Re: [PATCH 5/8] Keep read and write fds with each nlm_file

[Chuck Lever III <chuck.lever@oracle.com>]

Nit: short description should start with "nlm:"


> On Aug 20, 2021, at 5:02 PM, J. Bruce Fields <bfields@redhat.com> wrote:
> 
> From: "J. Bruce Fields" <bfields@redhat.com>
> 
> We shouldn't really be using a read-only file descriptor to take a write
> lock.
> 
> Most filesystems will put up with it.  But NFS, for example, won't.

Two overall concerns:

1. Would it be easy/possible to split this patch further?

2. What kind of testing would provide a level of confidence
   that no regressions have been introduced by this change?


> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> ---
> fs/lockd/svc4proc.c         |   4 +-
> fs/lockd/svclock.c          |  25 ++++++---
> fs/lockd/svcproc.c          |   4 +-
> fs/lockd/svcsubs.c          | 104 +++++++++++++++++++++++++-----------
> fs/nfsd/lockd.c             |   8 ++-
> include/linux/lockd/bind.h  |   3 +-
> include/linux/lockd/lockd.h |   9 +++-
> 7 files changed, 114 insertions(+), 43 deletions(-)
> 
> diff --git a/fs/lockd/svc4proc.c b/fs/lockd/svc4proc.c
> index aa8eca7c38a1..c7587de948e4 100644
> --- a/fs/lockd/svc4proc.c
> +++ b/fs/lockd/svc4proc.c
> @@ -40,12 +40,14 @@ nlm4svc_retrieve_args(struct svc_rqst *rqstp, struct nlm_args *argp,
> 
> 	/* Obtain file pointer. Not used by FREE_ALL call. */
> 	if (filp != NULL) {
> +		int mode = lock_to_openmode(&lock->fl);
> +
> 		if ((error = nlm_lookup_file(rqstp, &file, lock)) != 0)
> 			goto no_locks;
> 		*filp = file;
> 
> 		/* Set up the missing parts of the file_lock structure */
> -		lock->fl.fl_file  = file->f_file;
> +		lock->fl.fl_file  = file->f_file[mode];
> 		lock->fl.fl_pid = current->tgid;
> 		lock->fl.fl_lmops = &nlmsvc_lock_operations;
> 		nlmsvc_locks_init_private(&lock->fl, host, (pid_t)lock->svid);
> diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
> index bc1cf31f3cce..d60e6eea2d57 100644
> --- a/fs/lockd/svclock.c
> +++ b/fs/lockd/svclock.c
> @@ -471,6 +471,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
> {
> 	struct nlm_block	*block = NULL;
> 	int			error;
> +	int			mode;
> 	__be32			ret;
> 
> 	dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
> @@ -524,7 +525,8 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
> 
> 	if (!wait)
> 		lock->fl.fl_flags &= ~FL_SLEEP;
> -	error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
> +	mode = lock_to_openmode(&lock->fl);
> +	error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL);
> 	lock->fl.fl_flags &= ~FL_SLEEP;
> 
> 	dprintk("lockd: vfs_lock_file returned %d\n", error);
> @@ -577,6 +579,7 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
> 		struct nlm_lock *conflock, struct nlm_cookie *cookie)
> {
> 	int			error;
> +	int			mode;
> 	__be32			ret;
> 	struct nlm_lockowner	*test_owner;
> 
> @@ -595,7 +598,8 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
> 	/* If there's a conflicting lock, remember to clean up the test lock */
> 	test_owner = (struct nlm_lockowner *)lock->fl.fl_owner;
> 
> -	error = vfs_test_lock(file->f_file, &lock->fl);
> +	mode = lock_to_openmode(&lock->fl);
> +	error = vfs_test_lock(file->f_file[mode], &lock->fl);
> 	if (error) {
> 		/* We can't currently deal with deferred test requests */
> 		if (error == FILE_LOCK_DEFERRED)
> @@ -641,7 +645,7 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
> __be32
> nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
> {
> -	int	error;
> +	int	error = 0;
> 
> 	dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
> 				nlmsvc_file_inode(file)->i_sb->s_id,
> @@ -654,7 +658,12 @@ nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
> 	nlmsvc_cancel_blocked(net, file, lock);
> 
> 	lock->fl.fl_type = F_UNLCK;
> -	error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
> +	if (file->f_file[0])
> +		error = vfs_lock_file(file->f_file[0], F_SETLK,
> +					&lock->fl, NULL);
> +	if (file->f_file[1])
> +		error = vfs_lock_file(file->f_file[1], F_SETLK,
> +					&lock->fl, NULL);

Eschew raw integers :-) Should the f_file array be indexed
using O_ flags as the comment below suggests?


> 	return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
> }
> @@ -671,6 +680,7 @@ nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *l
> {
> 	struct nlm_block	*block;
> 	int status = 0;
> +	int mode;
> 
> 	dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
> 				nlmsvc_file_inode(file)->i_sb->s_id,
> @@ -686,7 +696,8 @@ nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *l
> 	block = nlmsvc_lookup_block(file, lock);
> 	mutex_unlock(&file->f_mutex);
> 	if (block != NULL) {
> -		vfs_cancel_lock(block->b_file->f_file,
> +		mode = lock_to_openmode(&lock->fl);
> +		vfs_cancel_lock(block->b_file->f_file[mode],
> 				&block->b_call->a_args.lock.fl);
> 		status = nlmsvc_unlink_block(block);
> 		nlmsvc_release_block(block);
> @@ -803,6 +814,7 @@ nlmsvc_grant_blocked(struct nlm_block *block)
> {
> 	struct nlm_file		*file = block->b_file;
> 	struct nlm_lock		*lock = &block->b_call->a_args.lock;
> +	int			mode;
> 	int			error;
> 	loff_t			fl_start, fl_end;
> 
> @@ -828,7 +840,8 @@ nlmsvc_grant_blocked(struct nlm_block *block)
> 	lock->fl.fl_flags |= FL_SLEEP;
> 	fl_start = lock->fl.fl_start;
> 	fl_end = lock->fl.fl_end;
> -	error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
> +	mode = lock_to_openmode(&lock->fl);
> +	error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL);
> 	lock->fl.fl_flags &= ~FL_SLEEP;
> 	lock->fl.fl_start = fl_start;
> 	lock->fl.fl_end = fl_end;
> diff --git a/fs/lockd/svcproc.c b/fs/lockd/svcproc.c
> index f4e5e0eb30fd..99696d3f6dd6 100644
> --- a/fs/lockd/svcproc.c
> +++ b/fs/lockd/svcproc.c
> @@ -55,6 +55,7 @@ nlmsvc_retrieve_args(struct svc_rqst *rqstp, struct nlm_args *argp,
> 	struct nlm_host		*host = NULL;
> 	struct nlm_file		*file = NULL;
> 	struct nlm_lock		*lock = &argp->lock;
> +	int			mode;
> 	__be32			error = 0;
> 
> 	/* nfsd callbacks must have been installed for this procedure */
> @@ -75,7 +76,8 @@ nlmsvc_retrieve_args(struct svc_rqst *rqstp, struct nlm_args *argp,
> 		*filp = file;
> 
> 		/* Set up the missing parts of the file_lock structure */
> -		lock->fl.fl_file  = file->f_file;
> +		mode = lock_to_openmode(&lock->fl);
> +		lock->fl.fl_file  = file->f_file[mode];
> 		lock->fl.fl_pid = current->tgid;
> 		lock->fl.fl_lmops = &nlmsvc_lock_operations;
> 		nlmsvc_locks_init_private(&lock->fl, host, (pid_t)lock->svid);
> diff --git a/fs/lockd/svcsubs.c b/fs/lockd/svcsubs.c
> index f43d89e89c45..a0adaee245ae 100644
> --- a/fs/lockd/svcsubs.c
> +++ b/fs/lockd/svcsubs.c
> @@ -71,14 +71,38 @@ static inline unsigned int file_hash(struct nfs_fh *f)
> 	return tmp & (FILE_NRHASH - 1);
> }
> 
> +int lock_to_openmode(struct file_lock *lock)
> +{
> +	if (lock->fl_type == F_WRLCK)
> +		return O_WRONLY;
> +	else
> +		return O_RDONLY;

Style: a ternary would be more consistent with other areas
of the code you change in this patch.


> +}
> +
> +/*
> + * Open the file. Note that if we're reexporting, for example,
> + * this could block the lockd thread for a while.
> + *
> + * We have to make sure we have the right credential to open
> + * the file.
> + */
> +static __be32 nlm_do_fopen(struct svc_rqst *rqstp,
> +			   struct nlm_file *file, int mode)
> +{
> +	struct file **fp = &file->f_file[mode];
> +	__be32	nfserr;
> +
> +	if (*fp)
> +		return 0;
> +	nfserr = nlmsvc_ops->fopen(rqstp, &file->f_handle, fp, mode);
> +	if (nfserr)
> +		dprintk("lockd: open failed (error %d)\n", nfserr);
> +	return nfserr;
> +}
> +
> /*
>  * Lookup file info. If it doesn't exist, create a file info struct
>  * and open a (VFS) file for the given inode.
> - *
> - * FIXME:
> - * Note that we open the file O_RDONLY even when creating write locks.
> - * This is not quite right, but for now, we assume the client performs
> - * the proper R/W checking.
>  */
> __be32
> nlm_lookup_file(struct svc_rqst *rqstp, struct nlm_file **result,
> @@ -87,41 +111,38 @@ nlm_lookup_file(struct svc_rqst *rqstp, struct nlm_file **result,
> 	struct nlm_file	*file;
> 	unsigned int	hash;
> 	__be32		nfserr;
> +	int		mode;
> 
> 	nlm_debug_print_fh("nlm_lookup_file", &lock->fh);
> 
> 	hash = file_hash(&lock->fh);
> +	mode = lock_to_openmode(&lock->fl);
> 
> 	/* Lock file table */
> 	mutex_lock(&nlm_file_mutex);
> 
> 	hlist_for_each_entry(file, &nlm_files[hash], f_list)
> -		if (!nfs_compare_fh(&file->f_handle, &lock->fh))
> +		if (!nfs_compare_fh(&file->f_handle, &lock->fh)) {
> +			mutex_lock(&file->f_mutex);
> +			nfserr = nlm_do_fopen(rqstp, file, mode);
> +			mutex_unlock(&file->f_mutex);
> 			goto found;
> -
> +		}
> 	nlm_debug_print_fh("creating file for", &lock->fh);
> 
> 	nfserr = nlm_lck_denied_nolocks;
> 	file = kzalloc(sizeof(*file), GFP_KERNEL);
> 	if (!file)
> -		goto out_unlock;
> +		goto out_free;
> 
> 	memcpy(&file->f_handle, &lock->fh, sizeof(struct nfs_fh));
> 	mutex_init(&file->f_mutex);
> 	INIT_HLIST_NODE(&file->f_list);
> 	INIT_LIST_HEAD(&file->f_blocks);
> 
> -	/*
> -	 * Open the file. Note that if we're reexporting, for example,
> -	 * this could block the lockd thread for a while.
> -	 *
> -	 * We have to make sure we have the right credential to open
> -	 * the file.
> -	 */
> -	if ((nfserr = nlmsvc_ops->fopen(rqstp, &lock->fh, &file->f_file)) != 0) {
> -		dprintk("lockd: open failed (error %d)\n", nfserr);
> -		goto out_free;
> -	}
> +	nfserr = nlm_do_fopen(rqstp, file, mode);
> +	if (nfserr)
> +		goto out_unlock;
> 
> 	hlist_add_head(&file->f_list, &nlm_files[hash]);
> 
> @@ -129,7 +150,6 @@ nlm_lookup_file(struct svc_rqst *rqstp, struct nlm_file **result,
> 	dprintk("lockd: found file %p (count %d)\n", file, file->f_count);
> 	*result = file;
> 	file->f_count++;
> -	nfserr = 0;
> 
> out_unlock:
> 	mutex_unlock(&nlm_file_mutex);
> @@ -149,13 +169,34 @@ nlm_delete_file(struct nlm_file *file)
> 	nlm_debug_print_file("closing file", file);
> 	if (!hlist_unhashed(&file->f_list)) {
> 		hlist_del(&file->f_list);
> -		nlmsvc_ops->fclose(file->f_file);
> +		if (file->f_file[O_RDONLY])
> +			nlmsvc_ops->fclose(file->f_file[O_RDONLY]);
> +		if (file->f_file[O_WRONLY])
> +			nlmsvc_ops->fclose(file->f_file[O_WRONLY]);
> 		kfree(file);
> 	} else {
> 		printk(KERN_WARNING "lockd: attempt to release unknown file!\n");
> 	}
> }
> 
> +static int nlm_unlock_files(struct nlm_file *file)
> +{
> +	struct file_lock lock;
> +	struct file *f;
> +
> +	lock.fl_type  = F_UNLCK;
> +	lock.fl_start = 0;
> +	lock.fl_end   = OFFSET_MAX;
> +	for (f = file->f_file[0]; f <= file->f_file[1]; f++) {
> +		if (f && vfs_lock_file(f, F_SETLK, &lock, NULL) < 0) {
> +			printk("lockd: unlock failure in %s:%d\n",
> +				__FILE__, __LINE__);

This needs a KERN_LEVEL and maybe a _once.


> +			return 1;
> +		}
> +	}
> +	return 0;
> +}
> +
> /*
>  * Loop over all locks on the given file and perform the specified
>  * action.
> @@ -183,17 +224,10 @@ nlm_traverse_locks(struct nlm_host *host, struct nlm_file *file,
> 
> 		lockhost = ((struct nlm_lockowner *)fl->fl_owner)->host;
> 		if (match(lockhost, host)) {
> -			struct file_lock lock = *fl;
> 
> 			spin_unlock(&flctx->flc_lock);
> -			lock.fl_type  = F_UNLCK;
> -			lock.fl_start = 0;
> -			lock.fl_end   = OFFSET_MAX;
> -			if (vfs_lock_file(file->f_file, F_SETLK, &lock, NULL) < 0) {
> -				printk("lockd: unlock failure in %s:%d\n",
> -						__FILE__, __LINE__);
> +			if (nlm_unlock_files(file))
> 				return 1;
> -			}
> 			goto again;
> 		}
> 	}
> @@ -247,6 +281,15 @@ nlm_file_inuse(struct nlm_file *file)
> 	return 0;
> }
> 
> +static void nlm_close_files(struct nlm_file *file)
> +{
> +	struct file *f;
> +
> +	for (f = file->f_file[0]; f <= file->f_file[1]; f++)
> +		if (f)
> +			nlmsvc_ops->fclose(f);
> +}
> +
> /*
>  * Loop over all files in the file table.
>  */
> @@ -277,7 +320,7 @@ nlm_traverse_files(void *data, nlm_host_match_fn_t match,
> 			if (list_empty(&file->f_blocks) && !file->f_locks
> 			 && !file->f_shares && !file->f_count) {
> 				hlist_del(&file->f_list);
> -				nlmsvc_ops->fclose(file->f_file);
> +				nlm_close_files(file);
> 				kfree(file);
> 			}
> 		}
> @@ -411,6 +454,7 @@ nlmsvc_invalidate_all(void)
> 	nlm_traverse_files(NULL, nlmsvc_is_client, NULL);
> }
> 
> +
> static int
> nlmsvc_match_sb(void *datap, struct nlm_file *file)
> {
> diff --git a/fs/nfsd/lockd.c b/fs/nfsd/lockd.c
> index 3f5b3d7b62b7..606fa155c28a 100644
> --- a/fs/nfsd/lockd.c
> +++ b/fs/nfsd/lockd.c
> @@ -25,9 +25,11 @@
>  * Note: we hold the dentry use count while the file is open.
>  */
> static __be32
> -nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp)
> +nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp,
> +		int mode)
> {
> 	__be32		nfserr;
> +	int		access;
> 	struct svc_fh	fh;
> 
> 	/* must initialize before using! but maxsize doesn't matter */
> @@ -36,7 +38,9 @@ nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp)
> 	memcpy((char*)&fh.fh_handle.fh_base, f->data, f->size);
> 	fh.fh_export = NULL;
> 
> -	nfserr = nfsd_open(rqstp, &fh, S_IFREG, NFSD_MAY_LOCK, filp);
> +	access = (mode == O_WRONLY) ? NFSD_MAY_WRITE : NFSD_MAY_READ;
> +	access |= NFSD_MAY_LOCK;
> +	nfserr = nfsd_open(rqstp, &fh, S_IFREG, access, filp);
> 	fh_put(&fh);
>  	/* We return nlm error codes as nlm doesn't know
> 	 * about nfsd, but nfsd does know about nlm..
> diff --git a/include/linux/lockd/bind.h b/include/linux/lockd/bind.h
> index 0520c0cd73f4..3bc9f7410e21 100644
> --- a/include/linux/lockd/bind.h
> +++ b/include/linux/lockd/bind.h
> @@ -27,7 +27,8 @@ struct rpc_task;
> struct nlmsvc_binding {
> 	__be32			(*fopen)(struct svc_rqst *,
> 						struct nfs_fh *,
> -						struct file **);
> +						struct file **,
> +						int mode);

Style: "mode_t mode" might be better internal documentation.


> 	void			(*fclose)(struct file *);
> };
> 
> diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
> index 81b71ad2040a..da319de7e557 100644
> --- a/include/linux/lockd/lockd.h
> +++ b/include/linux/lockd/lockd.h
> @@ -10,6 +10,8 @@
> #ifndef LINUX_LOCKD_LOCKD_H
> #define LINUX_LOCKD_LOCKD_H
> 
> +/* XXX: a lot of this should really be under fs/lockd. */
> +
> #include <linux/in.h>
> #include <linux/in6.h>
> #include <net/ipv6.h>
> @@ -154,7 +156,8 @@ struct nlm_rqst {
> struct nlm_file {
> 	struct hlist_node	f_list;		/* linked list */
> 	struct nfs_fh		f_handle;	/* NFS file handle */
> -	struct file *		f_file;		/* VFS file pointer */
> +	struct file *		f_file[2];	/* VFS file pointers,
> +						   indexed by O_ flags */

Right, except that the new code in this patch always indexes
f_file with raw integers, making the comment misleading. My
preference is to keep the comment and change the new code to
index f_file symbolically.


> 	struct nlm_share *	f_shares;	/* DOS shares */
> 	struct list_head	f_blocks;	/* blocked locks */
> 	unsigned int		f_locks;	/* guesstimate # of locks */
> @@ -267,6 +270,7 @@ typedef int	  (*nlm_host_match_fn_t)(void *cur, struct nlm_host *ref);
> /*
>  * Server-side lock handling
>  */
> +int		  lock_to_openmode(struct file_lock *);
> __be32		  nlmsvc_lock(struct svc_rqst *, struct nlm_file *,
> 			      struct nlm_host *, struct nlm_lock *, int,
> 			      struct nlm_cookie *, int);
> @@ -301,7 +305,8 @@ int           nlmsvc_unlock_all_by_ip(struct sockaddr *server_addr);
> 
> static inline struct inode *nlmsvc_file_inode(struct nlm_file *file)
> {
> -	return locks_inode(file->f_file);
> +	return locks_inode(file->f_file[0] ?
> +				file->f_file[0] : file->f_file[1]);
> }
> 
> static inline int __nlm_privileged_request4(const struct sockaddr *sap)
> -- 
> 2.31.1
> 

--
Chuck Lever