On Fri, Jul 04, 2008 at 03:34:11PM +0300, Benny Halevy wrote:
> On Jul. 03, 2008, 23:36 +0300, "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote:
> > We're just trying to enforce rfc 3530 14.2.19:
>
> OK. I see.
> Thanks for explaining!
> It is a bit mind boggling, maybe adding some comments explaining
> why the bitmap is needed would help...
Where do you think you would have looked for a comment? I figured just
before the helper functions here was one obvious place.
--b.
commit 4f83aa302f8f8b42397c6d3703d670f0588c03ec
Author: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>
Date: Mon Jul 7 15:02:02 2008 -0400
nfsd: document open share bit tracking
It's not immediately obvious from the code why we're doing this.
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>
Cc: Benny Halevy <bhalevy@xxxxxxxxxxx>
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index eca8aaa..c29b6ed 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1173,6 +1173,24 @@ static inline int deny_valid(u32 x)
return x <= NFS4_SHARE_DENY_BOTH;
}
+/*
+ * We store the NONE, READ, WRITE, and BOTH bits separately in the
+ * 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.
+ *
+ * XXX: This enforcement is actually incomplete, since we don't keep
+ * track of access/deny bit combinations; so, e.g., we allow:
+ *
+ * OPEN allow read, deny write
+ * OPEN allow both, deny none
+ * DOWNGRADE allow read, deny none
+ *
+ * which we should reject.
+ */
static void
set_access(unsigned int *access, unsigned long bmap) {
int i;
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
