afs: Move server rotation code into its own file

Move server rotation code into its own file.

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

1 files changed, 254 insertions, 0 deletions

diff --git a/fs/afs/rotate.c b/fs/afs/rotate.c
new file mode 100644
index 000000000000..c7975b3ba59a
--- /dev/null
+++ b/fs/afs/rotate.c
@@ -0,0 +1,254 @@
+/* Handle fileserver selection and rotation.
+ *
+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include "internal.h"
+
+/*
+ * Initialise a filesystem server cursor for iterating over FS servers.
+ */
+void afs_init_fs_cursor(struct afs_fs_cursor *fc, struct afs_vnode *vnode)
+{
+        memset(fc, 0, sizeof(*fc));
+}
+
+/*
+ * Set a filesystem server cursor for using a specific FS server.
+ */
+int afs_set_fs_cursor(struct afs_fs_cursor *fc, struct afs_vnode *vnode)
+{
+        afs_init_fs_cursor(fc, vnode);
+
+        read_seqlock_excl(&vnode->cb_lock);
+        if (vnode->cb_interest) {
+                if (vnode->cb_interest->server->fs_state == 0)
+                        fc->server = afs_get_server(vnode->cb_interest->server);
+                else
+                        fc->ac.error = vnode->cb_interest->server->fs_state;
+        } else {
+                fc->ac.error = -ESTALE;
+        }
+        read_sequnlock_excl(&vnode->cb_lock);
+
+        return fc->ac.error;
+}
+
+/*
+ * pick a server to use to try accessing this volume
+ * - returns with an elevated usage count on the server chosen
+ */
+bool afs_volume_pick_fileserver(struct afs_fs_cursor *fc, struct afs_vnode *vnode)
+{
+        struct afs_volume *volume = vnode->volume;
+        struct afs_server *server;
+        int ret, state, loop;
+
+        _enter("%s", volume->vlocation->vldb.name);
+
+        /* stick with the server we're already using if we can */
+        if (vnode->cb_interest && vnode->cb_interest->server->fs_state == 0) {
+                fc->server = afs_get_server(vnode->cb_interest->server);
+                goto set_server;
+        }
+
+        down_read(&volume->server_sem);
+
+        /* handle the no-server case */
+        if (volume->nservers == 0) {
+                fc->ac.error = volume->rjservers ? -ENOMEDIUM : -ESTALE;
+                up_read(&volume->server_sem);
+                _leave(" = f [no servers %d]", fc->ac.error);
+                return false;
+        }
+
+        /* basically, just search the list for the first live server and use
+         * that */
+        ret = 0;
+        for (loop = 0; loop < volume->nservers; loop++) {
+                server = volume->servers[loop];
+                state = server->fs_state;
+
+                _debug("consider %d [%d]", loop, state);
+
+                switch (state) {
+                case 0:
+                        goto picked_server;
+
+                case -ENETUNREACH:
+                        if (ret == 0)
+                                ret = state;
+                        break;
+
+                case -EHOSTUNREACH:
+                        if (ret == 0 ||
+                            ret == -ENETUNREACH)
+                                ret = state;
+                        break;
+
+                case -ECONNREFUSED:
+                        if (ret == 0 ||
+                            ret == -ENETUNREACH ||
+                            ret == -EHOSTUNREACH)
+                                ret = state;
+                        break;
+
+                default:
+                case -EREMOTEIO:
+                        if (ret == 0 ||
+                            ret == -ENETUNREACH ||
+                            ret == -EHOSTUNREACH ||
+                            ret == -ECONNREFUSED)
+                                ret = state;
+                        break;
+                }
+        }
+
+error:
+        fc->ac.error = ret;
+
+        /* no available servers
+         * - TODO: handle the no active servers case better
+         */
+        up_read(&volume->server_sem);
+        _leave(" = f [%d]", fc->ac.error);
+        return false;
+
+picked_server:
+        /* Found an apparently healthy server.  We need to register an interest
+         * in receiving callbacks before we talk to it.
+         */
+        ret = afs_register_server_cb_interest(vnode,
+                                              &volume->cb_interests[loop], server);
+        if (ret < 0)
+                goto error;
+
+        fc->server = afs_get_server(server);
+        up_read(&volume->server_sem);
+set_server:
+        fc->ac.alist = afs_get_addrlist(fc->server->addrs);
+        fc->ac.addr = &fc->ac.alist->addrs[0];
+        _debug("USING SERVER: %pIS\n", &fc->ac.addr->transport);
+        _leave(" = t (picked %pIS)", &fc->ac.addr->transport);
+        return true;
+}
+
+/*
+ * release a server after use
+ * - releases the ref on the server struct that was acquired by picking
+ * - records result of using a particular server to access a volume
+ * - return true to try again, false if okay or to issue error
+ * - the caller must release the server struct if result was false
+ */
+bool afs_iterate_fs_cursor(struct afs_fs_cursor *fc,
+                           struct afs_vnode *vnode)
+{
+        struct afs_volume *volume = vnode->volume;
+        struct afs_server *server = fc->server;
+        unsigned loop;
+
+        _enter("%s,%pIS,%d",
+               volume->vlocation->vldb.name, &fc->ac.addr->transport,
+               fc->ac.error);
+
+        switch (fc->ac.error) {
+                /* success */
+        case 0:
+                server->fs_state = 0;
+                _leave(" = f");
+                return false;
+
+                /* the fileserver denied all knowledge of the volume */
+        case -ENOMEDIUM:
+                down_write(&volume->server_sem);
+
+                /* firstly, find where the server is in the active list (if it
+                 * is) */
+                for (loop = 0; loop < volume->nservers; loop++)
+                        if (volume->servers[loop] == server)
+                                goto present;
+
+                /* no longer there - may have been discarded by another op */
+                goto try_next_server_upw;
+
+        present:
+                volume->nservers--;
+                memmove(&volume->servers[loop],
+                        &volume->servers[loop + 1],
+                        sizeof(volume->servers[loop]) *
+                        (volume->nservers - loop));
+                volume->servers[volume->nservers] = NULL;
+                afs_put_server(afs_v2net(vnode), server);
+                volume->rjservers++;
+
+                if (volume->nservers > 0)
+                        /* another server might acknowledge its existence */
+                        goto try_next_server_upw;
+
+                /* handle the case where all the fileservers have rejected the
+                 * volume
+                 * - TODO: try asking the fileservers for volume information
+                 * - TODO: contact the VL server again to see if the volume is
+                 *         no longer registered
+                 */
+                up_write(&volume->server_sem);
+                afs_put_server(afs_v2net(vnode), server);
+                fc->server = NULL;
+                _leave(" = f [completely rejected]");
+                return false;
+
+                /* problem reaching the server */
+        case -ENETUNREACH:
+        case -EHOSTUNREACH:
+        case -ECONNREFUSED:
+        case -ETIME:
+        case -ETIMEDOUT:
+        case -EREMOTEIO:
+                /* mark the server as dead
+                 * TODO: vary dead timeout depending on error
+                 */
+                spin_lock(&server->fs_lock);
+                if (!server->fs_state) {
+                        server->fs_state = fc->ac.error;
+                        printk("kAFS: SERVER DEAD state=%d\n", fc->ac.error);
+                }
+                spin_unlock(&server->fs_lock);
+                goto try_next_server;
+
+                /* miscellaneous error */
+        default:
+        case -ENOMEM:
+        case -ENONET:
+                /* tell the caller to accept the result */
+                afs_put_server(afs_v2net(vnode), server);
+                fc->server = NULL;
+                _leave(" = f [local failure]");
+                return false;
+        }
+
+        /* tell the caller to loop around and try the next server */
+try_next_server_upw:
+        up_write(&volume->server_sem);
+try_next_server:
+        afs_put_server(afs_v2net(vnode), server);
+        _leave(" = t [try next server]");
+        return true;
+}
+
+/*
+ * Clean up a fileserver cursor.
+ */
+int afs_end_fs_cursor(struct afs_fs_cursor *fc, struct afs_net *net)
+{
+        afs_end_cursor(&fc->ac);
+        afs_put_server(net, fc->server);
+        return fc->ac.error;
+}