brlock.c

samba-3.0.22.tar.gz 编译smb服务器的源码

/* 
   Unix SMB/CIFS implementation.
   byte range locking code
   Updated to handle range splits/merges.

   Copyright (C) Andrew Tridgell 1992-2000
   Copyright (C) Jeremy Allison 1992-2000
   
   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.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/* This module implements a tdb based byte range locking service,
   replacing the fcntl() based byte range locking previously
   used. This allows us to provide the same semantics as NT */

#include "includes.h"

#undef DBGC_CLASS
#define DBGC_CLASS DBGC_LOCKING

#define ZERO_ZERO 0

/* This contains elements that differentiate locks. The smbpid is a
   client supplied pid, and is essentially the locking context for
   this client */

struct lock_context {
	uint16 smbpid;
	uint16 tid;
	struct process_id pid;
};

/* The data in brlock records is an unsorted linear array of these
   records.  It is unnecessary to store the count as tdb provides the
   size of the record */

struct lock_struct {
	struct lock_context context;
	br_off start;
	br_off size;
	int fnum;
	enum brl_type lock_type;
};

/* The key used in the brlock database. */

struct lock_key {
	SMB_DEV_T device;
	SMB_INO_T inode;
};

/* The open brlock.tdb database. */

static TDB_CONTEXT *tdb;

/****************************************************************************
 Create a locking key - ensuring zero filled for pad purposes.
****************************************************************************/

static TDB_DATA locking_key(SMB_DEV_T dev, SMB_INO_T inode)
{
        static struct lock_key key;
        TDB_DATA kbuf;

        memset(&key, '\0', sizeof(key));
        key.device = dev;
        key.inode = inode;
        kbuf.dptr = (char *)&key;
        kbuf.dsize = sizeof(key);
        return kbuf;
}

/****************************************************************************
 See if two locking contexts are equal.
****************************************************************************/

static BOOL brl_same_context(struct lock_context *ctx1, 
			     struct lock_context *ctx2)
{
	return (procid_equal(&ctx1->pid, &ctx2->pid) &&
		(ctx1->smbpid == ctx2->smbpid) &&
		(ctx1->tid == ctx2->tid));
}

/****************************************************************************
 See if lck1 and lck2 overlap.
****************************************************************************/

static BOOL brl_overlap(struct lock_struct *lck1,
                        struct lock_struct *lck2)
{
	/* this extra check is not redundent - it copes with locks
	   that go beyond the end of 64 bit file space */
	if (lck1->size != 0 &&
	    lck1->start == lck2->start &&
	    lck1->size == lck2->size) {
		return True;
	}

	if (lck1->start >= (lck2->start+lck2->size) ||
	    lck2->start >= (lck1->start+lck1->size)) {
		return False;
	}
	return True;
}

/****************************************************************************
 See if lock2 can be added when lock1 is in place.
****************************************************************************/

static BOOL brl_conflict(struct lock_struct *lck1, 
			 struct lock_struct *lck2)
{
	if (lck1->lock_type == PENDING_LOCK || lck2->lock_type == PENDING_LOCK )
		return False;

	if (lck1->lock_type == READ_LOCK && lck2->lock_type == READ_LOCK) {
		return False;
	}

	if (brl_same_context(&lck1->context, &lck2->context) &&
	    lck2->lock_type == READ_LOCK && lck1->fnum == lck2->fnum) {
		return False;
	}

	return brl_overlap(lck1, lck2);
} 

#if ZERO_ZERO
static BOOL brl_conflict1(struct lock_struct *lck1, 
			 struct lock_struct *lck2)
{
	if (lck1->lock_type == PENDING_LOCK || lck2->lock_type == PENDING_LOCK )
		return False;

	if (lck1->lock_type == READ_LOCK && lck2->lock_type == READ_LOCK) {
		return False;
	}

	if (brl_same_context(&lck1->context, &lck2->context) &&
	    lck2->lock_type == READ_LOCK && lck1->fnum == lck2->fnum) {
		return False;
	}

	if (lck2->start == 0 && lck2->size == 0 && lck1->size != 0) {
		return True;
	}

	if (lck1->start >= (lck2->start + lck2->size) ||
	    lck2->start >= (lck1->start + lck1->size)) {
		return False;
	}
	    
	return True;
} 
#endif

/****************************************************************************
 Check to see if this lock conflicts, but ignore our own locks on the
 same fnum only.
****************************************************************************/

static BOOL brl_conflict_other(struct lock_struct *lck1, struct lock_struct *lck2)
{
	if (lck1->lock_type == PENDING_LOCK || lck2->lock_type == PENDING_LOCK )
		return False;

	if (lck1->lock_type == READ_LOCK && lck2->lock_type == READ_LOCK) 
		return False;

	/*
	 * Incoming WRITE locks conflict with existing READ locks even
	 * if the context is the same. JRA. See LOCKTEST7 in smbtorture.
	 */

	if (!(lck2->lock_type == WRITE_LOCK && lck1->lock_type == READ_LOCK)) {
		if (brl_same_context(&lck1->context, &lck2->context) &&
					lck1->fnum == lck2->fnum)
			return False;
	}

	return brl_overlap(lck1, lck2);
} 

/****************************************************************************
 Amazingly enough, w2k3 "remembers" whether the last lock failure
 is the same as this one and changes its error code. I wonder if any
 app depends on this ?
****************************************************************************/

static NTSTATUS brl_lock_failed(struct lock_struct *lock)
{
	static struct lock_struct last_lock_failure;

	if (brl_same_context(&lock->context, &last_lock_failure.context) &&
			lock->fnum == last_lock_failure.fnum &&
			lock->start == last_lock_failure.start &&
			lock->size == last_lock_failure.size) {
		return NT_STATUS_FILE_LOCK_CONFLICT;
	}
	last_lock_failure = *lock;
	if (lock->start >= 0xEF000000 &&
			(lock->start >> 63) == 0) {
		/* amazing the little things you learn with a test
		   suite. Locks beyond this offset (as a 64 bit
		   number!) always generate the conflict error code,
		   unless the top bit is set */
		return NT_STATUS_FILE_LOCK_CONFLICT;
	}
	return NT_STATUS_LOCK_NOT_GRANTED;
}

#if DONT_DO_THIS
	/* doing this traversal could kill solaris machines under high load (tridge) */
	/* delete any dead locks */

/****************************************************************************
 Delete a record if it is for a dead process, if check_self is true, then
 delete any records belonging to this pid also (there shouldn't be any).
****************************************************************************/

static int delete_fn(TDB_CONTEXT *ttdb, TDB_DATA kbuf, TDB_DATA dbuf, void *state)
{
	struct lock_struct *locks;
	int count, i;
	BOOL check_self = *(BOOL *)state;
	pid_t mypid = sys_getpid();

	tdb_chainlock(tdb, kbuf);

	locks = (struct lock_struct *)dbuf.dptr;

	count = dbuf.dsize / sizeof(*locks);
	for (i=0; i<count; i++) {
		struct lock_struct *lock = &locks[i];

		/* If check_self is true we want to remove our own records. */
		if (check_self && (mypid == lock->context.pid)) {

			DEBUG(0,("brlock : delete_fn. LOGIC ERROR ! Shutting down and a record for my pid (%u) exists !\n",
					(unsigned int)lock->context.pid ));

		} else if (process_exists(&lock->context.pid)) {

			DEBUG(10,("brlock : delete_fn. pid %u exists.\n", (unsigned int)lock->context.pid ));
			continue;
		}

		DEBUG(10,("brlock : delete_fn. Deleting record for process %u\n",
				(unsigned int)lock->context.pid ));

		if (count > 1 && i < count-1) {
			memmove(&locks[i], &locks[i+1], 
				sizeof(*locks)*((count-1) - i));
		}
		count--;
		i--;
	}

	if (count == 0) {
		tdb_delete(tdb, kbuf);
	} else if (count < (dbuf.dsize / sizeof(*locks))) {
		dbuf.dsize = count * sizeof(*locks);
		tdb_store(tdb, kbuf, dbuf, TDB_REPLACE);
	}

	tdb_chainunlock(tdb, kbuf);
	return 0;
}
#endif

/****************************************************************************
 Open up the brlock.tdb database.
****************************************************************************/

void brl_init(int read_only)
{
	if (tdb)
		return;
	tdb = tdb_open_log(lock_path("brlock.tdb"), 0,  TDB_DEFAULT|(read_only?0x0:TDB_CLEAR_IF_FIRST),
		       read_only?O_RDONLY:(O_RDWR|O_CREAT), 0644 );
	if (!tdb) {
		DEBUG(0,("Failed to open byte range locking database\n"));
		return;
	}

#if DONT_DO_THIS
	/* doing this traversal could kill solaris machines under high load (tridge) */
	/* delete any dead locks */
	if (!read_only) {
		BOOL check_self = False;
		tdb_traverse(tdb, delete_fn, &check_self);
	}
#endif
}

/****************************************************************************
 Close down the brlock.tdb database.
****************************************************************************/

void brl_shutdown(int read_only)
{
	if (!tdb)
		return;

#if DONT_DO_THIS
	/* doing this traversal could kill solaris machines under high load (tridge) */
	/* delete any dead locks */
	if (!read_only) {
		BOOL check_self = True;
		tdb_traverse(tdb, delete_fn, &check_self);
	}
#endif

	tdb_close(tdb);
}

#if ZERO_ZERO
/****************************************************************************
compare two locks for sorting
****************************************************************************/
static int lock_compare(struct lock_struct *lck1, 
			 struct lock_struct *lck2)
{
	if (lck1->start != lck2->start) return (lck1->start - lck2->start);
	if (lck2->size != lck1->size) {
		return ((int)lck1->size - (int)lck2->size);
	}
	return 0;
}
#endif

/****************************************************************************
 Lock a range of bytes.
****************************************************************************/

NTSTATUS brl_lock(SMB_DEV_T dev, SMB_INO_T ino, int fnum,
		  uint16 smbpid, struct process_id pid, uint16 tid,
		  br_off start, br_off size, 
		  enum brl_type lock_type, BOOL *my_lock_ctx)
{
	TDB_DATA kbuf, dbuf;
	int count, i;
	struct lock_struct lock, *locks;
	char *tp;
	NTSTATUS status = NT_STATUS_OK;

	*my_lock_ctx = False;
	kbuf = locking_key(dev,ino);

	dbuf.dptr = NULL;

#if !ZERO_ZERO
	if (start == 0 && size == 0) {
		DEBUG(0,("client sent 0/0 lock - please report this\n"));
	}
#endif