NFSD: Instantiate a struct file when creating a regular NFSv4 file

There have been reports of races that cause NFSv4 OPEN(CREATE) to return an error even though the requested file was created. NFSv4 does not provide a status code for this case. To mitigate some of these problems, reorganize the NFSv4 OPEN(CREATE) logic to allocate resources before the file is actually created, and open the new file while the parent directory is still locked. Two new APIs are added: + Add an API that works like nfsd_file_acquire() but does not open the underlying file. The OPEN(CREATE) path can use this API when it already has an open file. + Add an API that is kin to dentry_open(). NFSD needs to create a file and grab an open "struct file *" atomically. The alloc_empty_file() has to be done before the inode create. If it fails (for example, because the NFS server has exceeded its max_files limit), we avoid creating the file and can still return an error to the NFS client.

Chuck Lever committed 4 years ago

Commit fb70bf11 parent f4d84c57 files · +143 −14Browse files

Unified · Split

7 files

fs/nfsd/filecache.c +44 −7
fs/nfsd/filecache.h +2 −0
fs/nfsd/nfs4proc.c +39 −4
fs/nfsd/nfs4state.c +13 −3
fs/nfsd/xdr4.h +1 −0
fs/open.c +42 −0
include/linux/fs.h +2 −0

fs/nfsd/filecache.c+44−7

@@ -897,9 +897,9 @@ nfsd_file_is_cached(struct inode *inode) · 896 unmodified lines
897	return ret;	897	return ret;
898	}	898	}
899		899
900	__be32	900	static __be32
901	nfsd_file_acquire(struct svc_rqst rqstp, struct svc_fh fhp,	901	nfsd_do_file_acquire(struct svc_rqst rqstp, struct svc_fh fhp,
902	unsigned int may_flags, struct nfsd_file **pnf)	902	unsigned int may_flags, struct nfsd_file **pnf, bool open)
903	{	903	{
904	__be32 status;	904	__be32 status;
905	struct net *net = SVC_NET(rqstp);	905	struct net *net = SVC_NET(rqstp);
@@ -994,10 +994,13 @@ open_file: · 88 unmodified lines
994	nfsd_file_gc();	994	nfsd_file_gc();
995		995
996	nf->nf_mark = nfsd_file_mark_find_or_create(nf);	996	nf->nf_mark = nfsd_file_mark_find_or_create(nf);
997	if (nf->nf_mark)	997	if (nf->nf_mark) {
998	status = nfsd_open_verified(rqstp, fhp, may_flags,	998	if (open)
999	&nf->nf_file);	999	status = nfsd_open_verified(rqstp, fhp, may_flags,
1000	else	1000	&nf->nf_file);
		1001	else
		1002	status = nfs_ok;
		1003	} else
1001	status = nfserr_jukebox;	1004	status = nfserr_jukebox;
1002	/*	1005	/*
1003	* If construction failed, or we raced with a call to unlink()	1006	* If construction failed, or we raced with a call to unlink()
@@ -1017,6 +1020,40 @@ open_file: · 13 unmodified lines
1017	goto out;	1020	goto out;
1018	}	1021	}
1019		1022
		1023	/**
		1024	* nfsd_file_acquire - Get a struct nfsd_file with an open file
		1025	* @rqstp: the RPC transaction being executed
		1026	* @fhp: the NFS filehandle of the file to be opened
		1027	* @may_flags: NFSD_MAY_ settings for the file
		1028	* @pnf: OUT: new or found "struct nfsd_file" object
		1029	*
		1030	* Returns nfs_ok and sets @pnf on success; otherwise an nfsstat in
		1031	* network byte order is returned.
		1032	*/
		1033	__be32
		1034	nfsd_file_acquire(struct svc_rqst rqstp, struct svc_fh fhp,
		1035	unsigned int may_flags, struct nfsd_file **pnf)
		1036	{
		1037	return nfsd_do_file_acquire(rqstp, fhp, may_flags, pnf, true);
		1038	}
		1039
		1040	/**
		1041	* nfsd_file_create - Get a struct nfsd_file, do not open
		1042	* @rqstp: the RPC transaction being executed
		1043	* @fhp: the NFS filehandle of the file just created
		1044	* @may_flags: NFSD_MAY_ settings for the file
		1045	* @pnf: OUT: new or found "struct nfsd_file" object
		1046	*
		1047	* Returns nfs_ok and sets @pnf on success; otherwise an nfsstat in
		1048	* network byte order is returned.
		1049	*/
		1050	__be32
		1051	nfsd_file_create(struct svc_rqst rqstp, struct svc_fh fhp,
		1052	unsigned int may_flags, struct nfsd_file **pnf)
		1053	{
		1054	return nfsd_do_file_acquire(rqstp, fhp, may_flags, pnf, false);
		1055	}
		1056
1020	/*	1057	/*
1021	* Note that fields may be added, removed or reordered in the future. Programs	1058	* Note that fields may be added, removed or reordered in the future. Programs
1022	* scraping this file for info should test the labels to ensure they're	1059	* scraping this file for info should test the labels to ensure they're

fs/nfsd/filecache.h+2−0

@@ -59,5 +59,7 @@ void nfsd_file_close_inode_sync(struct inode *inode); · 58 unmodified lines
59	bool nfsd_file_is_cached(struct inode *inode);	59	bool nfsd_file_is_cached(struct inode *inode);
60	__be32 nfsd_file_acquire(struct svc_rqst rqstp, struct svc_fh fhp,	60	__be32 nfsd_file_acquire(struct svc_rqst rqstp, struct svc_fh fhp,
61	unsigned int may_flags, struct nfsd_file **nfp);	61	unsigned int may_flags, struct nfsd_file **nfp);
		62	__be32 nfsd_file_create(struct svc_rqst rqstp, struct svc_fh fhp,
		63	unsigned int may_flags, struct nfsd_file **nfp);
62	int nfsd_file_cache_stats_open(struct inode , struct file );	64	int nfsd_file_cache_stats_open(struct inode , struct file );
63	#endif /* _FS_NFSD_FILECACHE_H */	65	#endif /* _FS_NFSD_FILECACHE_H */

fs/nfsd/nfs4proc.c+39−4

@@ -243,6 +243,37 @@ static inline bool nfsd4_create_is_exclusive(int createmode) · 242 unmodified lines
243	createmode == NFS4_CREATE_EXCLUSIVE4_1;	243	createmode == NFS4_CREATE_EXCLUSIVE4_1;
244	}	244	}
245		245
		246	static __be32
		247	nfsd4_vfs_create(struct svc_fh fhp, struct dentry child,
		248	struct nfsd4_open *open)
		249	{
		250	struct file *filp;
		251	struct path path;
		252	int oflags;
		253
		254	oflags = O_CREAT \| O_LARGEFILE;
		255	switch (open->op_share_access & NFS4_SHARE_ACCESS_BOTH) {
		256	case NFS4_SHARE_ACCESS_WRITE:
		257	oflags \|= O_WRONLY;
		258	break;
		259	case NFS4_SHARE_ACCESS_BOTH:
		260	oflags \|= O_RDWR;
		261	break;
		262	default:
		263	oflags \|= O_RDONLY;
		264	}
		265
		266	path.mnt = fhp->fh_export->ex_path.mnt;
		267	path.dentry = child;
		268	filp = dentry_create(&path, oflags, open->op_iattr.ia_mode,
		269	current_cred());
		270	if (IS_ERR(filp))
		271	return nfserrno(PTR_ERR(filp));
		272
		273	open->op_filp = filp;
		274	return nfs_ok;
		275	}
		276
246	/*	277	/*
247	* Implement NFSv4's unchecked, guarded, and exclusive create	278	* Implement NFSv4's unchecked, guarded, and exclusive create
248	* semantics for regular files. Open state for this new file is	279	* semantics for regular files. Open state for this new file is
@@ -355,11 +386,9 @@ nfsd4_create_file(struct svc_rqst rqstp, struct svc_fh fhp, · 106 unmodified lines
355	if (!IS_POSIXACL(inode))	386	if (!IS_POSIXACL(inode))
356	iap->ia_mode &= ~current_umask();	387	iap->ia_mode &= ~current_umask();
357		388
358	host_err = vfs_create(&init_user_ns, inode, child, iap->ia_mode, true);	389	status = nfsd4_vfs_create(fhp, child, open);
359	if (host_err < 0) {	390	if (status != nfs_ok)
360	status = nfserrno(host_err);
361	goto out;	391	goto out;
362	}
363	open->op_created = true;	392	open->op_created = true;
364		393
365	/* A newly created file already has a file size of zero. */	394	/* A newly created file already has a file size of zero. */
@@ -517,6 +546,8 @@ nfsd4_open(struct svc_rqst rqstp, struct nfsd4_compound_state cstate, · 151 unmodified lines
517	(int)open->op_fnamelen, open->op_fname,	546	(int)open->op_fnamelen, open->op_fname,
518	open->op_openowner);	547	open->op_openowner);
519		548
		549	open->op_filp = NULL;
		550
520	/* This check required by spec. */	551	/* This check required by spec. */
521	if (open->op_create && open->op_claim_type != NFS4_OPEN_CLAIM_NULL)	552	if (open->op_create && open->op_claim_type != NFS4_OPEN_CLAIM_NULL)
522	return nfserr_inval;	553	return nfserr_inval;
@@ -613,6 +644,10 @@ nfsd4_open(struct svc_rqst rqstp, struct nfsd4_compound_state cstate, · 90 unmodified lines
613	if (reclaim && !status)	644	if (reclaim && !status)
614	nn->somebody_reclaimed = true;	645	nn->somebody_reclaimed = true;
615	out:	646	out:
		647	if (open->op_filp) {
		648	fput(open->op_filp);
		649	open->op_filp = NULL;
		650	}
616	if (resfh && resfh != &cstate->current_fh) {	651	if (resfh && resfh != &cstate->current_fh) {
617	fh_dup2(&cstate->current_fh, resfh);	652	fh_dup2(&cstate->current_fh, resfh);
618	fh_put(resfh);	653	fh_put(resfh);

fs/nfsd/nfs4state.c+13−3

@@ -5093,9 +5093,19 @@ static __be32 nfs4_get_vfs_file(struct svc_rqst rqstp, struct nfs4_file fp, · 5092 unmodified lines
5093		5093
5094	if (!fp->fi_fds[oflag]) {	5094	if (!fp->fi_fds[oflag]) {
5095	spin_unlock(&fp->fi_lock);	5095	spin_unlock(&fp->fi_lock);
5096	status = nfsd_file_acquire(rqstp, cur_fh, access, &nf);	5096
5097	if (status)	5097	if (!open->op_filp) {
5098	goto out_put_access;	5098	status = nfsd_file_acquire(rqstp, cur_fh, access, &nf);
		5099	if (status != nfs_ok)
		5100	goto out_put_access;
		5101	} else {
		5102	status = nfsd_file_create(rqstp, cur_fh, access, &nf);
		5103	if (status != nfs_ok)
		5104	goto out_put_access;
		5105	nf->nf_file = open->op_filp;
		5106	open->op_filp = NULL;
		5107	}
		5108
5099	spin_lock(&fp->fi_lock);	5109	spin_lock(&fp->fi_lock);
5100	if (!fp->fi_fds[oflag]) {	5110	if (!fp->fi_fds[oflag]) {
5101	fp->fi_fds[oflag] = nf;	5111	fp->fi_fds[oflag] = nf;

fs/nfsd/xdr4.h+1−0

@@ -273,6 +273,7 @@ struct nfsd4_open { · 272 unmodified lines
273	bool op_truncate; /* used during processing */	273	bool op_truncate; /* used during processing */
274	bool op_created; /* used during processing */	274	bool op_created; /* used during processing */
275	struct nfs4_openowner op_openowner; / used during processing */	275	struct nfs4_openowner op_openowner; / used during processing */
		276	struct file op_filp; / used during processing */
276	struct nfs4_file op_file; / used during processing */	277	struct nfs4_file op_file; / used during processing */
277	struct nfs4_ol_stateid op_stp; / used during processing */	278	struct nfs4_ol_stateid op_stp; / used during processing */
278	struct nfs4_clnt_odstate op_odstate; / used during processing */	279	struct nfs4_clnt_odstate op_odstate; / used during processing */

fs/open.c+42−0

@@ -981,6 +981,48 @@ struct file dentry_open(const struct path path, int flags, · 980 unmodified lines
981	}	981	}
982	EXPORT_SYMBOL(dentry_open);	982	EXPORT_SYMBOL(dentry_open);
983		983
		984	/**
		985	* dentry_create - Create and open a file
		986	* @path: path to create
		987	* @flags: O_ flags
		988	* @mode: mode bits for new file
		989	* @cred: credentials to use
		990	*
		991	* Caller must hold the parent directory's lock, and have prepared
		992	* a negative dentry, placed in @path->dentry, for the new file.
		993	*
		994	* Caller sets @path->mnt to the vfsmount of the filesystem where
		995	* the new file is to be created. The parent directory and the
		996	* negative dentry must reside on the same filesystem instance.
		997	*
		998	* On success, returns a "struct file *". Otherwise a ERR_PTR
		999	* is returned.
		1000	*/
		1001	struct file dentry_create(const struct path path, int flags, umode_t mode,
		1002	const struct cred *cred)
		1003	{
		1004	struct file *f;
		1005	int error;
		1006
		1007	validate_creds(cred);
		1008	f = alloc_empty_file(flags, cred);
		1009	if (IS_ERR(f))
		1010	return f;
		1011
		1012	error = vfs_create(mnt_user_ns(path->mnt),
		1013	d_inode(path->dentry->d_parent),
		1014	path->dentry, mode, true);
		1015	if (!error)
		1016	error = vfs_open(path, f);
		1017
		1018	if (unlikely(error)) {
		1019	fput(f);
		1020	return ERR_PTR(error);
		1021	}
		1022	return f;
		1023	}
		1024	EXPORT_SYMBOL(dentry_create);
		1025
984	struct file open_with_fake_path(const struct path path, int flags,	1026	struct file open_with_fake_path(const struct path path, int flags,
985	struct inode inode, const struct cred cred)	1027	struct inode inode, const struct cred cred)
986	{	1028	{

include/linux/fs.h+2−0

 			      name, flags, mode);
 }
 extern struct file * dentry_open(const struct path *, int, const struct cred *);
+extern struct file *dentry_create(const struct path *path, int flags,
+				  umode_t mode, const struct cred *cred);
 extern struct file * open_with_fake_path(const struct path *, int,
 					 struct inode*, const struct cred *);
 static inline struct file *file_clone_open(struct file *file)

NFSD: Instantiate a struct file when creating a regular NFSv4 file

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