ocfs2: skip existing hole when removing the last extent_rec in punching-hole codes.

In the case of removing a partial extent record which covers a hole, current
punching-hole logic will try to remove more than the length of whole extent
record, which leads to the failure of following assert(fs/ocfs2/alloc.c):

5507         BUG_ON(cpos < le32_to_cpu(rec->e_cpos) || trunc_range > rec_range);

This patch tries to skip existing hole at the last attempt of removing a partial
extent record, what's more, it also adds some necessary comments for better
understanding of punching-hole codes.

Signed-off-by: Tristan Ye <tristan.ye@oracle.com>
Signed-off-by: Joel Becker <jlbec@evilplan.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 41565ae52856..89659d6dc206 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -1607,6 +1607,9 @@ static void ocfs2_calc_trunc_pos(struct inode *inode,
         range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);
 
         if (le32_to_cpu(rec->e_cpos) >= trunc_start) {
+                /*
+                 * remove an entire extent record.
+                 */
                 *trunc_cpos = le32_to_cpu(rec->e_cpos);
                 /*
                  * Skip holes if any.
@@ -1617,7 +1620,16 @@ static void ocfs2_calc_trunc_pos(struct inode *inode,
                 *blkno = le64_to_cpu(rec->e_blkno);
                 *trunc_end = le32_to_cpu(rec->e_cpos);
         } else if (range > trunc_start) {
+                /*
+                 * remove a partial extent record, which means we're
+                 * removing the last extent record.
+                 */
                 *trunc_cpos = trunc_start;
+                /*
+                 * skip hole if any.
+                 */
+                if (range < *trunc_end)
+                        *trunc_end = range;
                 *trunc_len = *trunc_end - trunc_start;
                 coff = trunc_start - le32_to_cpu(rec->e_cpos);
                 *blkno = le64_to_cpu(rec->e_blkno) +