On Tue, May 27, 2014 at 03:44:28AM -0700, Christoph Hellwig wrote:
> On Fri, May 23, 2014 at 07:52:28AM -0400, Brian Foster wrote:
> > The scan owner field represents an optional inode number that is
> > responsible for the current scan. The purpose is to identify that an
> > inode is under iolock and as such, the iolock shouldn't be attempted
> > when trimming eofblocks. This is an internal only field.
> xfs_free_eofblocks already does a trylock, and without that calling it
> from one iolock holding process to another would be a deadlock waiting
> to happen.
> I have to say I'm still not very easy with iolock nesting, even if it's
> a trylock.
Right... maybe I'm not parsing your point. The purpose here is to avoid
the trylock entirely. E.g., Indicate that we have already acquired the
lock and can proceed with xfs_free_eofblocks(), rather than fail a
trylock and skip (which appears to be a potential infinite loop scenario
here due to how the AG walking code handles EAGAIN).