Commit ccf370e4 authored Feb 18, 2016 by Jan Kara

quota: Forbid Q_GETQUOTA and Q_GETNEXTQUOTA for frozen filesystem

Commit 7955118e (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>

parent 044c9b67

fs/quota/quota.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -765,11 +765,14 @@ static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id,
		/* 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:

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