On 04/25/13 17:41, Chandra Seetharaman wrote:
In which case something along the lines of
---
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 3806088..3fb2fa6 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -203,7 +203,13 @@ xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t
agno)
if (pag) {
ASSERT(atomic_read(&pag->pag_ref)>= 0);
ref = atomic_inc_return(&pag->pag_ref);
- }
+ } else
+ /*
+ * xfs_perag_get() is called with invalid agno,
+ * which cannot happen. This indicates a problem
+ * in the calling code.
+ */
+ BUG();
rcu_read_unlock();
trace_xfs_perag_get(mp, agno, ref, _RET_IP_);
return pag;
--------
would be useful ?. Since we have a NULL pag, we will trip somewhere
else. At least with this, there is a pointer to the debugger/sysadmin
about where/what to look for (may be with more valuable/correct comment
than above).
We will have to make sure the callers of xfs_perag_get() handle the NULL
before dereferencing it. Sometimes the NULL is normal and just means the
perag structure has not been initialize yet.
Properly handling the NULL from xfs_perag_get() in the caller will also
mean that the callers of the callers of xfs_perag_get() have to handle
the NULL returned to them. I will come back to this once the CRC stuff
has been put to rest.
--Mark.
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