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Subject[14/91] ocfs2: Count more refcount records in file system fragmentation.
2.6.34-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Tao Ma <tao.ma@oracle.com>

commit 8a2e70c40ff58f82dde67770e6623ca45f0cb0c8 upstream.

The refcount record calculation in ocfs2_calc_refcount_meta_credits
is too optimistic that we can always allocate contiguous clusters
and handle an already existed refcount rec as a whole. Actually
because of file system fragmentation, we may have the chance to split
a refcount record into 3 parts during the transaction. So consider
the worst case in record calculation.

Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/ocfs2/refcounttree.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
--- a/fs/ocfs2/refcounttree.c
+++ b/fs/ocfs2/refcounttree.c
@@ -2437,16 +2437,26 @@ static int ocfs2_calc_refcount_meta_cred
len = min((u64)cpos + clusters, le64_to_cpu(rec.r_cpos) +
le32_to_cpu(rec.r_clusters)) - cpos;
/*
- * If the refcount rec already exist, cool. We just need
- * to check whether there is a split. Otherwise we just need
- * to increase the refcount.
- * If we will insert one, increases recs_add.
- *
* We record all the records which will be inserted to the
* same refcount block, so that we can tell exactly whether
* we need a new refcount block or not.
+ *
+ * If we will insert a new one, this is easy and only happens
+ * during adding refcounted flag to the extent, so we don't
+ * have a chance of spliting. We just need one record.
+ *
+ * If the refcount rec already exists, that would be a little
+ * complicated. we may have to:
+ * 1) split at the beginning if the start pos isn't aligned.
+ * we need 1 more record in this case.
+ * 2) split int the end if the end pos isn't aligned.
+ * we need 1 more record in this case.
+ * 3) split in the middle because of file system fragmentation.
+ * we need 2 more records in this case(we can't detect this
+ * beforehand, so always think of the worst case).
*/
if (rec.r_refcount) {
+ recs_add += 2;
/* Check whether we need a split at the beginning. */
if (cpos == start_cpos &&
cpos != le64_to_cpu(rec.r_cpos))



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