This is a note to let you know that I've just added the patch titled
nfsd: improve stateid access bitmask documentation
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nfsd-improve-stateid-access-bitmask-documentation.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 08f67d1d92aef5009a0a869f8988419d49f4aac7
Author: J. Bruce Fields <bfields@xxxxxxxxxxxx>
Date: Tue Dec 7 17:32:21 2021 -0500
nfsd: improve stateid access bitmask documentation
[ Upstream commit 3dcd1d8aab00c5d3a0a3725253c86440b1a0f5a7 ]
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: J. Bruce Fields <bfields@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index e14b38d6751d8..f7e2beded6d7f 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -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)
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index e73bdbb1634ab..6eb3c7157214b 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -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;
