From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 95519C13C for ; Fri, 1 Nov 2024 12:28:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730464128; cv=none; b=k7/2BcWKD4cJhv+pA0GKIxyzLC8K+4V9DIZgc5QYxGfzWds1Dh3+l3CAyU7Gh8lat6oOWQrTdQtYFOW+wp8dMtMJp0gqcCltTYKAT/FgvwOm7EIJPxXGyNNipwXTQEsCRxZ2AwIDLi6KMio7L9rIUfspsFm13ROEcU3hHD//Pu4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730464128; c=relaxed/simple; bh=oslMXPJ3W6UUQlP6RYpNjJMllOWtEqARd/gcOczcz2M=; h=Message-ID:Subject:From:To:Cc:In-Reply-To:References:Content-Type: Date:MIME-Version; b=FQELOJgZHSxX1JpG7fZZY3nMvNdyTcUH9yFMjzWAhxTH8BlC+vQ45LkUqJzBczYCDgEm1Q6dYfZnNth4H8+qPzkWdWEVL4kLEhPR4mQjjf0CBmX27WslufU6CkZOOHlAtkanq7mQdcOMH6Xg/87ZYgrx+gLKvB3mALUcvinhCM4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BJwqjZDo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BJwqjZDo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F07FC4CECD; Fri, 1 Nov 2024 12:28:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730464128; bh=oslMXPJ3W6UUQlP6RYpNjJMllOWtEqARd/gcOczcz2M=; h=Subject:From:To:Cc:In-Reply-To:References:Date:From; b=BJwqjZDoE8Z9T3/dDvpYOFI7HkYWBerZ1kH1KwoKFfHA3NvC+CtOj0Cmn0tecKD3G 8/6BGSygW7LUm0FatiirIMFH/xQi5q67X92sGiqzin+4sp7ECLZE3aZgpqA1jxU03u Oo3xIW8aolIOI1s3AeC88GoTs6BwjEgilD4nNVZoPNQpjakzeKj6NoKi9hnFu6cEb5 TevQfbaHVzDNO4hWjN9Gp6SL5aKPZLpBmQvWZ9gY86HTW+udDnwN5nX78LQphAptXJ BbmDK4jzBB61gfqh+JbJeEp3cbcXfs+sqtsgVnBfAVQMhAlD5b1TJ2/Z3XW+Ycp+BI LZpEFJj37/6sQ== Message-ID: Subject: Re: [PATCH v3 2/8] NFSD: Fix nfsd4_shutdown_copy() From: Jeff Layton To: cel@kernel.org, Neil Brown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: linux-nfs@vger.kernel.org, Chuck Lever In-Reply-To: <20241031134000.53396-12-cel@kernel.org> References: <20241031134000.53396-10-cel@kernel.org> <20241031134000.53396-12-cel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV 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> while ((copy =3D nfsd4_get_copy(clp)) !=3D NULL) > nfsd4_stop_copy(copy); >=20 > nfsd4_get_copy() bumps @copy's reference count, preventing > nfsd4_stop_copy() from releasing @copy. >=20 > A while loop like this usually works by removing the first element > of the list, but neither nfsd4_get_copy() nor nfsd4_stop_copy() > alters the async_copies list. >=20 > Best I can tell, then, is that nfsd4_shutdown_copy() continues to > loop until other threads manage to remove all the items from this > list. The spinning loop blocks shutdown until these items are gone. >=20 > Possibly the reason we haven't seen this issue in the field is > because client_has_state() prevents __destroy_client() from calling > nfsd4_shutdown_copy() if there are any items on this list. In a > subsequent patch I plan to remove that restriction. >=20 > Fixes: e0639dc5805a ("NFSD introduce async copy feature") > Signed-off-by: Chuck Lever > --- > fs/nfsd/nfs4proc.c | 3 +++ > 1 file changed, 3 insertions(+) >=20 > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c > index 9f6617fa5412..8229bbfdd735 100644 > --- a/fs/nfsd/nfs4proc.c > +++ b/fs/nfsd/nfs4proc.c > @@ -1302,6 +1302,9 @@ static struct nfsd4_copy *nfsd4_get_copy(struct nfs= 4_client *clp) > copy =3D list_first_entry(&clp->async_copies, struct nfsd4_copy, > copies); > refcount_inc(©->refcount); > + copy->cp_clp =3D NULL; > + if (!list_empty(©->copies)) > + list_del_init(©->copies); > } > spin_unlock(&clp->async_lock); > return copy; My initial thought was: The problem sounds real, but is nfsd4_get_copy() the place for the above logic? But then I noticed that nfsd4_get_copy() is only called from nfsd4_shutdown_copy(). Maybe we should be rename nfsd4_get_copy() to nfsd4_find_and_unhash_copy() ? --=20 Jeff Layton