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

[Christoph Hellwig <hch@xxxxxx>]

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.