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Subject: Re: [PATCH v3 1/1] NFSv4.2: Fix NFS4ERR_STALE error when doing inter
 server copy
To:     "J. Bruce Fields" <bfields@fieldses.org>
Cc:     linux-nfs@vger.kernel.org
References: <20201009062819.92173-2-dai.ngo@oracle.com>
 <20201016175936.GA7332@fieldses.org>
From:   Dai Ngo <dai.ngo@oracle.com>
Message-ID: <675a9261-0be4-a55c-5174-bafd45adf3b4@oracle.com>
Date:   Fri, 16 Oct 2020 18:09:36 -0700
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Thanks Bruce for reviewing the patch.
I'll update the patch in v3.

-Dai

On 10/16/20 10:59 AM, J. Bruce Fields wrote:
> On Fri, Oct 09, 2020 at 02:28:19AM -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.
> This looks like a good start, but I think it could be a lot simpler:
>
>> Fixes: 3ac3711adb88 ("NFSD: Fix NFS server build errors")
>> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
>> ---
>> changes from v2: fix 0-day build issues.
>> ---
>>   fs/nfs/nfs4file.c       |  40 +++++++++++--
>>   fs/nfs/nfs4super.c      |   6 ++
>>   fs/nfs/super.c          |  20 +++++++
>>   fs/nfs_common/Makefile  |   1 +
>>   fs/nfs_common/nfs_ssc.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++
>>   fs/nfsd/Kconfig         |   2 +-
>>   fs/nfsd/nfs4proc.c      |   3 +-
>>   include/linux/nfs_ssc.h |  77 +++++++++++++++++++++++++
>>   8 files changed, 289 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..7d242fcb134a 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 +398,42 @@ 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_owner = THIS_MODULE,
>> +	.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:
>> + *   On success, returns 0
>> + *   %-EINVAL if validation check fails
>> + */
>> +int nfs42_ssc_register_ops(void)
>> +{
>> +	return 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..ed0c1f9fc890 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"
>> @@ -273,6 +274,10 @@ static int __init init_nfs_v4(void)
>>   	err = nfs4_xattr_cache_init();
>>   	if (err)
>>   		goto out2;
>> +
>> +	err = nfs42_ssc_register_ops();
>> +	if (err)
>> +		goto out2;
>>   #endif
>>   
>>   	err = nfs4_register_sysctl();
>> @@ -297,6 +302,7 @@ 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..65636fef6a00 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 +86,11 @@
>>   };
>>   EXPORT_SYMBOL_GPL(nfs_sops);
>>   
>> +static const struct nfs_ssc_client_ops nfs_ssc_clnt_ops_tbl = {
>> +	.sco_owner = THIS_MODULE,
>> +	.sco_sb_deactive = nfs_sb_deactive,
>> +};
>> +
>>   #if IS_ENABLED(CONFIG_NFS_V4)
>>   static int __init register_nfs4_fs(void)
>>   {
>> @@ -106,6 +112,16 @@ static void unregister_nfs4_fs(void)
>>   }
>>   #endif
>>   
>> +static int nfs_ssc_register_ops(void)
>> +{
>> +	return 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 +149,9 @@ int __init register_nfs_fs(void)
>>   	ret = register_shrinker(&acl_shrinker);
>>   	if (ret < 0)
>>   		goto error_3;
>> +	ret = nfs_ssc_register_ops();
>> +	if (ret < 0)
>> +		goto error_3;
>>   	return 0;
>>   error_3:
>>   	nfs_unregister_sysctl();
>> @@ -152,6 +171,7 @@ 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..6d99a6d2d6b9
>> --- /dev/null
>> +++ b/fs/nfs_common/nfs_ssc.c
>> @@ -0,0 +1,148 @@
>> +// 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@oracle.com>
>> + *
>> + * 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");
>> +
>> +/*
>> + * NFS_FS
>> + */
>> +static void nfs_sb_deactive_def(struct super_block *sb);
>> +
>> +static struct nfs_ssc_client_ops nfs_ssc_clnt_ops_def = {
>> +	.sco_owner = THIS_MODULE,
>> +	.sco_sb_deactive = nfs_sb_deactive_def,
>> +};
>> +
>> +/*
>> + * NFS_V4
>> + */
>> +static struct file *nfs42_ssc_open_def(struct vfsmount *ss_mnt,
>> +		struct nfs_fh *src_fh, nfs4_stateid *stateid);
>> +static void nfs42_ssc_close_def(struct file *filep);
>> +
>> +static struct nfs4_ssc_client_ops nfs4_ssc_clnt_ops_def = {
>> +	.sco_owner = THIS_MODULE,
>> +	.sco_open = nfs42_ssc_open_def,
>> +	.sco_close = nfs42_ssc_close_def,
>> +};
>> +
>> +
>> +struct nfs_ssc_client_ops_tbl nfs_ssc_client_tbl = {
>> +	.ssc_nfs4_ops	= &nfs4_ssc_clnt_ops_def,
>> +	.ssc_nfs_ops = &nfs_ssc_clnt_ops_def
>> +};
>> +EXPORT_SYMBOL_GPL(nfs_ssc_client_tbl);
>> +
>> +
>> +static struct file *nfs42_ssc_open_def(struct vfsmount *ss_mnt,
>> +		struct nfs_fh *src_fh, nfs4_stateid *stateid)
>> +{
>> +	return ERR_PTR(-EIO);
>> +}
>> +
>> +static void nfs42_ssc_close_def(struct file *filep)
>> +{
>> +}
> I don't think we need any of these "_def" ops.  We just shouldn't be
> calling any of these ops in the case the operations aren't loaded.
>
>> +
>> +#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:
>> + *   On success, return 0
>> + *   %-EINVAL  if validation check fails
>> + */
>> +int nfs42_ssc_register(const struct nfs4_ssc_client_ops *ops)
>> +{
>> +	if (ops == NULL || ops->sco_open == NULL || ops->sco_close == NULL)
>> +		return -EINVAL;
> This function only has one caller, and we know it won't do these things.
>
> It's not worth the check and the error handling in the caller for
> something so unlikely.
>
>> +	nfs_ssc_client_tbl.ssc_nfs4_ops = ops;
>> +	return 0;
>> +}
>> +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 = &nfs4_ssc_clnt_ops_def;
>> +}
>> +EXPORT_SYMBOL_GPL(nfs42_ssc_unregister);
>> +#endif /* CONFIG_NFS_V4_2 */
>> +
>> +/*
>> + * NFS_FS
>> + */
>> +static void nfs_sb_deactive_def(struct super_block *sb)
>> +{
>> +}
>> +
>> +#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:
>> + *   On success, return 0
>> + *   %-EINVAL  if validation check fails
>> + */
>> +int nfs_ssc_register(const struct nfs_ssc_client_ops *ops)
>> +{
>> +	if (ops == NULL || ops->sco_sb_deactive == NULL)
>> +		return -EINVAL;
> Ditto, let's drop these checks.
>
>> +	nfs_ssc_client_tbl.ssc_nfs_ops = ops;
>> +	return 0;
>> +}
>> +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 = &nfs_ssc_clnt_ops_def;
>> +}
>> +EXPORT_SYMBOL_GPL(nfs_ssc_unregister);
>> +
>> +#else
>> +int nfs_ssc_register(const struct nfs_ssc_client_ops *ops)
>> +{
>> +	return 0;
>> +}
>> +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..45a763bd6b0b
>> --- /dev/null
>> +++ b/include/linux/nfs_ssc.h
>> @@ -0,0 +1,77 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * include/linux/nfs_ssc.h
>> + *
>> + * Author: Dai Ngo <dai.ngo@oracle.com>
>> + *
>> + * 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 module *sco_owner;
>> +	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 {
>> +	struct module *sco_owner;
>> +	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 int nfs42_ssc_register_ops(void);
>> +extern void nfs42_ssc_unregister_ops(void);
>> +
>> +extern int 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)
>> +{
>> +	struct file *file;
>> +
>> +	if (!try_module_get(nfs_ssc_client_tbl.ssc_nfs4_ops->sco_owner))
>> +		return ERR_PTR(-EIO);
> The module load already happened back when we did the get_fs_type in
> nfsd4_interssc_connect(), and it's not going away at this point (or
> there's something already terribly wrong with ss_mnt).
>
> So I don't think we need any try_module_get()s or module_put()s.
>
> --b.
>
>> +	file = (*nfs_ssc_client_tbl.ssc_nfs4_ops->sco_open)(ss_mnt, src_fh, stateid);
>> +	module_put(nfs_ssc_client_tbl.ssc_nfs4_ops->sco_owner);
>> +	return file;
>> +}
>> +
>> +static inline void nfs42_ssc_close(struct file *filep)
>> +{
>> +	if (!try_module_get(nfs_ssc_client_tbl.ssc_nfs4_ops->sco_owner))
>> +		return;
>> +	(*nfs_ssc_client_tbl.ssc_nfs4_ops->sco_close)(filep);
>> +	module_put(nfs_ssc_client_tbl.ssc_nfs4_ops->sco_owner);
>> +}
>> +#endif
>> +
>> +/*
>> + * NFS_FS
>> + */
>> +extern int 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 (!try_module_get(nfs_ssc_client_tbl.ssc_nfs_ops->sco_owner))
>> +		return;
>> +	(*nfs_ssc_client_tbl.ssc_nfs_ops->sco_sb_deactive)(sb);
>> +	module_put(nfs_ssc_client_tbl.ssc_nfs_ops->sco_owner);
>> +}
>> -- 
>> 1.8.3.1