tree-wide: fix assorted typos all over the place
[safe/jmp/linux-2.6] / fs / ocfs2 / refcounttree.c
index 4e7df8b..d00c658 100644 (file)
@@ -32,6 +32,8 @@
 #include "dlmglue.h"
 #include "extent_map.h"
 #include "aops.h"
+#include "xattr.h"
+#include "namei.h"
 
 #include <linux/bio.h>
 #include <linux/blkdev.h>
 #include <linux/writeback.h>
 #include <linux/pagevec.h>
 #include <linux/swap.h>
+#include <linux/security.h>
+#include <linux/fsnotify.h>
+#include <linux/quotaops.h>
+#include <linux/namei.h>
+#include <linux/mount.h>
 
 struct ocfs2_cow_context {
        struct inode *inode;
        u32 cow_start;
        u32 cow_len;
-       struct ocfs2_extent_tree di_et;
-       struct ocfs2_caching_info *ref_ci;
+       struct ocfs2_extent_tree data_et;
+       struct ocfs2_refcount_tree *ref_tree;
        struct buffer_head *ref_root_bh;
        struct ocfs2_alloc_context *meta_ac;
        struct ocfs2_alloc_context *data_ac;
        struct ocfs2_cached_dealloc_ctxt dealloc;
+       void *cow_object;
+       struct ocfs2_post_refcount *post_refcount;
+       int extra_credits;
+       int (*get_clusters)(struct ocfs2_cow_context *context,
+                           u32 v_cluster, u32 *p_cluster,
+                           u32 *num_clusters,
+                           unsigned int *extent_flags);
+       int (*cow_duplicate_clusters)(handle_t *handle,
+                                     struct ocfs2_cow_context *context,
+                                     u32 cpos, u32 old_cluster,
+                                     u32 new_cluster, u32 new_len);
 };
 
 static inline struct ocfs2_refcount_tree *
@@ -915,6 +933,42 @@ out:
 }
 
 /*
+ * Try to remove refcount tree. The mechanism is:
+ * 1) Check whether i_clusters == 0, if no, exit.
+ * 2) check whether we have i_xattr_loc in dinode. if yes, exit.
+ * 3) Check whether we have inline xattr stored outside, if yes, exit.
+ * 4) Remove the tree.
+ */
+int ocfs2_try_remove_refcount_tree(struct inode *inode,
+                                  struct buffer_head *di_bh)
+{
+       int ret;
+       struct ocfs2_inode_info *oi = OCFS2_I(inode);
+       struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
+
+       down_write(&oi->ip_xattr_sem);
+       down_write(&oi->ip_alloc_sem);
+
+       if (oi->ip_clusters)
+               goto out;
+
+       if ((oi->ip_dyn_features & OCFS2_HAS_XATTR_FL) && di->i_xattr_loc)
+               goto out;
+
+       if (oi->ip_dyn_features & OCFS2_INLINE_XATTR_FL &&
+           ocfs2_has_inline_xattr_value_outside(inode, di))
+               goto out;
+
+       ret = ocfs2_remove_refcount_tree(inode, di_bh);
+       if (ret)
+               mlog_errno(ret);
+out:
+       up_write(&oi->ip_alloc_sem);
+       up_write(&oi->ip_xattr_sem);
+       return 0;
+}
+
+/*
  * Given a cpos and len, try to find the refcount record which contains cpos.
  * 1. If cpos can be found in one refcount record, return the record.
  * 2. If cpos can't be found, return a fake record which start from cpos
@@ -1099,7 +1153,7 @@ static void ocfs2_refcount_rec_merge(struct ocfs2_refcount_block *rb,
 static int ocfs2_change_refcount_rec(handle_t *handle,
                                     struct ocfs2_caching_info *ci,
                                     struct buffer_head *ref_leaf_bh,
-                                    int index, int change)
+                                    int index, int merge, int change)
 {
        int ret;
        struct ocfs2_refcount_block *rb =
@@ -1128,7 +1182,7 @@ static int ocfs2_change_refcount_rec(handle_t *handle,
                }
 
                le16_add_cpu(&rl->rl_used, -1);
-       } else
+       } else if (merge)
                ocfs2_refcount_rec_merge(rb, index);
 
        ret = ocfs2_journal_dirty(handle, ref_leaf_bh);
@@ -1604,7 +1658,7 @@ static int ocfs2_insert_refcount_rec(handle_t *handle,
                                     struct buffer_head *ref_root_bh,
                                     struct buffer_head *ref_leaf_bh,
                                     struct ocfs2_refcount_rec *rec,
-                                    int index,
+                                    int index, int merge,
                                     struct ocfs2_alloc_context *meta_ac)
 {
        int ret;
@@ -1662,7 +1716,8 @@ static int ocfs2_insert_refcount_rec(handle_t *handle,
 
        le16_add_cpu(&rf_list->rl_used, 1);
 
-       ocfs2_refcount_rec_merge(rb, index);
+       if (merge)
+               ocfs2_refcount_rec_merge(rb, index);
 
        ret = ocfs2_journal_dirty(handle, ref_leaf_bh);
        if (ret) {
@@ -1696,7 +1751,7 @@ static int ocfs2_split_refcount_rec(handle_t *handle,
                                    struct buffer_head *ref_root_bh,
                                    struct buffer_head *ref_leaf_bh,
                                    struct ocfs2_refcount_rec *split_rec,
-                                   int index,
+                                   int index, int merge,
                                    struct ocfs2_alloc_context *meta_ac,
                                    struct ocfs2_cached_dealloc_ctxt *dealloc)
 {
@@ -1834,7 +1889,8 @@ static int ocfs2_split_refcount_rec(handle_t *handle,
                     le32_to_cpu(split_rec->r_refcount),
                     (unsigned long long)ref_leaf_bh->b_blocknr, index);
 
-               ocfs2_refcount_rec_merge(rb, index);
+               if (merge)
+                       ocfs2_refcount_rec_merge(rb, index);
        }
 
        ret = ocfs2_journal_dirty(handle, ref_leaf_bh);
@@ -1849,7 +1905,7 @@ out:
 static int __ocfs2_increase_refcount(handle_t *handle,
                                     struct ocfs2_caching_info *ci,
                                     struct buffer_head *ref_root_bh,
-                                    u64 cpos, u32 len,
+                                    u64 cpos, u32 len, int merge,
                                     struct ocfs2_alloc_context *meta_ac,
                                     struct ocfs2_cached_dealloc_ctxt *dealloc)
 {
@@ -1889,7 +1945,8 @@ static int __ocfs2_increase_refcount(handle_t *handle,
                             "count %u\n", (unsigned long long)cpos, set_len,
                             le32_to_cpu(rec.r_refcount));
                        ret = ocfs2_change_refcount_rec(handle, ci,
-                                                       ref_leaf_bh, index, 1);
+                                                       ref_leaf_bh, index,
+                                                       merge, 1);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
@@ -1902,7 +1959,8 @@ static int __ocfs2_increase_refcount(handle_t *handle,
                             set_len);
                        ret = ocfs2_insert_refcount_rec(handle, ci, ref_root_bh,
                                                        ref_leaf_bh,
-                                                       &rec, index, meta_ac);
+                                                       &rec, index,
+                                                       merge, meta_ac);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
@@ -1920,7 +1978,7 @@ static int __ocfs2_increase_refcount(handle_t *handle,
                             set_len, le32_to_cpu(rec.r_refcount));
                        ret = ocfs2_split_refcount_rec(handle, ci,
                                                       ref_root_bh, ref_leaf_bh,
-                                                      &rec, index,
+                                                      &rec, index, merge,
                                                       meta_ac, dealloc);
                        if (ret) {
                                mlog_errno(ret);
@@ -2013,6 +2071,18 @@ out:
        return ret;
 }
 
+int ocfs2_increase_refcount(handle_t *handle,
+                           struct ocfs2_caching_info *ci,
+                           struct buffer_head *ref_root_bh,
+                           u64 cpos, u32 len,
+                           struct ocfs2_alloc_context *meta_ac,
+                           struct ocfs2_cached_dealloc_ctxt *dealloc)
+{
+       return __ocfs2_increase_refcount(handle, ci, ref_root_bh,
+                                        cpos, len, 1,
+                                        meta_ac, dealloc);
+}
+
 static int ocfs2_decrease_refcount_rec(handle_t *handle,
                                struct ocfs2_caching_info *ci,
                                struct buffer_head *ref_root_bh,
@@ -2033,7 +2103,7 @@ static int ocfs2_decrease_refcount_rec(handle_t *handle,
        if (cpos == le64_to_cpu(rec->r_cpos) &&
            len == le32_to_cpu(rec->r_clusters))
                ret = ocfs2_change_refcount_rec(handle, ci,
-                                               ref_leaf_bh, index, -1);
+                                               ref_leaf_bh, index, 1, -1);
        else {
                struct ocfs2_refcount_rec split = *rec;
                split.r_cpos = cpu_to_le64(cpos);
@@ -2049,7 +2119,7 @@ static int ocfs2_decrease_refcount_rec(handle_t *handle,
                     le32_to_cpu(rec->r_clusters));
                ret = ocfs2_split_refcount_rec(handle, ci,
                                               ref_root_bh, ref_leaf_bh,
-                                              &split, index,
+                                              &split, index, 1,
                                               meta_ac, dealloc);
        }
 
@@ -2076,7 +2146,8 @@ static int __ocfs2_decrease_refcount(handle_t *handle,
                                     struct buffer_head *ref_root_bh,
                                     u64 cpos, u32 len,
                                     struct ocfs2_alloc_context *meta_ac,
-                                    struct ocfs2_cached_dealloc_ctxt *dealloc)
+                                    struct ocfs2_cached_dealloc_ctxt *dealloc,
+                                    int delete)
 {
        int ret = 0, index = 0;
        struct ocfs2_refcount_rec rec;
@@ -2084,9 +2155,10 @@ static int __ocfs2_decrease_refcount(handle_t *handle,
        struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
        struct buffer_head *ref_leaf_bh = NULL;
 
-       mlog(0, "Tree owner %llu, decrease refcount start %llu, len %u\n",
+       mlog(0, "Tree owner %llu, decrease refcount start %llu, "
+            "len %u, delete %u\n",
             (unsigned long long)ocfs2_metadata_cache_owner(ci),
-            (unsigned long long)cpos, len);
+            (unsigned long long)cpos, len, delete);
 
        while (len) {
                ret = ocfs2_get_refcount_rec(ci, ref_root_bh,
@@ -2099,6 +2171,8 @@ static int __ocfs2_decrease_refcount(handle_t *handle,
 
                r_count = le32_to_cpu(rec.r_refcount);
                BUG_ON(r_count == 0);
+               if (!delete)
+                       BUG_ON(r_count > 1);
 
                r_len = min((u64)(cpos + len), le64_to_cpu(rec.r_cpos) +
                              le32_to_cpu(rec.r_clusters)) - cpos;
@@ -2112,7 +2186,7 @@ static int __ocfs2_decrease_refcount(handle_t *handle,
                        goto out;
                }
 
-               if (le32_to_cpu(rec.r_refcount) == 1) {
+               if (le32_to_cpu(rec.r_refcount) == 1 && delete) {
                        ret = ocfs2_cache_cluster_dealloc(dealloc,
                                          ocfs2_clusters_to_blocks(sb, cpos),
                                                          r_len);
@@ -2137,7 +2211,8 @@ out:
 int ocfs2_decrease_refcount(struct inode *inode,
                            handle_t *handle, u32 cpos, u32 len,
                            struct ocfs2_alloc_context *meta_ac,
-                           struct ocfs2_cached_dealloc_ctxt *dealloc)
+                           struct ocfs2_cached_dealloc_ctxt *dealloc,
+                           int delete)
 {
        int ret;
        u64 ref_blkno;
@@ -2167,7 +2242,7 @@ int ocfs2_decrease_refcount(struct inode *inode,
        }
 
        ret = __ocfs2_decrease_refcount(handle, &tree->rf_ci, ref_root_bh,
-                                       cpos, len, meta_ac, dealloc);
+                                       cpos, len, meta_ac, dealloc, delete);
        if (ret)
                mlog_errno(ret);
 out:
@@ -2356,7 +2431,7 @@ out:
  * we gonna touch and whether we need to create new blocks.
  *
  * Normally the refcount blocks store these refcount should be
- * continguous also, so that we can get the number easily.
+ * contiguous also, so that we can get the number easily.
  * As for meta_ac, we will at most add split 2 refcount record and
  * 2 more refcount block, so just check it in a rough way.
  *
@@ -2477,21 +2552,21 @@ static inline unsigned int ocfs2_cow_align_length(struct super_block *sb,
  *
  * cpos is vitual start cluster position we want to do CoW in a
  * file and write_len is the cluster length.
+ * max_cpos is the place where we want to stop CoW intentionally.
  *
  * Normal we will start CoW from the beginning of extent record cotaining cpos.
  * We try to break up extents on boundaries of MAX_CONTIG_BYTES so that we
  * get good I/O from the resulting extent tree.
  */
 static int ocfs2_refcount_cal_cow_clusters(struct inode *inode,
-                                          struct buffer_head *di_bh,
+                                          struct ocfs2_extent_list *el,
                                           u32 cpos,
                                           u32 write_len,
+                                          u32 max_cpos,
                                           u32 *cow_start,
                                           u32 *cow_len)
 {
        int ret = 0;
-       struct ocfs2_dinode *di = (struct ocfs2_dinode *) di_bh->b_data;
-       struct ocfs2_extent_list *el = &di->id2.i_list;
        int tree_height = le16_to_cpu(el->l_tree_depth), i;
        struct buffer_head *eb_bh = NULL;
        struct ocfs2_extent_block *eb = NULL;
@@ -2500,6 +2575,8 @@ static int ocfs2_refcount_cal_cow_clusters(struct inode *inode,
        int contig_clusters = ocfs2_cow_contig_clusters(inode->i_sb);
        int leaf_clusters;
 
+       BUG_ON(cpos + write_len > max_cpos);
+
        if (tree_height > 0) {
                ret = ocfs2_find_leaf(INODE_CACHE(inode), el, cpos, &eb_bh);
                if (ret) {
@@ -2544,15 +2621,20 @@ static int ocfs2_refcount_cal_cow_clusters(struct inode *inode,
                }
 
                /*
-                * If we encounter a hole or a non-refcounted record,
-                * stop the search.
+                * If we encounter a hole, a non-refcounted record or
+                * pass the max_cpos, stop the search.
                 */
                if ((!(rec->e_flags & OCFS2_EXT_REFCOUNTED)) ||
-                   (*cow_len && rec_end != le32_to_cpu(rec->e_cpos)))
+                   (*cow_len && rec_end != le32_to_cpu(rec->e_cpos)) ||
+                   (max_cpos <= le32_to_cpu(rec->e_cpos)))
                        break;
 
                leaf_clusters = le16_to_cpu(rec->e_leaf_clusters);
                rec_end = le32_to_cpu(rec->e_cpos) + leaf_clusters;
+               if (rec_end > max_cpos) {
+                       rec_end = max_cpos;
+                       leaf_clusters = rec_end - le32_to_cpu(rec->e_cpos);
+               }
 
                /*
                 * How many clusters do we actually need from
@@ -2755,13 +2837,13 @@ static int ocfs2_clear_cow_buffer(handle_t *handle, struct buffer_head *bh)
        return 0;
 }
 
-static int ocfs2_duplicate_clusters(handle_t *handle,
-                                   struct ocfs2_cow_context *context,
-                                   u32 cpos, u32 old_cluster,
-                                   u32 new_cluster, u32 new_len)
+static int ocfs2_duplicate_clusters_by_page(handle_t *handle,
+                                           struct ocfs2_cow_context *context,
+                                           u32 cpos, u32 old_cluster,
+                                           u32 new_cluster, u32 new_len)
 {
        int ret = 0, partial;
-       struct ocfs2_caching_info *ci = context->di_et.et_ci;
+       struct ocfs2_caching_info *ci = context->data_et.et_ci;
        struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
        u64 new_block = ocfs2_clusters_to_blocks(sb, new_cluster);
        struct page *page;
@@ -2828,6 +2910,65 @@ unlock:
        return ret;
 }
 
+static int ocfs2_duplicate_clusters_by_jbd(handle_t *handle,
+                                          struct ocfs2_cow_context *context,
+                                          u32 cpos, u32 old_cluster,
+                                          u32 new_cluster, u32 new_len)
+{
+       int ret = 0;
+       struct super_block *sb = context->inode->i_sb;
+       struct ocfs2_caching_info *ci = context->data_et.et_ci;
+       int i, blocks = ocfs2_clusters_to_blocks(sb, new_len);
+       u64 old_block = ocfs2_clusters_to_blocks(sb, old_cluster);
+       u64 new_block = ocfs2_clusters_to_blocks(sb, new_cluster);
+       struct ocfs2_super *osb = OCFS2_SB(sb);
+       struct buffer_head *old_bh = NULL;
+       struct buffer_head *new_bh = NULL;
+
+       mlog(0, "old_cluster %u, new %u, len %u\n", old_cluster,
+            new_cluster, new_len);
+
+       for (i = 0; i < blocks; i++, old_block++, new_block++) {
+               new_bh = sb_getblk(osb->sb, new_block);
+               if (new_bh == NULL) {
+                       ret = -EIO;
+                       mlog_errno(ret);
+                       break;
+               }
+
+               ocfs2_set_new_buffer_uptodate(ci, new_bh);
+
+               ret = ocfs2_read_block(ci, old_block, &old_bh, NULL);
+               if (ret) {
+                       mlog_errno(ret);
+                       break;
+               }
+
+               ret = ocfs2_journal_access(handle, ci, new_bh,
+                                          OCFS2_JOURNAL_ACCESS_CREATE);
+               if (ret) {
+                       mlog_errno(ret);
+                       break;
+               }
+
+               memcpy(new_bh->b_data, old_bh->b_data, sb->s_blocksize);
+               ret = ocfs2_journal_dirty(handle, new_bh);
+               if (ret) {
+                       mlog_errno(ret);
+                       break;
+               }
+
+               brelse(new_bh);
+               brelse(old_bh);
+               new_bh = NULL;
+               old_bh = NULL;
+       }
+
+       brelse(new_bh);
+       brelse(old_bh);
+       return ret;
+}
+
 static int ocfs2_clear_ext_refcount(handle_t *handle,
                                    struct ocfs2_extent_tree *et,
                                    u32 cpos, u32 p_cluster, u32 len,
@@ -2895,7 +3036,7 @@ static int ocfs2_replace_clusters(handle_t *handle,
                                  unsigned int ext_flags)
 {
        int ret;
-       struct ocfs2_caching_info *ci = context->di_et.et_ci;
+       struct ocfs2_caching_info *ci = context->data_et.et_ci;
        u64 ino = ocfs2_metadata_cache_owner(ci);
 
        mlog(0, "inode %llu, cpos %u, old %u, new %u, len %u, ext_flags %u\n",
@@ -2903,15 +3044,15 @@ static int ocfs2_replace_clusters(handle_t *handle,
 
        /*If the old clusters is unwritten, no need to duplicate. */
        if (!(ext_flags & OCFS2_EXT_UNWRITTEN)) {
-               ret = ocfs2_duplicate_clusters(handle, context, cpos,
-                                              old, new, len);
+               ret = context->cow_duplicate_clusters(handle, context, cpos,
+                                                     old, new, len);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
        }
 
-       ret = ocfs2_clear_ext_refcount(handle, &context->di_et,
+       ret = ocfs2_clear_ext_refcount(handle, &context->data_et,
                                       cpos, new, len, ext_flags,
                                       context->meta_ac, &context->dealloc);
        if (ret)
@@ -2969,19 +3110,35 @@ static int ocfs2_cow_sync_writeback(struct super_block *sb,
        return ret;
 }
 
+static int ocfs2_di_get_clusters(struct ocfs2_cow_context *context,
+                                u32 v_cluster, u32 *p_cluster,
+                                u32 *num_clusters,
+                                unsigned int *extent_flags)
+{
+       return ocfs2_get_clusters(context->inode, v_cluster, p_cluster,
+                                 num_clusters, extent_flags);
+}
+
 static int ocfs2_make_clusters_writable(struct super_block *sb,
                                        struct ocfs2_cow_context *context,
                                        u32 cpos, u32 p_cluster,
                                        u32 num_clusters, unsigned int e_flags)
 {
-       int ret, credits =  0;
+       int ret, delete, index, credits =  0;
        u32 new_bit, new_len;
+       unsigned int set_len;
        struct ocfs2_super *osb = OCFS2_SB(sb);
        handle_t *handle;
+       struct buffer_head *ref_leaf_bh = NULL;
+       struct ocfs2_caching_info *ref_ci = &context->ref_tree->rf_ci;
+       struct ocfs2_refcount_rec rec;
+
+       mlog(0, "cpos %u, p_cluster %u, num_clusters %u, e_flags %u\n",
+            cpos, p_cluster, num_clusters, e_flags);
 
        ret = ocfs2_lock_refcount_allocators(sb, p_cluster, num_clusters,
-                                            &context->di_et,
-                                            context->ref_ci,
+                                            &context->data_et,
+                                            ref_ci,
                                             context->ref_root_bh,
                                             &context->meta_ac,
                                             &context->data_ac, &credits);
@@ -2990,6 +3147,10 @@ static int ocfs2_make_clusters_writable(struct super_block *sb,
                return ret;
        }
 
+       if (context->post_refcount)
+               credits += context->post_refcount->credits;
+
+       credits += context->extra_credits;
        handle = ocfs2_start_trans(osb, credits);
        if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
@@ -2998,44 +3159,96 @@ static int ocfs2_make_clusters_writable(struct super_block *sb,
        }
 
        while (num_clusters) {
-               ret = __ocfs2_claim_clusters(osb, handle, context->data_ac,
-                                            1, num_clusters,
-                                            &new_bit, &new_len);
+               ret = ocfs2_get_refcount_rec(ref_ci, context->ref_root_bh,
+                                            p_cluster, num_clusters,
+                                            &rec, &index, &ref_leaf_bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out_commit;
                }
 
-               ret = ocfs2_replace_clusters(handle, context,
-                                            cpos, p_cluster, new_bit,
-                                            new_len, e_flags);
+               BUG_ON(!rec.r_refcount);
+               set_len = min((u64)p_cluster + num_clusters,
+                             le64_to_cpu(rec.r_cpos) +
+                             le32_to_cpu(rec.r_clusters)) - p_cluster;
+
+               /*
+                * There are many different situation here.
+                * 1. If refcount == 1, remove the flag and don't COW.
+                * 2. If refcount > 1, allocate clusters.
+                *    Here we may not allocate r_len once at a time, so continue
+                *    until we reach num_clusters.
+                */
+               if (le32_to_cpu(rec.r_refcount) == 1) {
+                       delete = 0;
+                       ret = ocfs2_clear_ext_refcount(handle,
+                                                      &context->data_et,
+                                                      cpos, p_cluster,
+                                                      set_len, e_flags,
+                                                      context->meta_ac,
+                                                      &context->dealloc);
+                       if (ret) {
+                               mlog_errno(ret);
+                               goto out_commit;
+                       }
+               } else {
+                       delete = 1;
+
+                       ret = __ocfs2_claim_clusters(osb, handle,
+                                                    context->data_ac,
+                                                    1, set_len,
+                                                    &new_bit, &new_len);
+                       if (ret) {
+                               mlog_errno(ret);
+                               goto out_commit;
+                       }
+
+                       ret = ocfs2_replace_clusters(handle, context,
+                                                    cpos, p_cluster, new_bit,
+                                                    new_len, e_flags);
+                       if (ret) {
+                               mlog_errno(ret);
+                               goto out_commit;
+                       }
+                       set_len = new_len;
+               }
+
+               ret = __ocfs2_decrease_refcount(handle, ref_ci,
+                                               context->ref_root_bh,
+                                               p_cluster, set_len,
+                                               context->meta_ac,
+                                               &context->dealloc, delete);
                if (ret) {
                        mlog_errno(ret);
                        goto out_commit;
                }
 
-               cpos += new_len;
-               p_cluster += new_len;
-               num_clusters -= new_len;
+               cpos += set_len;
+               p_cluster += set_len;
+               num_clusters -= set_len;
+               brelse(ref_leaf_bh);
+               ref_leaf_bh = NULL;
        }
 
-       ret = __ocfs2_decrease_refcount(handle, context->ref_ci,
-                                       context->ref_root_bh,
-                                       p_cluster, num_clusters,
-                                       context->meta_ac,
-                                       &context->dealloc);
-       if (ret) {
-               mlog_errno(ret);
-               goto out_commit;
+       /* handle any post_cow action. */
+       if (context->post_refcount && context->post_refcount->func) {
+               ret = context->post_refcount->func(context->inode, handle,
+                                               context->post_refcount->para);
+               if (ret) {
+                       mlog_errno(ret);
+                       goto out_commit;
+               }
        }
 
        /*
         * Here we should write the new page out first if we are
         * in write-back mode.
         */
-       ret = ocfs2_cow_sync_writeback(sb, context, cpos, num_clusters);
-       if (ret)
-               mlog_errno(ret);
+       if (context->get_clusters == ocfs2_di_get_clusters) {
+               ret = ocfs2_cow_sync_writeback(sb, context, cpos, num_clusters);
+               if (ret)
+                       mlog_errno(ret);
+       }
 
 out_commit:
        ocfs2_commit_trans(osb, handle);
@@ -3049,21 +3262,19 @@ out:
                ocfs2_free_alloc_context(context->meta_ac);
                context->meta_ac = NULL;
        }
+       brelse(ref_leaf_bh);
 
        return ret;
 }
 
-static int ocfs2_replace_cow(struct inode *inode,
-                            struct buffer_head *di_bh,
-                            struct buffer_head *ref_root_bh,
-                            struct ocfs2_caching_info *ref_ci,
-                            u32 cow_start, u32 cow_len)
+static int ocfs2_replace_cow(struct ocfs2_cow_context *context)
 {
        int ret = 0;
-       u32 p_cluster, num_clusters, start = cow_start;
+       struct inode *inode = context->inode;
+       u32 cow_start = context->cow_start, cow_len = context->cow_len;
+       u32 p_cluster, num_clusters;
        unsigned int ext_flags;
        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
-       struct ocfs2_cow_context *context;
 
        if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb))) {
                ocfs2_error(inode->i_sb, "Inode %lu want to use refcount "
@@ -3072,26 +3283,11 @@ static int ocfs2_replace_cow(struct inode *inode,
                return -EROFS;
        }
 
-       context = kzalloc(sizeof(struct ocfs2_cow_context), GFP_NOFS);
-       if (!context) {
-               ret = -ENOMEM;
-               mlog_errno(ret);
-               return ret;
-       }
-
-       context->inode = inode;
-       context->cow_start = cow_start;
-       context->cow_len = cow_len;
-       context->ref_ci = ref_ci;
-       context->ref_root_bh = ref_root_bh;
-
        ocfs2_init_dealloc_ctxt(&context->dealloc);
-       ocfs2_init_dinode_extent_tree(&context->di_et,
-                                     INODE_CACHE(inode), di_bh);
 
        while (cow_len) {
-               ret = ocfs2_get_clusters(inode, cow_start, &p_cluster,
-                                        &num_clusters, &ext_flags);
+               ret = context->get_clusters(context, cow_start, &p_cluster,
+                                           &num_clusters, &ext_flags);
                if (ret) {
                        mlog_errno(ret);
                        break;
@@ -3114,30 +3310,22 @@ static int ocfs2_replace_cow(struct inode *inode,
                cow_start += num_clusters;
        }
 
-
-       /*
-        * truncate the extent map here since no matter whether we meet with
-        * any error during the action, we shouldn't trust cached extent map
-        * any more.
-        */
-       ocfs2_extent_map_trunc(inode, start);
-
        if (ocfs2_dealloc_has_cluster(&context->dealloc)) {
                ocfs2_schedule_truncate_log_flush(osb, 1);
                ocfs2_run_deallocs(osb, &context->dealloc);
        }
 
-       kfree(context);
        return ret;
 }
 
 /*
- * Starting at cpos, try to CoW write_len clusters.
- * This will stop when it runs into a hole or an unrefcounted extent.
+ * Starting at cpos, try to CoW write_len clusters.  Don't CoW
+ * past max_cpos.  This will stop when it runs into a hole or an
+ * unrefcounted extent.
  */
 static int ocfs2_refcount_cow_hunk(struct inode *inode,
                                   struct buffer_head *di_bh,
-                                  u32 cpos, u32 write_len)
+                                  u32 cpos, u32 write_len, u32 max_cpos)
 {
        int ret;
        u32 cow_start = 0, cow_len = 0;
@@ -3146,21 +3334,31 @@ static int ocfs2_refcount_cow_hunk(struct inode *inode,
        struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
        struct buffer_head *ref_root_bh = NULL;
        struct ocfs2_refcount_tree *ref_tree;
+       struct ocfs2_cow_context *context = NULL;
 
        BUG_ON(!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));
 
-       ret = ocfs2_refcount_cal_cow_clusters(inode, di_bh, cpos, write_len,
+       ret = ocfs2_refcount_cal_cow_clusters(inode, &di->id2.i_list,
+                                             cpos, write_len, max_cpos,
                                              &cow_start, &cow_len);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }
+
        mlog(0, "CoW inode %lu, cpos %u, write_len %u, cow_start %u, "
             "cow_len %u\n", inode->i_ino,
             cpos, write_len, cow_start, cow_len);
 
        BUG_ON(cow_len == 0);
 
+       context = kzalloc(sizeof(struct ocfs2_cow_context), GFP_NOFS);
+       if (!context) {
+               ret = -ENOMEM;
+               mlog_errno(ret);
+               goto out;
+       }
+
        ret = ocfs2_lock_refcount_tree(osb, le64_to_cpu(di->i_refcount_loc),
                                       1, &ref_tree, &ref_root_bh);
        if (ret) {
@@ -3168,25 +3366,43 @@ static int ocfs2_refcount_cow_hunk(struct inode *inode,
                goto out;
        }
 
-       ret = ocfs2_replace_cow(inode, di_bh, ref_root_bh, &ref_tree->rf_ci,
-                               cow_start, cow_len);
+       context->inode = inode;
+       context->cow_start = cow_start;
+       context->cow_len = cow_len;
+       context->ref_tree = ref_tree;
+       context->ref_root_bh = ref_root_bh;
+       context->cow_duplicate_clusters = ocfs2_duplicate_clusters_by_page;
+       context->get_clusters = ocfs2_di_get_clusters;
+
+       ocfs2_init_dinode_extent_tree(&context->data_et,
+                                     INODE_CACHE(inode), di_bh);
+
+       ret = ocfs2_replace_cow(context);
        if (ret)
                mlog_errno(ret);
 
+       /*
+        * truncate the extent map here since no matter whether we meet with
+        * any error during the action, we shouldn't trust cached extent map
+        * any more.
+        */
+       ocfs2_extent_map_trunc(inode, cow_start);
+
        ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
        brelse(ref_root_bh);
 out:
+       kfree(context);
        return ret;
 }
 
 /*
  * CoW any and all clusters between cpos and cpos+write_len.
- * If this returns successfully, all clusters between cpos and
- * cpos+write_len are safe to modify.
+ * Don't CoW past max_cpos.  If this returns successfully, all
+ * clusters between cpos and cpos+write_len are safe to modify.
  */
 int ocfs2_refcount_cow(struct inode *inode,
                       struct buffer_head *di_bh,
-                      u32 cpos, u32 write_len)
+                      u32 cpos, u32 write_len, u32 max_cpos)
 {
        int ret = 0;
        u32 p_cluster, num_clusters;
@@ -3205,7 +3421,7 @@ int ocfs2_refcount_cow(struct inode *inode,
 
                if (ext_flags & OCFS2_EXT_REFCOUNTED) {
                        ret = ocfs2_refcount_cow_hunk(inode, di_bh, cpos,
-                                                     num_clusters);
+                                                     num_clusters, max_cpos);
                        if (ret) {
                                mlog_errno(ret);
                                break;
@@ -3218,3 +3434,880 @@ int ocfs2_refcount_cow(struct inode *inode,
 
        return ret;
 }
+
+static int ocfs2_xattr_value_get_clusters(struct ocfs2_cow_context *context,
+                                         u32 v_cluster, u32 *p_cluster,
+                                         u32 *num_clusters,
+                                         unsigned int *extent_flags)
+{
+       struct inode *inode = context->inode;
+       struct ocfs2_xattr_value_root *xv = context->cow_object;
+
+       return ocfs2_xattr_get_clusters(inode, v_cluster, p_cluster,
+                                       num_clusters, &xv->xr_list,
+                                       extent_flags);
+}
+
+/*
+ * Given a xattr value root, calculate the most meta/credits we need for
+ * refcount tree change if we truncate it to 0.
+ */
+int ocfs2_refcounted_xattr_delete_need(struct inode *inode,
+                                      struct ocfs2_caching_info *ref_ci,
+                                      struct buffer_head *ref_root_bh,
+                                      struct ocfs2_xattr_value_root *xv,
+                                      int *meta_add, int *credits)
+{
+       int ret = 0, index, ref_blocks = 0;
+       u32 p_cluster, num_clusters;
+       u32 cpos = 0, clusters = le32_to_cpu(xv->xr_clusters);
+       struct ocfs2_refcount_block *rb;
+       struct ocfs2_refcount_rec rec;
+       struct buffer_head *ref_leaf_bh = NULL;
+
+       while (cpos < clusters) {
+               ret = ocfs2_xattr_get_clusters(inode, cpos, &p_cluster,
+                                              &num_clusters, &xv->xr_list,
+                                              NULL);
+               if (ret) {
+                       mlog_errno(ret);
+                       goto out;
+               }
+
+               cpos += num_clusters;
+
+               while (num_clusters) {
+                       ret = ocfs2_get_refcount_rec(ref_ci, ref_root_bh,
+                                                    p_cluster, num_clusters,
+                                                    &rec, &index,
+                                                    &ref_leaf_bh);
+                       if (ret) {
+                               mlog_errno(ret);
+                               goto out;
+                       }
+
+                       BUG_ON(!rec.r_refcount);
+
+                       rb = (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
+
+                       /*
+                        * We really don't know whether the other clusters is in
+                        * this refcount block or not, so just take the worst
+                        * case that all the clusters are in this block and each
+                        * one will split a refcount rec, so totally we need
+                        * clusters * 2 new refcount rec.
+                        */
+                       if (le64_to_cpu(rb->rf_records.rl_used) + clusters * 2 >
+                           le16_to_cpu(rb->rf_records.rl_count))
+                               ref_blocks++;
+
+                       *credits += 1;
+                       brelse(ref_leaf_bh);
+                       ref_leaf_bh = NULL;
+
+                       if (num_clusters <= le32_to_cpu(rec.r_clusters))
+                               break;
+                       else
+                               num_clusters -= le32_to_cpu(rec.r_clusters);
+                       p_cluster += num_clusters;
+               }
+       }
+
+       *meta_add += ref_blocks;
+       if (!ref_blocks)
+               goto out;
+
+       rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;
+       if (le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL)
+               *credits += OCFS2_EXPAND_REFCOUNT_TREE_CREDITS;
+       else {
+               struct ocfs2_extent_tree et;
+
+               ocfs2_init_refcount_extent_tree(&et, ref_ci, ref_root_bh);
+               *credits += ocfs2_calc_extend_credits(inode->i_sb,
+                                                     et.et_root_el,
+                                                     ref_blocks);
+       }
+
+out:
+       brelse(ref_leaf_bh);
+       return ret;
+}
+
+/*
+ * Do CoW for xattr.
+ */
+int ocfs2_refcount_cow_xattr(struct inode *inode,
+                            struct ocfs2_dinode *di,
+                            struct ocfs2_xattr_value_buf *vb,
+                            struct ocfs2_refcount_tree *ref_tree,
+                            struct buffer_head *ref_root_bh,
+                            u32 cpos, u32 write_len,
+                            struct ocfs2_post_refcount *post)
+{
+       int ret;
+       struct ocfs2_xattr_value_root *xv = vb->vb_xv;
+       struct ocfs2_inode_info *oi = OCFS2_I(inode);
+       struct ocfs2_cow_context *context = NULL;
+       u32 cow_start, cow_len;
+
+       BUG_ON(!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));
+
+       ret = ocfs2_refcount_cal_cow_clusters(inode, &xv->xr_list,
+                                             cpos, write_len, UINT_MAX,
+                                             &cow_start, &cow_len);
+       if (ret) {
+               mlog_errno(ret);
+               goto out;
+       }
+
+       BUG_ON(cow_len == 0);
+
+       context = kzalloc(sizeof(struct ocfs2_cow_context), GFP_NOFS);
+       if (!context) {
+               ret = -ENOMEM;
+               mlog_errno(ret);
+               goto out;
+       }
+
+       context->inode = inode;
+       context->cow_start = cow_start;
+       context->cow_len = cow_len;
+       context->ref_tree = ref_tree;
+       context->ref_root_bh = ref_root_bh;;
+       context->cow_object = xv;
+
+       context->cow_duplicate_clusters = ocfs2_duplicate_clusters_by_jbd;
+       /* We need the extra credits for duplicate_clusters by jbd. */
+       context->extra_credits =
+               ocfs2_clusters_to_blocks(inode->i_sb, 1) * cow_len;
+       context->get_clusters = ocfs2_xattr_value_get_clusters;
+       context->post_refcount = post;
+
+       ocfs2_init_xattr_value_extent_tree(&context->data_et,
+                                          INODE_CACHE(inode), vb);
+
+       ret = ocfs2_replace_cow(context);
+       if (ret)
+               mlog_errno(ret);
+
+out:
+       kfree(context);
+       return ret;
+}
+
+/*
+ * Insert a new extent into refcount tree and mark a extent rec
+ * as refcounted in the dinode tree.
+ */
+int ocfs2_add_refcount_flag(struct inode *inode,
+                           struct ocfs2_extent_tree *data_et,
+                           struct ocfs2_caching_info *ref_ci,
+                           struct buffer_head *ref_root_bh,
+                           u32 cpos, u32 p_cluster, u32 num_clusters,
+                           struct ocfs2_cached_dealloc_ctxt *dealloc,
+                           struct ocfs2_post_refcount *post)
+{
+       int ret;
+       handle_t *handle;
+       int credits = 1, ref_blocks = 0;
+       struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+       struct ocfs2_alloc_context *meta_ac = NULL;
+
+       ret = ocfs2_calc_refcount_meta_credits(inode->i_sb,
+                                              ref_ci, ref_root_bh,
+                                              p_cluster, num_clusters,
+                                              &ref_blocks, &credits);
+       if (ret) {
+               mlog_errno(ret);
+               goto out;
+       }
+
+       mlog(0, "reserve new metadata %d, credits = %d\n",
+            ref_blocks, credits);
+
+       if (ref_blocks) {
+               ret = ocfs2_reserve_new_metadata_blocks(OCFS2_SB(inode->i_sb),
+                                                       ref_blocks, &meta_ac);
+               if (ret) {
+                       mlog_errno(ret);
+                       goto out;
+               }
+       }
+
+       if (post)
+               credits += post->credits;
+
+       handle = ocfs2_start_trans(osb, credits);
+       if (IS_ERR(handle)) {
+               ret = PTR_ERR(handle);
+               mlog_errno(ret);
+               goto out;
+       }
+
+       ret = ocfs2_mark_extent_refcounted(inode, data_et, handle,
+                                          cpos, num_clusters, p_cluster,
+                                          meta_ac, dealloc);
+       if (ret) {
+               mlog_errno(ret);
+               goto out_commit;
+       }
+
+       ret = __ocfs2_increase_refcount(handle, ref_ci, ref_root_bh,
+                                       p_cluster, num_clusters, 0,
+                                       meta_ac, dealloc);
+       if (ret) {
+               mlog_errno(ret);
+               goto out_commit;
+       }
+
+       if (post && post->func) {
+               ret = post->func(inode, handle, post->para);
+               if (ret)
+                       mlog_errno(ret);
+       }
+
+out_commit:
+       ocfs2_commit_trans(osb, handle);
+out:
+       if (meta_ac)
+               ocfs2_free_alloc_context(meta_ac);
+       return ret;
+}
+
+static int ocfs2_change_ctime(struct inode *inode,
+                             struct buffer_head *di_bh)
+{
+       int ret;
+       handle_t *handle;
+       struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
+
+       handle = ocfs2_start_trans(OCFS2_SB(inode->i_sb),
+                                  OCFS2_INODE_UPDATE_CREDITS);
+       if (IS_ERR(handle)) {
+               ret = PTR_ERR(handle);
+               mlog_errno(ret);
+               goto out;
+       }
+
+       ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
+                                     OCFS2_JOURNAL_ACCESS_WRITE);
+       if (ret) {
+               mlog_errno(ret);
+               goto out_commit;
+       }
+
+       inode->i_ctime = CURRENT_TIME;
+       di->i_ctime = cpu_to_le64(inode->i_ctime.tv_sec);
+       di->i_ctime_nsec = cpu_to_le32(inode->i_ctime.tv_nsec);
+
+       ocfs2_journal_dirty(handle, di_bh);
+
+out_commit:
+       ocfs2_commit_trans(OCFS2_SB(inode->i_sb), handle);
+out:
+       return ret;
+}
+
+static int ocfs2_attach_refcount_tree(struct inode *inode,
+                                     struct buffer_head *di_bh)
+{
+       int ret, data_changed = 0;
+       struct buffer_head *ref_root_bh = NULL;
+       struct ocfs2_inode_info *oi = OCFS2_I(inode);
+       struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
+       struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+       struct ocfs2_refcount_tree *ref_tree;
+       unsigned int ext_flags;
+       loff_t size;
+       u32 cpos, num_clusters, clusters, p_cluster;
+       struct ocfs2_cached_dealloc_ctxt dealloc;
+       struct ocfs2_extent_tree di_et;
+
+       ocfs2_init_dealloc_ctxt(&dealloc);
+
+       if (!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL)) {
+               ret = ocfs2_create_refcount_tree(inode, di_bh);
+               if (ret) {
+                       mlog_errno(ret);
+                       goto out;
+               }
+       }
+
+       BUG_ON(!di->i_refcount_loc);
+       ret = ocfs2_lock_refcount_tree(osb,
+                                      le64_to_cpu(di->i_refcount_loc), 1,
+                                      &ref_tree, &ref_root_bh);
+       if (ret) {
+               mlog_errno(ret);
+               goto out;
+       }
+
+       ocfs2_init_dinode_extent_tree(&di_et, INODE_CACHE(inode), di_bh);
+
+       size = i_size_read(inode);
+       clusters = ocfs2_clusters_for_bytes(inode->i_sb, size);
+
+       cpos = 0;
+       while (cpos < clusters) {
+               ret = ocfs2_get_clusters(inode, cpos, &p_cluster,
+                                        &num_clusters, &ext_flags);
+
+               if (p_cluster && !(ext_flags & OCFS2_EXT_REFCOUNTED)) {
+                       ret = ocfs2_add_refcount_flag(inode, &di_et,
+                                                     &ref_tree->rf_ci,
+                                                     ref_root_bh, cpos,
+                                                     p_cluster, num_clusters,
+                                                     &dealloc, NULL);
+                       if (ret) {
+                               mlog_errno(ret);
+                               goto unlock;
+                       }
+
+                       data_changed = 1;
+               }
+               cpos += num_clusters;
+       }
+
+       if (oi->ip_dyn_features & OCFS2_HAS_XATTR_FL) {
+               ret = ocfs2_xattr_attach_refcount_tree(inode, di_bh,
+                                                      &ref_tree->rf_ci,
+                                                      ref_root_bh,
+                                                      &dealloc);
+               if (ret) {
+                       mlog_errno(ret);
+                       goto unlock;
+               }
+       }
+
+       if (data_changed) {
+               ret = ocfs2_change_ctime(inode, di_bh);
+               if (ret)
+                       mlog_errno(ret);
+       }
+
+unlock:
+       ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
+       brelse(ref_root_bh);
+
+       if (!ret && ocfs2_dealloc_has_cluster(&dealloc)) {
+               ocfs2_schedule_truncate_log_flush(osb, 1);
+               ocfs2_run_deallocs(osb, &dealloc);
+       }
+out:
+       /*
+        * Empty the extent map so that we may get the right extent
+        * record from the disk.
+        */
+       ocfs2_extent_map_trunc(inode, 0);
+
+       return ret;
+}
+
+static int ocfs2_add_refcounted_extent(struct inode *inode,
+                                  struct ocfs2_extent_tree *et,
+                                  struct ocfs2_caching_info *ref_ci,
+                                  struct buffer_head *ref_root_bh,
+                                  u32 cpos, u32 p_cluster, u32 num_clusters,
+                                  unsigned int ext_flags,
+                                  struct ocfs2_cached_dealloc_ctxt *dealloc)
+{
+       int ret;
+       handle_t *handle;
+       int credits = 0;
+       struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+       struct ocfs2_alloc_context *meta_ac = NULL;
+
+       ret = ocfs2_lock_refcount_allocators(inode->i_sb,
+                                            p_cluster, num_clusters,
+                                            et, ref_ci,
+                                            ref_root_bh, &meta_ac,
+                                            NULL, &credits);
+       if (ret) {
+               mlog_errno(ret);
+               goto out;
+       }
+
+       handle = ocfs2_start_trans(osb, credits);
+       if (IS_ERR(handle)) {
+               ret = PTR_ERR(handle);
+               mlog_errno(ret);
+               goto out;
+       }
+
+       ret = ocfs2_insert_extent(handle, et, cpos,
+                       cpu_to_le64(ocfs2_clusters_to_blocks(inode->i_sb,
+                                                            p_cluster)),
+                       num_clusters, ext_flags, meta_ac);
+       if (ret) {
+               mlog_errno(ret);
+               goto out_commit;
+       }
+
+       ret = ocfs2_increase_refcount(handle, ref_ci, ref_root_bh,
+                                     p_cluster, num_clusters,
+                                     meta_ac, dealloc);
+       if (ret)
+               mlog_errno(ret);
+
+out_commit:
+       ocfs2_commit_trans(osb, handle);
+out:
+       if (meta_ac)
+               ocfs2_free_alloc_context(meta_ac);
+       return ret;
+}
+
+static int ocfs2_duplicate_extent_list(struct inode *s_inode,
+                               struct inode *t_inode,
+                               struct buffer_head *t_bh,
+                               struct ocfs2_caching_info *ref_ci,
+                               struct buffer_head *ref_root_bh,
+                               struct ocfs2_cached_dealloc_ctxt *dealloc)
+{
+       int ret = 0;
+       u32 p_cluster, num_clusters, clusters, cpos;
+       loff_t size;
+       unsigned int ext_flags;
+       struct ocfs2_extent_tree et;
+
+       ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(t_inode), t_bh);
+
+       size = i_size_read(s_inode);
+       clusters = ocfs2_clusters_for_bytes(s_inode->i_sb, size);
+
+       cpos = 0;
+       while (cpos < clusters) {
+               ret = ocfs2_get_clusters(s_inode, cpos, &p_cluster,
+                                        &num_clusters, &ext_flags);
+
+               if (p_cluster) {
+                       ret = ocfs2_add_refcounted_extent(t_inode, &et,
+                                                         ref_ci, ref_root_bh,
+                                                         cpos, p_cluster,
+                                                         num_clusters,
+                                                         ext_flags,
+                                                         dealloc);
+                       if (ret) {
+                               mlog_errno(ret);
+                               goto out;
+                       }
+               }
+
+               cpos += num_clusters;
+       }
+
+out:
+       return ret;
+}
+
+/*
+ * change the new file's attributes to the src.
+ *
+ * reflink creates a snapshot of a file, that means the attributes
+ * must be identical except for three exceptions - nlink, ino, and ctime.
+ */
+static int ocfs2_complete_reflink(struct inode *s_inode,
+                                 struct buffer_head *s_bh,
+                                 struct inode *t_inode,
+                                 struct buffer_head *t_bh,
+                                 bool preserve)
+{
+       int ret;
+       handle_t *handle;
+       struct ocfs2_dinode *s_di = (struct ocfs2_dinode *)s_bh->b_data;
+       struct ocfs2_dinode *di = (struct ocfs2_dinode *)t_bh->b_data;
+       loff_t size = i_size_read(s_inode);
+
+       handle = ocfs2_start_trans(OCFS2_SB(t_inode->i_sb),
+                                  OCFS2_INODE_UPDATE_CREDITS);
+       if (IS_ERR(handle)) {
+               ret = PTR_ERR(handle);
+               mlog_errno(ret);
+               return ret;
+       }
+
+       ret = ocfs2_journal_access_di(handle, INODE_CACHE(t_inode), t_bh,
+                                     OCFS2_JOURNAL_ACCESS_WRITE);
+       if (ret) {
+               mlog_errno(ret);
+               goto out_commit;
+       }
+
+       spin_lock(&OCFS2_I(t_inode)->ip_lock);
+       OCFS2_I(t_inode)->ip_clusters = OCFS2_I(s_inode)->ip_clusters;
+       OCFS2_I(t_inode)->ip_attr = OCFS2_I(s_inode)->ip_attr;
+       OCFS2_I(t_inode)->ip_dyn_features = OCFS2_I(s_inode)->ip_dyn_features;
+       spin_unlock(&OCFS2_I(t_inode)->ip_lock);
+       i_size_write(t_inode, size);
+
+       di->i_xattr_inline_size = s_di->i_xattr_inline_size;
+       di->i_clusters = s_di->i_clusters;
+       di->i_size = s_di->i_size;
+       di->i_dyn_features = s_di->i_dyn_features;
+       di->i_attr = s_di->i_attr;
+
+       if (preserve) {
+               di->i_uid = s_di->i_uid;
+               di->i_gid = s_di->i_gid;
+               di->i_mode = s_di->i_mode;
+
+               /*
+                * update time.
+                * we want mtime to appear identical to the source and
+                * update ctime.
+                */
+               t_inode->i_ctime = CURRENT_TIME;
+
+               di->i_ctime = cpu_to_le64(t_inode->i_ctime.tv_sec);
+               di->i_ctime_nsec = cpu_to_le32(t_inode->i_ctime.tv_nsec);
+
+               t_inode->i_mtime = s_inode->i_mtime;
+               di->i_mtime = s_di->i_mtime;
+               di->i_mtime_nsec = s_di->i_mtime_nsec;
+       }
+
+       ocfs2_journal_dirty(handle, t_bh);
+
+out_commit:
+       ocfs2_commit_trans(OCFS2_SB(t_inode->i_sb), handle);
+       return ret;
+}
+
+static int ocfs2_create_reflink_node(struct inode *s_inode,
+                                    struct buffer_head *s_bh,
+                                    struct inode *t_inode,
+                                    struct buffer_head *t_bh,
+                                    bool preserve)
+{
+       int ret;
+       struct buffer_head *ref_root_bh = NULL;
+       struct ocfs2_cached_dealloc_ctxt dealloc;
+       struct ocfs2_super *osb = OCFS2_SB(s_inode->i_sb);
+       struct ocfs2_refcount_block *rb;
+       struct ocfs2_dinode *di = (struct ocfs2_dinode *)s_bh->b_data;
+       struct ocfs2_refcount_tree *ref_tree;
+
+       ocfs2_init_dealloc_ctxt(&dealloc);
+
+       ret = ocfs2_set_refcount_tree(t_inode, t_bh,
+                                     le64_to_cpu(di->i_refcount_loc));
+       if (ret) {
+               mlog_errno(ret);
+               goto out;
+       }
+
+       ret = ocfs2_lock_refcount_tree(osb, le64_to_cpu(di->i_refcount_loc),
+                                      1, &ref_tree, &ref_root_bh);
+       if (ret) {
+               mlog_errno(ret);
+               goto out;
+       }
+       rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;
+
+       ret = ocfs2_duplicate_extent_list(s_inode, t_inode, t_bh,
+                                         &ref_tree->rf_ci, ref_root_bh,
+                                         &dealloc);
+       if (ret) {
+               mlog_errno(ret);
+               goto out_unlock_refcount;
+       }
+
+       ret = ocfs2_complete_reflink(s_inode, s_bh, t_inode, t_bh, preserve);
+       if (ret)
+               mlog_errno(ret);
+
+out_unlock_refcount:
+       ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
+       brelse(ref_root_bh);
+out:
+       if (ocfs2_dealloc_has_cluster(&dealloc)) {
+               ocfs2_schedule_truncate_log_flush(osb, 1);
+               ocfs2_run_deallocs(osb, &dealloc);
+       }
+
+       return ret;
+}
+
+static int __ocfs2_reflink(struct dentry *old_dentry,
+                          struct buffer_head *old_bh,
+                          struct inode *new_inode,
+                          bool preserve)
+{
+       int ret;
+       struct inode *inode = old_dentry->d_inode;
+       struct buffer_head *new_bh = NULL;
+
+       ret = filemap_fdatawrite(inode->i_mapping);
+       if (ret) {
+               mlog_errno(ret);
+               goto out;
+       }
+
+       ret = ocfs2_attach_refcount_tree(inode, old_bh);
+       if (ret) {
+               mlog_errno(ret);
+               goto out;
+       }
+
+       mutex_lock(&new_inode->i_mutex);
+       ret = ocfs2_inode_lock(new_inode, &new_bh, 1);
+       if (ret) {
+               mlog_errno(ret);
+               goto out_unlock;
+       }
+
+       ret = ocfs2_create_reflink_node(inode, old_bh,
+                                       new_inode, new_bh, preserve);
+       if (ret) {
+               mlog_errno(ret);
+               goto inode_unlock;
+       }
+
+       if (OCFS2_I(inode)->ip_dyn_features & OCFS2_HAS_XATTR_FL) {
+               ret = ocfs2_reflink_xattrs(inode, old_bh,
+                                          new_inode, new_bh,
+                                          preserve);
+               if (ret)
+                       mlog_errno(ret);
+       }
+inode_unlock:
+       ocfs2_inode_unlock(new_inode, 1);
+       brelse(new_bh);
+out_unlock:
+       mutex_unlock(&new_inode->i_mutex);
+out:
+       if (!ret) {
+               ret = filemap_fdatawait(inode->i_mapping);
+               if (ret)
+                       mlog_errno(ret);
+       }
+       return ret;
+}
+
+static int ocfs2_reflink(struct dentry *old_dentry, struct inode *dir,
+                        struct dentry *new_dentry, bool preserve)
+{
+       int error;
+       struct inode *inode = old_dentry->d_inode;
+       struct buffer_head *old_bh = NULL;
+       struct inode *new_orphan_inode = NULL;
+
+       if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb)))
+               return -EOPNOTSUPP;
+
+       error = ocfs2_create_inode_in_orphan(dir, inode->i_mode,
+                                            &new_orphan_inode);
+       if (error) {
+               mlog_errno(error);
+               goto out;
+       }
+
+       error = ocfs2_inode_lock(inode, &old_bh, 1);
+       if (error) {
+               mlog_errno(error);
+               goto out;
+       }
+
+       down_write(&OCFS2_I(inode)->ip_xattr_sem);
+       down_write(&OCFS2_I(inode)->ip_alloc_sem);
+       error = __ocfs2_reflink(old_dentry, old_bh,
+                               new_orphan_inode, preserve);
+       up_write(&OCFS2_I(inode)->ip_alloc_sem);
+       up_write(&OCFS2_I(inode)->ip_xattr_sem);
+
+       ocfs2_inode_unlock(inode, 1);
+       brelse(old_bh);
+
+       if (error) {
+               mlog_errno(error);
+               goto out;
+       }
+
+       /* If the security isn't preserved, we need to re-initialize them. */
+       if (!preserve) {
+               error = ocfs2_init_security_and_acl(dir, new_orphan_inode);
+               if (error)
+                       mlog_errno(error);
+       }
+out:
+       if (!error) {
+               error = ocfs2_mv_orphaned_inode_to_new(dir, new_orphan_inode,
+                                                      new_dentry);
+               if (error)
+                       mlog_errno(error);
+       }
+
+       if (new_orphan_inode) {
+               /*
+                * We need to open_unlock the inode no matter whether we
+                * succeed or not, so that other nodes can delete it later.
+                */
+               ocfs2_open_unlock(new_orphan_inode);
+               if (error)
+                       iput(new_orphan_inode);
+       }
+
+       return error;
+}
+
+/*
+ * Below here are the bits used by OCFS2_IOC_REFLINK() to fake
+ * sys_reflink().  This will go away when vfs_reflink() exists in
+ * fs/namei.c.
+ */
+
+/* copied from may_create in VFS. */
+static inline int ocfs2_may_create(struct inode *dir, struct dentry *child)
+{
+       if (child->d_inode)
+               return -EEXIST;
+       if (IS_DEADDIR(dir))
+               return -ENOENT;
+       return inode_permission(dir, MAY_WRITE | MAY_EXEC);
+}
+
+/* copied from user_path_parent. */
+static int ocfs2_user_path_parent(const char __user *path,
+                                 struct nameidata *nd, char **name)
+{
+       char *s = getname(path);
+       int error;
+
+       if (IS_ERR(s))
+               return PTR_ERR(s);
+
+       error = path_lookup(s, LOOKUP_PARENT, nd);
+       if (error)
+               putname(s);
+       else
+               *name = s;
+
+       return error;
+}
+
+/**
+ * ocfs2_vfs_reflink - Create a reference-counted link
+ *
+ * @old_dentry:        source dentry + inode
+ * @dir:       directory to create the target
+ * @new_dentry:        target dentry
+ * @preserve:  if true, preserve all file attributes
+ */
+int ocfs2_vfs_reflink(struct dentry *old_dentry, struct inode *dir,
+                     struct dentry *new_dentry, bool preserve)
+{
+       struct inode *inode = old_dentry->d_inode;
+       int error;
+
+       if (!inode)
+               return -ENOENT;
+
+       error = ocfs2_may_create(dir, new_dentry);
+       if (error)
+               return error;
+
+       if (dir->i_sb != inode->i_sb)
+               return -EXDEV;
+
+       /*
+        * A reflink to an append-only or immutable file cannot be created.
+        */
+       if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
+               return -EPERM;
+
+       /* Only regular files can be reflinked. */
+       if (!S_ISREG(inode->i_mode))
+               return -EPERM;
+
+       /*
+        * If the caller wants to preserve ownership, they require the
+        * rights to do so.
+        */
+       if (preserve) {
+               if ((current_fsuid() != inode->i_uid) && !capable(CAP_CHOWN))
+                       return -EPERM;
+               if (!in_group_p(inode->i_gid) && !capable(CAP_CHOWN))
+                       return -EPERM;
+       }
+
+       /*
+        * If the caller is modifying any aspect of the attributes, they
+        * are not creating a snapshot.  They need read permission on the
+        * file.
+        */
+       if (!preserve) {
+               error = inode_permission(inode, MAY_READ);
+               if (error)
+                       return error;
+       }
+
+       mutex_lock(&inode->i_mutex);
+       vfs_dq_init(dir);
+       error = ocfs2_reflink(old_dentry, dir, new_dentry, preserve);
+       mutex_unlock(&inode->i_mutex);
+       if (!error)
+               fsnotify_create(dir, new_dentry);
+       return error;
+}
+/*
+ * Most codes are copied from sys_linkat.
+ */
+int ocfs2_reflink_ioctl(struct inode *inode,
+                       const char __user *oldname,
+                       const char __user *newname,
+                       bool preserve)
+{
+       struct dentry *new_dentry;
+       struct nameidata nd;
+       struct path old_path;
+       int error;
+       char *to = NULL;
+
+       if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb)))
+               return -EOPNOTSUPP;
+
+       error = user_path_at(AT_FDCWD, oldname, 0, &old_path);
+       if (error) {
+               mlog_errno(error);
+               return error;
+       }
+
+       error = ocfs2_user_path_parent(newname, &nd, &to);
+       if (error) {
+               mlog_errno(error);
+               goto out;
+       }
+
+       error = -EXDEV;
+       if (old_path.mnt != nd.path.mnt)
+               goto out_release;
+       new_dentry = lookup_create(&nd, 0);
+       error = PTR_ERR(new_dentry);
+       if (IS_ERR(new_dentry)) {
+               mlog_errno(error);
+               goto out_unlock;
+       }
+
+       error = mnt_want_write(nd.path.mnt);
+       if (error) {
+               mlog_errno(error);
+               goto out_dput;
+       }
+
+       error = ocfs2_vfs_reflink(old_path.dentry,
+                                 nd.path.dentry->d_inode,
+                                 new_dentry, preserve);
+       mnt_drop_write(nd.path.mnt);
+out_dput:
+       dput(new_dentry);
+out_unlock:
+       mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+out_release:
+       path_put(&nd.path);
+       putname(to);
+out:
+       path_put(&old_path);
+
+       return error;
+}