commit 50e0bdbe9f48f98bb02eac7030d682f4716884ae
author Darrick J. Wong <darrick.wong@oracle.com> Tue Jun 27 10:19:45 2017 -0700
committer Darrick J. Wong <darrick.wong@oracle.com> Tue Jun 27 18:23:22 2017 -0700
tree a4f2d4b9cc5e1fad8be1f0ff3598d11a9864d326
parent 244e3dea58818e9520bf3dbaf4404a60b105bfb1

xfs: grab dquots without taking the ilock

Add a new dqget flag that grabs the dquot without taking the ilock.
This will be used by the scrubber (which will have already grabbed
the ilock) to perform basic sanity checking of the quota data.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

fs/xfs/libxfs/xfs_quota_defs.h

diff --git a/fs/xfs/libxfs/xfs_quota_defs.h b/fs/xfs/libxfs/xfs_quota_defs.h
index d69c772..2834574 100644
--- a/fs/xfs/libxfs/xfs_quota_defs.h
+++ b/fs/xfs/libxfs/xfs_quota_defs.h
@@ -136,6 +136,8 @@
  */
 #define XFS_QMOPT_INHERIT	0x1000000
 
+#define XFS_QMOPT_NOLOCK	0x2000000 /* don't ilock during dqget */
+
 /*
  * flags to xfs_trans_mod_dquot.
  */

fs/xfs/xfs_dquot.c

diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c
index e57c6cc..7966814 100644
--- a/fs/xfs/xfs_dquot.c
+++ b/fs/xfs/xfs_dquot.c
@@ -472,18 +472,23 @@
 	struct xfs_mount	*mp = dqp->q_mount;
 	xfs_dqid_t		id = be32_to_cpu(dqp->q_core.d_id);
 	struct xfs_trans	*tp = (tpp ? *tpp : NULL);
-	uint			lock_mode;
+	uint			lock_mode = 0;
 
 	quotip = xfs_quota_inode(dqp->q_mount, dqp->dq_flags);
 	dqp->q_fileoffset = (xfs_fileoff_t)id / mp->m_quotainfo->qi_dqperchunk;
 
-	lock_mode = xfs_ilock_data_map_shared(quotip);
+	ASSERT(!(flags & XFS_QMOPT_NOLOCK) ||
+		xfs_isilocked(quotip, XFS_ILOCK_SHARED) ||
+		xfs_isilocked(quotip, XFS_ILOCK_EXCL));
+	if (!(flags & XFS_QMOPT_NOLOCK))
+		lock_mode = xfs_ilock_data_map_shared(quotip);
 	if (!xfs_this_quota_on(dqp->q_mount, dqp->dq_flags)) {
 		/*
 		 * Return if this type of quotas is turned off while we
 		 * didn't have the quota inode lock.
 		 */
-		xfs_iunlock(quotip, lock_mode);
+		if (lock_mode)
+			xfs_iunlock(quotip, lock_mode);
 		return -ESRCH;
 	}
 
@@ -493,7 +498,8 @@
 	error = xfs_bmapi_read(quotip, dqp->q_fileoffset,
 			       XFS_DQUOT_CLUSTER_SIZE_FSB, &map, &nmaps, 0);
 
-	xfs_iunlock(quotip, lock_mode);
+	if (lock_mode)
+		xfs_iunlock(quotip, lock_mode);
 	if (error)
 		return error;