Re: [PATCH] fs: dcache: Avoid livelock between d_alloc_parallel and __d_add

[Matthew Wilcox]

On Tue, Feb 13, 2018 at 12:58:51PM +0000, Will Deacon wrote:
> This patch resolves the livelock by not taking hlist_bl_lock in
> d_alloc_parallel if the sequence counter is odd, since any subsequent
> masked comparison with i_dir_seq will fail anyway.
> 
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Will Deacon <will.deacon@xxxxxxx>

Reviewed-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>

I wonder whether it makes sense to turn i_dir_seq into a seqcount_t,
which would give us the lockdep checking as well.