Commit 3dcd1d8a authored by J. Bruce Fields's avatar J. Bruce Fields Committed by Chuck Lever
Browse files

nfsd: improve stateid access bitmask documentation 



The use of the bitmaps is confusing.  Add a cross-reference to make it
easier to find the existing comment.  Add an updated reference with URL
to make it quicker to look up.  And a bit more editorializing about the
value of this.

Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent 70e94d75

fs/nfsd/nfs4state.c

+10 −4
Original line number Diff line number Diff line
@@ -360,11 +360,13 @@ static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops = { 
 * st_{access,deny}_bmap field of the stateid, in order to track not

 * only what share bits are currently in force, but also what

 * combinations of share bits previous opens have used.  This allows us

 * to enforce the recommendation of rfc 3530 14.2.19 that the server

 * return an error if the client attempt to downgrade to a combination

 * of share bits not explicable by closing some of its previous opens.

 * to enforce the recommendation in

 * https://datatracker.ietf.org/doc/html/rfc7530#section-16.19.4 that

 * the server return an error if the client attempt to downgrade to a

 * combination of share bits not explicable by closing some of its

 * previous opens.

 *

 * XXX: This enforcement is actually incomplete, since we don't keep

 * This enforcement is arguably incomplete, since we don't keep

 * track of access/deny bit combinations; so, e.g., we allow:

 *

 *	OPEN allow read, deny write
@@ -372,6 +374,10 @@ static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops = { 
 *	DOWNGRADE allow read, deny none

 *

 * which we should reject.

 *

 * But you could also argue that our current code is already overkill,

 * since it only exists to return NFS4ERR_INVAL on incorrect client

 * behavior.

 */

static unsigned int

bmap_to_share_mode(unsigned long bmap)

fs/nfsd/state.h

+4 −0
Original line number Diff line number Diff line
@@ -568,6 +568,10 @@ struct nfs4_ol_stateid { 
	struct list_head		st_locks;

	struct nfs4_stateowner		*st_stateowner;

	struct nfs4_clnt_odstate	*st_clnt_odstate;

/*

 * These bitmasks use 3 separate bits for READ, ALLOW, and BOTH; see the

 * comment above bmap_to_share_mode() for explanation:

 */

	unsigned char			st_access_bmap;

	unsigned char			st_deny_bmap;

	struct nfs4_ol_stateid		*st_openstp;