Commit e7a8ebc3 authored by Dai Ngo's avatar Dai Ngo Committed by Chuck Lever
Browse files

NFSD: Offer write delegation for OPEN with OPEN4_SHARE_ACCESS_WRITE 



RFC8881, section 9.1.2 says:

  "In the case of READ, the server may perform the corresponding
   check on the access mode, or it may choose to allow READ for
   OPEN4_SHARE_ACCESS_WRITE, to accommodate clients whose WRITE
   implementation may unavoidably do reads (e.g., due to buffer cache
   constraints)."

and in section 10.4.1:
   "Similarly, when closing a file opened for OPEN4_SHARE_ACCESS_WRITE/
   OPEN4_SHARE_ACCESS_BOTH and if an OPEN_DELEGATE_WRITE delegation
   is in effect"

This patch allows READ using write delegation stateid granted on OPENs
with OPEN4_SHARE_ACCESS_WRITE only, to accommodate clients whose WRITE
implementation may unavoidably do (e.g., due to buffer cache
constraints).

For write delegation granted for OPEN with OPEN4_SHARE_ACCESS_WRITE
a new nfsd_file and a struct file are allocated to use for reads.
The nfsd_file is freed when the file is closed by release_all_access.

Suggested-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarDai Ngo <dai.ngo@oracle.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent 347e9f50

fs/nfsd/nfs4state.c

+47 −28
Original line number Diff line number Diff line
@@ -633,18 +633,6 @@ find_readable_file(struct nfs4_file *f) 
	return ret;

}



static struct nfsd_file *

find_rw_file(struct nfs4_file *f)

{

	struct nfsd_file *ret;



	spin_lock(&f->fi_lock);

	ret = nfsd_file_get(f->fi_fds[O_RDWR]);

	spin_unlock(&f->fi_lock);



	return ret;

}



struct nfsd_file *

find_any_file(struct nfs4_file *f)

{
@@ -6000,14 +5988,19 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp, 
	 *  "An OPEN_DELEGATE_WRITE delegation allows the client to handle,

	 *   on its own, all opens."

	 *

	 * Furthermore the client can use a write delegation for most READ

	 * operations as well, so we require a O_RDWR file here.

	 * Furthermore, section 9.1.2 says:

	 *

	 *  "In the case of READ, the server may perform the corresponding

	 *  check on the access mode, or it may choose to allow READ for

	 *  OPEN4_SHARE_ACCESS_WRITE, to accommodate clients whose WRITE

	 *  implementation may unavoidably do reads (e.g., due to buffer

	 *  cache constraints)."

	 *

	 * Offer a write delegation in the case of a BOTH open, and ensure

	 * we get the O_RDWR descriptor.

	 *  We choose to offer a write delegation for OPEN with the

	 *  OPEN4_SHARE_ACCESS_WRITE access mode to accommodate such clients.

	 */

	if ((open->op_share_access & NFS4_SHARE_ACCESS_BOTH) == NFS4_SHARE_ACCESS_BOTH) {

		nf = find_rw_file(fp);

	if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) {

		nf = find_writeable_file(fp);

		dl_type = deleg_ts ? OPEN_DELEGATE_WRITE_ATTRS_DELEG : OPEN_DELEGATE_WRITE;

	}
@@ -6138,7 +6131,7 @@ static bool 
nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh,

		     struct kstat *stat)

{

	struct nfsd_file *nf = find_rw_file(dp->dl_stid.sc_file);

	struct nfsd_file *nf = find_writeable_file(dp->dl_stid.sc_file);

	struct path path;

	int rc;
@@ -6156,6 +6149,33 @@ nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh, 
	return rc == 0;

}



/*

 * Add NFS4_SHARE_ACCESS_READ to the write delegation granted on OPEN

 * with NFS4_SHARE_ACCESS_WRITE by allocating separate nfsd_file and

 * struct file to be used for read with delegation stateid.

 *

 */

static bool

nfsd4_add_rdaccess_to_wrdeleg(struct svc_rqst *rqstp, struct nfsd4_open *open,

			      struct svc_fh *fh, struct nfs4_ol_stateid *stp)

{

	struct nfs4_file *fp;

	struct nfsd_file *nf = NULL;



	if ((open->op_share_access & NFS4_SHARE_ACCESS_BOTH) ==

			NFS4_SHARE_ACCESS_WRITE) {

		if (nfsd_file_acquire_opened(rqstp, fh, NFSD_MAY_READ, NULL, &nf))

			return (false);

		fp = stp->st_stid.sc_file;

		spin_lock(&fp->fi_lock);

		__nfs4_file_get_access(fp, NFS4_SHARE_ACCESS_READ);

		fp = stp->st_stid.sc_file;

		fp->fi_fds[O_RDONLY] = nf;

		spin_unlock(&fp->fi_lock);

	}

	return true;

}



/*

 * The Linux NFS server does not offer write delegations to NFSv4.0

 * clients in order to avoid conflicts between write delegations and
@@ -6181,8 +6201,9 @@ nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh, 
 * open or lock state.

 */

static void

nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,

		     struct svc_fh *currentfh)

nfs4_open_delegation(struct svc_rqst *rqstp, struct nfsd4_open *open,

		     struct nfs4_ol_stateid *stp, struct svc_fh *currentfh,

		     struct svc_fh *fh)

{

	struct nfs4_openowner *oo = openowner(stp->st_stateowner);

	bool deleg_ts = nfsd4_want_deleg_timestamps(open);
@@ -6227,7 +6248,8 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp, 
	memcpy(&open->op_delegate_stateid, &dp->dl_stid.sc_stateid, sizeof(dp->dl_stid.sc_stateid));



	if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) {

		if (!nfs4_delegation_stat(dp, currentfh, &stat)) {

		if (!nfsd4_add_rdaccess_to_wrdeleg(rqstp, open, fh, stp) ||

				!nfs4_delegation_stat(dp, currentfh, &stat)) {

			nfs4_put_stid(&dp->dl_stid);

			destroy_delegation(dp);

			goto out_no_deleg;
@@ -6383,7 +6405,8 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf 
	* Attempt to hand out a delegation. No error return, because the

	* OPEN succeeds even if we fail.

	*/

	nfs4_open_delegation(open, stp, &resp->cstate.current_fh);

	nfs4_open_delegation(rqstp, open, stp,

		&resp->cstate.current_fh, current_fh);



	/*

	 * If there is an existing open stateid, it must be updated and
@@ -7076,7 +7099,7 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate, 
		return_revoked = true;

	if (typemask & SC_TYPE_DELEG)

		/* Always allow REVOKED for DELEG so we can

		 * retturn the appropriate error.

		 * return the appropriate error.

		 */

		statusmask |= SC_STATUS_REVOKED;
@@ -7119,10 +7142,6 @@ nfs4_find_file(struct nfs4_stid *s, int flags) 


	switch (s->sc_type) {

	case SC_TYPE_DELEG:

		spin_lock(&s->sc_file->fi_lock);

		ret = nfsd_file_get(s->sc_file->fi_deleg_file);

		spin_unlock(&s->sc_file->fi_lock);

		break;

	case SC_TYPE_OPEN:

	case SC_TYPE_LOCK:

		if (flags & RD_STATE)