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>

1 files changed, 12 insertions, 34 deletions

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;