Re: [PATCH] xfs: i_state of inode is changed after the inode is freed

Masayuki Saito
2006-08-22T07:59:29Z

Hi Nathan, David,

I had the vacation too.

David Chinner <dgc@sgi.com> wrote:
>Hmmm - Idon't think we should iput() before we wake up any pinned waiters.
>When we have a waiter on i_ipin_wait (called from xfs_iflush()), we have
>a thread sleeping with the inode locked.
>
>If we then call iput() and it drops the last reference, we can call back
>into the filesystem and start transactions. Those transactions will need
>to lock the inode. Hence I think the above can deadlock when racing against
>an inode flush.
>
>The code should probably read:
>
> if (dropped last pincount) {
> int need_iput = 0;
> struct inode *inode;
>
> spin_lock(i_flags_lock)
> if (!reclaimable) {
> if (!vp) {
> if (!(i_state & (NEW|CLEAR))) {
> inode = igrab(inode)
> if (inode) {
> need_iput = 1
> mark_inode_dirty_sync(inode)
> }
> }
> }
> }
> spin_unlock(i_flags_lock)
> wake_up(&ip->i_ipin_wait)
> if (need_iput)
> iput(inode);
> }
>
>to avoid this possible deadlock.

OK, I see your point. There is wait_event(in xfs_iunpin_wait) that should
be wake_up'ed(in xfs_iunpin), so deadlock can occur.

I'll update my patch and test it. Please wait for a few moments.