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>

diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index dcf7db91fc95372712af1daa1832de46048cb541..9fde5cd84f8dd4cb4137e49f6b52c9a08947abfe 100644 (file)
--- 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;
 }