ocfs2: teach extend/truncate about sparse files

For ocfs2_truncate_file(), we eliminate the "simple" truncate case which no
longer exists since i_size is not tied to i_clusters. In
ocfs2_extend_file(), we skip the allocation / page zeroing code for file
systems which understand sparse files.

The core truncate code is changed to do a bottom up tree traversal. This
gets abstracted out into it's own function. To make things more readable,
most of the special case handling for in-inode extents from
ocfs2_do_truncate() is also removed.

Though write support for sparse files comes in a later patch, we at least
update ocfs2_prepare_inode_for_write() to skip allocation for sparse files.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

3 files changed, 320 insertions, 237 deletions

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index 85a05f120249..9a40603c4d4b 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -2921,12 +2921,13 @@ int ocfs2_truncate_log_init(struct ocfs2_super *osb)
  * block will be so we can update his h_next_leaf_blk field, as well
  * as the dinodes i_last_eb_blk */
 static int ocfs2_find_new_last_ext_blk(struct inode *inode,
-                                       u32 new_i_clusters,
+                                       unsigned int clusters_to_del,
                                        struct ocfs2_path *path,
                                        struct buffer_head **new_last_eb)
 {
-        int ret = 0;
+        int next_free, ret = 0;
         u32 cpos;
+        struct ocfs2_extent_rec *rec;
         struct ocfs2_extent_block *eb;
         struct ocfs2_extent_list *el;
         struct buffer_head *bh = NULL;
@@ -2939,20 +2940,48 @@ static int ocfs2_find_new_last_ext_blk(struct inode *inode,
 
         /* trunc to zero special case - this makes tree_depth = 0
          * regardless of what it is.  */
-        if (!new_i_clusters)
+        if (OCFS2_I(inode)->ip_clusters == clusters_to_del)
                 goto out;
 
         el = path_leaf_el(path);
         BUG_ON(!el->l_next_free_rec);
 
-        /* Make sure that this guy will actually be empty after we
-         * clear away the data. */
+        /*
+         * Make sure that this extent list will actually be empty
+         * after we clear away the data. We can shortcut out if
+         * there's more than one non-empty extent in the
+         * list. Otherwise, a check of the remaining extent is
+         * necessary.
+         */
+        next_free = le16_to_cpu(el->l_next_free_rec);
+        rec = NULL;
         if (ocfs2_is_empty_extent(&el->l_recs[0])) {
-                if (le16_to_cpu(el->l_next_free_rec) > 1 &&
-                    le32_to_cpu(el->l_recs[1].e_cpos) < new_i_clusters)
+                if (next_free > 2)
                         goto out;
-        } else if (le32_to_cpu(el->l_recs[0].e_cpos) < new_i_clusters)
-                goto out;
+
+                /* We may have a valid extent in index 1, check it. */
+                if (next_free == 2)
+                        rec = &el->l_recs[1];
+
+                /*
+                 * Fall through - no more nonempty extents, so we want
+                 * to delete this leaf.
+                 */
+        } else {
+                if (next_free > 1)
+                        goto out;
+
+                rec = &el->l_recs[0];
+        }
+
+        if (rec) {
+                /*
+                 * Check it we'll only be trimming off the end of this
+                 * cluster.
+                 */
+                if (le16_to_cpu(rec->e_clusters) > clusters_to_del)
+                        goto out;
+        }
 
         ret = ocfs2_find_cpos_for_left_leaf(inode->i_sb, path, &cpos);
         if (ret) {
@@ -2984,6 +3013,223 @@ out:
         return ret;
 }
 
+/*
+ * Trim some clusters off the rightmost edge of a tree. Only called
+ * during truncate.
+ *
+ * The caller needs to:
+ *   - start journaling of each path component.
+ *   - compute and fully set up any new last ext block
+ */
+static int ocfs2_trim_tree(struct inode *inode, struct ocfs2_path *path,
+                           handle_t *handle, struct ocfs2_truncate_context *tc,
+                           u32 clusters_to_del, u64 *delete_start)
+{
+        int ret, i, index = path->p_tree_depth;
+        u32 new_edge = 0;
+        u64 deleted_eb = 0;
+        struct buffer_head *bh;
+        struct ocfs2_extent_list *el;
+        struct ocfs2_extent_rec *rec;
+
+        *delete_start = 0;
+
+        while (index >= 0) {
+                bh = path->p_node[index].bh;
+                el = path->p_node[index].el;
+
+                mlog(0, "traveling tree (index = %d, block = %llu)\n",
+                     index,  (unsigned long long)bh->b_blocknr);
+
+                BUG_ON(le16_to_cpu(el->l_next_free_rec) == 0);
+
+                if (index !=
+                    (path->p_tree_depth - le16_to_cpu(el->l_tree_depth))) {
+                        ocfs2_error(inode->i_sb,
+                                    "Inode %lu has invalid ext. block %llu",
+                                    inode->i_ino,
+                                    (unsigned long long)bh->b_blocknr);
+                        ret = -EROFS;
+                        goto out;
+                }
+
+find_tail_record:
+                i = le16_to_cpu(el->l_next_free_rec) - 1;
+                rec = &el->l_recs[i];
+
+                mlog(0, "Extent list before: record %d: (%u, %u, %llu), "
+                     "next = %u\n", i, le32_to_cpu(rec->e_cpos),
+                     le32_to_cpu(rec->e_clusters),
+                     (unsigned long long)le64_to_cpu(rec->e_blkno),
+                     le16_to_cpu(el->l_next_free_rec));
+
+                BUG_ON(le32_to_cpu(rec->e_clusters) < clusters_to_del);
+
+                if (le16_to_cpu(el->l_tree_depth) == 0) {
+                        /*
+                         * If the leaf block contains a single empty
+                         * extent and no records, we can just remove
+                         * the block.
+                         */
+                        if (i == 0 && ocfs2_is_empty_extent(rec)) {
+                                memset(rec, 0,
+                                       sizeof(struct ocfs2_extent_rec));
+                                el->l_next_free_rec = cpu_to_le16(0);
+
+                                goto delete;
+                        }
+
+                        /*
+                         * Remove any empty extents by shifting things
+                         * left. That should make life much easier on
+                         * the code below. This condition is rare
+                         * enough that we shouldn't see a performance
+                         * hit.
+                         */
+                        if (ocfs2_is_empty_extent(&el->l_recs[0])) {
+                                le16_add_cpu(&el->l_next_free_rec, -1);
+
+                                for(i = 0;
+                                    i < le16_to_cpu(el->l_next_free_rec); i++)
+                                        el->l_recs[i] = el->l_recs[i + 1];
+
+                                memset(&el->l_recs[i], 0,
+                                       sizeof(struct ocfs2_extent_rec));
+
+                                /*
+                                 * We've modified our extent list. The
+                                 * simplest way to handle this change
+                                 * is to being the search from the
+                                 * start again.
+                                 */
+                                goto find_tail_record;
+                        }
+
+                        le32_add_cpu(&rec->e_clusters, -clusters_to_del);
+
+                        /*
+                         * We'll use "new_edge" on our way back up the
+                         * tree to know what our rightmost cpos is.
+                         */
+                        new_edge = le32_to_cpu(rec->e_clusters);
+                        new_edge += le32_to_cpu(rec->e_cpos);
+
+                        /*
+                         * The caller will use this to delete data blocks.
+                         */
+                        *delete_start = le64_to_cpu(rec->e_blkno)
+                                + ocfs2_clusters_to_blocks(inode->i_sb,
+                                        le32_to_cpu(rec->e_clusters));
+
+                        /*
+                         * If it's now empty, remove this record.
+                         */
+                        if (le32_to_cpu(rec->e_clusters) == 0) {
+                                memset(rec, 0,
+                                       sizeof(struct ocfs2_extent_rec));
+                                le16_add_cpu(&el->l_next_free_rec, -1);
+                        }
+                } else {
+                        if (le64_to_cpu(rec->e_blkno) == deleted_eb) {
+                                memset(rec, 0,
+                                       sizeof(struct ocfs2_extent_rec));
+                                le16_add_cpu(&el->l_next_free_rec, -1);
+
+                                goto delete;
+                        }
+
+                        /* Can this actually happen? */
+                        if (le16_to_cpu(el->l_next_free_rec) == 0)
+                                goto delete;
+
+                        /*
+                         * We never actually deleted any clusters
+                         * because our leaf was empty. There's no
+                         * reason to adjust the rightmost edge then.
+                         */
+                        if (new_edge == 0)
+                                goto delete;
+
+                        rec->e_clusters = cpu_to_le32(new_edge);
+                        le32_add_cpu(&rec->e_clusters,
+                                     -le32_to_cpu(rec->e_cpos));
+
+                         /*
+                          * A deleted child record should have been
+                          * caught above.
+                          */
+                         BUG_ON(le32_to_cpu(rec->e_clusters) == 0);
+                }
+
+delete:
+                ret = ocfs2_journal_dirty(handle, bh);
+                if (ret) {
+                        mlog_errno(ret);
+                        goto out;
+                }
+
+                mlog(0, "extent list container %llu, after: record %d: "
+                     "(%u, %u, %llu), next = %u.\n",
+                     (unsigned long long)bh->b_blocknr, i,
+                     le32_to_cpu(rec->e_cpos), le32_to_cpu(rec->e_clusters),
+                     (unsigned long long)le64_to_cpu(rec->e_blkno),
+                     le16_to_cpu(el->l_next_free_rec));
+
+                /*
+                 * We must be careful to only attempt delete of an
+                 * extent block (and not the root inode block).
+                 */
+                if (index > 0 && le16_to_cpu(el->l_next_free_rec) == 0) {
+                        struct ocfs2_extent_block *eb =
+                                (struct ocfs2_extent_block *)bh->b_data;
+
+                        /*
+                         * Save this for use when processing the
+                         * parent block.
+                         */
+                        deleted_eb = le64_to_cpu(eb->h_blkno);
+
+                        mlog(0, "deleting this extent block.\n");
+
+                        ocfs2_remove_from_cache(inode, bh);
+
+                        BUG_ON(le32_to_cpu(el->l_recs[0].e_clusters));
+                        BUG_ON(le32_to_cpu(el->l_recs[0].e_cpos));
+                        BUG_ON(le64_to_cpu(el->l_recs[0].e_blkno));
+
+                        if (le16_to_cpu(eb->h_suballoc_slot) == 0) {
+                                /*
+                                 * This code only understands how to
+                                 * lock the suballocator in slot 0,
+                                 * which is fine because allocation is
+                                 * only ever done out of that
+                                 * suballocator too. A future version
+                                 * might change that however, so avoid
+                                 * a free if we don't know how to
+                                 * handle it. This way an fs incompat
+                                 * bit will not be necessary.
+                                 */
+                                ret = ocfs2_free_extent_block(handle,
+                                                              tc->tc_ext_alloc_inode,
+                                                              tc->tc_ext_alloc_bh,
+                                                              eb);
+
+                                /* An error here is not fatal. */
+                                if (ret < 0)
+                                        mlog_errno(ret);
+                        }
+                } else {
+                        deleted_eb = 0;
+                }
+
+                index--;
+        }
+
+        ret = 0;
+out:
+        return ret;
+}
+
 static int ocfs2_do_truncate(struct ocfs2_super *osb,
                              unsigned int clusters_to_del,
                              struct inode *inode,
@@ -2992,20 +3238,16 @@ static int ocfs2_do_truncate(struct ocfs2_super *osb,
                              struct ocfs2_truncate_context *tc,
                              struct ocfs2_path *path)
 {
-        int status, i, index;
+        int status;
         struct ocfs2_dinode *fe;
-        struct ocfs2_extent_block *eb;
         struct ocfs2_extent_block *last_eb = NULL;
         struct ocfs2_extent_list *el;
-        struct buffer_head *eb_bh = NULL;
         struct buffer_head *last_eb_bh = NULL;
         u64 delete_blk = 0;
 
         fe = (struct ocfs2_dinode *) fe_bh->b_data;
 
-        status = ocfs2_find_new_last_ext_blk(inode,
-                                             le32_to_cpu(fe->i_clusters) -
-                                             clusters_to_del,
+        status = ocfs2_find_new_last_ext_blk(inode, clusters_to_del,
                                              path, &last_eb_bh);
         if (status < 0) {
                 mlog_errno(status);
@@ -3016,14 +3258,10 @@ static int ocfs2_do_truncate(struct ocfs2_super *osb,
          * Each component will be touched, so we might as well journal
          * here to avoid having to handle errors later.
          */
-        for (i = 0; i < path_num_items(path); i++) {
-                status = ocfs2_journal_access(handle, inode,
-                                              path->p_node[i].bh,
-                                              OCFS2_JOURNAL_ACCESS_WRITE);
-                if (status < 0) {
-                        mlog_errno(status);
-                        goto bail;
-                }
+        status = ocfs2_journal_access_path(inode, handle, path);
+        if (status < 0) {
+                mlog_errno(status);
+                goto bail;
         }
 
         if (last_eb_bh) {
@@ -3047,6 +3285,7 @@ static int ocfs2_do_truncate(struct ocfs2_super *osb,
                 ocfs2_error(inode->i_sb,
                             "Inode %lu has an empty extent record, depth %u\n",
                             inode->i_ino, le16_to_cpu(el->l_tree_depth));
+                status = -EROFS;
                 goto bail;
         }
 
@@ -3056,38 +3295,11 @@ static int ocfs2_do_truncate(struct ocfs2_super *osb,
         spin_unlock(&OCFS2_I(inode)->ip_lock);
         le32_add_cpu(&fe->i_clusters, -clusters_to_del);
 
-        i = le16_to_cpu(el->l_next_free_rec) - 1;
-
-        BUG_ON(le32_to_cpu(el->l_recs[i].e_clusters) < clusters_to_del);
-        le32_add_cpu(&el->l_recs[i].e_clusters, -clusters_to_del);
-        /* tree depth zero, we can just delete the clusters, otherwise
-         * we need to record the offset of the next level extent block
-         * as we may overwrite it. */
-        if (!el->l_tree_depth) {
-                delete_blk = le64_to_cpu(el->l_recs[i].e_blkno)
-                        + ocfs2_clusters_to_blocks(osb->sb,
-                                        le32_to_cpu(el->l_recs[i].e_clusters));
-
-                if (!el->l_recs[i].e_clusters) {
-                        /* if we deleted the whole extent record, then clear
-                         * out the other fields and update the extent
-                         * list.
-                         */
-                        el->l_recs[i].e_cpos = 0;
-                        el->l_recs[i].e_blkno = 0;
-                        BUG_ON(!el->l_next_free_rec);
-                        le16_add_cpu(&el->l_next_free_rec, -1);
-
-                        /*
-                         * The leftmost record might be an empty extent -
-                         * delete it here too.
-                         */
-                        if (i == 1 && ocfs2_is_empty_extent(&el->l_recs[0])) {
-                                el->l_recs[0].e_cpos = 0;
-                                el->l_recs[0].e_blkno = 0;
-                                el->l_next_free_rec = 0;
-                        }
-                }
+        status = ocfs2_trim_tree(inode, path, handle, tc,
+                                 clusters_to_del, &delete_blk);
+        if (status) {
+                mlog_errno(status);
+                goto bail;
         }
 
         if (le32_to_cpu(fe->i_clusters) == 0) {
@@ -3115,125 +3327,13 @@ static int ocfs2_do_truncate(struct ocfs2_super *osb,
                 }
         }
 
-        index = 1;
-        /* if our tree depth > 0, update all the tree blocks below us. */
-        while (index <= path->p_tree_depth) {
-                eb_bh = path->p_node[index].bh;
-                eb = (struct ocfs2_extent_block *)eb_bh->b_data;
-                el = path->p_node[index].el;
-
-                mlog(0, "traveling tree (index = %d, extent block: %llu)\n",
-                     index,  (unsigned long long)eb_bh->b_blocknr);
-
-                BUG_ON(le16_to_cpu(el->l_next_free_rec) == 0);
-                if (index !=
-                    (path->p_tree_depth - le16_to_cpu(el->l_tree_depth))) {
-                        ocfs2_error(inode->i_sb,
-                                    "Inode %lu has invalid ext. block %llu\n",
-                                    inode->i_ino,
-                                    (unsigned long long)eb_bh->b_blocknr);
-                        goto bail;
-                }
-
-                i = le16_to_cpu(el->l_next_free_rec) - 1;
-
-                mlog(0, "extent block %llu, before: record %d: "
-                     "(%u, %u, %llu), next = %u\n",
-                     (unsigned long long)le64_to_cpu(eb->h_blkno), i,
-                     le32_to_cpu(el->l_recs[i].e_cpos),
-                     le32_to_cpu(el->l_recs[i].e_clusters),
-                     (unsigned long long)le64_to_cpu(el->l_recs[i].e_blkno),
-                     le16_to_cpu(el->l_next_free_rec));
-
-                BUG_ON(le32_to_cpu(el->l_recs[i].e_clusters) < clusters_to_del);
-                le32_add_cpu(&el->l_recs[i].e_clusters, -clusters_to_del);
-
-                /* bottom-most block requires us to delete data.*/
-                if (!el->l_tree_depth)
-                        delete_blk = le64_to_cpu(el->l_recs[i].e_blkno)
-                                + ocfs2_clusters_to_blocks(osb->sb,
-                                        le32_to_cpu(el->l_recs[i].e_clusters));
-                if (!el->l_recs[i].e_clusters) {
-                        el->l_recs[i].e_cpos = 0;
-                        el->l_recs[i].e_blkno = 0;
-                        BUG_ON(!el->l_next_free_rec);
-                        le16_add_cpu(&el->l_next_free_rec, -1);
-                }
-                if (i == 1 && ocfs2_is_empty_extent(&el->l_recs[0])) {
-                        el->l_recs[0].e_cpos = 0;
-                        el->l_recs[0].e_blkno = 0;
-                        el->l_next_free_rec = 0;
-                }
-
-                mlog(0, "extent block %llu, after: record %d: "
-                     "(%u, %u, %llu), next = %u\n",
-                     (unsigned long long)le64_to_cpu(eb->h_blkno), i,
-                     le32_to_cpu(el->l_recs[i].e_cpos),
-                     le32_to_cpu(el->l_recs[i].e_clusters),
-                     (unsigned long long)le64_to_cpu(el->l_recs[i].e_blkno),
-                     le16_to_cpu(el->l_next_free_rec));
-
-                status = ocfs2_journal_dirty(handle, eb_bh);
+        if (delete_blk) {
+                status = ocfs2_truncate_log_append(osb, handle, delete_blk,
+                                                   clusters_to_del);
                 if (status < 0) {
                         mlog_errno(status);
                         goto bail;
                 }
-
-                if (!el->l_next_free_rec) {
-                        mlog(0, "deleting this extent block.\n");
-
-                        ocfs2_remove_from_cache(inode, eb_bh);
-
-                        BUG_ON(el->l_recs[0].e_clusters);
-                        BUG_ON(el->l_recs[0].e_cpos);
-                        BUG_ON(el->l_recs[0].e_blkno);
-
-                        /*
-                         * We need to remove this extent block from
-                         * the list above it.
-                         *
-                         * Since we've passed it already in this loop,
-                         * no need to worry about journaling.
-                         */
-                        el = path->p_node[index - 1].el;
-                        i = le16_to_cpu(el->l_next_free_rec) - 1;
-                        BUG_ON(i < 0);
-                        el->l_recs[i].e_cpos = 0;
-                        el->l_recs[i].e_clusters = 0;
-                        el->l_recs[i].e_blkno = 0;
-                        le16_add_cpu(&el->l_next_free_rec, -1);
-
-                        if (eb->h_suballoc_slot == 0) {
-                                /*
-                                 * This code only understands how to
-                                 * lock the suballocator in slot 0,
-                                 * which is fine because allocation is
-                                 * only ever done out of that
-                                 * suballocator too. A future version
-                                 * might change that however, so avoid
-                                 * a free if we don't know how to
-                                 * handle it. This way an fs incompat
-                                 * bit will not be necessary.
-                                 */
-                                status = ocfs2_free_extent_block(handle,
-                                                                 tc->tc_ext_alloc_inode,
-                                                                 tc->tc_ext_alloc_bh,
-                                                                 eb);
-                                if (status < 0) {
-                                        mlog_errno(status);
-                                        goto bail;
-                                }
-                        }
-                }
-                index++;
-        }
-
-        BUG_ON(!delete_blk);
-        status = ocfs2_truncate_log_append(osb, handle, delete_blk,
-                                           clusters_to_del);
-        if (status < 0) {
-                mlog_errno(status);
-                goto bail;
         }
         status = 0;
 bail:
@@ -3275,6 +3375,14 @@ int ocfs2_commit_truncate(struct ocfs2_super *osb,
         }
 start:
         /*
+         * Check that we still have allocation to delete.
+         */
+        if (OCFS2_I(inode)->ip_clusters == 0) {
+                status = 0;
+                goto bail;
+        }
+
+        /*
          * Truncate always works against the rightmost tree branch.
          */
         status = ocfs2_find_path(inode, path, UINT_MAX);
@@ -3298,6 +3406,15 @@ start:
          * - no record needs to be removed (truncate has completed)
          */
         el = path_leaf_el(path);
+        if (le16_to_cpu(el->l_next_free_rec) == 0) {
+                ocfs2_error(inode->i_sb,
+                            "Inode %llu has empty extent block at %llu\n",
+                            (unsigned long long)OCFS2_I(inode)->ip_blkno,
+                            (unsigned long long)path_leaf_bh(path)->b_blocknr);
+                status = -EROFS;
+                goto bail;
+        }
+
         i = le16_to_cpu(el->l_next_free_rec) - 1;
         range = le32_to_cpu(el->l_recs[i].e_cpos) +
                 le32_to_cpu(el->l_recs[i].e_clusters);
@@ -3359,10 +3476,11 @@ start:
         ocfs2_reinit_path(path, 1);
 
         /*
-         * Only loop if we still have allocation.
+         * The check above will catch the case where we've truncated
+         * away all allocation.
          */
-        if (OCFS2_I(inode)->ip_clusters)
-                goto start;
+        goto start;
+
 bail:
         up_write(&OCFS2_I(inode)->ip_alloc_sem);
 
@@ -3414,22 +3532,6 @@ int ocfs2_prepare_truncate(struct ocfs2_super *osb,
              "%llu\n", fe->i_clusters, new_i_clusters,
              (unsigned long long)fe->i_size);
 
-        if (!ocfs2_sparse_alloc(osb) &&
-            le32_to_cpu(fe->i_clusters) <= new_i_clusters) {
-                ocfs2_error(inode->i_sb, "Dinode %llu has cluster count "
-                            "%u and size %llu whereas struct inode has "
-                            "cluster count %u and size %llu which caused an "
-                            "invalid truncate to %u clusters.",
-                            (unsigned long long)le64_to_cpu(fe->i_blkno),
-                            le32_to_cpu(fe->i_clusters),
-                            (unsigned long long)le64_to_cpu(fe->i_size),
-                            OCFS2_I(inode)->ip_clusters, i_size_read(inode),
-                            new_i_clusters);
-                mlog_meta_lvb(ML_ERROR, &OCFS2_I(inode)->ip_meta_lockres);
-                status = -EIO;
-                goto bail;
-        }
-
         *tc = kzalloc(sizeof(struct ocfs2_truncate_context), GFP_KERNEL);
         if (!(*tc)) {
                 status = -ENOMEM;
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 8c97fa1c45f6..edc0b617f409 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -344,18 +344,6 @@ static int ocfs2_truncate_file(struct inode *inode,
         }
         ocfs2_data_unlock(inode, 1);
 
-        if (le32_to_cpu(fe->i_clusters) ==
-            ocfs2_clusters_for_bytes(osb->sb, new_i_size)) {
-                mlog(0, "fe->i_clusters = %u, so we do a simple truncate\n",
-                     fe->i_clusters);
-                /* No allocation change is required, so lets fast path
-                 * this truncate. */
-                status = ocfs2_simple_size_update(inode, di_bh, new_i_size);
-                if (status < 0)
-                        mlog_errno(status);
-                goto bail;
-        }
-
         /* alright, we're going to need to do a full blown alloc size
          * change. Orphan the inode so that recovery can complete the
          * truncate if necessary. This does the task of marking
@@ -785,7 +773,7 @@ static int ocfs2_extend_file(struct inode *inode,
                              size_t tail_to_skip)
 {
         int ret = 0;
-        u32 clusters_to_add;
+        u32 clusters_to_add = 0;
 
         BUG_ON(!tail_to_skip && !di_bh);
 
@@ -797,6 +785,11 @@ static int ocfs2_extend_file(struct inode *inode,
                 goto out;
         BUG_ON(new_i_size < i_size_read(inode));
 
+        if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
+                BUG_ON(tail_to_skip != 0);
+                goto out_update_size;
+        }
+
         clusters_to_add = ocfs2_clusters_for_bytes(inode->i_sb, new_i_size) - 
                 OCFS2_I(inode)->ip_clusters;
 
@@ -832,6 +825,7 @@ static int ocfs2_extend_file(struct inode *inode,
                 goto out_unlock;
         }
 
+out_update_size:
         if (!tail_to_skip) {
                 /* We're being called from ocfs2_setattr() which wants
                  * us to update i_size */
@@ -841,7 +835,8 @@ static int ocfs2_extend_file(struct inode *inode,
         }
 
 out_unlock:
-        ocfs2_data_unlock(inode, 1);
+        if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
+                ocfs2_data_unlock(inode, 1);
 
 out:
         return ret;
@@ -1097,6 +1092,14 @@ static int ocfs2_prepare_inode_for_write(struct dentry *dentry,
                 } else {
                         saved_pos = *ppos;
                 }
+
+                /*
+                 * The rest of this loop is concerned with legacy file
+                 * systems which don't support sparse files.
+                 */
+                if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
+                        break;
+
                 newsize = count + saved_pos;
 
                 mlog(0, "pos=%lld newsize=%lld cursize=%lld\n",
diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 5ff8549eb1a3..0bd86a137591 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -487,7 +487,6 @@ static int ocfs2_truncate_for_delete(struct ocfs2_super *osb,
                                      struct buffer_head *fe_bh)
 {
         int status = 0;
-        handle_t *handle = NULL;
         struct ocfs2_truncate_context *tc = NULL;
         struct ocfs2_dinode *fe;
 
@@ -495,41 +494,20 @@ static int ocfs2_truncate_for_delete(struct ocfs2_super *osb,
 
         fe = (struct ocfs2_dinode *) fe_bh->b_data;
 
-        /* zero allocation, zero truncate :) */
-        if (!fe->i_clusters)
-                goto bail;
-
-        handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
-        if (IS_ERR(handle)) {
-                status = PTR_ERR(handle);
-                handle = NULL;
-                mlog_errno(status);
-                goto bail;
-        }
-
-        status = ocfs2_set_inode_size(handle, inode, fe_bh, 0ULL);
-        if (status < 0) {
-                mlog_errno(status);
-                goto bail;
-        }
-
-        ocfs2_commit_trans(osb, handle);
-        handle = NULL;
-
-        status = ocfs2_prepare_truncate(osb, inode, fe_bh, &tc);
-        if (status < 0) {
-                mlog_errno(status);
-                goto bail;
-        }
+        if (fe->i_clusters) {
+                status = ocfs2_prepare_truncate(osb, inode, fe_bh, &tc);
+                if (status < 0) {
+                        mlog_errno(status);
+                        goto out;
+                }
 
-        status = ocfs2_commit_truncate(osb, inode, fe_bh, tc);
-        if (status < 0) {
-                mlog_errno(status);
-                goto bail;
+                status = ocfs2_commit_truncate(osb, inode, fe_bh, tc);
+                if (status < 0) {
+                        mlog_errno(status);
+                        goto out;
+                }
         }
-bail:
-        if (handle)
-                ocfs2_commit_trans(osb, handle);
+out:
 
         mlog_exit(status);
         return status;