[0/7,V3] quota: add new quotactl Q_GETNEXTQUOTA

Commit Message

Jan Kara Jan. 26, 2016, 1:10 p.m. UTC

Just for reference attached are two patches that implement support for
Q_GETNEXTQUOTA and Q_XGETNEXTQUOTA in quota-tools. I have used it for
testing XFS and VFS infrastructure for these new quotactls.

								Honza
On Fri 22-01-16 12:25:29, Eric Sandeen wrote:
> This adds a new quotactl, Q_GETNEXTQUOTA.
> 
> Q_GETNEXTQUOTA is exactly like Q_GETQUOTA, except that it will
> return quota information for the id equal to or greater than
> the id requested.  In other words, if the specified id has
> no quota, the command will return quota information for the
> next higher id which does have a quota set.  If no higher id
> has an active quota, -ESRCH is returned.
> 
> So if you ask for id X, you can get back quota for id X,
> id X+N, or -ESRCH if no higher id has a quota.
> 
> This allows filesystems to do efficient iteration in kernelspace,
> much like extN filesystems do in userspace when asked to report
> all active quotas.
> 
> Today, filesystems such as XFS require getpwent()-style iterations,
> and for systems which have i.e. LDAP backends, this can be very
> slow, or even impossible if iteration is not allowed in the
> configuration.
> 
> Patches 1 and 4 are just small fixups that turned up along the way;
> 2 and 3 add the actual quota plumbing, and the rest are xfs-specific
> to allow xfs to support this new interface.
> 
> For non-xfs quota, this does require a new structure which is
> able to pass back the discovered ID along with the quota info.
> For xfs-quota, the id is already present in the structure.
> 
> V3:
> * Remove 32-bit compat stuff (i686/x86_64 at least works w/o it...)
> * Require CAP_SYS_ADMIN for these calls
> * Pass back found ID in &qid passed to ->get_nextdqblk, rather
>   than modifying struct qc_dqblk
> * Munge that found ID back through user-namespace conversions
>   before returning it in the user structure.
> 
> Thanks,
> -Eric

Patch

From 304bed24716fdbb7c636ea8df0462d4f979f23a0 Mon Sep 17 00:00:00 2001
From: Jan Kara <[e-mail]>
Date: Tue, 26 Jan 2016 14:06:59 +0100
Subject: [PATCH 2/2] Add support for scanning using Q_XGETNEXTQUOTA

Add support for scanning of all available quota structures using
Q_XGETNEXTQUOTA quotactl.

Signed-off-by: Jan Kara <[e-mail]>
---
 quotaio_xfs.c | 42 +++++++++++++++++++++++++++++++++++++++---
 quotaio_xfs.h |  1 +
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/quotaio_xfs.c b/quotaio_xfs.c
index 903c03e6d3f8..14646411dbab 100644
--- a/quotaio_xfs.c
+++ b/quotaio_xfs.c
@@ -191,15 +191,51 @@  static int xfs_get_dquot(struct dquot *dq)
 	return 0;
 }
 
+static int xfs_kernel_scan_dquots(struct quota_handle *h,
+		int (*process_dquot)(struct dquot *dquot, char *dqname))
+{
+	struct dquot *dquot = get_empty_dquot();
+	qid_t id = 0;
+	struct xfs_kern_dqblk xdqblk;
+	int ret;
+
+	dquot->dq_h = h;
+	while (1) {
+		ret = quotactl(QCMD(Q_XGETNEXTQUOTA, h->qh_type),
+			       h->qh_quotadev, id, (void *)&xdqblk);
+		if (ret < 0)
+			break;
+
+		xfs_kern2utildqblk(&dquot->dq_dqb, &xdqblk);
+		dquot->dq_id = xdqblk.d_id;
+		ret = process_dquot(dquot, NULL);
+		if (ret < 0)
+			break;
+		id = xdqblk.d_id + 1;
+	}
+	free(dquot);
+
+	if (errno == ESRCH)
+		return 0;
+	return ret;
+}
+
 /*
  *	Scan all known dquots and call callback on each
  */
 static int xfs_scan_dquots(struct quota_handle *h, int (*process_dquot) (struct dquot *dquot, char *dqname))
 {
-	if (!XFS_USRQUOTA(h) && !XFS_GRPQUOTA(h))
-		return 0;
+	int ret;
+	struct xfs_kern_dqblk xdqblk;
 
-	return generic_scan_dquots(h, process_dquot, xfs_get_dquot);
+	ret = quotactl(QCMD(Q_XGETNEXTQUOTA, h->qh_type), h->qh_quotadev, 0,
+		       (void *)&xdqblk);
+	if (ret < 0 && (errno == ENOSYS || errno == EINVAL)) {
+		if (!XFS_USRQUOTA(h) && !XFS_GRPQUOTA(h))
+			return 0;
+		return generic_scan_dquots(h, process_dquot, xfs_get_dquot);
+	}
+	return xfs_kernel_scan_dquots(h, process_dquot);
 }
 
 /*
diff --git a/quotaio_xfs.h b/quotaio_xfs.h
index 54725b044d63..2236da48f832 100644
--- a/quotaio_xfs.h
+++ b/quotaio_xfs.h
@@ -46,6 +46,7 @@ 
 #define Q_XSETQLIM   XQM_CMD(0x4)	/* set disk limits only */
 #define Q_XGETQSTAT  XQM_CMD(0x5)	/* returns fs_quota_stat_t struct */
 #define Q_XQUOTARM   XQM_CMD(0x6)	/* free quota files' space */
+#define Q_XGETNEXTQUOTA	XQM_CMD(0x9)	/* get disk limits and usage >= ID */
 
 /*
  * fs_disk_quota structure:
-- 
2.6.2