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lfs_inode.c revision 1.22.2.1.4.1
      1 /*	$NetBSD: lfs_inode.c,v 1.22.2.1.4.1 1999/11/30 13:36:23 itojun Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1999 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Konrad E. Schroder <perseant (at) hhhh.org>.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *      This product includes software developed by the NetBSD
     21  *      Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 /*
     39  * Copyright (c) 1986, 1989, 1991, 1993
     40  *	The Regents of the University of California.  All rights reserved.
     41  *
     42  * Redistribution and use in source and binary forms, with or without
     43  * modification, are permitted provided that the following conditions
     44  * are met:
     45  * 1. Redistributions of source code must retain the above copyright
     46  *    notice, this list of conditions and the following disclaimer.
     47  * 2. Redistributions in binary form must reproduce the above copyright
     48  *    notice, this list of conditions and the following disclaimer in the
     49  *    documentation and/or other materials provided with the distribution.
     50  * 3. All advertising materials mentioning features or use of this software
     51  *    must display the following acknowledgement:
     52  *	This product includes software developed by the University of
     53  *	California, Berkeley and its contributors.
     54  * 4. Neither the name of the University nor the names of its contributors
     55  *    may be used to endorse or promote products derived from this software
     56  *    without specific prior written permission.
     57  *
     58  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     59  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     60  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     61  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     62  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     63  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     64  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     65  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     66  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     67  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     68  * SUCH DAMAGE.
     69  *
     70  *	@(#)lfs_inode.c	8.9 (Berkeley) 5/8/95
     71  */
     72 
     73 #if defined(_KERNEL) && !defined(_LKM)
     74 #include "opt_quota.h"
     75 #endif
     76 
     77 #include <sys/param.h>
     78 #include <sys/systm.h>
     79 #include <sys/mount.h>
     80 #include <sys/proc.h>
     81 #include <sys/file.h>
     82 #include <sys/buf.h>
     83 #include <sys/vnode.h>
     84 #include <sys/kernel.h>
     85 #include <sys/malloc.h>
     86 
     87 #include <vm/vm.h>
     88 
     89 #include <ufs/ufs/quota.h>
     90 #include <ufs/ufs/inode.h>
     91 #include <ufs/ufs/ufsmount.h>
     92 #include <ufs/ufs/ufs_extern.h>
     93 
     94 #include <ufs/lfs/lfs.h>
     95 #include <ufs/lfs/lfs_extern.h>
     96 
     97 static int lfs_vinvalbuf __P((struct vnode *, struct ucred *, struct proc *, ufs_daddr_t));
     98 
     99 /* Search a block for a specific dinode. */
    100 struct dinode *
    101 lfs_ifind(fs, ino, dip)
    102 	struct lfs *fs;
    103 	ino_t ino;
    104 	register struct dinode *dip;
    105 {
    106 	register int cnt;
    107 	register struct dinode *ldip;
    108 
    109 	for (cnt = INOPB(fs), ldip = dip + (cnt - 1); cnt--; --ldip)
    110 		if (ldip->di_inumber == ino)
    111 			return (ldip);
    112 
    113 	panic("lfs_ifind: dinode %u not found", ino);
    114 	/* NOTREACHED */
    115 }
    116 
    117 int
    118 lfs_update(v)
    119 	void *v;
    120 {
    121 	struct vop_update_args /* {
    122 				  struct vnode *a_vp;
    123 				  struct timespec *a_access;
    124 				  struct timespec *a_modify;
    125 				  int a_waitfor;
    126 				  } */ *ap = v;
    127 	struct inode *ip;
    128 	struct vnode *vp = ap->a_vp;
    129 	int mod, oflag;
    130 	struct timespec ts;
    131 
    132 	if (vp->v_mount->mnt_flag & MNT_RDONLY)
    133 		return (0);
    134 	ip = VTOI(vp);
    135 
    136 	/*
    137 	 * If we are called from vinvalbuf, and the file's blocks have
    138 	 * already been scheduled for writing, but the writes have not
    139 	 * yet completed, lfs_vflush will not be called, and vinvalbuf
    140 	 * will cause a panic.  So, we must wait until any pending write
    141 	 * for our inode completes, if we are called with LFS_SYNC set.
    142 	 */
    143 	while((ap->a_waitfor & LFS_SYNC) && WRITEINPROG(vp)) {
    144 #ifdef DEBUG_LFS
    145 		printf("lfs_update: sleeping on inode %d\n",ip->i_number);
    146 #endif
    147 		tsleep(vp, (PRIBIO+1), "lfs_update", 0);
    148 	}
    149 	mod = ip->i_flag & IN_MODIFIED;
    150 	oflag = ip->i_flag;
    151 	TIMEVAL_TO_TIMESPEC(&time, &ts);
    152 	LFS_ITIMES(ip,
    153 		   ap->a_access ? ap->a_access : &ts,
    154 		   ap->a_modify ? ap->a_modify : &ts, &ts);
    155 	if (!mod && (ip->i_flag & IN_MODIFIED))
    156 		ip->i_lfs->lfs_uinodes++;
    157 	if ((ip->i_flag & (IN_MODIFIED|IN_CLEANING)) == 0) {
    158 		return (0);
    159 	}
    160 
    161 	/* If sync, push back the vnode and any dirty blocks it may have. */
    162 	return (ap->a_waitfor & LFS_SYNC ? lfs_vflush(vp) : 0);
    163 }
    164 
    165 /* Update segment usage information when removing a block. */
    166 #define UPDATE_SEGUSE \
    167 	if (lastseg != -1) { \
    168 		LFS_SEGENTRY(sup, fs, lastseg, sup_bp); \
    169 		if (num > sup->su_nbytes) { \
    170 			printf("lfs_truncate: negative bytes: segment %d short by %d\n", \
    171 			      lastseg, num - sup->su_nbytes); \
    172 			panic("lfs_truncate: negative bytes"); \
    173 		      sup->su_nbytes = 0; \
    174 		} else \
    175 		sup->su_nbytes -= num; \
    176 		e1 = VOP_BWRITE(sup_bp); \
    177 		fragsreleased += numfrags(fs, num); \
    178 	}
    179 
    180 #define SEGDEC(S) { \
    181 	if (daddr != 0) { \
    182 		if (lastseg != (seg = datosn(fs, daddr))) { \
    183 			UPDATE_SEGUSE; \
    184 			num = (S); \
    185 			lastseg = seg; \
    186 		} else \
    187 			num += (S); \
    188 	} \
    189 }
    190 
    191 /*
    192  * Truncate the inode ip to at most length size.  Update segment usage
    193  * table information.
    194  */
    195 /* ARGSUSED */
    196 int
    197 lfs_truncate(v)
    198 	void *v;
    199 {
    200 	struct vop_truncate_args /* {
    201 		struct vnode *a_vp;
    202 		off_t a_length;
    203 		int a_flags;
    204 		struct ucred *a_cred;
    205 		struct proc *a_p;
    206 	} */ *ap = v;
    207 	register struct indir *inp;
    208 	register int i;
    209 	register ufs_daddr_t *daddrp;
    210 	register struct vnode *vp = ap->a_vp;
    211 	off_t length = ap->a_length;
    212 	struct buf *bp, *sup_bp;
    213 	struct ifile *ifp;
    214 	struct inode *ip;
    215 	struct lfs *fs;
    216 	struct indir a[NIADDR + 2], a_end[NIADDR + 2];
    217 	SEGUSE *sup;
    218 	ufs_daddr_t daddr, lastblock, lbn, olastblock;
    219 	ufs_daddr_t oldsize_lastblock, oldsize_newlast, newsize;
    220 	long off, a_released, fragsreleased, i_released;
    221 	int e1, e2, depth, lastseg, num, offset, seg, freesize;
    222 
    223 	ip = VTOI(vp);
    224 
    225 	if (vp->v_type == VLNK && vp->v_mount->mnt_maxsymlinklen > 0) {
    226 #ifdef DIAGNOSTIC
    227 		if (length != 0)
    228 			panic("lfs_truncate: partial truncate of symlink");
    229 #endif
    230 		bzero((char *)&ip->i_ffs_shortlink, (u_int)ip->i_ffs_size);
    231 		ip->i_ffs_size = 0;
    232 		ip->i_flag |= IN_CHANGE | IN_UPDATE;
    233 		return (VOP_UPDATE(vp, NULL, NULL, 0));
    234 	}
    235 	uvm_vnp_setsize(vp, length);
    236 
    237 	fs = ip->i_lfs;
    238 	lfs_imtime(fs);
    239 
    240 	/* If length is larger than the file, just update the times. */
    241 	if (ip->i_ffs_size <= length) {
    242 		ip->i_flag |= IN_CHANGE | IN_UPDATE;
    243 		return (VOP_UPDATE(vp, NULL, NULL, 0));
    244 	}
    245 
    246 	/*
    247 	 * Make sure no writes happen while we're truncating.
    248 	 * Otherwise, blocks which are accounted for on the inode
    249 	 * *and* which have been created for cleaning can coexist,
    250 	 * and cause us to overcount, and panic below.
    251 	 *
    252 	 * XXX KS - too restrictive?  Maybe only when cleaning?
    253 	 */
    254 	while(fs->lfs_seglock) {
    255 		tsleep(&fs->lfs_seglock, (PRIBIO+1), "lfs_truncate", 0);
    256 	}
    257 
    258 	/*
    259 	 * Calculate index into inode's block list of last direct and indirect
    260 	 * blocks (if any) which we want to keep.  Lastblock is 0 when the
    261 	 * file is truncated to 0.
    262 	 */
    263 	lastblock = lblkno(fs, length + fs->lfs_bsize - 1);
    264 	olastblock = lblkno(fs, ip->i_ffs_size + fs->lfs_bsize - 1) - 1;
    265 
    266 	/*
    267 	 * Update the size of the file. If the file is not being truncated to
    268 	 * a block boundry, the contents of the partial block following the end
    269 	 * must be zero'd in case it ever becomes accessible again
    270 	 * because of subsequent file growth.  For this part of the code,
    271 	 * oldsize_newlast refers to the old size of the new last block in the
    272 	 * file.
    273 	 */
    274 	offset = blkoff(fs, length);
    275 	lbn = lblkno(fs, length);
    276 	oldsize_newlast = blksize(fs, ip, lbn);
    277 
    278 	/* Now set oldsize to the current size of the current last block */
    279 	oldsize_lastblock = blksize(fs, ip, olastblock);
    280 	if (offset == 0)
    281 		ip->i_ffs_size = length;
    282 	else {
    283 #ifdef QUOTA
    284 		if ((e1 = getinoquota(ip)) != 0)
    285 			return (e1);
    286 #endif
    287 		if ((e1 = bread(vp, lbn, oldsize_newlast, NOCRED, &bp)) != 0) {
    288 			printf("lfs_truncate: bread: %d\n",e1);
    289 			brelse(bp);
    290 			return (e1);
    291 		}
    292 		ip->i_ffs_size = length;
    293 		(void)uvm_vnp_uncache(vp);
    294 		newsize = blksize(fs, ip, lbn);
    295 		bzero((char *)bp->b_data + offset, (u_int)(newsize - offset));
    296 #ifdef DEBUG
    297 		if(bp->b_flags & B_CALL)
    298 		    panic("Can't allocbuf malloced buffer!");
    299 		else
    300 #endif
    301 			allocbuf(bp, newsize);
    302 		if(oldsize_newlast > newsize)
    303 			ip->i_ffs_blocks -= btodb(oldsize_newlast - newsize);
    304 		if ((e1 = VOP_BWRITE(bp)) != 0) {
    305 			printf("lfs_truncate: bwrite: %d\n",e1);
    306 			return (e1);
    307 		}
    308 	}
    309 	/*
    310 	 * Modify sup->su_nbyte counters for each deleted block; keep track
    311 	 * of number of blocks removed for ip->i_ffs_blocks.
    312 	 */
    313 	fragsreleased = 0;
    314 	num = 0;
    315 	lastseg = -1;
    316 
    317 	for (lbn = olastblock; lbn >= lastblock;) {
    318 		/* XXX use run length from bmap array to make this faster */
    319 		ufs_bmaparray(vp, lbn, &daddr, a, &depth, NULL);
    320 		if (lbn == olastblock) {
    321 			for (i = NIADDR + 2; i--;)
    322 				a_end[i] = a[i];
    323 			freesize = oldsize_lastblock;
    324 		} else
    325 			freesize = fs->lfs_bsize;
    326 		switch (depth) {
    327 		case 0:		/* Direct block. */
    328 			daddr = ip->i_ffs_db[lbn];
    329 			SEGDEC(freesize);
    330 			ip->i_ffs_db[lbn] = 0;
    331 			--lbn;
    332 			break;
    333 #ifdef DIAGNOSTIC
    334 		case 1:		/* An indirect block. */
    335 			panic("lfs_truncate: ufs_bmaparray returned depth 1");
    336 			/* NOTREACHED */
    337 #endif
    338 		default:	/* Chain of indirect blocks. */
    339 			inp = a + --depth;
    340 			if (inp->in_off > 0 && lbn != lastblock) {
    341 				lbn -= inp->in_off < lbn - lastblock ?
    342 					inp->in_off : lbn - lastblock;
    343 				break;
    344 			}
    345 			for (; depth && (inp->in_off == 0 || lbn == lastblock);
    346 			     --inp, --depth) {
    347 				if (bread(vp,
    348 					  inp->in_lbn, fs->lfs_bsize, NOCRED, &bp))
    349 					panic("lfs_truncate: bread bno %d",
    350 					      inp->in_lbn);
    351 				daddrp = (ufs_daddr_t *)bp->b_data + inp->in_off;
    352 				for (i = inp->in_off;
    353 				     i++ <= a_end[depth].in_off;) {
    354 					daddr = *daddrp++;
    355 					SEGDEC(freesize);
    356 				}
    357 				a_end[depth].in_off = NINDIR(fs) - 1;
    358 				if (inp->in_off == 0)
    359 					brelse (bp);
    360 				else {
    361 					bzero((ufs_daddr_t *)bp->b_data +
    362 					      inp->in_off, fs->lfs_bsize -
    363 					      inp->in_off * sizeof(ufs_daddr_t));
    364 					if ((e1 = VOP_BWRITE(bp)) != 0) {
    365 						printf("lfs_truncate: indir bwrite: %d\n",e1);
    366 						return (e1);
    367 					}
    368 				}
    369 			}
    370 			if (depth == 0 && a[1].in_off == 0) {
    371 				off = a[0].in_off;
    372 				daddr = ip->i_ffs_ib[off];
    373 				SEGDEC(freesize);
    374 				ip->i_ffs_ib[off] = 0;
    375 			}
    376 			if (lbn == lastblock || lbn <= NDADDR)
    377 				--lbn;
    378 			else {
    379 				lbn -= NINDIR(fs);
    380 				if (lbn < lastblock)
    381 					lbn = lastblock;
    382 			}
    383 		}
    384 	}
    385 	UPDATE_SEGUSE;
    386 
    387 	/* If truncating the file to 0, update the version number. */
    388 	if (length == 0) {
    389 		LFS_IENTRY(ifp, fs, ip->i_number, bp);
    390 		++ifp->if_version;
    391 		(void) VOP_BWRITE(bp);
    392 	}
    393 #ifdef DIAGNOSTIC
    394 	if (ip->i_ffs_blocks < fragstodb(fs, fragsreleased)) {
    395 		panic("lfs_truncate: frag count < 0 (%d<%ld), ino %d\n",
    396 			    ip->i_ffs_blocks, fragstodb(fs, fragsreleased),
    397 			    ip->i_number);
    398 		fragsreleased = dbtofrags(fs, ip->i_ffs_blocks);
    399 	}
    400 #endif
    401 	ip->i_ffs_blocks -= fragstodb(fs, fragsreleased);
    402 	fs->lfs_bfree +=  fragstodb(fs, fragsreleased);
    403 	ip->i_flag |= IN_CHANGE | IN_UPDATE;
    404 	/*
    405 	 * Traverse dirty block list counting number of dirty buffers
    406 	 * that are being deleted out of the cache, so that the lfs_avail
    407 	 * field can be updated.
    408 	 */
    409 	a_released = 0;
    410 	i_released = 0;
    411 	for (bp = vp->v_dirtyblkhd.lh_first; bp; bp = bp->b_vnbufs.le_next) {
    412 
    413 		/* XXX KS - Don't miscount if we're not truncating to zero. */
    414 		if(length>0 && !(bp->b_lblkno >= 0 && bp->b_lblkno > lastblock)
    415 		   && !(bp->b_lblkno < 0 && bp->b_lblkno < -lastblock-NIADDR))
    416 			continue;
    417 
    418 		if (bp->b_flags & B_LOCKED) {
    419 			a_released += numfrags(fs, bp->b_bcount);
    420 			/*
    421 			 * XXX
    422 			 * When buffers are created in the cache, their block
    423 			 * number is set equal to their logical block number.
    424 			 * If that is still true, we are assuming that the
    425 			 * blocks are new (not yet on disk) and weren't
    426 			 * counted above.  However, there is a slight chance
    427 			 * that a block's disk address is equal to its logical
    428 			 * block number in which case, we'll get an overcounting
    429 			 * here.
    430 			 */
    431 			if (bp->b_blkno == bp->b_lblkno) {
    432 				i_released += numfrags(fs, bp->b_bcount);
    433 			}
    434 		}
    435 	}
    436 	fragsreleased = i_released;
    437 #ifdef DIAGNOSTIC
    438 	if (fragsreleased > dbtofrags(fs, ip->i_ffs_blocks)) {
    439 		printf("lfs_inode: %ld frags released > %d in inode %d\n",
    440 		       fragsreleased, dbtofrags(fs, ip->i_ffs_blocks),
    441 		       ip->i_number);
    442 		fragsreleased = dbtofrags(fs, ip->i_ffs_blocks);
    443 	}
    444 #endif
    445 	fs->lfs_bfree += fragstodb(fs, fragsreleased);
    446 	ip->i_ffs_blocks -= fragstodb(fs, fragsreleased);
    447 #ifdef DIAGNOSTIC
    448 	if (length == 0 && ip->i_ffs_blocks != 0) {
    449 		printf("lfs_inode: trunc to zero, but %d blocks left on inode %d\n",
    450 		       ip->i_ffs_blocks, ip->i_number);
    451 		panic("lfs_inode\n");
    452 	}
    453 #endif
    454 	fs->lfs_avail += fragstodb(fs, a_released);
    455 	if(length>0)
    456 		e1 = lfs_vinvalbuf(vp, ap->a_cred, ap->a_p, lastblock-1);
    457 	else
    458 		e1 = vinvalbuf(vp, 0, ap->a_cred, ap->a_p, 0, 0);
    459 	e2 = VOP_UPDATE(vp, NULL, NULL, 0);
    460 	if(e1)
    461 		printf("lfs_truncate: vinvalbuf: %d\n",e1);
    462 	if(e2)
    463 		printf("lfs_truncate: update: %d\n",e2);
    464 
    465 	return (e1 ? e1 : e2 ? e2 : 0);
    466 }
    467 
    468 /*
    469  * Get rid of blocks a la vinvalbuf; but only blocks that are of a higher
    470  * lblkno than the file size allows.
    471  */
    472 int
    473 lfs_vinvalbuf(vp, cred, p, maxblk)
    474 	register struct vnode *vp;
    475 	struct ucred *cred;
    476 	struct proc *p;
    477 	ufs_daddr_t maxblk;
    478 {
    479 	register struct buf *bp;
    480 	struct buf *nbp, *blist;
    481 	int i, s, error, dirty;
    482 
    483       top:
    484 	dirty=0;
    485 	for (i=0;i<2;i++) {
    486 		if(i==0)
    487 			blist = vp->v_cleanblkhd.lh_first;
    488 		else /* i == 1 */
    489 			blist = vp->v_dirtyblkhd.lh_first;
    490 
    491 		for (bp = blist; bp; bp = nbp) {
    492 			nbp = bp->b_vnbufs.le_next;
    493 
    494 			s = splbio();
    495 			if (bp->b_flags & B_GATHERED) {
    496 				error = tsleep(vp, PRIBIO+1, "lfs_vin2", 0);
    497 				splx(s);
    498 				if(error)
    499 					return error;
    500 				goto top;
    501 			}
    502 			if (bp->b_flags & B_BUSY) {
    503 				bp->b_flags |= B_WANTED;
    504 				error = tsleep((caddr_t)bp,
    505 					(PRIBIO + 1), "lfs_vinval", 0);
    506 				splx(s);
    507 				if (error)
    508 					return (error);
    509 				goto top;
    510 			}
    511 
    512 			bp->b_flags |= B_BUSY;
    513 			splx(s);
    514 			if((bp->b_lblkno >= 0 && bp->b_lblkno > maxblk)
    515 			   || (bp->b_lblkno < 0 && bp->b_lblkno < -maxblk-(NIADDR-1)))
    516 			{
    517 				bp->b_flags |= B_INVAL | B_VFLUSH;
    518 				if(bp->b_flags & B_CALL) {
    519 					lfs_freebuf(bp);
    520 				} else {
    521 					brelse(bp);
    522 				}
    523 				++dirty;
    524 			} else {
    525 				/*
    526 				 * This buffer is still on its free list.
    527 				 * So don't brelse, but wake up any sleepers.
    528 				 */
    529 				bp->b_flags &= ~B_BUSY;
    530 				if(bp->b_flags & B_WANTED) {
    531 					bp->b_flags &= ~(B_WANTED|B_AGE);
    532 					wakeup(bp);
    533 				}
    534 			}
    535 		}
    536 	}
    537 	if(dirty)
    538 		goto top;
    539 	return (0);
    540 }
    541