Messages in this thread | | | Subject | Re: [Ocfs2-devel] [PATCH v2] ocfs2: Fix handle refcount leak in two exception handling paths | From | Joseph Qi <> | Date | Fri, 10 Sep 2021 09:53:57 +0800 |
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On 9/10/21 1:48 AM, Wengang Wang wrote: > > > On Sep 9, 2021, at 4:07 AM, Joseph Qi <joseph.qi@linux.alibaba.com<mailto:joseph.qi@linux.alibaba.com>> wrote: > > Hi Wengang, > > On 9/9/21 1:12 AM, Wengang Wang wrote: > Hi, > > Sorry for late involving, but this doesn’t look right to me. > > On Sep 8, 2021, at 3:51 AM, Joseph Qi <joseph.qi@linux.alibaba.com<mailto:joseph.qi@linux.alibaba.com>> wrote: > > > > On 9/8/21 6:20 PM, Chenyuan Mi wrote: > The reference counting issue happens in two exception handling paths > of ocfs2_replay_truncate_records(). When executing these two exception > handling paths, the function forgets to decrease the refcount of handle > increased by ocfs2_start_trans(), causing a refcount leak. > > Fix this issue by using ocfs2_commit_trans() to decrease the refcount > of handle in two handling paths. > > Signed-off-by: Chenyuan Mi <cymi20@fudan.edu.cn<mailto:cymi20@fudan.edu.cn>> > Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn<mailto:xiyuyang19@fudan.edu.cn>> > Signed-off-by: Xin Tan <tanxin.ctf@gmail.com<mailto:tanxin.ctf@gmail.com>> > > Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com<mailto:joseph.qi@linux.alibaba.com>> > --- > fs/ocfs2/alloc.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c > index f1cc8258d34a..b05fde7edc3a 100644 > --- a/fs/ocfs2/alloc.c > +++ b/fs/ocfs2/alloc.c > @@ -5940,6 +5940,7 @@ static int ocfs2_replay_truncate_records(struct ocfs2_super *osb, > status = ocfs2_journal_access_di(handle, INODE_CACHE(tl_inode), tl_bh, > OCFS2_JOURNAL_ACCESS_WRITE); > if (status < 0) { > + ocfs2_commit_trans(osb, handle); > mlog_errno(status); > goto bail; > } > @@ -5964,6 +5965,7 @@ static int ocfs2_replay_truncate_records(struct ocfs2_super *osb, > data_alloc_bh, start_blk, > num_clusters); > if (status < 0) { > + ocfs2_commit_trans(osb, handle); > > As a transaction, stuff expected to be in the same handle should be treated as atomic. > Here the stuff includes the tl_bh and other metadata block which will be modified in ocfs2_free_clusters(). > Coming here, some of related meta blocks may be in the handle but others are not due to the error happened. > If you do a commit, partial meta blocks are committed to log. — that breaks the atomic idea, it will cause FS inconsistency. > So what’s reason you want to commit the meta block changes, which is not all of expected, in this handle to journal log? > > Do you really see a hit on the failure? or just you detected the refcount leak by code review? > > You may want to look at ocfs2_journal_dirty() for the error handling part. > > > For the first error handling, since we don't call ocfs2_journal_dirty() > yet, so won't be a problem. > For the second error handling, I think we don't have a better way. Look > at other callers of ocfs2_free_clusters(), we simply ignore the error > code. > Anyway, we should commit transaction if starts, otherwise journal will > be abnormal. > > I don't think so. If error happened, we should fail ocfs2, rather than do a partial committing. >
Umm... not exactly... Take ocfs2_free_clusters() for example, when it fails in case of EIO or ENOMEM, we can't just abort journal in such cases, because it is not so serious, only a bit blocks still occupied and they will recovery during the next mount. That's why we have "errors=continue" in most filesystems, we should always consider the business continuity first. Also you can look at ext4_free_blocks() for reference.
Thanks, Joseph
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