map.c

早期freebsd实现

/*-
 * Copyright (c) 1990 Jan-Simon Pendry
 * Copyright (c) 1990 Imperial College of Science, Technology & Medicine
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Jan-Simon Pendry at Imperial College, London.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $Id: map.c,v 5.2.2.1 1992/02/09 15:08:36 jsp beta $
 */

#ifndef lint
static char sccsid[] = "@(#)map.c	8.1 (Berkeley) 6/6/93";
#endif /* not lint */

#include "am.h"

/*
 * Generation Numbers.
 *
 * Generation numbers are allocated to every node created
 * by amd.  When a filehandle is computed and sent to the
 * kernel, the generation number makes sure that it is safe
 * to reallocate a node slot even when the kernel has a cached
 * reference to its old incarnation.
 * No garbage collection is done, since it is assumed that
 * there is no way that 2^32 generation numbers could ever
 * be allocated by a single run of amd - there is simply
 * not enough cpu time available.
 */
static unsigned int am_gen = 2;	/* Initial generation number */
#define new_gen() (am_gen++)

am_node **exported_ap = (am_node **) 0;
int exported_ap_size = 0;
int first_free_map = 0;		/* First available free slot */
int last_used_map = -1;		/* Last unavailable used slot */
static int timeout_mp_id;	/* Id from last call to timeout */

/*
 * This is the default attributes field which
 * is copied into every new node to be created.
 * The individual filesystem fs_init() routines
 * patch the copy to represent the particular
 * details for the relevant filesystem type
 */
static struct fattr gen_fattr = {
	NFLNK,				/* type */
	NFSMODE_LNK | 0777,		/* mode */
	1,				/* nlink */
	0,				/* uid */
	0,				/* gid */
	0,				/* size */
	4096,				/* blocksize */
	0,				/* rdev */
	1,				/* blocks */
	0,				/* fsid */
	0,				/* fileid */
	{ 0, 0 },			/* atime */
	{ 0, 0 },			/* mtime */
	{ 0, 0 },			/* ctime */
};

/*
 * Resize exported_ap map
 */
static int exported_ap_realloc_map P((int nsize));
static int exported_ap_realloc_map(nsize)
int nsize;
{
#ifdef notdef
	/*
	 * If a second realloc occasionally causes Amd to die
	 * in then include this check.
	 */
	if (exported_ap_size != 0)	/* XXX */
		return 0;
#endif

	/*
	 * this shouldn't happen, but...
	 */
	if (nsize < 0 || nsize == exported_ap_size)
		return 0;

	exported_ap = (am_node **) xrealloc((voidp) exported_ap, nsize * sizeof(am_node*));

	if (nsize > exported_ap_size)
		bzero((char*) (exported_ap+exported_ap_size),
			(nsize - exported_ap_size) * sizeof(am_node*));
	exported_ap_size = nsize;

	return 1;
}

	
/*
 * The root of the mount tree.
 */
am_node *root_node;

/*
 * Allocate a new mount slot and create
 * a new node.
 * Fills in the map number of the node,
 * but leaves everything else uninitialised.
 */
am_node *exported_ap_alloc(P_void)
{
	am_node *mp, **mpp;

	/*
	 * First check if there are any slots left, realloc if needed
	 */
	if (first_free_map >= exported_ap_size)
		if (!exported_ap_realloc_map(exported_ap_size + NEXP_AP))
			return 0;

	/*
	 * Grab the next free slot
	 */
	mpp = exported_ap + first_free_map;
	mp = *mpp = ALLOC(am_node);
	bzero((char *) mp, sizeof(*mp));

	mp->am_mapno = first_free_map++;

	/*
	 * Update free pointer
	 */
	while (first_free_map < exported_ap_size && exported_ap[first_free_map])
		first_free_map++;

	if (first_free_map > last_used_map)
		last_used_map = first_free_map - 1;

	/*
	 * Shrink exported_ap if reasonable
	 */
	if (last_used_map < exported_ap_size - (NEXP_AP + NEXP_AP_MARGIN))
		exported_ap_realloc_map(exported_ap_size - NEXP_AP);

#ifdef DEBUG
	/*dlog("alloc_exp: last_used_map = %d, first_free_map = %d\n",
		last_used_map, first_free_map);*/
#endif /* DEBUG */

	return mp;
}

/*
 * Free a mount slot
 */
void exported_ap_free P((am_node *mp));
void exported_ap_free(mp)
am_node *mp;
{
	/*
	 * Sanity check
	 */
	if (!mp)
		return;

	/*
	 * Zero the slot pointer to avoid double free's
	 */
	exported_ap[mp->am_mapno] = 0;

	/*
	 * Update the free and last_used indices
	 */
	if (mp->am_mapno == last_used_map)
		while (last_used_map >= 0 && exported_ap[last_used_map] == 0)
			--last_used_map;

	if (first_free_map > mp->am_mapno)
		first_free_map = mp->am_mapno;

#ifdef DEBUG
	/*dlog("free_exp: last_used_map = %d, first_free_map = %d\n",
		last_used_map, first_free_map);*/
#endif /* DEBUG */

	/*
	 * Free the mount node
	 */
	free((voidp) mp);
}

/*
 * Insert mp into the correct place,
 * where p_mp is its parent node.
 * A new node gets placed as the youngest sibling
 * of any other children, and the parent's child
 * pointer is adjusted to point to the new child node.
 */
void insert_am(mp, p_mp)
am_node *mp;
am_node *p_mp;
{
	/*
	 * If this is going in at the root then flag it
	 * so that it cannot be unmounted by amq.
	 */
	if (p_mp == root_node)
		mp->am_flags |= AMF_ROOT;
	/*
	 * Fill in n-way links
	 */
	mp->am_parent = p_mp;
	mp->am_osib = p_mp->am_child;
	if (mp->am_osib)
		mp->am_osib->am_ysib = mp;
	p_mp->am_child = mp;
}

/*
 * Remove am from its place in the mount tree
 */
void remove_am(mp)
am_node *mp;
{
	/*
	 * 1.  Consistency check
	 */
	if (mp->am_child && mp->am_parent) {
		plog(XLOG_WARNING, "children of \"%s\" still exist - deleting anyway", mp->am_path);
	}

	/*
	 * 2.  Update parent's child pointer
	 */
	if (mp->am_parent && mp->am_parent->am_child == mp)
		mp->am_parent->am_child = mp->am_osib;

	/*
	 * 3.  Unlink from sibling chain
	 */
	if (mp->am_ysib)
		mp->am_ysib->am_osib = mp->am_osib;
	if (mp->am_osib)
		mp->am_osib->am_ysib = mp->am_ysib;
}

/*
 * Compute a new time to live value for a node.
 */
void new_ttl(mp)
am_node *mp;
{
	mp->am_timeo_w = 0;

	mp->am_ttl = clocktime();
	mp->am_fattr.atime.seconds = mp->am_ttl;
	mp->am_ttl += mp->am_timeo;	/* sun's -tl option */
}

void mk_fattr P((am_node *mp, ftype vntype));
void mk_fattr(mp, vntype)
am_node *mp;
ftype vntype;
{
	switch (vntype) {
	case NFDIR:
		mp->am_fattr.type = NFDIR;
		mp->am_fattr.mode = NFSMODE_DIR | 0555;
		mp->am_fattr.nlink = 2;
		mp->am_fattr.size = 512;
		break;
	case NFLNK:
		mp->am_fattr.type = NFLNK;
		mp->am_fattr.mode = NFSMODE_LNK | 0777;
		mp->am_fattr.nlink = 1;
		mp->am_fattr.size = 0;
		break;
	default:
		plog(XLOG_FATAL, "Unknown fattr type %d - ignored", vntype);
		break;
	}
}

/*
 * Initialise an allocated mount node.
 * It is assumed that the mount node was bzero'd
 * before getting here so anything that would
 * be set to zero isn't done here.
 */
void init_map(mp, dir)
am_node *mp;
char *dir;
{
	/* mp->am_mapno initalised by exported_ap_alloc */
	mp->am_mnt = new_mntfs();
	mp->am_name = strdup(dir);
	mp->am_path = strdup(dir);
	/*mp->am_link = 0;*/
	/*mp->am_parent = 0;*/
	/*mp->am_ysib = 0;*/
	/*mp->am_osib = 0;*/
	/*mp->am_child = 0;*/
	/*mp->am_flags = 0;*/
	/*mp->am_error = 0;*/
	mp->am_gen = new_gen();
	/*mp->am_pref = 0;*/

	mp->am_timeo = am_timeo;
	mp->am_attr.status = NFS_OK;
	mp->am_fattr = gen_fattr;
	mp->am_fattr.fsid = 42;
	mp->am_fattr.fileid = 0;
	mp->am_fattr.atime.seconds = clocktime();
	mp->am_fattr.atime.useconds = 0;
	mp->am_fattr.mtime = mp->am_fattr.ctime = mp->am_fattr.atime;

	new_ttl(mp);
	mp->am_stats.s_mtime = mp->am_fattr.atime.seconds;
	/*mp->am_private = 0;*/
}

/*
 * Free a mount node.
 * The node must be already unmounted.
 */
void free_map(mp)
am_node *mp;
{
	remove_am(mp);

	if (mp->am_link)
		free(mp->am_link);
	if (mp->am_name)
		free(mp->am_name);
	if (mp->am_path)
		free(mp->am_path);
	if (mp->am_pref)
		free(mp->am_pref);

	if (mp->am_mnt)
		free_mntfs(mp->am_mnt);

	exported_ap_free(mp);
}

/*
 * Convert from file handle to
 * automount node.
 */
am_node *fh_to_mp3(fhp, rp, c_or_d)
nfs_fh *fhp;
int *rp;
int c_or_d;
{
	struct am_fh *fp = (struct am_fh *) fhp;
	am_node *ap = 0;

	/*
	 * Check process id matches
	 * If it doesn't then it is probably
	 * from an old kernel cached filehandle
	 * which is now out of date.
	 */
	if (fp->fhh_pid != mypid)
		goto drop;

	/*
	 * Make sure the index is valid before
	 * exported_ap is referenced.
	 */
	if (fp->fhh_id < 0 || fp->fhh_id >= exported_ap_size)
		goto drop;

	/*
	 * Get hold of the supposed mount node
	 */
	ap = exported_ap[fp->fhh_id];

	/*
	 * If it exists then maybe...
	 */
	if (ap) {
		/*
		 * Check the generation number in the node
		 * matches the one from the kernel.  If not
		 * then the old node has been timed out and
		 * a new one allocated.
		 */
		if (ap->am_gen != fp->fhh_gen) {
			ap = 0;
			goto drop;
		}

		/*
		 * If the node is hung then locate a new node
		 * for it.  This implements the replicated filesystem
		 * retries.
		 */
		if (ap->am_mnt && FSRV_ISDOWN(ap->am_mnt->mf_server) && ap->am_parent) {
			int error;
			am_node *orig_ap = ap;
#ifdef DEBUG
			dlog("fh_to_mp3: %s (%s) is hung:- call lookup",
					orig_ap->am_path, orig_ap->am_mnt->mf_info);
#endif /* DEBUG */
			/*
			 * Update modify time of parent node.
			 * With any luck the kernel will re-stat
			 * the child node and get new information.
			 */
			orig_ap->am_fattr.mtime.seconds = clocktime();

			/*
			 * Call the parent's lookup routine for an object
			 * with the same name.  This may return -1 in error
			 * if a mount is in progress.  In any case, if no
			 * mount node is returned the error code is propagated
			 * to the caller.
			 */
			if (c_or_d == VLOOK_CREATE) {
				ap = (*orig_ap->am_parent->am_mnt->mf_ops->lookuppn)(orig_ap->am_parent,
						orig_ap->am_name, &error, c_or_d);
			} else {
				ap = 0;
				error = ESTALE;
			}
			if (ap == 0) {
				if (error < 0 && amd_state == Finishing)
					error = ENOENT;
				*rp = error;
				return 0;
			}
			/*
			 * Update last access to original node.  This
			 * avoids timing it out and so sending ESTALE
			 * back to the kernel.
			 * XXX - Not sure we need this anymore (jsp, 90/10/6).
			 */
			new_ttl(orig_ap);

		}
		/*
		 * Disallow references to objects being unmounted, unless
		 * they are automount points.
		 */
		if (ap->am_mnt && (ap->am_mnt->mf_flags & MFF_UNMOUNTING) &&
				!(ap->am_flags & AMF_ROOT)) {
			if (amd_state == Finishing)
				*rp = ENOENT;
			else
				*rp = -1;
			return 0;
		}
		new_ttl(ap);
	}

drop:
	if (!ap || !ap->am_mnt) {
		/*
		 * If we are shutting down then it is likely
		 * that this node has disappeared because of
		 * a fast timeout.  To avoid things thrashing
		 * just pretend it doesn't exist at all.  If
		 * ESTALE is returned, some NFS clients just
		 * keep retrying (stupid or what - if it's
		 * stale now, what's it going to be in 5 minutes?)
		 */
		if (amd_state == Finishing)
			*rp = ENOENT;
		else
			*rp = ESTALE;
		amd_stats.d_stale++;
	}

	return ap;
}

am_node *fh_to_mp(fhp)
nfs_fh *fhp;
{
	int dummy;
	return fh_to_mp2(fhp, &dummy);
}

/*
 * Convert from automount node to
 * file handle.
 */
void mp_to_fh(mp, fhp)
am_node *mp;
struct nfs_fh *fhp;
{
	struct am_fh *fp = (struct am_fh *) fhp;

	/*
	 * Take the process id
	 */
	fp->fhh_pid = mypid;
	/*
	 * .. the map number
	 */
	fp->fhh_id = mp->am_mapno;
	/*
	 * .. and the generation number
	 */
	fp->fhh_gen = mp->am_gen;
	/*
	 * .. to make a "unique" triple that will never
	 * be reallocated except across reboots (which doesn't matter)
	 * or if we are unlucky enough to be given the same
	 * pid as a previous amd (very unlikely).
	 */
}

static am_node *find_ap2 P((char *dir, am_node *mp));
static am_node *find_ap2(dir, mp)
char *dir;
am_node *mp;
{
	if (mp) {
		am_node *mp2;
		if (strcmp(mp->am_path, dir) == 0)
			return mp;

		if ((mp->am_mnt->mf_flags & MFF_MOUNTED) &&
			strcmp(mp->am_mnt->mf_mount, dir) == 0)
			return mp;

		mp2 = find_ap2(dir, mp->am_osib);
		if (mp2)
			return mp2;
		return find_ap2(dir, mp->am_child);
	}

	return 0;
}

/*
 * Find the mount node corresponding
 * to dir.  dir can match either the
 * automount path or, if the node is
 * mounted, the mount location.
 */
am_node *find_ap P((char *dir));