From f5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Fri, 22 May 2026 16:37:23 -0400 Subject: [PATCH] nfsd: Reset write verifier when async COPY writeback fails Async COPY captures nn->writeverf at request time and reports it to the client via CB_OFFLOAD after the worker kthread completes. When the post-copy vfs_fsync_range() or filemap_check_wb_err() in _nfsd_copy_file_range() reports an error, the worker correctly leaves NFSD4_COPY_F_COMMITTED clear so that CB_OFFLOAD encodes wr_stable_how as NFS_UNSTABLE, but the server's write verifier is not rotated. A client that receives NFS_UNSTABLE in CB_OFFLOAD follows up with COMMIT to make the copied data durable. With the verifier unchanged, COMMIT returns the same value the client just received via CB_OFFLOAD, and the client concludes the copy is durable -- silently dropping the data whose writeback in fact failed. This violates the UNSTABLE+COMMIT durability contract (RFC 7862 section 15.1, RFC 8881 section 18.32) and matches the bug just fixed in nfsd_vfs_write() and nfsd_commit(). Rotate nn->writeverf at the writeback-failure site. The async COPY worker has no svc_rqst, so commit_reset_write_verifier() is not available here; calling nfsd_reset_write_verifier() directly mirrors the trace-less reset already used by nfsd_file_check_write_error() for the same purpose. Filter out -EAGAIN and -ESTALE, matching commit_reset_write_verifier(), since neither indicates a durable-storage failure. Fixes: eac0b17a77fb ("NFSD add vfs_fsync after async copy is done") Cc: stable@vger.kernel.org Assisted-by: kres:claude-opus-4-7 Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260522203723.446841-1-cel@kernel.org Signed-off-by: Chuck Lever --- fs/nfsd/nfs4proc.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c index 8561540ab2db..93fcaf90d6ae 100644 --- a/fs/nfsd/nfs4proc.c +++ b/fs/nfsd/nfs4proc.c @@ -1972,6 +1972,8 @@ static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy, status = filemap_check_wb_err(dst->f_mapping, since); if (!status) set_bit(NFSD4_COPY_F_COMMITTED, ©->cp_flags); + else if (status != -EAGAIN && status != -ESTALE) + nfsd_reset_write_verifier(copy->cp_nn); } return bytes_copied; }