ocfs2: Fix start offset to ocfs2_zero_range_for_truncate()

If we punch a hole on a reflink such that following conditions are met:

1. start offset is on a cluster boundary
2. end offset is not on a cluster boundary
3. (end offset is somewhere in another extent) or
   (hole range > MAX_CONTIG_BYTES(1MB)),

we dont COW the first cluster starting at the start offset. But in this
case, we were wrongly passing this cluster to
ocfs2_zero_range_for_truncate() to zero out. This will modify the cluster
in place and zero it in the source too.

Fix this by skipping this cluster in such a scenario.

Orabug: 24516161

Reported-by: Saar Maoz <saar.maoz@oracle.com>
Signed-off-by: Ashish Samant <ashish.samant@oracle.com>
Reviewed-by: Srinivas Eeda <srinivas.eeda@oracle.com>

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 19cf01b958ab37b892b961cdfee56cc4eab821e7..71e645b874cf2bdfef2987126603c937116836be 100644 (file)
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -1536,7 +1536,8 @@ static int ocfs2_zero_partial_clusters(struct inode *inode,
                                       u64 start, u64 len)
 {
        int ret = 0;
-       u64 tmpend, end = start + len;
+       u64 tmpend = 0;
+       u64 end = start + len;
        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
        unsigned int csize = osb->s_clustersize;
        handle_t *handle;
@@ -1568,18 +1569,31 @@ static int ocfs2_zero_partial_clusters(struct inode *inode,
        }
 
        /*
-        * We want to get the byte offset of the end of the 1st cluster.
+        * If start is on a cluster boundary and end is somewhere in another
+        * cluster, we have not COWed the cluster starting at start, unless
+        * end is also within the same cluster. So, in this case, we skip this
+        * first call to ocfs2_zero_range_for_truncate() truncate and move on
+        * to the next one.
         */
-       tmpend = (u64)osb->s_clustersize + (start & ~(osb->s_clustersize - 1));
-       if (tmpend > end)
-               tmpend = end;
+       if ((start & (csize - 1)) != 0) {
+               /*
+                * We want to get the byte offset of the end of the 1st
+                * cluster.
+                */
+               tmpend = (u64)osb->s_clustersize +
+                       (start & ~(osb->s_clustersize - 1));
+               if (tmpend > end)
+                       tmpend = end;
 
-       trace_ocfs2_zero_partial_clusters_range1((unsigned long long)start,
-                                                (unsigned long long)tmpend);
+               trace_ocfs2_zero_partial_clusters_range1(
+                       (unsigned long long)start,
+                       (unsigned long long)tmpend);
 
-       ret = ocfs2_zero_range_for_truncate(inode, handle, start, tmpend);
-       if (ret)
-               mlog_errno(ret);
+               ret = ocfs2_zero_range_for_truncate(inode, handle, start,
+                                                   tmpend);
+               if (ret)
+                       mlog_errno(ret);
+       }
 
        if (tmpend < end) {
                /*