
         }
 
+        sb = quotactl_block(special);
+        if (IS_ERR(sb))
+                return PTR_ERR(sb);
+
         ret = check_quotactl_valid(sb, type, cmds, id);
         if (ret >= 0)
                 ret = do_quotactl(sb, type, cmds, id, addr);
-        if (sb)
-                drop_super(sb);
 
+        drop_super(sb);
         return ret;
 }