From: John Spray <john.spray@redhat.com>
Date: Mon, 5 Jun 2017 10:30:45 +0000 (+0100)
Subject: client: avoid returning negative space available
X-Git-Tag: v12.1.0~76^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=0144fde1b1639a6917e487f78490f2b84dceeae6;p=ceph.git

client: avoid returning negative space available

...when a quota is set and the used bytes exceed
the quota.

Fixes: http://tracker.ceph.com/issues/20178
Signed-off-by: John Spray <john.spray@redhat.com>
---

diff --git a/src/client/Client.cc b/src/client/Client.cc
index cbb216aa7682..9d5ad6bc140e 100644
--- a/src/client/Client.cc
+++ b/src/client/Client.cc
@@ -9361,8 +9361,9 @@ int Client::statfs(const char *path, struct statvfs *stbuf,
     // as the filesystem statistics.
     const fsblkcnt_t total = quota_root->quota.max_bytes >> CEPH_BLOCK_SHIFT;
     const fsblkcnt_t used = quota_root->rstat.rbytes >> CEPH_BLOCK_SHIFT;
-    const fsblkcnt_t free = total - used;
-
+    // It is possible for a quota to be exceeded: arithmetic here must
+    // handle case where used > total.
+    const fsblkcnt_t free = total > used ? total - used : 0;
 
     stbuf->f_blocks = total;
     stbuf->f_bfree = free;