1 /* 2 * Copyright (c) 2010 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 /* 36 * Implements new VFS/VM coherency functions. For conforming VFSs 37 * we treat the backing VM object slightly differently. Instead of 38 * maintaining a number of pages to exactly fit the size of the file 39 * we instead maintain pages to fit the entire contents of the last 40 * buffer cache buffer used by the file. 41 * 42 * For VFSs like NFS and HAMMER which use (generally speaking) fixed 43 * sized buffers this greatly reduces the complexity of VFS/VM interactions. 44 * 45 * Truncations no longer invalidate pages covered by the buffer cache 46 * beyond the file EOF which still fit within the file's last buffer. 47 * We simply unmap them and do not allow userland to fault them in. 48 * 49 * The VFS is no longer responsible for zero-filling buffers during a 50 * truncation, the last buffer will be automatically zero-filled by 51 * nvtruncbuf(). 52 * 53 * This code is intended to (eventually) replace vtruncbuf() and 54 * vnode_pager_setsize(). 55 */ 56 57 #include <sys/param.h> 58 #include <sys/systm.h> 59 #include <sys/buf.h> 60 #include <sys/conf.h> 61 #include <sys/fcntl.h> 62 #include <sys/file.h> 63 #include <sys/kernel.h> 64 #include <sys/malloc.h> 65 #include <sys/mount.h> 66 #include <sys/proc.h> 67 #include <sys/socket.h> 68 #include <sys/stat.h> 69 #include <sys/sysctl.h> 70 #include <sys/unistd.h> 71 #include <sys/vmmeter.h> 72 #include <sys/vnode.h> 73 74 #include <machine/limits.h> 75 76 #include <vm/vm.h> 77 #include <vm/vm_object.h> 78 #include <vm/vm_extern.h> 79 #include <vm/vm_kern.h> 80 #include <vm/pmap.h> 81 #include <vm/vm_map.h> 82 #include <vm/vm_page.h> 83 #include <vm/vm_pager.h> 84 #include <vm/vnode_pager.h> 85 #include <vm/vm_zone.h> 86 87 #include <sys/buf2.h> 88 #include <sys/thread2.h> 89 #include <sys/sysref2.h> 90 #include <vm/vm_page2.h> 91 92 static int nvtruncbuf_bp_trunc_cmp(struct buf *bp, void *data); 93 static int nvtruncbuf_bp_trunc(struct buf *bp, void *data); 94 static int nvtruncbuf_bp_metasync_cmp(struct buf *bp, void *data); 95 static int nvtruncbuf_bp_metasync(struct buf *bp, void *data); 96 97 /* 98 * Truncate a file's buffer and pages to a specified length. The 99 * byte-granular length of the file is specified along with the block 100 * size of the buffer containing that offset. 101 * 102 * If the last buffer straddles the length its contents will be zero-filled 103 * as appropriate. All buffers and pages after the last buffer will be 104 * destroyed. The last buffer itself will be destroyed only if the length 105 * is exactly aligned with it. 106 * 107 * UFS typically passes the old block size prior to the actual truncation, 108 * then later resizes the block based on the new file size. NFS uses a 109 * fixed block size and doesn't care. HAMMER uses a block size based on 110 * the offset which is fixed for any particular offset. 111 * 112 * When zero-filling we must bdwrite() to avoid a window of opportunity 113 * where the kernel might throw away a clean buffer and the filesystem 114 * then attempts to bread() it again before completing (or as part of) 115 * the extension. The filesystem is still responsible for zero-filling 116 * any remainder when writing to the media in the strategy function when 117 * it is able to do so without the page being mapped. The page may still 118 * be mapped by userland here. 119 * 120 * When modifying a buffer we must clear any cached raw disk offset. 121 * bdwrite() will call BMAP on it again. Some filesystems, like HAMMER, 122 * never overwrite existing data blocks. 123 */ 124 125 struct truncbuf_info { 126 struct vnode *vp; 127 off_t truncloffset; /* truncation point */ 128 int clean; /* clean tree, else dirty tree */ 129 }; 130 131 int 132 nvtruncbuf(struct vnode *vp, off_t length, int blksize, int boff, int trivial) 133 { 134 struct truncbuf_info info; 135 off_t truncboffset; 136 const char *filename; 137 struct buf *bp; 138 int count; 139 int error; 140 141 /* 142 * Round up to the *next* block, then destroy the buffers in question. 143 * Since we are only removing some of the buffers we must rely on the 144 * scan count to determine whether a loop is necessary. 145 * 146 * Destroy any pages beyond the last buffer. 147 */ 148 if (boff < 0) 149 boff = (int)(length % blksize); 150 if (boff) 151 info.truncloffset = length + (blksize - boff); 152 else 153 info.truncloffset = length; 154 info.vp = vp; 155 lwkt_gettoken(&vp->v_token); 156 do { 157 info.clean = 1; 158 count = RB_SCAN(buf_rb_tree, &vp->v_rbclean_tree, 159 nvtruncbuf_bp_trunc_cmp, 160 nvtruncbuf_bp_trunc, &info); 161 info.clean = 0; 162 count += RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, 163 nvtruncbuf_bp_trunc_cmp, 164 nvtruncbuf_bp_trunc, &info); 165 } while(count); 166 167 nvnode_pager_setsize(vp, length, blksize, boff); 168 169 /* 170 * Zero-fill the area beyond the file EOF that still fits within 171 * the last buffer. We must mark the buffer as dirty even though 172 * the modified area is beyond EOF to avoid races where the kernel 173 * might flush the buffer before the filesystem is able to reallocate 174 * the block. 175 * 176 * The VFS is responsible for dealing with the actual truncation. 177 * 178 * Only do this if trivial is zero, otherwise it is up to the 179 * VFS to handle the block straddling the EOF. 180 */ 181 if (boff && trivial == 0) { 182 truncboffset = length - boff; 183 error = bread(vp, truncboffset, blksize, &bp); 184 if (error == 0) { 185 bzero(bp->b_data + boff, blksize - boff); 186 if (bp->b_flags & B_DELWRI) { 187 if (bp->b_dirtyoff > boff) 188 bp->b_dirtyoff = boff; 189 if (bp->b_dirtyend > boff) 190 bp->b_dirtyend = boff; 191 } 192 bp->b_bio2.bio_offset = NOOFFSET; 193 bdwrite(bp); 194 } 195 } else { 196 error = 0; 197 } 198 199 /* 200 * For safety, fsync any remaining metadata if the file is not being 201 * truncated to 0. Since the metadata does not represent the entire 202 * dirty list we have to rely on the hit count to ensure that we get 203 * all of it. 204 * 205 * This is typically applicable only to UFS. NFS and HAMMER do 206 * not store indirect blocks in the per-vnode buffer cache. 207 */ 208 if (length > 0) { 209 do { 210 count = RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, 211 nvtruncbuf_bp_metasync_cmp, 212 nvtruncbuf_bp_metasync, &info); 213 } while (count); 214 } 215 216 /* 217 * It is possible to have in-progress I/O from buffers that were 218 * not part of the truncation. This should not happen if we 219 * are truncating to 0-length. 220 */ 221 bio_track_wait(&vp->v_track_write, 0, 0); 222 223 /* 224 * Debugging only 225 */ 226 spin_lock(&vp->v_spin); 227 filename = TAILQ_FIRST(&vp->v_namecache) ? 228 TAILQ_FIRST(&vp->v_namecache)->nc_name : "?"; 229 spin_unlock(&vp->v_spin); 230 231 /* 232 * Make sure no buffers were instantiated while we were trying 233 * to clean out the remaining VM pages. This could occur due 234 * to busy dirty VM pages being flushed out to disk. 235 */ 236 do { 237 info.clean = 1; 238 count = RB_SCAN(buf_rb_tree, &vp->v_rbclean_tree, 239 nvtruncbuf_bp_trunc_cmp, 240 nvtruncbuf_bp_trunc, &info); 241 info.clean = 0; 242 count += RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, 243 nvtruncbuf_bp_trunc_cmp, 244 nvtruncbuf_bp_trunc, &info); 245 if (count) { 246 kprintf("Warning: vtruncbuf(): Had to re-clean %d " 247 "left over buffers in %s\n", count, filename); 248 } 249 } while(count); 250 251 lwkt_reltoken(&vp->v_token); 252 253 return (error); 254 } 255 256 /* 257 * The callback buffer is beyond the new file EOF and must be destroyed. 258 * Note that the compare function must conform to the RB_SCAN's requirements. 259 */ 260 static 261 int 262 nvtruncbuf_bp_trunc_cmp(struct buf *bp, void *data) 263 { 264 struct truncbuf_info *info = data; 265 266 if (bp->b_loffset >= info->truncloffset) 267 return(0); 268 return(-1); 269 } 270 271 static 272 int 273 nvtruncbuf_bp_trunc(struct buf *bp, void *data) 274 { 275 struct truncbuf_info *info = data; 276 277 /* 278 * Do not try to use a buffer we cannot immediately lock, 279 * but sleep anyway to prevent a livelock. The code will 280 * loop until all buffers can be acted upon. 281 */ 282 if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) { 283 atomic_add_int(&bp->b_refs, 1); 284 if (BUF_LOCK(bp, LK_EXCLUSIVE|LK_SLEEPFAIL) == 0) 285 BUF_UNLOCK(bp); 286 atomic_subtract_int(&bp->b_refs, 1); 287 } else if ((info->clean && (bp->b_flags & B_DELWRI)) || 288 (info->clean == 0 && (bp->b_flags & B_DELWRI) == 0) || 289 bp->b_vp != info->vp || 290 nvtruncbuf_bp_trunc_cmp(bp, data)) { 291 BUF_UNLOCK(bp); 292 } else { 293 bremfree(bp); 294 bp->b_flags |= (B_INVAL | B_RELBUF | B_NOCACHE); 295 brelse(bp); 296 } 297 lwkt_yield(); 298 return(1); 299 } 300 301 /* 302 * Fsync all meta-data after truncating a file to be non-zero. Only metadata 303 * blocks (with a negative loffset) are scanned. 304 * Note that the compare function must conform to the RB_SCAN's requirements. 305 */ 306 static int 307 nvtruncbuf_bp_metasync_cmp(struct buf *bp, void *data __unused) 308 { 309 if (bp->b_loffset < 0) 310 return(0); 311 lwkt_yield(); 312 return(1); 313 } 314 315 static int 316 nvtruncbuf_bp_metasync(struct buf *bp, void *data) 317 { 318 struct truncbuf_info *info = data; 319 320 /* 321 * Do not try to use a buffer we cannot immediately lock, 322 * but sleep anyway to prevent a livelock. The code will 323 * loop until all buffers can be acted upon. 324 */ 325 if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) { 326 atomic_add_int(&bp->b_refs, 1); 327 if (BUF_LOCK(bp, LK_EXCLUSIVE|LK_SLEEPFAIL) == 0) 328 BUF_UNLOCK(bp); 329 atomic_subtract_int(&bp->b_refs, 1); 330 } else if ((bp->b_flags & B_DELWRI) == 0 || 331 bp->b_vp != info->vp || 332 nvtruncbuf_bp_metasync_cmp(bp, data)) { 333 BUF_UNLOCK(bp); 334 } else { 335 bremfree(bp); 336 bawrite(bp); 337 } 338 lwkt_yield(); 339 return(1); 340 } 341 342 /* 343 * Extend a file's buffer and pages to a new, larger size. The block size 344 * at both the old and new length must be passed, but buffer cache operations 345 * will only be performed on the old block. The new nlength/nblksize will 346 * be used to properly set the VM object size. 347 * 348 * To make this explicit we require the old length to passed even though 349 * we can acquire it from vp->v_filesize, which also avoids potential 350 * corruption if the filesystem and vp get desynchronized somehow. 351 * 352 * If the caller intends to immediately write into the newly extended 353 * space pass trivial == 1. If trivial is 0 the original buffer will be 354 * zero-filled as necessary to clean out any junk in the extended space. 355 * If non-zero the original buffer (straddling EOF) is not touched. 356 * 357 * When zero-filling we must bdwrite() to avoid a window of opportunity 358 * where the kernel might throw away a clean buffer and the filesystem 359 * then attempts to bread() it again before completing (or as part of) 360 * the extension. The filesystem is still responsible for zero-filling 361 * any remainder when writing to the media in the strategy function when 362 * it is able to do so without the page being mapped. The page may still 363 * be mapped by userland here. 364 * 365 * When modifying a buffer we must clear any cached raw disk offset. 366 * bdwrite() will call BMAP on it again. Some filesystems, like HAMMER, 367 * never overwrite existing data blocks. 368 */ 369 int 370 nvextendbuf(struct vnode *vp, off_t olength, off_t nlength, 371 int oblksize, int nblksize, int oboff, int nboff, int trivial) 372 { 373 off_t truncboffset; 374 struct buf *bp; 375 int error; 376 377 error = 0; 378 nvnode_pager_setsize(vp, nlength, nblksize, nboff); 379 if (trivial == 0) { 380 if (oboff < 0) 381 oboff = (int)(olength % oblksize); 382 truncboffset = olength - oboff; 383 384 if (oboff) { 385 error = bread(vp, truncboffset, oblksize, &bp); 386 if (error == 0) { 387 bzero(bp->b_data + oboff, oblksize - oboff); 388 bp->b_bio2.bio_offset = NOOFFSET; 389 bdwrite(bp); 390 } 391 } 392 } 393 return (error); 394 } 395 396 /* 397 * Set vp->v_filesize and vp->v_object->size, destroy pages beyond 398 * the last buffer when truncating. 399 * 400 * This function does not do any zeroing or invalidating of partially 401 * overlapping pages. Zeroing is the responsibility of nvtruncbuf(). 402 * However, it does unmap VM pages from the user address space on a 403 * page-granular (verses buffer cache granular) basis. 404 * 405 * If boff is passed as -1 the base offset of the buffer cache buffer is 406 * calculated from length and blksize. Filesystems such as UFS which deal 407 * with fragments have to specify a boff >= 0 since the base offset cannot 408 * be calculated from length and blksize. 409 * 410 * For UFS blksize is the 'new' blocksize, used only to determine how large 411 * the VM object must become. 412 */ 413 void 414 nvnode_pager_setsize(struct vnode *vp, off_t length, int blksize, int boff) 415 { 416 vm_pindex_t nobjsize; 417 vm_pindex_t oobjsize; 418 vm_pindex_t pi; 419 vm_object_t object; 420 vm_page_t m; 421 off_t truncboffset; 422 423 /* 424 * Degenerate conditions 425 */ 426 if ((object = vp->v_object) == NULL) 427 return; 428 vm_object_hold(object); 429 if (length == vp->v_filesize) { 430 vm_object_drop(object); 431 return; 432 } 433 434 /* 435 * Calculate the size of the VM object, coverage includes 436 * the buffer straddling EOF. If EOF is buffer-aligned 437 * we don't bother. 438 * 439 * Buffers do not have to be page-aligned. Make sure 440 * nobjsize is beyond the last page of the buffer. 441 */ 442 if (boff < 0) 443 boff = (int)(length % blksize); 444 truncboffset = length - boff; 445 oobjsize = object->size; 446 if (boff) 447 nobjsize = OFF_TO_IDX(truncboffset + blksize + PAGE_MASK); 448 else 449 nobjsize = OFF_TO_IDX(truncboffset + PAGE_MASK); 450 object->size = nobjsize; 451 452 if (length < vp->v_filesize) { 453 /* 454 * File has shrunk, toss any cached pages beyond 455 * the end of the buffer (blksize aligned) for the 456 * new EOF. 457 */ 458 vp->v_filesize = length; 459 if (nobjsize < oobjsize) { 460 vm_object_page_remove(object, nobjsize, oobjsize, 461 FALSE); 462 } 463 464 /* 465 * Unmap any pages (page aligned) beyond the new EOF. 466 * The pages remain part of the (last) buffer and are not 467 * invalidated. 468 */ 469 pi = OFF_TO_IDX(length + PAGE_MASK); 470 while (pi < nobjsize) { 471 m = vm_page_lookup_busy_wait(object, pi, FALSE, "vmpg"); 472 if (m) { 473 vm_page_protect(m, VM_PROT_NONE); 474 vm_page_wakeup(m); 475 } 476 ++pi; 477 lwkt_yield(); 478 } 479 } else { 480 /* 481 * File has expanded. 482 */ 483 vp->v_filesize = length; 484 } 485 vm_object_drop(object); 486 } 487