From: Jinke Han hanjinke.666@bytedance.com
stable inclusion from stable-v5.10.150 commit 74d2a398d2d8c54d6468bc1e9da60ed9f3c4739f category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I6D0XA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit d1052d236eddf6aa851434db1897b942e8db9921 upstream.
In our product environment, we encounter some jbd hung waiting handles to stop while several writters were doing memory reclaim for buffer head allocation in delay alloc write path. Ext4 do buffer head allocation with holding transaction handle which may be blocked too long if the reclaim works not so smooth. According to our bcc trace, the reclaim time in buffer head allocation can reach 258s and the jbd transaction commit also take almost the same time meanwhile. Except for these extreme cases, we often see several seconds delays for cgroup memory reclaim on our servers. This is more likely to happen considering docker environment.
One thing to note, the allocation of buffer heads is as often as page allocation or more often when blocksize less than page size. Just like page cache allocation, we should also place the buffer head allocation before startting the handle.
Cc: stable@kernel.org Signed-off-by: Jinke Han hanjinke.666@bytedance.com Link: https://lore.kernel.org/r/20220903012429.22555-1-hanjinke.666@bytedance.com Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- fs/ext4/inode.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 91e3c112d0f3..cb74c2f7903c 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1180,6 +1180,13 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping, page = grab_cache_page_write_begin(mapping, index, flags); if (!page) return -ENOMEM; + /* + * The same as page allocation, we prealloc buffer heads before + * starting the handle. + */ + if (!page_has_buffers(page)) + create_empty_buffers(page, inode->i_sb->s_blocksize, 0); + unlock_page(page);
retry_journal: