quota: Forbid Q_GETQUOTA and Q_GETNEXTQUOTA for frozen filesystem
Commit 7955118eafc4 (quota: Allow Q_GETQUOTA for frozen filesystem)
allowed Q_GETQUOTA call for frozen filesystem. It makes sense on the
first look but zero-day testing has shown that with this change ext4
warns about starting a transaction for frozen filesystem. This happens
because ext4_acquire_dquot() prepares for allocating space for new quota
structure. Although it would be possible to implement Q_GETQUOTA for
ext4 without allocating space for non-existent structures, the matter
further complicates because OCFS2 needs to update on-disk structure use
count when a new cluster node loads quota information from disk. So just
revert the change and forbid Q_GETQUOTA together with Q_GETNEXTQUOTA for
frozen filesystem. Add comment to quotactl_cmd_write() to save us from
repeating this excercise in a few years when I forget again.
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 8e297c9..0f10ee9 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -765,11 +765,14 @@
/* Return 1 if 'cmd' will block on frozen filesystem */
static int quotactl_cmd_write(int cmd)
{
+ /*
+ * We cannot allow Q_GETQUOTA and Q_GETNEXTQUOTA without write access
+ * as dquot_acquire() may allocate space for new structure and OCFS2
+ * needs to increment on-disk use count.
+ */
switch (cmd) {
case Q_GETFMT:
case Q_GETINFO:
- case Q_GETQUOTA:
- case Q_GETNEXTQUOTA:
case Q_SYNC:
case Q_XGETQSTAT:
case Q_XGETQSTATV: