afs: Overhaul volume and server record caching and fileserver rotation

The current code assumes that volumes and servers are per-cell and are
never shared, but this is not enforced, and, indeed, public cells do exist
that are aliases of each other.  Further, an organisation can, say, set up
a public cell and a private cell with overlapping, but not identical, sets
of servers.  The difference is purely in the database attached to the VL
servers.

The current code will malfunction if it sees a server in two cells as it
assumes global address -> server record mappings and that each server is in
just one cell.

Further, each server may have multiple addresses - and may have addresses
of different families (IPv4 and IPv6, say).

To this end, the following structural changes are made:

 (1) Server record management is overhauled:

     (a) Server records are made independent of cell.  The namespace keeps
     	 track of them, volume records have lists of them and each vnode
     	 has a server on which its callback interest currently resides.

     (b) The cell record no longer keeps a list of servers known to be in
     	 that cell.

     (c) The server records are now kept in a flat list because there's no
     	 single address to sort on.

     (d) Server records are now keyed by their UUID within the namespace.

     (e) The addresses for a server are obtained with the VL.GetAddrsU
     	 rather than with VL.GetEntryByName, using the server's UUID as a
     	 parameter.

     (f) Cached server records are garbage collected after a period of
     	 non-use and are counted out of existence before purging is allowed
     	 to complete.  This protects the work functions against rmmod.

     (g) The servers list is now in /proc/fs/afs/servers.

 (2) Volume record management is overhauled:

     (a) An RCU-replaceable server list is introduced.  This tracks both
     	 servers and their coresponding callback interests.

     (b) The superblock is now keyed on cell record and numeric volume ID.

     (c) The volume record is now tied to the superblock which mounts it,
     	 and is activated when mounted and deactivated when unmounted.
     	 This makes it easier to handle the cache cookie without causing a
     	 double-use in fscache.

     (d) The volume record is loaded from the VLDB using VL.GetEntryByNameU
     	 to get the server UUID list.

     (e) The volume name is updated if it is seen to have changed when the
     	 volume is updated (the update is keyed on the volume ID).

 (3) The vlocation record is got rid of and VLDB records are no longer
     cached.  Sufficient information is stored in the volume record, though
     an update to a volume record is now no longer shared between related
     volumes (volumes come in bundles of three: R/W, R/O and backup).

and the following procedural changes are made:

 (1) The fileserver cursor introduced previously is now fleshed out and
     used to iterate over fileservers and their addresses.

 (2) Volume status is checked during iteration, and the server list is
     replaced if a change is detected.

 (3) Server status is checked during iteration, and the address list is
     replaced if a change is detected.

 (4) The abort code is saved into the address list cursor and -ECONNABORTED
     returned in afs_make_call() if a remote abort happened rather than
     translating the abort into an error message.  This allows actions to
     be taken depending on the abort code more easily.

     (a) If a VMOVED abort is seen then this is handled by rechecking the
     	 volume and restarting the iteration.

     (b) If a VBUSY, VRESTARTING or VSALVAGING abort is seen then this is
         handled by sleeping for a short period and retrying and/or trying
         other servers that might serve that volume.  A message is also
         displayed once until the condition has cleared.

     (c) If a VOFFLINE abort is seen, then this is handled as VBUSY for the
     	 moment.

     (d) If a VNOVOL abort is seen, the volume is rechecked in the VLDB to
     	 see if it has been deleted; if not, the fileserver is probably
     	 indicating that the volume couldn't be attached and needs
     	 salvaging.

     (e) If statfs() sees one of these aborts, it does not sleep, but
     	 rather returns an error, so as not to block the umount program.

 (5) The fileserver iteration functions in vnode.c are now merged into
     their callers and more heavily macroised around the cursor.  vnode.c
     is removed.

 (6) Operations on a particular vnode are serialised on that vnode because
     the server will lock that vnode whilst it operates on it, so a second
     op sent will just have to wait.

 (7) Fileservers are probed with FS.GetCapabilities before being used.
     This is where service upgrade will be done.

 (8) A callback interest on a fileserver is set up before an FS operation
     is performed and passed through to afs_make_call() so that it can be
     set on the vnode if the operation returns a callback.  The callback
     interest is passed through to afs_iget() also so that it can be set
     there too.

In general, record updating is done on an as-needed basis when we try to
access servers, volumes or vnodes rather than offloading it to work items
and special threads.

Notes:

 (1) Pre AFS-3.4 servers are no longer supported, though this can be added
     back if necessary (AFS-3.4 was released in 1998).

 (2) VBUSY is retried forever for the moment at intervals of 1s.

 (3) /proc/fs/afs/<cell>/servers no longer exists.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 306 insertions, 120 deletions

diff --git a/fs/afs/volume.c b/fs/afs/volume.c
index 3c5ad1cc50f3..2295dd4f9b15 100644
--- a/fs/afs/volume.c
+++ b/fs/afs/volume.c
@@ -13,11 +13,148 @@
 #include <linux/slab.h>
 #include "internal.h"
 
-static const char *afs_voltypes[] = { "R/W", "R/O", "BAK" };
+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" };
 
 /*
- * lookup a volume by name
- * - this can be one of the following:
+ * Allocate a volume record and load it up from a vldb record.
+ */
+static struct afs_volume *afs_alloc_volume(struct afs_mount_params *params,
+					   struct afs_vldb_entry *vldb,
+					   unsigned long type_mask)
+{
+	struct afs_server_list *slist;
+	struct afs_server *server;
+	struct afs_volume *volume;
+	int ret = -ENOMEM, nr_servers = 0, i, j;
+
+	for (i = 0; i < vldb->nr_servers; i++)
+		if (vldb->fs_mask[i] & type_mask)
+			nr_servers++;
+
+	volume = kzalloc(sizeof(struct afs_volume), GFP_KERNEL);
+	if (!volume)
+		goto error_0;
+
+	volume->vid		= vldb->vid[params->type];
+	volume->update_at	= ktime_get_real_seconds() + afs_volume_record_life;
+	volume->cell		= afs_get_cell(params->cell);
+	volume->type		= params->type;
+	volume->type_force	= params->force;
+	volume->name_len	= vldb->name_len;
+
+	atomic_set(&volume->usage, 1);
+	INIT_LIST_HEAD(&volume->proc_link);
+	rwlock_init(&volume->servers_lock);
+	memcpy(volume->name, vldb->name, vldb->name_len + 1);
+
+	slist = afs_alloc_server_list(params->cell, params->key, vldb, type_mask);
+	if (IS_ERR(slist)) {
+		ret = PTR_ERR(slist);
+		goto error_1;
+	}
+
+	refcount_set(&slist->usage, 1);
+	volume->servers = slist;
+
+	/* Make sure a records exists for each server this volume occupies. */
+	for (i = 0; i < nr_servers; i++) {
+		if (!(vldb->fs_mask[i] & type_mask))
+			continue;
+
+		server = afs_lookup_server(params->cell, params->key,
+					   &vldb->fs_server[i]);
+		if (IS_ERR(server)) {
+			ret = PTR_ERR(server);
+			if (ret == -ENOENT)
+				continue;
+			goto error_2;
+		}
+
+		/* Insertion-sort by server pointer */
+		for (j = 0; j < slist->nr_servers; j++)
+			if (slist->servers[j].server >= server)
+				break;
+		if (j < slist->nr_servers) {
+			if (slist->servers[j].server == server) {
+				afs_put_server(params->net, server);
+				continue;
+			}
+
+			memmove(slist->servers + j + 1,
+				slist->servers + j,
+				(slist->nr_servers - j) * sizeof(struct afs_server_entry));
+		}
+
+		slist->servers[j].server = server;
+		slist->nr_servers++;
+	}
+
+	if (slist->nr_servers == 0) {
+		ret = -EDESTADDRREQ;
+		goto error_2;
+	}
+
+	return volume;
+
+error_2:
+	afs_put_serverlist(params->net, slist);
+error_1:
+	kfree(volume);
+error_0:
+	return ERR_PTR(ret);
+}
+
+/*
+ * Look up a VLDB record for a volume.
+ */
+static struct afs_vldb_entry *afs_vl_lookup_vldb(struct afs_cell *cell,
+						 struct key *key,
+						 const char *volname,
+						 size_t volnamesz)
+{
+	struct afs_addr_cursor ac;
+	struct afs_vldb_entry *vldb;
+	int ret;
+
+	ret = afs_set_vl_cursor(&ac, cell);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	while (afs_iterate_addresses(&ac)) {
+		vldb = afs_vl_get_entry_by_name_u(cell->net, &ac, key,
+						  volname, volnamesz);
+		switch (ac.error) {
+		case 0:
+			afs_end_cursor(&ac);
+			return vldb;
+		case -ECONNABORTED:
+			ac.error = afs_abort_to_error(ac.abort_code);
+			goto error;
+		case -ENOMEM:
+		case -ENONET:
+			goto error;
+		case -ENETUNREACH:
+		case -EHOSTUNREACH:
+		case -ECONNREFUSED:
+			break;
+		default:
+			ac.error = -EIO;
+			goto error;
+		}
+	}
+
+error:
+	return ERR_PTR(afs_end_cursor(&ac));
+}
+
+/*
+ * Look up a volume in the VL server and create a candidate volume record for
+ * it.
+ *
+ * The volume name can be one of the following:
  *	"%[cell:]volume[.]"		R/W volume
  *	"#[cell:]volume[.]"		R/O or R/W volume (rwparent=0),
  *					 or R/W (rwparent=1) volume
@@ -37,169 +174,218 @@ static const char *afs_voltypes[] = { "R/W", "R/O", "BAK" };
  * - Rule 3: If parent volume is R/W, then only mount R/W volume unless
  *           explicitly told otherwise
  */
-struct afs_volume *afs_volume_lookup(struct afs_mount_params *params)
+struct afs_volume *afs_create_volume(struct afs_mount_params *params)
 {
-	struct afs_vlocation *vlocation = NULL;
-	struct afs_volume *volume = NULL;
-	struct afs_server *server = NULL;
-	char srvtmask;
-	int ret, loop;
-
-	_enter("{%*.*s,%d}",
-	       params->volnamesz, params->volnamesz, params->volname, params->rwpath);
-
-	/* lookup the volume location record */
-	vlocation = afs_vlocation_lookup(params->net, params->cell, params->key,
-					 params->volname, params->volnamesz);
-	if (IS_ERR(vlocation)) {
-		ret = PTR_ERR(vlocation);
-		vlocation = NULL;
-		goto error;
-	}
+	struct afs_vldb_entry *vldb;
+	struct afs_volume *volume;
+	unsigned long type_mask = 1UL << params->type;
 
-	/* make the final decision on the type we want */
-	ret = -ENOMEDIUM;
-	if (params->force && !(vlocation->vldb.vidmask & (1 << params->type)))
-		goto error;
+	vldb = afs_vl_lookup_vldb(params->cell, params->key,
+				  params->volname, params->volnamesz);
+	if (IS_ERR(vldb))
+		return ERR_CAST(vldb);
 
-	srvtmask = 0;
-	for (loop = 0; loop < vlocation->vldb.nservers; loop++)
-		srvtmask |= vlocation->vldb.srvtmask[loop];
+	if (test_bit(AFS_VLDB_QUERY_ERROR, &vldb->flags)) {
+		volume = ERR_PTR(vldb->error);
+		goto error;
+	}
 
+	/* Make the final decision on the type we want */
+	volume = ERR_PTR(-ENOMEDIUM);
 	if (params->force) {
-		if (!(srvtmask & (1 << params->type)))
+		if (!(vldb->flags & type_mask))
 			goto error;
-	} else if (srvtmask & AFS_VOL_VTM_RO) {
+	} else if (test_bit(AFS_VLDB_HAS_RO, &vldb->flags)) {
 		params->type = AFSVL_ROVOL;
-	} else if (srvtmask & AFS_VOL_VTM_RW) {
+	} else if (test_bit(AFS_VLDB_HAS_RW, &vldb->flags)) {
 		params->type = AFSVL_RWVOL;
 	} else {
 		goto error;
 	}
 
-	down_write(&params->cell->vl_sem);
+	type_mask = 1UL << params->type;
+	volume = afs_alloc_volume(params, vldb, type_mask);
 
-	/* is the volume already active? */
-	if (vlocation->vols[params->type]) {
-		/* yes - re-use it */
-		volume = vlocation->vols[params->type];
-		afs_get_volume(volume);
-		goto success;
-	}
+error:
+	kfree(vldb);
+	return volume;
+}
 
-	/* create a new volume record */
-	_debug("creating new volume record");
+/*
+ * Destroy a volume record
+ */
+static void afs_destroy_volume(struct afs_net *net, struct afs_volume *volume)
+{
+	_enter("%p", volume);
 
-	ret = -ENOMEM;
-	volume = kzalloc(sizeof(struct afs_volume), GFP_KERNEL);
-	if (!volume)
-		goto error_up;
+#ifdef CONFIG_AFS_FSCACHE
+	ASSERTCMP(volume->cache, ==, NULL);
+#endif
 
-	atomic_set(&volume->usage, 1);
-	volume->type		= params->type;
-	volume->type_force	= params->force;
-	volume->cell		= params->cell;
-	volume->vid		= vlocation->vldb.vid[params->type];
-
-	init_rwsem(&volume->server_sem);
-
-	/* look up all the applicable server records */
-	for (loop = 0; loop < 8; loop++) {
-		if (vlocation->vldb.srvtmask[loop] & (1 << volume->type)) {
-			server = afs_lookup_server(
-			       volume->cell, &vlocation->vldb.servers[loop]);
-			if (IS_ERR(server)) {
-				ret = PTR_ERR(server);
-				goto error_discard;
-			}
+	afs_put_serverlist(net, volume->servers);
+	afs_put_cell(net, volume->cell);
+	kfree(volume);
 
-			volume->servers[volume->nservers] = server;
-			volume->nservers++;
-		}
+	_leave(" [destroyed]");
+}
+
+/*
+ * Drop a reference on a volume record.
+ */
+void afs_put_volume(struct afs_cell *cell, struct afs_volume *volume)
+{
+	if (volume) {
+		_enter("%s", volume->name);
+
+		if (atomic_dec_and_test(&volume->usage))
+			afs_destroy_volume(cell->net, volume);
 	}
+}
 
-	/* attach the cache and volume location */
+/*
+ * Activate a volume.
+ */
+void afs_activate_volume(struct afs_volume *volume)
+{
 #ifdef CONFIG_AFS_FSCACHE
 	volume->cache = fscache_acquire_cookie(volume->cell->cache,
 					       &afs_volume_cache_index_def,
 					       volume, true);
 #endif
-	afs_get_vlocation(vlocation);
-	volume->vlocation = vlocation;
-
-	vlocation->vols[volume->type] = volume;
 
-success:
-	_debug("kAFS selected %s volume %08x",
-	       afs_voltypes[volume->type], volume->vid);
-	up_write(&params->cell->vl_sem);
-	afs_put_vlocation(params->net, vlocation);
-	_leave(" = %p", volume);
-	return volume;
+	write_lock(&volume->cell->proc_lock);
+	list_add_tail(&volume->proc_link, &volume->cell->proc_volumes);
+	write_unlock(&volume->cell->proc_lock);
+}
 
-	/* clean up */
-error_up:
-	up_write(&params->cell->vl_sem);
-error:
-	afs_put_vlocation(params->net, vlocation);
-	_leave(" = %d", ret);
-	return ERR_PTR(ret);
+/*
+ * Deactivate a volume.
+ */
+void afs_deactivate_volume(struct afs_volume *volume)
+{
+	_enter("%s", volume->name);
 
-error_discard:
-	up_write(&params->cell->vl_sem);
+	write_lock(&volume->cell->proc_lock);
+	list_del_init(&volume->proc_link);
+	write_unlock(&volume->cell->proc_lock);
 
-	for (loop = volume->nservers - 1; loop >= 0; loop--) {
-		afs_put_cb_interest(params->net, volume->cb_interests[loop]);
-		afs_put_server(params->net, volume->servers[loop]);
-	}
+#ifdef CONFIG_AFS_FSCACHE
+	fscache_relinquish_cookie(volume->cache,
+				  test_bit(AFS_VOLUME_DELETED, &volume->flags));
+	volume->cache = NULL;
+#endif
 
-	kfree(volume);
-	goto error;
+	_leave("");
 }
 
 /*
- * destroy a volume record
+ * Query the VL service to update the volume status.
  */
-void afs_put_volume(struct afs_cell *cell, struct afs_volume *volume)
+static int afs_update_volume_status(struct afs_volume *volume, struct key *key)
 {
-	struct afs_vlocation *vlocation;
-	int loop;
+	struct afs_server_list *new, *old, *discard;
+	struct afs_vldb_entry *vldb;
+	char idbuf[16];
+	int ret, idsz;
 
-	if (!volume)
-		return;
+	_enter("");
 
-	_enter("%p", volume);
+	/* We look up an ID by passing it as a decimal string in the
+	 * operation's name parameter.
+	 */
+	idsz = sprintf(idbuf, "%u", volume->vid);
 
-	ASSERTCMP(atomic_read(&volume->usage), >, 0);
+	vldb = afs_vl_lookup_vldb(volume->cell, key, idbuf, idsz);
+	if (IS_ERR(vldb)) {
+		ret = PTR_ERR(vldb);
+		goto error;
+	}
 
-	vlocation = volume->vlocation;
+	/* See if the volume got renamed. */
+	if (vldb->name_len != volume->name_len ||
+	    memcmp(vldb->name, volume->name, vldb->name_len) != 0) {
+		/* TODO: Use RCU'd string. */
+		memcpy(volume->name, vldb->name, AFS_MAXVOLNAME);
+		volume->name_len = vldb->name_len;
+	}
+
+	/* See if the volume's server list got updated. */
+	new = afs_alloc_server_list(volume->cell, key,
+				      vldb, (1 << volume->type));
+	if (IS_ERR(new)) {
+		ret = PTR_ERR(new);
+		goto error_vldb;
+	}
 
-	/* to prevent a race, the decrement and the dequeue must be effectively
-	 * atomic */
-	down_write(&cell->vl_sem);
+	write_lock(&volume->servers_lock);
 
-	if (likely(!atomic_dec_and_test(&volume->usage))) {
-		up_write(&vlocation->cell->vl_sem);
-		_leave("");
-		return;
+	discard = new;
+	old = volume->servers;
+	if (afs_annotate_server_list(new, old)) {
+		new->seq = volume->servers_seq + 1;
+		volume->servers = new;
+		smp_wmb();
+		volume->servers_seq++;
+		discard = old;
 	}
 
-	vlocation->vols[volume->type] = NULL;
+	volume->update_at = ktime_get_real_seconds() + afs_volume_record_life;
+	clear_bit(AFS_VOLUME_NEEDS_UPDATE, &volume->flags);
+	write_unlock(&volume->servers_lock);
+	ret = 0;
 
-	up_write(&cell->vl_sem);
+	afs_put_serverlist(volume->cell->net, discard);
+error_vldb:
+	kfree(vldb);
+error:
+	_leave(" = %d", ret);
+	return ret;
+}
 
-	/* finish cleaning up the volume */
-#ifdef CONFIG_AFS_FSCACHE
-	fscache_relinquish_cookie(volume->cache, 0);
-#endif
-	afs_put_vlocation(cell->net, vlocation);
+/*
+ * Make sure the volume record is up to date.
+ */
+int afs_check_volume_status(struct afs_volume *volume, struct key *key)
+{
+	time64_t now = ktime_get_real_seconds();
+	int ret, retries = 0;
 
-	for (loop = volume->nservers - 1; loop >= 0; loop--) {
-		afs_put_cb_interest(cell->net, volume->cb_interests[loop]);
-		afs_put_server(cell->net, volume->servers[loop]);
+	_enter("");
+
+	if (volume->update_at <= now)
+		set_bit(AFS_VOLUME_NEEDS_UPDATE, &volume->flags);
+
+retry:
+	if (!test_bit(AFS_VOLUME_NEEDS_UPDATE, &volume->flags) &&
+	    !test_bit(AFS_VOLUME_WAIT, &volume->flags)) {
+		_leave(" = 0");
+		return 0;
 	}
 
-	kfree(volume);
+	if (!test_and_set_bit_lock(AFS_VOLUME_UPDATING, &volume->flags)) {
+		ret = afs_update_volume_status(volume, key);
+		clear_bit_unlock(AFS_VOLUME_WAIT, &volume->flags);
+		clear_bit_unlock(AFS_VOLUME_UPDATING, &volume->flags);
+		wake_up_bit(&volume->flags, AFS_VOLUME_WAIT);
+		_leave(" = %d", ret);
+		return ret;
+	}
 
-	_leave(" [destroyed]");
+	if (!test_bit(AFS_VOLUME_WAIT, &volume->flags)) {
+		_leave(" = 0 [no wait]");
+		return 0;
+	}
+
+	ret = wait_on_bit(&volume->flags, AFS_VOLUME_WAIT, TASK_INTERRUPTIBLE);
+	if (ret == -ERESTARTSYS) {
+		_leave(" = %d", ret);
+		return ret;
+	}
+
+	retries++;
+	if (retries == 4) {
+		_leave(" = -ESTALE");
+		return -ESTALE;
+	}
+	goto retry;
 }