vlocation.c

linux 内核源代码

/* AFS volume location management
 *
 * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([e-mail])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include "internal.h"

static unsigned afs_vlocation_timeout = 10;	/* volume location timeout in seconds */
static unsigned afs_vlocation_update_timeout = 10 * 60;

static void afs_vlocation_reaper(struct work_struct *);
static void afs_vlocation_updater(struct work_struct *);

static LIST_HEAD(afs_vlocation_updates);
static LIST_HEAD(afs_vlocation_graveyard);
static DEFINE_SPINLOCK(afs_vlocation_updates_lock);
static DEFINE_SPINLOCK(afs_vlocation_graveyard_lock);
static DECLARE_DELAYED_WORK(afs_vlocation_reap, afs_vlocation_reaper);
static DECLARE_DELAYED_WORK(afs_vlocation_update, afs_vlocation_updater);
static struct workqueue_struct *afs_vlocation_update_worker;

/*
 * iterate through the VL servers in a cell until one of them admits knowing
 * about the volume in question
 */
static int afs_vlocation_access_vl_by_name(struct afs_vlocation *vl,
					   struct key *key,
					   struct afs_cache_vlocation *vldb)
{
	struct afs_cell *cell = vl->cell;
	struct in_addr addr;
	int count, ret;

	_enter("%s,%s", cell->name, vl->vldb.name);

	down_write(&vl->cell->vl_sem);
	ret = -ENOMEDIUM;
	for (count = cell->vl_naddrs; count > 0; count--) {
		addr = cell->vl_addrs[cell->vl_curr_svix];

		_debug("CellServ[%hu]: %08x", cell->vl_curr_svix, addr.s_addr);

		/* attempt to access the VL server */
		ret = afs_vl_get_entry_by_name(&addr, key, vl->vldb.name, vldb,
					       &afs_sync_call);
		switch (ret) {
		case 0:
			goto out;
		case -ENOMEM:
		case -ENONET:
		case -ENETUNREACH:
		case -EHOSTUNREACH:
		case -ECONNREFUSED:
			if (ret == -ENOMEM || ret == -ENONET)
				goto out;
			goto rotate;
		case -ENOMEDIUM:
			goto out;
		default:
			ret = -EIO;
			goto rotate;
		}

		/* rotate the server records upon lookup failure */
	rotate:
		cell->vl_curr_svix++;
		cell->vl_curr_svix %= cell->vl_naddrs;
	}

out:
	up_write(&vl->cell->vl_sem);
	_leave(" = %d", ret);
	return ret;
}

/*
 * iterate through the VL servers in a cell until one of them admits knowing
 * about the volume in question
 */
static int afs_vlocation_access_vl_by_id(struct afs_vlocation *vl,
					 struct key *key,
					 afs_volid_t volid,
					 afs_voltype_t voltype,
					 struct afs_cache_vlocation *vldb)
{
	struct afs_cell *cell = vl->cell;
	struct in_addr addr;
	int count, ret;

	_enter("%s,%x,%d,", cell->name, volid, voltype);

	down_write(&vl->cell->vl_sem);
	ret = -ENOMEDIUM;
	for (count = cell->vl_naddrs; count > 0; count--) {
		addr = cell->vl_addrs[cell->vl_curr_svix];

		_debug("CellServ[%hu]: %08x", cell->vl_curr_svix, addr.s_addr);

		/* attempt to access the VL server */
		ret = afs_vl_get_entry_by_id(&addr, key, volid, voltype, vldb,
					     &afs_sync_call);
		switch (ret) {
		case 0:
			goto out;
		case -ENOMEM:
		case -ENONET:
		case -ENETUNREACH:
		case -EHOSTUNREACH:
		case -ECONNREFUSED:
			if (ret == -ENOMEM || ret == -ENONET)
				goto out;
			goto rotate;
		case -EBUSY:
			vl->upd_busy_cnt++;
			if (vl->upd_busy_cnt <= 3) {
				if (vl->upd_busy_cnt > 1) {
					/* second+ BUSY - sleep a little bit */
					set_current_state(TASK_UNINTERRUPTIBLE);
					schedule_timeout(1);
					__set_current_state(TASK_RUNNING);
				}
				continue;
			}
			break;
		case -ENOMEDIUM:
			vl->upd_rej_cnt++;
			goto rotate;
		default:
			ret = -EIO;
			goto rotate;
		}

		/* rotate the server records upon lookup failure */
	rotate:
		cell->vl_curr_svix++;
		cell->vl_curr_svix %= cell->vl_naddrs;
		vl->upd_busy_cnt = 0;
	}

out:
	if (ret < 0 && vl->upd_rej_cnt > 0) {
		printk(KERN_NOTICE "kAFS:"
		       " Active volume no longer valid '%s'\n",
		       vl->vldb.name);
		vl->valid = 0;
		ret = -ENOMEDIUM;
	}

	up_write(&vl->cell->vl_sem);
	_leave(" = %d", ret);
	return ret;
}

/*
 * allocate a volume location record
 */
static struct afs_vlocation *afs_vlocation_alloc(struct afs_cell *cell,
						 const char *name,
						 size_t namesz)
{
	struct afs_vlocation *vl;

	vl = kzalloc(sizeof(struct afs_vlocation), GFP_KERNEL);
	if (vl) {
		vl->cell = cell;
		vl->state = AFS_VL_NEW;
		atomic_set(&vl->usage, 1);
		INIT_LIST_HEAD(&vl->link);
		INIT_LIST_HEAD(&vl->grave);
		INIT_LIST_HEAD(&vl->update);
		init_waitqueue_head(&vl->waitq);
		spin_lock_init(&vl->lock);
		memcpy(vl->vldb.name, name, namesz);
	}

	_leave(" = %p", vl);
	return vl;
}

/*
 * update record if we found it in the cache
 */
static int afs_vlocation_update_record(struct afs_vlocation *vl,
				       struct key *key,
				       struct afs_cache_vlocation *vldb)
{
	afs_voltype_t voltype;
	afs_volid_t vid;
	int ret;

	/* try to look up a cached volume in the cell VL databases by ID */
	_debug("Locally Cached: %s %02x { %08x(%x) %08x(%x) %08x(%x) }",
	       vl->vldb.name,
	       vl->vldb.vidmask,
	       ntohl(vl->vldb.servers[0].s_addr),
	       vl->vldb.srvtmask[0],
	       ntohl(vl->vldb.servers[1].s_addr),
	       vl->vldb.srvtmask[1],
	       ntohl(vl->vldb.servers[2].s_addr),
	       vl->vldb.srvtmask[2]);

	_debug("Vids: %08x %08x %08x",
	       vl->vldb.vid[0],
	       vl->vldb.vid[1],
	       vl->vldb.vid[2]);

	if (vl->vldb.vidmask & AFS_VOL_VTM_RW) {
		vid = vl->vldb.vid[0];
		voltype = AFSVL_RWVOL;
	} else if (vl->vldb.vidmask & AFS_VOL_VTM_RO) {
		vid = vl->vldb.vid[1];
		voltype = AFSVL_ROVOL;
	} else if (vl->vldb.vidmask & AFS_VOL_VTM_BAK) {
		vid = vl->vldb.vid[2];
		voltype = AFSVL_BACKVOL;
	} else {
		BUG();
		vid = 0;
		voltype = 0;
	}

	/* contact the server to make sure the volume is still available
	 * - TODO: need to handle disconnected operation here
	 */
	ret = afs_vlocation_access_vl_by_id(vl, key, vid, voltype, vldb);
	switch (ret) {
		/* net error */
	default:
		printk(KERN_WARNING "kAFS:"
		       " failed to update volume '%s' (%x) up in '%s': %d\n",
		       vl->vldb.name, vid, vl->cell->name, ret);
		_leave(" = %d", ret);
		return ret;

		/* pulled from local cache into memory */
	case 0:
		_leave(" = 0");
		return 0;

		/* uh oh... looks like the volume got deleted */
	case -ENOMEDIUM:
		printk(KERN_ERR "kAFS:"
		       " volume '%s' (%x) does not exist '%s'\n",
		       vl->vldb.name, vid, vl->cell->name);

		/* TODO: make existing record unavailable */
		_leave(" = %d", ret);
		return ret;
	}
}

/*
 * apply the update to a VL record
 */
static void afs_vlocation_apply_update(struct afs_vlocation *vl,
				       struct afs_cache_vlocation *vldb)
{
	_debug("Done VL Lookup: %s %02x { %08x(%x) %08x(%x) %08x(%x) }",
	       vldb->name, vldb->vidmask,
	       ntohl(vldb->servers[0].s_addr), vldb->srvtmask[0],
	       ntohl(vldb->servers[1].s_addr), vldb->srvtmask[1],
	       ntohl(vldb->servers[2].s_addr), vldb->srvtmask[2]);

	_debug("Vids: %08x %08x %08x",
	       vldb->vid[0], vldb->vid[1], vldb->vid[2]);

	if (strcmp(vldb->name, vl->vldb.name) != 0)
		printk(KERN_NOTICE "kAFS:"
		       " name of volume '%s' changed to '%s' on server\n",
		       vl->vldb.name, vldb->name);

	vl->vldb = *vldb;

#ifdef AFS_CACHING_SUPPORT
	/* update volume entry in local cache */
	cachefs_update_cookie(vl->cache);
#endif
}

/*
 * fill in a volume location record, consulting the cache and the VL server
 * both
 */
static int afs_vlocation_fill_in_record(struct afs_vlocation *vl,
					struct key *key)
{
	struct afs_cache_vlocation vldb;
	int ret;

	_enter("");

	ASSERTCMP(vl->valid, ==, 0);

	memset(&vldb, 0, sizeof(vldb));

	/* see if we have an in-cache copy (will set vl->valid if there is) */
#ifdef AFS_CACHING_SUPPORT
	cachefs_acquire_cookie(cell->cache,
			       &afs_volume_cache_index_def,
			       vlocation,
			       &vl->cache);
#endif

	if (vl->valid) {
		/* try to update a known volume in the cell VL databases by
		 * ID as the name may have changed */
		_debug("found in cache");
		ret = afs_vlocation_update_record(vl, key, &vldb);
	} else {
		/* try to look up an unknown volume in the cell VL databases by
		 * name */
		ret = afs_vlocation_access_vl_by_name(vl, key, &vldb);
		if (ret < 0) {
			printk("kAFS: failed to locate '%s' in cell '%s'\n",
			       vl->vldb.name, vl->cell->name);
			return ret;
		}
	}

	afs_vlocation_apply_update(vl, &vldb);
	_leave(" = 0");
	return 0;
}

/*
 * queue a vlocation record for updates
 */
static void afs_vlocation_queue_for_updates(struct afs_vlocation *vl)
{
	struct afs_vlocation *xvl;

	/* wait at least 10 minutes before updating... */
	vl->update_at = get_seconds() + afs_vlocation_update_timeout;

	spin_lock(&afs_vlocation_updates_lock);

	if (!list_empty(&afs_vlocation_updates)) {
		/* ... but wait at least 1 second more than the newest record
		 * already queued so that we don't spam the VL server suddenly
		 * with lots of requests
		 */
		xvl = list_entry(afs_vlocation_updates.prev,
				 struct afs_vlocation, update);
		if (vl->update_at <= xvl->update_at)
			vl->update_at = xvl->update_at + 1;
	} else {
		queue_delayed_work(afs_vlocation_update_worker,
				   &afs_vlocation_update,
				   afs_vlocation_update_timeout * HZ);
	}

	list_add_tail(&vl->update, &afs_vlocation_updates);