Re: [PATCH v4 0/9] nfs: prepare for locking changes.

[Anna Schumaker]

Hi Neil,

On Tue, Oct 27, 2026, at 9:06 PM, NeilBrown wrote:
> Now that the requirement for this are upstream this could go via the NFS
> tree or the VFS tree.

Sounds good! I think we should plan to take this through the NFS tree.

Thanks,
Anna

>
> Thanks,
> NeilBrown
>
>
> This v4 fixes the problems with patch 1 which Jonathan Flynn helped me
> to understand.  And *actually* adds Anna's Acked-by.
>
> Before this v3 fixed three bugs found by Sashiko - all
> error-path related.
>
> 1/ patch 5 - make sure d_drop() gets called in all error cases
> 2/ patch 8 - dput() sdentry on all error paths
> 3/ patch 9 - check error return from d_duplicate() correctly.
>
> Original intro:
> I am working on changes to directory locking.  The medium term goal is
> to lift d_alloc_parallel() locking above i_rwsem, so d_alloc_paralle()
> can be run unlocked, and consequently cannot be called when ->i_rwsem is
> held.
>
> The requires:
>  1/ the d_alloc_parallel() not be called while i_rwsem is held.  NFS does
>     this in a few places. New interfaces d_alloc_trylock() and d_duplicate()
>     are now available and can be used instead.
>
>  2/ a dentry must not be d_drop()ed while an operation is ongoing, as an
>     unlocked d_alloc_parallel() would then be able to create a new
>     dentry with the same name.  In particular d_rehash() must be phased
>     out as it won't be safe.  Various techiniques are used to avoid the
>     need for d_drop(), particularly that d_splice_alias() is now able to
>     splice a hashed alias.
>
> Further, the first two patches here fixes bugs that I found while
> developing and reviewing these changes.
>
>
>  [PATCH v4 1/9] nfs: fix open-blocking with d_fsdata
>  [PATCH v4 2/9] nfs: fix nfs_call_unlink()
>  [PATCH v4 3/9] nfs: remove d_drop()/d_alloc_parallel() from
>  [PATCH v4 4/9] nfs: use d_splice_alias() in nfs_link()
>  [PATCH v4 5/9] nfs: don't d_drop() before d_splice_alias()
>  [PATCH v4 6/9] nfs: don't d_drop() before d_splice_alias() in
>  [PATCH v4 7/9] nfs: Use d_alloc_trylock() in nfs_prime_dcache()
>  [PATCH v4 8/9] nfs: use d_alloc_trylock() in silly-rename
>  [PATCH v4 9/9] nfs: use d_duplicate()