ocfs2: Rework transaction rollback in ocfs2_relink_block_group()

From: Jie Liu <[email protected]>

In ocfs2_relink_block_group(), we roll back all those changes if notify intent to modify buffers for metadata update failed even if the relevant buffer has not yet been modified/got dirty at that point, that are not quite right because of:

- None buffer has been modified/dirty if failed to call ocfs2_journal_access_gd() against the previous block group buffer
- Only the previous block group buffer has got dirty if failed to call ocfs2_journal_access_gd() against the block group buffer
- There is no need to roll back the change for file entry buffer at all

Those problems will not cause anything wrong but unnecessary. This patch fix them and kill the useless bg_ptr variable as well.

Signed-off-by Jie Liu <[email protected]>

---
 fs/ocfs2/suballoc.c |   25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

fs/ocfs2/suballoc.c +0 -0

index b7e74b5..101d16d 100644

fs/ocfs2/suballoc.c +11 -12

 	struct ocfs2_group_desc *prev_bg = (struct ocfs2_group_desc *) prev_bg_bh->b_data;

@@ -1437,7 +1437,6 @@ static int ocfs2_relink_block_group(handle_t *handle,
 		(unsigned long long)le64_to_cpu(bg->bg_blkno),
 		(unsigned long long)le64_to_cpu(prev_bg->bg_blkno));
 
-	fe_ptr = le64_to_cpu(fe->id2.i_chain.cl_recs[chain].c_blkno);
 	bg_ptr = le64_to_cpu(bg->bg_next_group);
 	prev_bg_ptr = le64_to_cpu(prev_bg->bg_next_group);
 

@@ -1446,7 +1445,7 @@ static int ocfs2_relink_block_group(handle_t *handle,
 					 OCFS2_JOURNAL_ACCESS_WRITE);
 	if (status < 0) {
 		mlog_errno(status);
-		goto out_rollback;
+		goto out;
 	}
 
 	prev_bg->bg_next_group = bg->bg_next_group;

@@ -1456,7 +1455,7 @@ static int ocfs2_relink_block_group(handle_t *handle,
 					 bg_bh, OCFS2_JOURNAL_ACCESS_WRITE);
 	if (status < 0) {
 		mlog_errno(status);
-		goto out_rollback;
+		goto out_rollback_prev_bg;
 	}
 
 	bg->bg_next_group = fe->id2.i_chain.cl_recs[chain].c_blkno;

@@ -1466,21 +1465,21 @@ static int ocfs2_relink_block_group(handle_t *handle,
 					 fe_bh, OCFS2_JOURNAL_ACCESS_WRITE);
 	if (status < 0) {
 		mlog_errno(status);
-		goto out_rollback;
+		goto out_rollback_bg;
 	}
 
 	fe->id2.i_chain.cl_recs[chain].c_blkno = bg->bg_blkno;
 	ocfs2_journal_dirty(handle, fe_bh);
 
-out_rollback:
-	if (status < 0) {
-		fe->id2.i_chain.cl_recs[chain].c_blkno = cpu_to_le64(fe_ptr);
-		bg->bg_next_group = cpu_to_le64(bg_ptr);
-		prev_bg->bg_next_group = cpu_to_le64(prev_bg_ptr);
-	}
+out:
+	return status;
 
-	if (status)
-		mlog_errno(status);
+out_rollback_bg:
+	bg->bg_next_group = cpu_to_le64(bg_ptr);
+out_rollback_prev_bg:
+	prev_bg->bg_next_group = cpu_to_le64(prev_bg_ptr);
+
+	mlog_errno(status);
 	return status;
 }
 

Hi Jeff,
There may be a mistake in the patch. See my comments below.

Quoted 21 lines · Jeff Liu

From: Jie Liu <[email protected]>

In ocfs2_relink_block_group(), we roll back all those changes if notify intent to modify buffers for metadata update failed even if the relevant buffer has not yet been modified/got dirty at that point, that are not quite right because of:

- None buffer has been modified/dirty if failed to call ocfs2_journal_access_gd() against the previous block group buffer
- Only the previous block group buffer has got dirty if failed to call ocfs2_journal_access_gd() against the block group buffer
- There is no need to roll back the change for file entry buffer at all

Those problems will not cause anything wrong but unnecessary. This patch fix them and kill the useless bg_ptr variable as well.

Signed-off-by Jie Liu <[email protected]>

---
 fs/ocfs2/suballoc.c |   25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

fs/ocfs2/suballoc.c static int ocfs2_relink_block_group(handle_t *handle, · line 1425

Quoted 9 lines

fs/ocfs2/suballoc.c +0 -1

index b7e74b5..101d16d 100644
@@ -1422,7 +1422,7 @@ static int ocfs2_relink_block_group(handle_t *handle,
 	int status;
 	/* there is a really tiny chance the journal calls could fail,
 	 * but we wouldn't want inconsistent blocks in *any* case. */
-	u64 fe_ptr, bg_ptr, prev_bg_ptr;

Why remove bg_ptr and prev_bg_ptr from the context? bg_ptr and prev_bg_ptr are also usable.

Quoted 60 lines

fs/ocfs2/suballoc.c +11 -12

 	struct ocfs2_group_desc *prev_bg = (struct ocfs2_group_desc *) prev_bg_bh->b_data;

@@ -1437,7 +1437,6 @@ static int ocfs2_relink_block_group(handle_t *handle,
 		(unsigned long long)le64_to_cpu(bg->bg_blkno),
 		(unsigned long long)le64_to_cpu(prev_bg->bg_blkno));
 
-	fe_ptr = le64_to_cpu(fe->id2.i_chain.cl_recs[chain].c_blkno);
 	bg_ptr = le64_to_cpu(bg->bg_next_group);
 	prev_bg_ptr = le64_to_cpu(prev_bg->bg_next_group);
 

@@ -1446,7 +1445,7 @@ static int ocfs2_relink_block_group(handle_t *handle,
 					 OCFS2_JOURNAL_ACCESS_WRITE);
 	if (status < 0) {
 		mlog_errno(status);
-		goto out_rollback;
+		goto out;
 	}
 
 	prev_bg->bg_next_group = bg->bg_next_group;

@@ -1456,7 +1455,7 @@ static int ocfs2_relink_block_group(handle_t *handle,
 					 bg_bh, OCFS2_JOURNAL_ACCESS_WRITE);
 	if (status < 0) {
 		mlog_errno(status);
-		goto out_rollback;
+		goto out_rollback_prev_bg;
 	}
 
 	bg->bg_next_group = fe->id2.i_chain.cl_recs[chain].c_blkno;

@@ -1466,21 +1465,21 @@ static int ocfs2_relink_block_group(handle_t *handle,
 					 fe_bh, OCFS2_JOURNAL_ACCESS_WRITE);
 	if (status < 0) {
 		mlog_errno(status);
-		goto out_rollback;
+		goto out_rollback_bg;
 	}
 
 	fe->id2.i_chain.cl_recs[chain].c_blkno = bg->bg_blkno;
 	ocfs2_journal_dirty(handle, fe_bh);
 
-out_rollback:
-	if (status < 0) {
-		fe->id2.i_chain.cl_recs[chain].c_blkno = cpu_to_le64(fe_ptr);
-		bg->bg_next_group = cpu_to_le64(bg_ptr);
-		prev_bg->bg_next_group = cpu_to_le64(prev_bg_ptr);
-	}
+out:
+	return status;
 
-	if (status)
-		mlog_errno(status);
+out_rollback_bg:
+	bg->bg_next_group = cpu_to_le64(bg_ptr);
+out_rollback_prev_bg:
+	prev_bg->bg_next_group = cpu_to_le64(prev_bg_ptr);
+
+	mlog_errno(status);
 	return status;
 }