Re: [BACKPORT 4.4.y 20/25] Hang/soft lockup in d_invalidate with simultaneous calls

[Greg KH]

On Fri, Mar 22, 2019 at 04:44:11PM +0100, Arnd Bergmann wrote:
> From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> 
> It's not hard to trigger a bunch of d_invalidate() on the same
> dentry in parallel.  They end up fighting each other - any
> dentry picked for removal by one will be skipped by the rest
> and we'll go for the next iteration through the entire
> subtree, even if everything is being skipped.  Morevoer, we
> immediately go back to scanning the subtree.  The only thing
> we really need is to dissolve all mounts in the subtree and
> as soon as we've nothing left to do, we can just unhash the
> dentry and bugger off.
> 
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> (cherry picked from commit 81be24d263dbeddaba35827036d6f6787a59c2c3)
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  fs/dcache.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)

Also added to 4.9.y