ocfs2: CoW a reflinked cluster when it is truncated.

When we truncate a file to a specific size which resides in a reflinked
cluster, we need to CoW it since ocfs2_zero_range_for_truncate will
zero the space after the size(just another type of write).

So we add a "max_cpos" in ocfs2_refcount_cow so that it will stop when
it hit the max cluster offset.

Signed-off-by: Tao Ma <tao.ma@oracle.com>

1 files changed, 45 insertions, 1 deletions

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 6ee20e82bcc5..75f5b81805b5 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -335,6 +335,39 @@ out:
         return ret;
 }
 
+static int ocfs2_cow_file_pos(struct inode *inode,
+                              struct buffer_head *fe_bh,
+                              u64 offset)
+{
+        int status;
+        u32 phys, cpos = offset >> OCFS2_SB(inode->i_sb)->s_clustersize_bits;
+        unsigned int num_clusters = 0;
+        unsigned int ext_flags = 0;
+
+        /*
+         * If the new offset is aligned to the range of the cluster, there is
+         * no space for ocfs2_zero_range_for_truncate to fill, so no need to
+         * CoW either.
+         */
+        if ((offset & (OCFS2_SB(inode->i_sb)->s_clustersize - 1)) == 0)
+                return 0;
+
+        status = ocfs2_get_clusters(inode, cpos, &phys,
+                                    &num_clusters, &ext_flags);
+        if (status) {
+                mlog_errno(status);
+                goto out;
+        }
+
+        if (!(ext_flags & OCFS2_EXT_REFCOUNTED))
+                goto out;
+
+        return ocfs2_refcount_cow(inode, fe_bh, cpos, 1, cpos+1);
+
+out:
+        return status;
+}
+
 static int ocfs2_orphan_for_truncate(struct ocfs2_super *osb,
                                      struct inode *inode,
                                      struct buffer_head *fe_bh,
@@ -347,6 +380,17 @@ static int ocfs2_orphan_for_truncate(struct ocfs2_super *osb,
 
         mlog_entry_void();
 
+        /*
+         * We need to CoW the cluster contains the offset if it is reflinked
+         * since we will call ocfs2_zero_range_for_truncate later which will
+         * write "0" from offset to the end of the cluster.
+         */
+        status = ocfs2_cow_file_pos(inode, fe_bh, new_i_size);
+        if (status) {
+                mlog_errno(status);
+                return status;
+        }
+
         /* TODO: This needs to actually orphan the inode in this
          * transaction. */
 
@@ -1713,7 +1757,7 @@ static int ocfs2_prepare_inode_for_refcount(struct inode *inode,
 
         *meta_level = 1;
 
-        ret = ocfs2_refcount_cow(inode, di_bh, cpos, clusters);
+        ret = ocfs2_refcount_cow(inode, di_bh, cpos, clusters, UINT_MAX);
         if (ret)
                 mlog_errno(ret);
 out: