xfs: only update mount/resv fields on success in __xfs_ag_resv_init

Try to reserve the blocks first and only then update the fields in
or hanging off the mount structure.  This way we can call __xfs_ag_resv_init
again after a previous failure.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 14 insertions, 9 deletions

diff --git a/fs/xfs/libxfs/xfs_ag_resv.c b/fs/xfs/libxfs/xfs_ag_resv.c
index d346d42c54d1..94234bff40dc 100644
--- a/fs/xfs/libxfs/xfs_ag_resv.c
+++ b/fs/xfs/libxfs/xfs_ag_resv.c
@@ -200,22 +200,27 @@ __xfs_ag_resv_init(
         struct xfs_mount                *mp = pag->pag_mount;
         struct xfs_ag_resv              *resv;
         int                             error;
+        xfs_extlen_t                    reserved;
 
-        resv = xfs_perag_resv(pag, type);
         if (used > ask)
                 ask = used;
-        resv->ar_asked = ask;
-        resv->ar_reserved = resv->ar_orig_reserved = ask - used;
-        mp->m_ag_max_usable -= ask;
+        reserved = ask - used;
 
-        trace_xfs_ag_resv_init(pag, type, ask);
-
-        error = xfs_mod_fdblocks(mp, -(int64_t)resv->ar_reserved, true);
-        if (error)
+        error = xfs_mod_fdblocks(mp, -(int64_t)reserved, true);
+        if (error) {
                 trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno,
                                 error, _RET_IP_);
+                return error;
+        }
 
-        return error;
+        mp->m_ag_max_usable -= ask;
+
+        resv = xfs_perag_resv(pag, type);
+        resv->ar_asked = ask;
+        resv->ar_reserved = resv->ar_orig_reserved = reserved;
+
+        trace_xfs_ag_resv_init(pag, type, ask);
+        return 0;
 }
 
 /* Create a per-AG block reservation. */