Ocfs2 devel - Jan 2015 - [PATCH 1/4] quota: Don't store flags for v2 quota format

Currently, v2 quota format blindly stored flags from in-memory dqinfo on
disk, although there are no flags supported. Since it is stupid to store
flags which have no effect, just store 0 unconditionally and don't
bother loading it from disk.

Note that userspace could have stored some flags there via Q_SETINFO
quotactl and then later read them (although flags have no effect) but
I'm pretty sure noone does that (most definitely quota-tools don't and
quota interface doesn't have too much other users).

Signed-off-by: Jan Kara <jack at suse.cz>
---
 fs/quota/quota_v2.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/quota/quota_v2.c b/fs/quota/quota_v2.c
index 02751ec695c5..b291602e1193 100644
--- a/fs/quota/quota_v2.c
+++ b/fs/quota/quota_v2.c
@@ -126,7 +126,8 @@ static int v2_read_file_info(struct super_block *sb, int
type)
 	}
 	info->dqi_bgrace = le32_to_cpu(dinfo.dqi_bgrace);
 	info->dqi_igrace = le32_to_cpu(dinfo.dqi_igrace);
-	info->dqi_flags = le32_to_cpu(dinfo.dqi_flags);
+	/* No flags currently supported */
+	info->dqi_flags = le32_to_cpu(0);
 	qinfo->dqi_sb = sb;
 	qinfo->dqi_type = type;
 	qinfo->dqi_blocks = le32_to_cpu(dinfo.dqi_blocks);
@@ -157,7 +158,8 @@ static int v2_write_file_info(struct super_block *sb, int
type)
 	info->dqi_flags &= ~DQF_INFO_DIRTY;
 	dinfo.dqi_bgrace = cpu_to_le32(info->dqi_bgrace);
 	dinfo.dqi_igrace = cpu_to_le32(info->dqi_igrace);
-	dinfo.dqi_flags = cpu_to_le32(info->dqi_flags & DQF_MASK);
+	/* No flags currently supported */
+	dinfo.dqi_flags = 0;
 	spin_unlock(&dq_data_lock);
 	dinfo.dqi_blocks = cpu_to_le32(qinfo->dqi_blocks);
 	dinfo.dqi_free_blk = cpu_to_le32(qinfo->dqi_free_blk);
-- 
2.1.2

On Wed, Jan 14, 2015 at 07:27:08PM +0100, Jan Kara
wrote:
> Currently, v2 quota format blindly stored flags from in-memory dqinfo on
> disk, although there are no flags supported. Since it is stupid to store
> flags which have no effect, just store 0 unconditionally and don't
> bother loading it from disk.
> 
> Note that userspace could have stored some flags there via Q_SETINFO
> quotactl and then later read them (although flags have no effect) but
> I'm pretty sure noone does that (most definitely quota-tools don't
and
> quota interface doesn't have too much other users).
What about future proofing?  Current kernels can store flags on disk,
so the best is to reserve the currently (and possibly previously)
assigned values, and mask them out when reading from disk.