From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794257094; b=AikRLYWm05B72nEIR50K0JGqzz12VoEBKt85UVsGm5J5dakXH+2nn/lpvJPm+6KPLzDq 5ivnWqVO/i48CmAC/bfOyZY4q6OBCRL8nnNXmwZO5/yKVi61pqKARNH4EEZXB23bdu2QS gJ8u1L2Rra/LY4IBTOoVND/ZTPATi68FK8eh6fqPbKX0exSiy1tk6j/N8pbEQFo2iHYmo KLRfDWf7rXbre+gDpttSQgw4GefmH7j4oys2VnvpJ8NjImw9t4nAXTt1ZSPUVWnCn+DhJ Sj0hkqFC+uXGHKl6YQVEpWBZcHC8w16OSs4g7Rv4kF11g3YxGGd1cFeqiUGGiEmstDQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794257094; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=wg3N0zeCU+V87W+DhVAiPtVIVV/pYPZTF3215VLc+s4=; b=qT5IhSfdTCML4wi0Ylou6q/v7c/K6opxhcfcQ5lkIY3eSjfQwKe2i1CKMSsvW3ouRtFN 920YHk0B7mCEhuI2/Ma96lagUPvIFIGhKAb/IvPhy4nEyPLUFYIj1Vl4ZMDHU5rcQV9FS W7YG+vlaReduPN3zGaeRpxvaBau7kAe0GKWu2nnwZUmp2taH9vB/KsXbpvvlgSlXrq+XE C4y2cRz1aKvIpqG8mHhk+HUwzc+lBQGxbZhMsqSytT95mrgziGq+6mIo9lW2UCKWRB++C Vm3gmiZOTYCuPAq2F2BLosScU2GPnUhMJSLM5xWAzGRqv4OfghtW0Dn3L5Z7CztvKNw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=XoHtTmRL; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E455D606A331; Mon, 9 Nov 2026 20:44:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=XoHtTmRL Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D6931F008A3; Mon, 9 Nov 2026 20:44:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794257093; bh=wg3N0zeCU+V87W+DhVAiPtVIVV/pYPZTF3215VLc+s4=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=XoHtTmRLHgVdiYjcxOxjlSkkFUd/FtDJPlYIXUcHtgPg40sZQg+ai2KLHjfS+HOYp 09XtAvC4nBLhSky06yhv9SVSqL94MrMKpy0pO/Ccbgkf4aBvgx7Kc1M8mt9k64PmM4 /8+XtXVZGSrGkZnnFLS167d4fKug1ear4srGKwEpuqQ/QehBRA9WFZgK0h1YgonAAi 02qz6kuApOLY2l3xxGNtWfjpFHiy59aRimbLvZCeHUapzIINrDjhJAw9zQ8wZh2rmr upyJY4McJQhUGsjOCKmCR1vERgdPSd6qmzBYYeJoXWQpXBgWMLJlfj8FzfhSgqG2Kz KkuDubC+xsOqg== From: Jeff Layton Date: Mon, 09 Nov 2026 15:44:47 -0500 Subject: [PATCH v2 1/3] NFS: don't let delegated c/mtime stamps go backward X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261109-delegts-nfs-v2-1-9d1e926cc3d5@kernel.org> References: <20261109-delegts-nfs-v2-0-9d1e926cc3d5@kernel.org> In-Reply-To: <20261109-delegts-nfs-v2-0-9d1e926cc3d5@kernel.org> To: Trond Myklebust , Anna Schumaker , Lance Shelton , Olga Kornievskaia Cc: Thomas Haynes , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, Jeff Layton X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=3172; i=jlayton@kernel.org; h=from:subject:message-id; bh=/i+WgRkUTNLoT+wZXDiWG93r/fsgNbR+dFkibZFuirs=; b=owEBbQKS/ZANAwAKAQAOaEEZVoIVAcsmYgBq8jDDiVYldjueX0OrVuKTDBFgjmWyCDfaZE83J 2HosYwTPyOJAjMEAAEKAB0WIQRLwNeyRHGyoYTq9dMADmhBGVaCFQUCavIwwwAKCRAADmhBGVaC FZRIEACCPS6FuiAmKDRj+am+Ge8Lbyhg0lzWzZwAq0N60XemXTowRN2l08BjLOZV5ERwJ/uiufx RhfS+ANphcgSlTeAMYSzhhsFD8GWf1fD2zfN1HhkL5BBeEzCyOwdCawMBwFBJA/eyrOWqCHoBch 0OGjpg0GDf/PU6WbfPBPyG1cyNvA5S4GCUW3DdV1eJPYF51tl+EwblQkO37+CJzuYEM0hoLkyD7 XhPdP3Nd36K+VCSVvDeZ9LDl13scPpcZA5ExAHKL3i+y4VAHIQ5DUiZ8CGThJs4BbsA9ehpoxND L8/p4SRcbdtgM8MVderZhOTsoR9znBKNSTKduXPzeNCsQanChoqG8S9C5goYRu9WVfPF5agaApa SHHaRaasaKeBQXYN6RdZg5vtXnl7IY5l9F/tWE8YPCZtRVE5djArzbCmRwKv9MYdjF/Ep8H9MsX sugsT+m6033nj35gR3bkfLF3bQc9TM0m2uM0y6h16LAI5QvLRxZU1qmn474waqZISVHVxRCX5NY 8Y8AQQpxPXtbHKROLZPWB551fIwdx9kmOTN/CgscpWfWRtddnNRjVzDSwnSqAaPSzRkebCiwqbX GwcPnFzvnpMT8rNZ23yF7T75mB4LzF8+w5LMJOugOpVQhDmyQe+val6bQ3FIe1qBmwR25kENYhb zcB/OAQDYjSxImQ== X-Developer-Key: i=jlayton@kernel.org; a=openpgp; fpr=4BC0D7B24471B2A184EAF5D3000E684119568215 With a timestamp delegation the client stamps c/mtime from its own coarse clock. That can land before the server's fine-grained ctime the client cached from the OPEN or SETATTR reply, e.g. on a WRITE right after an exclusive create. The server then either rejects the times (they don't pass dl_ctime) or can't apply the ctime, since inode_set_ctime_deleg() never moves ctime backward. Either way the c/mtime the client reported while holding the delegation changes after DELEGRETURN; git t1092 over NFSv4.2 sees a stat-dirty file. When a delegated stamp isn't after the cached ctime, use the cached ctime + 1ns instead. Compute the stamp before storing it, so lockless readers (getattr, CB_GETATTR) never see the trailing coarse time. Fixes: e12912d94137 ("NFSv4: Add support for delegated atime and mtime attributes") Signed-off-by: Jeff Layton --- fs/nfs/inode.c | 40 ++++++++++++++++++++++++++-------------- 1 file changed, 26 insertions(+), 14 deletions(-) diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c index 9839087cf373..98d8a34fab9d 100644 --- a/fs/nfs/inode.c +++ b/fs/nfs/inode.c @@ -629,25 +629,33 @@ nfs_fattr_fixup_delegated(struct inode *inode, struct nfs_fattr *fattr) } } +/* + * With delegated timestamps, the client's coarse clock can trail the + * server's fine-grained ctime cached from an OPEN or SETATTR reply. The + * server won't move ctime backward when the times are returned, so a + * new stamp must land after the cached ctime. + */ +static struct timespec64 nfs_delegated_stamp(struct inode *inode) +{ + struct timespec64 ctime = inode_get_ctime(inode); + struct timespec64 now = current_time(inode); + + if (timespec64_compare(&now, &ctime) <= 0) { + now = ctime; + timespec64_add_ns(&now, 1); + } + return now; +} + static void nfs_set_timestamps_to_ts(struct inode *inode, struct iattr *attr) { unsigned int cache_flags = 0; if (attr->ia_valid & ATTR_MTIME_SET) { - struct timespec64 ctime = inode_get_ctime(inode); - struct timespec64 mtime = inode_get_mtime(inode); - struct timespec64 now; - bool updated = false; - - now = inode_set_ctime_current(inode); - if (!timespec64_equal(&now, &ctime)) - updated = true; - + /* The stamp is always after the old ctime */ + inode_set_ctime_to_ts(inode, nfs_delegated_stamp(inode)); inode_set_mtime_to_ts(inode, attr->ia_mtime); - if (!timespec64_equal(&now, &mtime)) - updated = true; - - inode_maybe_inc_iversion(inode, updated); + inode_maybe_inc_iversion(inode, true); cache_flags |= NFS_INO_INVALID_CTIME | NFS_INO_INVALID_MTIME; } if (attr->ia_valid & ATTR_ATIME) { @@ -665,7 +673,11 @@ static void nfs_update_atime(struct inode *inode) static void nfs_update_mtime(struct inode *inode) { - inode_update_time(inode, FS_UPD_CMTIME, 0); + struct timespec64 now = nfs_delegated_stamp(inode); + + /* Not inode_update_time(): lockless readers would see its stamp */ + inode_set_ctime_to_ts(inode, now); + inode_set_mtime_to_ts(inode, now); NFS_I(inode)->cache_validity &= ~(NFS_INO_INVALID_CTIME | NFS_INO_INVALID_MTIME); } -- 2.56.0