Re: [PATCH v4 1/1] NFSv4.2: Fix NFS4ERR_STALE error when doing inter server copy

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On 10/20/20 10:01 AM, J. Bruce Fields wrote:
On Sun, Oct 18, 2020 at 11:42:49PM -0400, Dai Ngo wrote:
NFS_FS=y as dependency of CONFIG_NFSD_V4_2_INTER_SSC still have
build errors and some configs with NFSD=m to get NFS4ERR_STALE
error when doing inter server copy.

Added ops table in nfs_common for knfsd to access NFS client modules.
OK, looks reasonable to me, applying.  Does this resolve all the
problems you've seen, or is there any bad case left?

Thanks Bruce.

With this patch, I no longer see the NFS4ERR_STALE in any config.

The problem with NFS4ERR_STALE was because of a bug in nfs42_ssc_open.
When CONFIG_NFSD_V4_2_INTER_SSC is not defined, nfs42_ssc_open
returns NULL which is incorrect allowing the operation to continue
until nfsd4_putfh which does not have the code to handle nfserr_stale.

With this patch, when CONFIG_NFSD_V4_2_INTER_SSC is not defined the
new nfs42_ssc_open returns ERR_PTR(-EIO) which causes the NFS client
to switch over to the split copying (read src and write to dst).

The other problem that I see was the "use-after-free" which I think
happens only on the 1st inter server copy. I will look into this:


 Sep 23 01:08:10 nfsvmf24 kernel: ------------[ cut here ]------------
Sep 23 01:08:10 nfsvmf24 kernel: refcount_t: underflow; use-after-free.
Sep 23 01:08:10 nfsvmf24 kernel: WARNING: CPU: 0 PID: 4217 at lib/refcount.c:28 refcount_warn_saturate+0xae/0xf0
Sep 23 01:08:10 nfsvmf24 kernel: Modules linked in: cts rpcsec_gss_krb5 xt_REDIRECT xt_nat ip6table_nat ip6_tables iptable_nat nf_nat nf_conntrack btrfs nf_defrag_ipv6 nf_defrag_ipv4 blake2b_generic xor zstd_compress rfkill raid6_pq sb_edac intel_powerclamp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel crypto_simd cryptd glue_helper sg pcspkr i2c_piix4 video ip_tables xfs libcrc32c sd_mod t10_pi ahci libahci libata e1000 crc32c_intel serio_raw dm_mirror dm_region_hash dm_log dm_mod
Sep 23 01:08:10 nfsvmf24 kernel: CPU: 0 PID: 4217 Comm: copy thread Not tainted 5.9.0-rc5+ #14
Sep 23 01:08:10 nfsvmf24 kernel: Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
Sep 23 01:08:10 nfsvmf24 kernel: RIP: 0010:refcount_warn_saturate+0xae/0xf0
Sep 23 01:08:10 nfsvmf24 kernel: Code: 99 83 31 01 01 e8 27 ba b6 ff 0f 0b 5d c3 80 3d 86 83 31 01 00 75 91 48 c7 c7 20 d3 3a 84 c6 05 76 83 31 01 01 e8 07 ba b6 ff <0f> 0b 5d c3 80 3d 64 83 31 01 00 0f 85 6d ff ff ff 48 c7 c7 78 d3
Sep 23 01:08:10 nfsvmf24 kernel: RSP: 0000:ffffc20300403e68 EFLAGS: 00010286
Sep 23 01:08:10 nfsvmf24 kernel: RAX: 0000000000000000 RBX: 0000000000000010 RCX: 0000000000000027
Sep 23 01:08:10 nfsvmf24 kernel: RDX: 0000000000000027 RSI: 0000000000000086 RDI: ffff9e8c97c18c48
Sep 23 01:08:10 nfsvmf24 kernel: RBP: ffffc20300403e68 R08: ffff9e8c97c18c40 R09: 0000000000000004
Sep 23 01:08:10 nfsvmf24 kernel: R10: 0000000000000000 R11: 0000000000000001 R12: ffff9e8c96693300
Sep 23 01:08:10 nfsvmf24 kernel: R13: ffff9e8c96693300 R14: ffff9e8c8a6e3000 R15: ffff9e8c959c5520
Sep 23 01:08:10 nfsvmf24 kernel: FS:  0000000000000000(0000) GS:ffff9e8c97c00000(0000) knlGS:0000000000000000
Sep 23 01:08:10 nfsvmf24 kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Sep 23 01:08:10 nfsvmf24 kernel: CR2: 000055aedfd031a8 CR3: 000000020ee6e000 CR4: 00000000000406f0
Sep 23 01:08:10 nfsvmf24 kernel: Call Trace:
Sep 23 01:08:10 nfsvmf24 kernel: nfsd_file_put_noref+0x8f/0xa0
Sep 23 01:08:10 nfsvmf24 kernel: nfsd_file_put+0x3e/0x90
Sep 23 01:08:10 nfsvmf24 kernel: nfsd4_do_copy+0xe5/0x150
Sep 23 01:08:10 nfsvmf24 kernel: nfsd4_do_async_copy+0x84/0x200
Sep 23 01:08:10 nfsvmf24 kernel: kthread+0x114/0x150
Sep 23 01:08:10 nfsvmf24 kernel: ? nfsd4_copy+0x4e0/0x4e0
Sep 23 01:08:10 nfsvmf24 kernel: ? kthread_park+0x90/0x90
Sep 23 01:08:10 nfsvmf24 kernel: ret_from_fork+0x22/0x30

-Dai


--b.

Fixes: 3ac3711adb88 ("NFSD: Fix NFS server build errors")
Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
---
changes from v2: fix 0-day build issues.
changes from v3: reacted to Bruce's comments, removed paranoid error checking.
---
  fs/nfs/nfs4file.c       | 38 ++++++++++++++++----
  fs/nfs/nfs4super.c      |  5 +++
  fs/nfs/super.c          | 17 +++++++++
  fs/nfs_common/Makefile  |  1 +
  fs/nfs_common/nfs_ssc.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++
  fs/nfsd/Kconfig         |  2 +-
  fs/nfsd/nfs4proc.c      |  3 +-
  include/linux/nfs_ssc.h | 67 +++++++++++++++++++++++++++++++++++
  8 files changed, 219 insertions(+), 8 deletions(-)
  create mode 100644 fs/nfs_common/nfs_ssc.c
  create mode 100644 include/linux/nfs_ssc.h

diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index fdfc77486ace..984938024011 100644
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -9,6 +9,7 @@
  #include <linux/falloc.h>
  #include <linux/mount.h>
  #include <linux/nfs_fs.h>
+#include <linux/nfs_ssc.h>
  #include "delegation.h"
  #include "internal.h"
  #include "iostat.h"
@@ -314,9 +315,8 @@ static loff_t nfs42_remap_file_range(struct file *src_file, loff_t src_off,
  static int read_name_gen = 1;
  #define SSC_READ_NAME_BODY "ssc_read_%d"
-struct file *
-nfs42_ssc_open(struct vfsmount *ss_mnt, struct nfs_fh *src_fh,
-		nfs4_stateid *stateid)
+static struct file *__nfs42_ssc_open(struct vfsmount *ss_mnt,
+		struct nfs_fh *src_fh, nfs4_stateid *stateid)
  {
  	struct nfs_fattr fattr;
  	struct file *filep, *res;
@@ -398,14 +398,40 @@ struct file *
  	fput(filep);
  	goto out_free_name;
  }
-EXPORT_SYMBOL_GPL(nfs42_ssc_open);
-void nfs42_ssc_close(struct file *filep)
+
+static void __nfs42_ssc_close(struct file *filep)
  {
  	struct nfs_open_context *ctx = nfs_file_open_context(filep);
ctx->state->flags = 0;
  }
-EXPORT_SYMBOL_GPL(nfs42_ssc_close);
+
+static const struct nfs4_ssc_client_ops nfs4_ssc_clnt_ops_tbl = {
+	.sco_open = __nfs42_ssc_open,
+	.sco_close = __nfs42_ssc_close,
+};
+
+/**
+ * nfs42_ssc_register_ops - Wrapper to register NFS_V4 ops in nfs_common
+ *
+ * Return values:
+ *   None
+ */
+void nfs42_ssc_register_ops(void)
+{
+	nfs42_ssc_register(&nfs4_ssc_clnt_ops_tbl);
+}
+
+/**
+ * nfs42_ssc_unregister_ops - wrapper to un-register NFS_V4 ops in nfs_common
+ *
+ * Return values:
+ *   None.
+ */
+void nfs42_ssc_unregister_ops(void)
+{
+	nfs42_ssc_unregister(&nfs4_ssc_clnt_ops_tbl);
+}
  #endif /* CONFIG_NFS_V4_2 */
const struct file_operations nfs4_file_operations = {
diff --git a/fs/nfs/nfs4super.c b/fs/nfs/nfs4super.c
index 0c1ab846b83d..93f5c1678ec2 100644
--- a/fs/nfs/nfs4super.c
+++ b/fs/nfs/nfs4super.c
@@ -7,6 +7,7 @@
  #include <linux/mount.h>
  #include <linux/nfs4_mount.h>
  #include <linux/nfs_fs.h>
+#include <linux/nfs_ssc.h>
  #include "delegation.h"
  #include "internal.h"
  #include "nfs4_fs.h"
@@ -279,6 +280,9 @@ static int __init init_nfs_v4(void)
  	if (err)
  		goto out2;
+#ifdef CONFIG_NFS_V4_2
+	nfs42_ssc_register_ops();
+#endif
  	register_nfs_version(&nfs_v4);
  	return 0;
  out2:
@@ -297,6 +301,7 @@ static void __exit exit_nfs_v4(void)
  	unregister_nfs_version(&nfs_v4);
  #ifdef CONFIG_NFS_V4_2
  	nfs4_xattr_cache_exit();
+	nfs42_ssc_unregister_ops();
  #endif
  	nfs4_unregister_sysctl();
  	nfs_idmap_quit();
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 7a70287f21a2..f7dad8227a5f 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -57,6 +57,7 @@
  #include <linux/rcupdate.h>
#include <linux/uaccess.h>
+#include <linux/nfs_ssc.h>
#include "nfs4_fs.h"
  #include "callback.h"
@@ -85,6 +86,10 @@
  };
  EXPORT_SYMBOL_GPL(nfs_sops);
+static const struct nfs_ssc_client_ops nfs_ssc_clnt_ops_tbl = {
+	.sco_sb_deactive = nfs_sb_deactive,
+};
+
  #if IS_ENABLED(CONFIG_NFS_V4)
  static int __init register_nfs4_fs(void)
  {
@@ -106,6 +111,16 @@ static void unregister_nfs4_fs(void)
  }
  #endif
+static void nfs_ssc_register_ops(void)
+{
+	nfs_ssc_register(&nfs_ssc_clnt_ops_tbl);
+}
+
+static void nfs_ssc_unregister_ops(void)
+{
+	nfs_ssc_unregister(&nfs_ssc_clnt_ops_tbl);
+}
+
  static struct shrinker acl_shrinker = {
  	.count_objects	= nfs_access_cache_count,
  	.scan_objects	= nfs_access_cache_scan,
@@ -133,6 +148,7 @@ int __init register_nfs_fs(void)
  	ret = register_shrinker(&acl_shrinker);
  	if (ret < 0)
  		goto error_3;
+	nfs_ssc_register_ops();
  	return 0;
  error_3:
  	nfs_unregister_sysctl();
@@ -152,6 +168,7 @@ void __exit unregister_nfs_fs(void)
  	unregister_shrinker(&acl_shrinker);
  	nfs_unregister_sysctl();
  	unregister_nfs4_fs();
+	nfs_ssc_unregister_ops();
  	unregister_filesystem(&nfs_fs_type);
  }
diff --git a/fs/nfs_common/Makefile b/fs/nfs_common/Makefile
index 4bebe834c009..fa82f5aaa6d9 100644
--- a/fs/nfs_common/Makefile
+++ b/fs/nfs_common/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_NFS_ACL_SUPPORT) += nfs_acl.o
  nfs_acl-objs := nfsacl.o
obj-$(CONFIG_GRACE_PERIOD) += grace.o
+obj-$(CONFIG_GRACE_PERIOD) += nfs_ssc.o
diff --git a/fs/nfs_common/nfs_ssc.c b/fs/nfs_common/nfs_ssc.c
new file mode 100644
index 000000000000..f43bbb373913
--- /dev/null
+++ b/fs/nfs_common/nfs_ssc.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * fs/nfs_common/nfs_ssc_comm.c
+ *
+ * Helper for knfsd's SSC to access ops in NFS client modules
+ *
+ * Author: Dai Ngo <dai.ngo@xxxxxxxxxx>
+ *
+ * Copyright (c) 2020, Oracle and/or its affiliates.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/nfs_ssc.h>
+#include "../nfs/nfs4_fs.h"
+
+MODULE_LICENSE("GPL");
+
+struct nfs_ssc_client_ops_tbl nfs_ssc_client_tbl;
+EXPORT_SYMBOL_GPL(nfs_ssc_client_tbl);
+
+#ifdef CONFIG_NFS_V4_2
+/**
+ * nfs42_ssc_register - install the NFS_V4 client ops in the nfs_ssc_client_tbl
+ * @ops: NFS_V4 ops to be installed
+ *
+ * Return values:
+ *   None
+ */
+void nfs42_ssc_register(const struct nfs4_ssc_client_ops *ops)
+{
+	nfs_ssc_client_tbl.ssc_nfs4_ops = ops;
+}
+EXPORT_SYMBOL_GPL(nfs42_ssc_register);
+
+/**
+ * nfs42_ssc_unregister - uninstall the NFS_V4 client ops from
+ *				the nfs_ssc_client_tbl
+ * @ops: ops to be uninstalled
+ *
+ * Return values:
+ *   None
+ */
+void nfs42_ssc_unregister(const struct nfs4_ssc_client_ops *ops)
+{
+	if (nfs_ssc_client_tbl.ssc_nfs4_ops != ops)
+		return;
+
+	nfs_ssc_client_tbl.ssc_nfs4_ops = NULL;
+}
+EXPORT_SYMBOL_GPL(nfs42_ssc_unregister);
+#endif /* CONFIG_NFS_V4_2 */
+
+#ifdef CONFIG_NFS_V4_2
+/**
+ * nfs_ssc_register - install the NFS_FS client ops in the nfs_ssc_client_tbl
+ * @ops: NFS_FS ops to be installed
+ *
+ * Return values:
+ *   None
+ */
+void nfs_ssc_register(const struct nfs_ssc_client_ops *ops)
+{
+	nfs_ssc_client_tbl.ssc_nfs_ops = ops;
+}
+EXPORT_SYMBOL_GPL(nfs_ssc_register);
+
+/**
+ * nfs_ssc_unregister - uninstall the NFS_FS client ops from
+ *				the nfs_ssc_client_tbl
+ * @ops: ops to be uninstalled
+ *
+ * Return values:
+ *   None
+ */
+void nfs_ssc_unregister(const struct nfs_ssc_client_ops *ops)
+{
+	if (nfs_ssc_client_tbl.ssc_nfs_ops != ops)
+		return;
+	nfs_ssc_client_tbl.ssc_nfs_ops = NULL;
+}
+EXPORT_SYMBOL_GPL(nfs_ssc_unregister);
+
+#else
+void nfs_ssc_register(const struct nfs_ssc_client_ops *ops)
+{
+}
+EXPORT_SYMBOL_GPL(nfs_ssc_register);
+
+void nfs_ssc_unregister(const struct nfs_ssc_client_ops *ops)
+{
+}
+EXPORT_SYMBOL_GPL(nfs_ssc_unregister);
+#endif /* CONFIG_NFS_V4_2 */
diff --git a/fs/nfsd/Kconfig b/fs/nfsd/Kconfig
index 99d2cae91bd6..f368f3215f88 100644
--- a/fs/nfsd/Kconfig
+++ b/fs/nfsd/Kconfig
@@ -136,7 +136,7 @@ config NFSD_FLEXFILELAYOUT
config NFSD_V4_2_INTER_SSC
  	bool "NFSv4.2 inter server to server COPY"
-	depends on NFSD_V4 && NFS_V4_1 && NFS_V4_2 && NFS_FS=y
+	depends on NFSD_V4 && NFS_V4_1 && NFS_V4_2
  	help
  	  This option enables support for NFSv4.2 inter server to
  	  server copy where the destination server calls the NFSv4.2
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index eaf50eafa935..84e10aef1417 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -38,6 +38,7 @@
  #include <linux/slab.h>
  #include <linux/kthread.h>
  #include <linux/sunrpc/addr.h>
+#include <linux/nfs_ssc.h>
#include "idmap.h"
  #include "cache.h"
@@ -1247,7 +1248,7 @@ extern struct file *nfs42_ssc_open(struct vfsmount *ss_mnt,
  static void
  nfsd4_interssc_disconnect(struct vfsmount *ss_mnt)
  {
-	nfs_sb_deactive(ss_mnt->mnt_sb);
+	nfs_do_sb_deactive(ss_mnt->mnt_sb);
  	mntput(ss_mnt);
  }
diff --git a/include/linux/nfs_ssc.h b/include/linux/nfs_ssc.h
new file mode 100644
index 000000000000..f5ba0fbff72f
--- /dev/null
+++ b/include/linux/nfs_ssc.h
@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * include/linux/nfs_ssc.h
+ *
+ * Author: Dai Ngo <dai.ngo@xxxxxxxxxx>
+ *
+ * Copyright (c) 2020, Oracle and/or its affiliates.
+ */
+
+#include <linux/nfs_fs.h>
+
+extern struct nfs_ssc_client_ops_tbl nfs_ssc_client_tbl;
+
+/*
+ * NFS_V4
+ */
+struct nfs4_ssc_client_ops {
+	struct file *(*sco_open)(struct vfsmount *ss_mnt,
+		struct nfs_fh *src_fh, nfs4_stateid *stateid);
+	void (*sco_close)(struct file *filep);
+};
+
+/*
+ * NFS_FS
+ */
+struct nfs_ssc_client_ops {
+	void (*sco_sb_deactive)(struct super_block *sb);
+};
+
+struct nfs_ssc_client_ops_tbl {
+	const struct nfs4_ssc_client_ops *ssc_nfs4_ops;
+	const struct nfs_ssc_client_ops *ssc_nfs_ops;
+};
+
+extern void nfs42_ssc_register_ops(void);
+extern void nfs42_ssc_unregister_ops(void);
+
+extern void nfs42_ssc_register(const struct nfs4_ssc_client_ops *ops);
+extern void nfs42_ssc_unregister(const struct nfs4_ssc_client_ops *ops);
+
+#ifdef CONFIG_NFSD_V4_2_INTER_SSC
+static inline struct file *nfs42_ssc_open(struct vfsmount *ss_mnt,
+		struct nfs_fh *src_fh, nfs4_stateid *stateid)
+{
+	if (nfs_ssc_client_tbl.ssc_nfs4_ops)
+		return (*nfs_ssc_client_tbl.ssc_nfs4_ops->sco_open)(ss_mnt, src_fh, stateid);
+	return ERR_PTR(-EIO);
+}
+
+static inline void nfs42_ssc_close(struct file *filep)
+{
+	if (nfs_ssc_client_tbl.ssc_nfs4_ops)
+		(*nfs_ssc_client_tbl.ssc_nfs4_ops->sco_close)(filep);
+}
+#endif
+
+/*
+ * NFS_FS
+ */
+extern void nfs_ssc_register(const struct nfs_ssc_client_ops *ops);
+extern void nfs_ssc_unregister(const struct nfs_ssc_client_ops *ops);
+
+static inline void nfs_do_sb_deactive(struct super_block *sb)
+{
+	if (nfs_ssc_client_tbl.ssc_nfs_ops)
+		(*nfs_ssc_client_tbl.ssc_nfs_ops->sco_sb_deactive)(sb);
+}
--
1.8.3.1



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