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>

diff --git a/fs/xfs/libxfs/xfs_quota_defs.h b/fs/xfs/libxfs/xfs_quota_defs.h
index d69c772..2834574 100644 (file)
--- a/fs/xfs/libxfs/xfs_quota_defs.h
+++ b/fs/xfs/libxfs/xfs_quota_defs.h
@@ -136,6 +136,8 @@ typedef uint16_t    xfs_qwarncnt_t;
  */
 #define XFS_QMOPT_INHERIT      0x1000000
 
+#define XFS_QMOPT_NOLOCK       0x2000000 /* don't ilock during dqget */
+
 /*
  * flags to xfs_trans_mod_dquot.
  */

diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c
index e57c6cc..7966814 100644 (file)
--- a/fs/xfs/xfs_dquot.c
+++ b/fs/xfs/xfs_dquot.c
@@ -472,18 +472,23 @@ xfs_qm_dqtobp(
        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 @@ xfs_qm_dqtobp(
        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;