Re: [PATCH] nfsd: fix inverted cp_ttl check in async copy reaper

[Jeff Layton <jlayton@kernel.org>]

On Thu, 2026-05-21 at 09:25 -0400, Jeff Layton wrote:
> nfsd4_async_copy_reaper() is supposed to keep completed async copy
> state around for NFSD_COPY_INITIAL_TTL (10) laundromat ticks so
> that OFFLOAD_STATUS can report the result, then reap the state once
> the countdown expires.
> 
> The TTL predicate is inverted: `if (--copy->cp_ttl)` is true while
> ticks remain and false when the counter reaches zero.  This causes
> the copy to be reaped on the very first tick (cp_ttl goes from 10
> to 9, which is non-zero) instead of after all 10 ticks elapse.
> Once reaped, OFFLOAD_STATUS returns NFS4ERR_BAD_STATEID because
> the copy state has already been freed.
> 
> A secondary consequence: if cp_ttl ever reached zero (not possible
> with the current initial value of 10 since the copy is reaped at
> 9), the copy would never be added to the reaplist and would leak
> indefinitely on clp->async_copies.
> 
> Fix by negating the test so that cleanup runs when the TTL expires.
> 
> Fixes: 26e6e6939369 ("NFSD: Add nfsd4_copy time-to-live")
> Cc: stable@vger.kernel.org

Mea culpa. This doesn't need to go to stable so we can drop that tag.
It's a bug, but not one that results in a crash or data corruption or
anything. Also, this should have:

Assisted-by: kres:claude-opus-4-6

> Reported-by: Chris Mason <clm@meta.com>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  fs/nfsd/nfs4proc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 85e94c30285a..72f410fd7a8a 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -1467,7 +1467,7 @@ void nfsd4_async_copy_reaper(struct nfsd_net *nn)
>  		list_for_each_safe(pos, next, &clp->async_copies) {
>  			copy = list_entry(pos, struct nfsd4_copy, copies);
>  			if (test_bit(NFSD4_COPY_F_OFFLOAD_DONE, &copy->cp_flags)) {
> -				if (--copy->cp_ttl) {
> +				if (!--copy->cp_ttl) {
>  					list_del_init(&copy->copies);
>  					list_add(&copy->copies, &reaplist);
>  				}
> 
> ---
> base-commit: e91f16e59f513a1e3fc052e2b630efebeaf9a4f2
> change-id: 20260521-async_copy_reaper_cp_ttl_inverted-697a0a3c850b
> 
> Best regards,

-- 
Jeff Layton <jlayton@kernel.org>