[Ocfs2-devel] Ocfs2-devel Digest, Vol 135, Issue 28
Zhangguanghui
zhang.guanghui at h3c.com
Wed Jun 10 20:05:04 PDT 2015
I think the patch has a potential risk. as follows
Callback： ocfs2_write_end_nolock->ocfs2_journal_access_di->__ocfs2_journal_access->buffer_uptodate
So it increases the probability triggering BUG in the __ocfs2_journal_access().
In addition, test results have been confirmed.
Finally, any feedback about this process (positive or negative) would be greatly appreciated.
From: ocfs2-devel-bounces at oss.oracle.com<mailto:ocfs2-devel-bounces at oss.oracle.com>
Date: 2015-05-31 03:00
To: ocfs2-devel at oss.oracle.com<mailto:ocfs2-devel at oss.oracle.com>
Subject: Ocfs2-devel Digest, Vol 135, Issue 28
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Today's Topics:
1. [PATCH V2] ocfs2: call ocfs2_journal_access_di() before
ocfs2_journal_dirty() in ocfs2_write_end_nolock() (yangwenfang)
----------------------------------------------------------------------
Message: 1
Date: Sat, 30 May 2015 18:08:43 +0800
From: yangwenfang <vicky.yangwenfang at huawei.com>
Subject: [Ocfs2-devel] [PATCH V2] ocfs2: call
ocfs2_journal_access_di() before ocfs2_journal_dirty() in
ocfs2_write_end_nolock()
To: Andrew Morton <akpm at linux-foundation.org>, <mfasheh at suse.com>
Cc: ocfs2-devel at oss.oracle.com
Message-ID: <55698C2B.9000801 at huawei.com>
Content-Type: text/plain; charset="ISO-8859-1"
1.After we call ocfs2_journal_access_di() in ocfs2_write_begin(),
jbd2_journal_restart() may also be called, in this function
transaction A's t_updates-- and obtains a new transaction B.
If jbd2_journal_commit_transaction() is happened to commit
transaction A, when t_updates==0, it will continue to complete
commit and unfile buffer.
So when jbd2_journal_dirty_metadata(), the handle is pointed a new
transaction B, and the buffer head's journal head is already freed,
jh->b_transaction == NULL, jh->b_next_transaction == NULL,
it returns EINVAL, So it triggers the BUG_ON(status).
thread 1 jbd2
ocfs2_write_begin jbd2_journal_commit_transaction
ocfs2_write_begin_nolock
ocfs2_start_trans
jbd2__journal_start(t_updates+1,
transaction A)
ocfs2_journal_access_di
ocfs2_write_cluster_by_desc
ocfs2_mark_extent_written
ocfs2_change_extent_flag
ocfs2_split_extent
ocfs2_extend_rotate_transaction
jbd2_journal_restart
(t_updates-1,transaction B) t_updates==0
__jbd2_journal_refile_buffer
(jh->b_transaction = NULL)
ocfs2_write_end
ocfs2_write_end_nolock
ocfs2_journal_dirty
jbd2_journal_dirty_metadata(bug)
ocfs2_commit_trans
2. In ext4, I found that: jbd2_journal_get_write_access() called by
ext4_write_end.
ext4_write_begin
ext4_journal_start
__ext4_journal_start_sb
ext4_journal_check_start
jbd2__journal_start
ext4_write_end
ext4_mark_inode_dirty
ext4_reserve_inode_write
ext4_journal_get_write_access
jbd2_journal_get_write_access
ext4_mark_iloc_dirty
ext4_do_update_inode
ext4_handle_dirty_metadata
jbd2_journal_dirty_metadata
3.So I think we should put ocfs2_journal_access_di before
ocfs2_journal_dirty in the ocfs2_write_end.
and it works well after my modification.
Signed-off-by: vicky <vicky.yangwenfang at huawei.com>
---
fs/ocfs2/aops.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index f906a25..f3d7e52 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -2176,10 +2176,7 @@ try_again:
if (ret)
goto out_commit;
}
- /*
- * We don't want this to fail in ocfs2_write_end(), so do it
- * here.
- */
+
ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), wc->w_di_bh,
OCFS2_JOURNAL_ACCESS_WRITE);
if (ret) {
@@ -2336,7 +2333,7 @@ int ocfs2_write_end_nolock(struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
struct page *page, void *fsdata)
{
- int i;
+ int i, ret;
unsigned from, to, start = pos & (PAGE_CACHE_SIZE - 1);
struct inode *inode = mapping->host;
struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
@@ -2345,6 +2342,14 @@ int ocfs2_write_end_nolock(struct address_space *mapping,
handle_t *handle = wc->w_handle;
struct page *tmppage;
+ ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), wc->w_di_bh,
+ OCFS2_JOURNAL_ACCESS_WRITE);
+ if (ret) {
+ copied = ret;
+ mlog_errno(ret);
+ goto out;
+ }
+
if (OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) {
ocfs2_write_end_inline(inode, pos, len, &copied, di, wc);
goto out_write_size;
@@ -2400,6 +2405,7 @@ out_write_size:
ocfs2_update_inode_fsync_trans(handle, inode, 1);
ocfs2_journal_dirty(handle, wc->w_di_bh);
+out:
/* unlock pages before dealloc since it needs acquiring j_trans_barrier
* lock, or it will cause a deadlock since journal commit threads holds
* this lock and will ask for the page lock when flushing the data.
--
1.7.12.4
------------------------------
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