Hi Ben, Thanks for your reply. On 2017/12/5 23:49, Ben Hutchings wrote: > On Wed, 2017-11-22 at 11:12 +0100, Greg Kroah-Hartman wrote: >> 4.4-stable review patch. If anyone has any objections, please let me know. >> >> ------------------ >> >> From: alex chen <alex.chen@xxxxxxxxxx> >> >> commit 28f5a8a7c033cbf3e32277f4cc9c6afd74f05300 upstream. >> >> we should wait dio requests to finish before inode lock in >> ocfs2_setattr(), otherwise the following deadlock will happen: > [...] > > I looked at the kernel-doc for inode_dio_wait(): > > /** > * inode_dio_wait - wait for outstanding DIO requests to finish > * @inode: inode to wait for > * > * Waits for all pending direct I/O requests to finish so that we can > * proceed with a truncate or equivalent operation. > * > * Must be called under a lock that serializes taking new references > * to i_dio_count, usually by inode->i_mutex. > */ > > Now that ocfs2_setattr() calls this outside of the inode locked region, > what prevents another task adding a new dio request immediately > afterward? > In the kernel 4.6, firstly, we use the inode_lock() in do_truncate() to prevent another bio to be issued from this node. Furthermore, we use the ocfs2_rw_lock() and ocfs2_inode_lock() in ocfs2_setattr() to guarantee no more bio will be issued from the other nodes in this cluster. > Also, ocfs2_dio_end_io_write() was introduced in 4.6 and it looks like > the dio completion path didn't previously take the inode lock. So it > doesn't look this fix is needed in 3.18 or 4.4. Yes, ocfs2_dio_end_io_write() was introduced in 4.6 and the problem this patch fixes is only exist in the kernel 4.6 and above 4.6. I'm sorry that I don't clearly point out which the stable version of kernel this patch will fixes. Thanks, Alex > > Ben. >