Messages in this thread | | | Date | Wed, 6 Dec 2017 09:02:42 +0800 | From | alex chen <> | Subject | Re: [PATCH 4.4 13/16] ocfs2: should wait dio before inode lock in ocfs2_setattr() |
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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@huawei.com> >> >> 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. >
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