AFS development

Tested-by: Marc Dionne <marc.dionne@auristor.com>
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Merge tag 'afs-next-20190915' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull AFS updates from David Howells:
 "Here's a set of patches for AFS. The first three are trivial, deleting
  unused symbols and rolling out a wrapper function.

  The fourth and fifth patches make use of the previously added RCU-safe
  request_key facility to allow afs_permission() and afs_d_revalidate()
  to attempt to operate without dropping out of RCU-mode pathwalk. Under
  certain conditions, such as conflict with another client, we still
  have to drop out anyway, take a lock and consult the server"

* tag 'afs-next-20190915' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  afs: Support RCU pathwalk
  afs: Provide an RCU-capable key lookup
  afs: Use afs_extract_discard() rather than iov_iter_discard()
  afs: remove unused variable 'afs_zero_fid'
  afs: remove unused variable 'afs_voltypes'

fs/afs/dir.c

@@ -965,6 +965,58 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
 	return d;
 }
 
+/*
+ * Check the validity of a dentry under RCU conditions.
+ */
+static int afs_d_revalidate_rcu(struct dentry *dentry)
+{
+	struct afs_vnode *dvnode, *vnode;
+	struct dentry *parent;
+	struct inode *dir, *inode;
+	long dir_version, de_version;
+
+	_enter("%p", dentry);
+
+	/* Check the parent directory is still valid first. */
+	parent = READ_ONCE(dentry->d_parent);
+	dir = d_inode_rcu(parent);
+	if (!dir)
+		return -ECHILD;
+	dvnode = AFS_FS_I(dir);
+	if (test_bit(AFS_VNODE_DELETED, &dvnode->flags))
+		return -ECHILD;
+
+	if (!afs_check_validity(dvnode))
+		return -ECHILD;
+
+	/* We only need to invalidate a dentry if the server's copy changed
+	 * behind our back.  If we made the change, it's no problem.  Note that
+	 * on a 32-bit system, we only have 32 bits in the dentry to store the
+	 * version.
+	 */
+	dir_version = (long)READ_ONCE(dvnode->status.data_version);
+	de_version = (long)READ_ONCE(dentry->d_fsdata);
+	if (de_version != dir_version) {
+		dir_version = (long)READ_ONCE(dvnode->invalid_before);
+		if (de_version - dir_version < 0)
+			return -ECHILD;
+	}
+
+	/* Check to see if the vnode referred to by the dentry still
+	 * has a callback.
+	 */
+	if (d_really_is_positive(dentry)) {
+		inode = d_inode_rcu(dentry);
+		if (inode) {
+			vnode = AFS_FS_I(inode);
+			if (!afs_check_validity(vnode))
+				return -ECHILD;
+		}
+	}
+
+	return 1; /* Still valid */
+}
+
 /*
  * check that a dentry lookup hit has found a valid entry
  * - NOTE! the hit can be a negative hit too, so we can't assume we have an
@@ -982,7 +1034,7 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
 	int ret;
 
 	if (flags & LOOKUP_RCU)
-		return -ECHILD;
+		return afs_d_revalidate_rcu(dentry);
 
 	if (d_really_is_positive(dentry)) {
 		vnode = AFS_FS_I(d_inode(dentry));

fs/afs/fsclient.c

@@ -15,8 +15,6 @@
 #include "xdr_fs.h"
 #include "protocol_yfs.h"
 
-static const struct afs_fid afs_zero_fid;
-
 static inline void afs_use_fs_server(struct afs_call *call, struct afs_cb_interest *cbi)
 {
 	call->cbi = afs_get_cb_interest(cbi);
@@ -394,7 +392,7 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
 			goto no_more_data;
 
 		/* Discard any excess data the server gave us */
-		iov_iter_discard(&call->iter, READ, req->actual_len - req->len);
+		afs_extract_discard(call, req->actual_len - req->len);
 		call->unmarshall = 3;
 		/* Fall through */
 
@@ -1872,7 +1870,7 @@ static int afs_deliver_fs_get_capabilities(struct afs_call *call)
 
 		call->count = count;
 		call->count2 = count;
-		iov_iter_discard(&call->iter, READ, count * sizeof(__be32));
+		afs_extract_discard(call, count * sizeof(__be32));
 		call->unmarshall++;
 		/* Fall through */
 

fs/afs/internal.h

@@ -1217,6 +1217,7 @@ extern void afs_cache_permit(struct afs_vnode *, struct key *, unsigned int,
 			     struct afs_status_cb *);
 extern void afs_zap_permits(struct rcu_head *);
 extern struct key *afs_request_key(struct afs_cell *);
+extern struct key *afs_request_key_rcu(struct afs_cell *);
 extern int afs_check_permit(struct afs_vnode *, struct key *, afs_access_t *);
 extern int afs_permission(struct inode *, int);
 extern void __exit afs_clean_up_permit_cache(void);

fs/afs/security.c

@@ -27,8 +27,37 @@ struct key *afs_request_key(struct afs_cell *cell)
 	_enter("{%x}", key_serial(cell->anonymous_key));
 
 	_debug("key %s", cell->anonymous_key->description);
-	key = request_key(&key_type_rxrpc, cell->anonymous_key->description,
-			  NULL);
+	key = request_key_net(&key_type_rxrpc, cell->anonymous_key->description,
+			      cell->net->net, NULL);
+	if (IS_ERR(key)) {
+		if (PTR_ERR(key) != -ENOKEY) {
+			_leave(" = %ld", PTR_ERR(key));
+			return key;
+		}
+
+		/* act as anonymous user */
+		_leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
+		return key_get(cell->anonymous_key);
+	} else {
+		/* act as authorised user */
+		_leave(" = {%x} [auth]", key_serial(key));
+		return key;
+	}
+}
+
+/*
+ * Get a key when pathwalk is in rcuwalk mode.
+ */
+struct key *afs_request_key_rcu(struct afs_cell *cell)
+{
+	struct key *key;
+
+	_enter("{%x}", key_serial(cell->anonymous_key));
+
+	_debug("key %s", cell->anonymous_key->description);
+	key = request_key_net_rcu(&key_type_rxrpc,
+				  cell->anonymous_key->description,
+				  cell->net->net);
 	if (IS_ERR(key)) {
 		if (PTR_ERR(key) != -ENOKEY) {
 			_leave(" = %ld", PTR_ERR(key));
@@ -274,6 +303,40 @@ someone_else_changed_it:
 	return;
 }
 
+static bool afs_check_permit_rcu(struct afs_vnode *vnode, struct key *key,
+				 afs_access_t *_access)
+{
+	const struct afs_permits *permits;
+	int i;
+
+	_enter("{%llx:%llu},%x",
+	       vnode->fid.vid, vnode->fid.vnode, key_serial(key));
+
+	/* check the permits to see if we've got one yet */
+	if (key == vnode->volume->cell->anonymous_key) {
+		*_access = vnode->status.anon_access;
+		_leave(" = t [anon %x]", *_access);
+		return true;
+	}
+
+	permits = rcu_dereference(vnode->permit_cache);
+	if (permits) {
+		for (i = 0; i < permits->nr_permits; i++) {
+			if (permits->permits[i].key < key)
+				continue;
+			if (permits->permits[i].key > key)
+				break;
+
+			*_access = permits->permits[i].access;
+			_leave(" = %u [perm %x]", !permits->invalidated, *_access);
+			return !permits->invalidated;
+		}
+	}
+
+	_leave(" = f");
+	return false;
+}
+
 /*
  * check with the fileserver to see if the directory or parent directory is
  * permitted to be accessed with this authorisation, and if so, what access it
@@ -340,14 +403,21 @@ int afs_permission(struct inode *inode, int mask)
 	struct afs_vnode *vnode = AFS_FS_I(inode);
 	afs_access_t uninitialized_var(access);
 	struct key *key;
-	int ret;
-
-	if (mask & MAY_NOT_BLOCK)
-		return -ECHILD;
+	int ret = 0;
 
 	_enter("{{%llx:%llu},%lx},%x,",
 	       vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);
 
+	if (mask & MAY_NOT_BLOCK) {
+		key = afs_request_key_rcu(vnode->volume->cell);
+		if (IS_ERR(key))
+			return -ECHILD;
+
+		ret = -ECHILD;
+		if (!afs_check_validity(vnode) ||
+		    !afs_check_permit_rcu(vnode, key, &access))
+			goto error;
+	} else {
 		key = afs_request_key(vnode->volume->cell);
 		if (IS_ERR(key)) {
 			_leave(" = %ld [key]", PTR_ERR(key));
@@ -362,11 +432,13 @@ int afs_permission(struct inode *inode, int mask)
 		ret = afs_check_permit(vnode, key, &access);
 		if (ret < 0)
 			goto error;
+	}
 
 	/* interpret the access mask */
 	_debug("REQ %x ACC %x on %s",
 	       mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");
 
+	ret = 0;
 	if (S_ISDIR(inode->i_mode)) {
 		if (mask & (MAY_EXEC | MAY_READ | MAY_CHDIR)) {
 			if (!(access & AFS_ACE_LOOKUP))

fs/afs/volume.c

@@ -12,8 +12,6 @@
 unsigned __read_mostly afs_volume_gc_delay = 10;
 unsigned __read_mostly afs_volume_record_life = 60 * 60;
 
-static const char *const afs_voltypes[] = { "R/W", "R/O", "BAK" };
-
 /*
  * Allocate a volume record and load it up from a vldb record.
  */

fs/afs/yfsclient.c

@@ -505,7 +505,7 @@ static int yfs_deliver_fs_fetch_data64(struct afs_call *call)
 			goto no_more_data;
 
 		/* Discard any excess data the server gave us */
-		iov_iter_discard(&call->iter, READ, req->actual_len - req->len);
+		afs_extract_discard(call, req->actual_len - req->len);
 		call->unmarshall = 3;
 		/* Fall through */
 
@@ -2007,7 +2007,7 @@ static int yfs_deliver_fs_fetch_opaque_acl(struct afs_call *call)
 			acl->size = call->count2;
 			afs_extract_begin(call, acl->data, size);
 		} else {
-			iov_iter_discard(&call->iter, READ, size);
+			afs_extract_discard(call, size);
 		}
 		call->unmarshall++;
 		/* Fall through */
@@ -2039,7 +2039,7 @@ static int yfs_deliver_fs_fetch_opaque_acl(struct afs_call *call)
 			acl->size = call->count2;
 			afs_extract_begin(call, acl->data, size);
 		} else {
-			iov_iter_discard(&call->iter, READ, size);
+			afs_extract_discard(call, size);
 		}
 		call->unmarshall++;
 		/* Fall through */

include/linux/key.h

@@ -324,7 +324,7 @@ static inline struct key *request_key(struct key_type *type,
 }
 
 #ifdef CONFIG_NET
-/*
+/**
  * request_key_net - Request a key for a net namespace and wait for construction
  * @type: Type of key.
  * @description: The searchable description of the key.
@@ -341,6 +341,18 @@ static inline struct key *request_key(struct key_type *type,
  */
 #define request_key_net(type, description, net, callout_info) \
 	request_key_tag(type, description, net->key_domain, callout_info);
+
+/**
+ * request_key_net_rcu - Request a key for a net namespace under RCU conditions
+ * @type: Type of key.
+ * @description: The searchable description of the key.
+ * @net: The network namespace that is the key's domain of operation.
+ *
+ * As for request_key_rcu() except that only keys that operate the specified
+ * network namespace are used.
+ */
+#define request_key_net_rcu(type, description, net) \
+	request_key_rcu(type, description, net->key_domain);
 #endif /* CONFIG_NET */
 
 extern int wait_for_key_construction(struct key *key, bool intr);