[PATCH 3/4] xfs: make xfs_inode_set_eofblocks_tag cheaper for the common case

[Brian Foster]

On Fri, Aug 26, 2016 at 04:26:16PM +0200, Christoph Hellwig wrote:
> On Thu, Aug 25, 2016 at 08:38:09AM -0400, Brian Foster wrote:
> > I'm guessing the lockless check is intentional, but is that really
> > necessary? E.g., it doesn't seem like using ->i_flags_lock
> > unconditionally should affect performance in the way the AG lock or
> > radix tree work does, particularly since we're already holding
> > IOLOCK_EXCL in the current implementation. I could be wrong, but FWIW,
> > we do already have xfs_iflags_test_and_set() sitting around as well...
> 
> I don't think taking it should be too bad, but given the ops ordering
> it also seems entirely pointless to even take it.
> 

Then why are we taking it? I assumed it at least served as a memory
barrier...

Brian

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