xfs: flatten the dquot lock ordering

Introduce a new XFS_DQ_FREEING flag that tells lookup and mplist walks
to skip a dquot that is beeing freed, and use this avoid the trylock
on the hash and mplist locks in xfs_qm_dqreclaim_one.  Also simplify
xfs_dqpurge by moving the inodes to a dispose list after marking them
XFS_DQ_FREEING and avoid the locker ordering constraints.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/xfs/xfs_quota.h b/fs/xfs/xfs_quota.h
index 487653ddbef0..b86c62f5eeba 100644
--- a/fs/xfs/xfs_quota.h
+++ b/fs/xfs/xfs_quota.h
@@ -87,6 +87,7 @@ typedef struct xfs_dqblk {
 #define XFS_DQ_PROJ             0x0002          /* project quota */
 #define XFS_DQ_GROUP            0x0004          /* a group quota */
 #define XFS_DQ_DIRTY            0x0008          /* dquot is dirty */
+#define XFS_DQ_FREEING          0x0010          /* dquot is beeing torn down */
 
 #define XFS_DQ_ALLTYPES         (XFS_DQ_USER|XFS_DQ_PROJ|XFS_DQ_GROUP)
 
@@ -94,7 +95,8 @@ typedef struct xfs_dqblk {
         { XFS_DQ_USER,          "USER" }, \
         { XFS_DQ_PROJ,          "PROJ" }, \
         { XFS_DQ_GROUP,         "GROUP" }, \
-        { XFS_DQ_DIRTY,         "DIRTY" }
+        { XFS_DQ_DIRTY,         "DIRTY" }, \
+        { XFS_DQ_FREEING,       "FREEING" }
 
 /*
  * In the worst case, when both user and group quotas are on,