Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_physio.c
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1 /* $NetBSD: kern_physio.c,v 1.76 2006/11/01 10:17:58 yamt Exp $ */ 2 3 /*- 4 * Copyright (c) 1982, 1986, 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * (c) UNIX System Laboratories, Inc. 7 * All or some portions of this file are derived from material licensed 8 * to the University of California by American Telephone and Telegraph 9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 10 * the permission of UNIX System Laboratories, Inc. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)kern_physio.c 8.1 (Berkeley) 6/10/93 37 */ 38 39 /*- 40 * Copyright (c) 1994 Christopher G. Demetriou 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 * @(#)kern_physio.c 8.1 (Berkeley) 6/10/93 71 */ 72 73 #include <sys/cdefs.h> 74 __KERNEL_RCSID(0, "$NetBSD: kern_physio.c,v 1.76 2006/11/01 10:17:58 yamt Exp $"); 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/buf.h> 79 #include <sys/proc.h> 80 #include <sys/once.h> 81 #include <sys/workqueue.h> 82 83 #include <uvm/uvm_extern.h> 84 85 ONCE_DECL(physio_initialized); 86 struct workqueue *physio_workqueue; 87 88 /* 89 * The routines implemented in this file are described in: 90 * Leffler, et al.: The Design and Implementation of the 4.3BSD 91 * UNIX Operating System (Addison Welley, 1989) 92 * on pages 231-233. 93 * 94 * The routines "getphysbuf" and "putphysbuf" steal and return a swap 95 * buffer. Leffler, et al., says that swap buffers are used to do the 96 * I/O, so raw I/O requests don't have to be single-threaded. Of course, 97 * NetBSD doesn't use "swap buffers" -- we have our own memory pool for 98 * buffer descriptors. 99 */ 100 101 /* #define PHYSIO_DEBUG */ 102 #if defined(PHYSIO_DEBUG) 103 #define DPRINTF(a) printf a 104 #else /* defined(PHYSIO_DEBUG) */ 105 #define DPRINTF(a) /* nothing */ 106 #endif /* defined(PHYSIO_DEBUG) */ 107 108 /* abuse these members/flags of struct buf */ 109 #define b_running b_freelistindex 110 #define b_endoffset b_lblkno 111 #define B_DONTFREE B_AGE 112 113 /* 114 * allocate a buffer structure for use in physical I/O. 115 */ 116 static struct buf * 117 getphysbuf(void) 118 { 119 struct buf *bp; 120 121 bp = getiobuf(); 122 bp->b_error = 0; 123 bp->b_flags = B_BUSY; 124 return(bp); 125 } 126 127 /* 128 * get rid of a swap buffer structure which has been used in physical I/O. 129 */ 130 static void 131 putphysbuf(struct buf *bp) 132 { 133 134 if ((bp->b_flags & B_DONTFREE) != 0) { 135 return; 136 } 137 138 if (__predict_false(bp->b_flags & B_WANTED)) 139 panic("putphysbuf: private buf B_WANTED"); 140 putiobuf(bp); 141 } 142 143 static void 144 physio_done(struct work *wk, void *dummy) 145 { 146 struct buf *bp = (void *)wk; 147 size_t todo = bp->b_bufsize; 148 size_t done = bp->b_bcount - bp->b_resid; 149 struct buf *mbp = bp->b_private; 150 151 KASSERT(&bp->b_work == wk); 152 KASSERT(bp->b_bcount <= todo); 153 KASSERT(bp->b_resid <= bp->b_bcount); 154 KASSERT((bp->b_flags & B_PHYS) != 0); 155 KASSERT(dummy == NULL); 156 157 vunmapbuf(bp, todo); 158 uvm_vsunlock(bp->b_proc->p_vmspace, bp->b_data, todo); 159 160 simple_lock(&mbp->b_interlock); 161 if (__predict_false(done != todo)) { 162 off_t endoffset = dbtob(bp->b_blkno) + done; 163 164 /* 165 * we got an error or hit EOM. 166 * 167 * we only care about the first one. 168 * ie. the one at the lowest offset. 169 */ 170 171 KASSERT(mbp->b_endoffset != endoffset); 172 DPRINTF(("%s: error=%d at %" PRIu64 " - %" PRIu64 173 ", blkno=%" PRIu64 ", bcount=%d, flags=0x%x\n", 174 __func__, bp->b_error, dbtob(bp->b_blkno), endoffset, 175 bp->b_blkno, bp->b_bcount, bp->b_flags)); 176 177 if (mbp->b_endoffset == -1 || endoffset < mbp->b_endoffset) { 178 int error; 179 180 if ((bp->b_flags & B_ERROR) != 0) { 181 if (bp->b_error == 0) { 182 error = EIO; /* XXX */ 183 } else { 184 error = bp->b_error; 185 } 186 } else { 187 error = 0; /* EOM */ 188 } 189 190 DPRINTF(("%s: mbp=%p, error %d -> %d, endoff %" PRIu64 191 " -> %" PRIu64 "\n", 192 __func__, mbp, 193 mbp->b_error, error, 194 mbp->b_endoffset, endoffset)); 195 196 mbp->b_endoffset = endoffset; 197 mbp->b_error = error; 198 } 199 mbp->b_flags |= B_ERROR; 200 } else { 201 KASSERT((bp->b_flags & B_ERROR) == 0); 202 } 203 204 mbp->b_running--; 205 if ((mbp->b_flags & B_WANTED) != 0) { 206 mbp->b_flags &= ~B_WANTED; 207 wakeup(mbp); 208 } 209 simple_unlock(&mbp->b_interlock); 210 211 putphysbuf(bp); 212 } 213 214 static void 215 physio_biodone(struct buf *bp) 216 { 217 #if defined(DIAGNOSTIC) 218 struct buf *mbp = bp->b_private; 219 size_t todo = bp->b_bufsize; 220 221 KASSERT(mbp->b_running > 0); 222 KASSERT(bp->b_bcount <= todo); 223 KASSERT(bp->b_resid <= bp->b_bcount); 224 #endif /* defined(DIAGNOSTIC) */ 225 226 workqueue_enqueue(physio_workqueue, &bp->b_work); 227 } 228 229 static int 230 physio_wait(struct buf *bp, int n, const char *wchan) 231 { 232 int error = 0; 233 234 LOCK_ASSERT(simple_lock_held(&bp->b_interlock)); 235 236 while (bp->b_running > n) { 237 bp->b_flags |= B_WANTED; 238 error = ltsleep(bp, PRIBIO + 1, wchan, 0, &bp->b_interlock); 239 if (error) { 240 break; 241 } 242 } 243 244 return error; 245 } 246 247 static int 248 physio_init(void) 249 { 250 int error; 251 252 KASSERT(physio_workqueue == NULL); 253 254 error = workqueue_create(&physio_workqueue, "physiod", 255 physio_done, NULL, PRIBIO, 0/* IPL_BIO notyet */, 0); 256 257 return error; 258 } 259 260 #define PHYSIO_CONCURRENCY 16 /* XXX tune */ 261 262 /* 263 * Do "physical I/O" on behalf of a user. "Physical I/O" is I/O directly 264 * from the raw device to user buffers, and bypasses the buffer cache. 265 * 266 * Comments in brackets are from Leffler, et al.'s pseudo-code implementation. 267 */ 268 int 269 physio(void (*strategy)(struct buf *), struct buf *obp, dev_t dev, int flags, 270 void (*min_phys)(struct buf *), struct uio *uio) 271 { 272 struct iovec *iovp; 273 struct lwp *l = curlwp; 274 struct proc *p = l->l_proc; 275 int i, s; 276 int error; 277 int error2; 278 struct buf *bp = NULL; 279 struct buf *mbp; 280 int concurrency = PHYSIO_CONCURRENCY - 1; 281 282 error = RUN_ONCE(&physio_initialized, physio_init); 283 if (__predict_false(error != 0)) { 284 return error; 285 } 286 287 DPRINTF(("%s: called: off=%" PRIu64 ", resid=%zu\n", 288 __func__, uio->uio_offset, uio->uio_resid)); 289 290 flags &= B_READ | B_WRITE; 291 292 /* Make sure we have a buffer, creating one if necessary. */ 293 if (obp != NULL) { 294 /* [raise the processor priority level to splbio;] */ 295 s = splbio(); 296 simple_lock(&obp->b_interlock); 297 298 /* [while the buffer is marked busy] */ 299 while (obp->b_flags & B_BUSY) { 300 /* [mark the buffer wanted] */ 301 obp->b_flags |= B_WANTED; 302 /* [wait until the buffer is available] */ 303 ltsleep(obp, PRIBIO+1, "physbuf", 0, &obp->b_interlock); 304 } 305 306 /* Mark it busy, so nobody else will use it. */ 307 obp->b_flags = B_BUSY | B_DONTFREE; 308 309 /* [lower the priority level] */ 310 simple_unlock(&obp->b_interlock); 311 splx(s); 312 313 concurrency = 0; /* see "XXXkludge" comment below */ 314 } 315 316 mbp = getphysbuf(); 317 mbp->b_running = 0; 318 mbp->b_endoffset = -1; 319 320 PHOLD(l); 321 322 for (i = 0; i < uio->uio_iovcnt; i++) { 323 boolean_t sync = TRUE; 324 325 iovp = &uio->uio_iov[i]; 326 while (iovp->iov_len > 0) { 327 size_t todo; 328 vaddr_t endp; 329 330 simple_lock(&mbp->b_interlock); 331 if ((mbp->b_flags & B_ERROR) != 0) { 332 goto done_locked; 333 } 334 error = physio_wait(mbp, sync ? 0 : concurrency, 335 "physio1"); 336 if (error) { 337 goto done_locked; 338 } 339 simple_unlock(&mbp->b_interlock); 340 if (obp != NULL) { 341 /* 342 * XXXkludge 343 * some drivers use "obp" as an identifier. 344 */ 345 bp = obp; 346 } else { 347 bp = getphysbuf(); 348 } 349 bp->b_dev = dev; 350 bp->b_proc = p; 351 bp->b_private = mbp; 352 bp->b_vp = NULL; 353 354 /* 355 * [mark the buffer busy for physical I/O] 356 * (i.e. set B_PHYS (because it's an I/O to user 357 * memory, and B_RAW, because B_RAW is to be 358 * "Set by physio for raw transfers.", in addition 359 * to the "busy" and read/write flag.) 360 */ 361 bp->b_flags = (bp->b_flags & B_DONTFREE) | 362 B_BUSY | B_PHYS | B_RAW | B_CALL | flags; 363 bp->b_iodone = physio_biodone; 364 365 /* [set up the buffer for a maximum-sized transfer] */ 366 bp->b_blkno = btodb(uio->uio_offset); 367 if (dbtob(bp->b_blkno) != uio->uio_offset) { 368 error = EINVAL; 369 goto done; 370 } 371 bp->b_bcount = MIN(MAXPHYS, iovp->iov_len); 372 bp->b_data = iovp->iov_base; 373 374 /* 375 * [call minphys to bound the transfer size] 376 * and remember the amount of data to transfer, 377 * for later comparison. 378 */ 379 (*min_phys)(bp); 380 todo = bp->b_bufsize = bp->b_bcount; 381 #if defined(DIAGNOSTIC) 382 if (todo > MAXPHYS) 383 panic("todo(%zu) > MAXPHYS; minphys broken", 384 todo); 385 #endif /* defined(DIAGNOSTIC) */ 386 387 sync = FALSE; 388 endp = (vaddr_t)bp->b_data + todo; 389 if (trunc_page(endp) != endp) { 390 /* 391 * following requests can overlap. 392 * note that uvm_vslock does round_page. 393 */ 394 sync = TRUE; 395 } 396 397 /* 398 * [lock the part of the user address space involved 399 * in the transfer] 400 * Beware vmapbuf(); it clobbers b_data and 401 * saves it in b_saveaddr. However, vunmapbuf() 402 * restores it. 403 */ 404 error = uvm_vslock(p->p_vmspace, bp->b_data, todo, 405 (flags & B_READ) ? VM_PROT_WRITE : VM_PROT_READ); 406 if (error) { 407 goto done; 408 } 409 vmapbuf(bp, todo); 410 411 BIO_SETPRIO(bp, BPRIO_TIMECRITICAL); 412 413 simple_lock(&mbp->b_interlock); 414 mbp->b_running++; 415 simple_unlock(&mbp->b_interlock); 416 417 /* [call strategy to start the transfer] */ 418 (*strategy)(bp); 419 bp = NULL; 420 421 iovp->iov_len -= todo; 422 iovp->iov_base = (caddr_t)iovp->iov_base + todo; 423 uio->uio_offset += todo; 424 uio->uio_resid -= todo; 425 } 426 } 427 428 done: 429 simple_lock(&mbp->b_interlock); 430 done_locked: 431 error2 = physio_wait(mbp, 0, "physio2"); 432 if (error == 0) { 433 error = error2; 434 } 435 simple_unlock(&mbp->b_interlock); 436 437 if ((mbp->b_flags & B_ERROR) != 0) { 438 off_t delta; 439 440 delta = uio->uio_offset - mbp->b_endoffset; 441 KASSERT(delta > 0); 442 uio->uio_resid += delta; 443 /* uio->uio_offset = mbp->b_endoffset; */ 444 } else { 445 KASSERT(mbp->b_endoffset == -1); 446 } 447 if (bp != NULL) { 448 putphysbuf(bp); 449 } 450 if (error == 0) { 451 error = mbp->b_error; 452 } 453 putphysbuf(mbp); 454 455 /* 456 * [clean up the state of the buffer] 457 * Remember if somebody wants it, so we can wake them up below. 458 * Also, if we had to steal it, give it back. 459 */ 460 if (obp != NULL) { 461 KASSERT((obp->b_flags & B_BUSY) != 0); 462 KASSERT((obp->b_flags & B_DONTFREE) != 0); 463 464 /* 465 * [if another process is waiting for the raw I/O buffer, 466 * wake up processes waiting to do physical I/O; 467 */ 468 s = splbio(); 469 simple_lock(&obp->b_interlock); 470 obp->b_flags &= 471 ~(B_BUSY | B_PHYS | B_RAW | B_CALL | B_DONTFREE); 472 if ((obp->b_flags & B_WANTED) != 0) { 473 obp->b_flags &= ~B_WANTED; 474 wakeup(obp); 475 } 476 simple_unlock(&obp->b_interlock); 477 splx(s); 478 } 479 PRELE(l); 480 481 DPRINTF(("%s: done: off=%" PRIu64 ", resid=%zu\n", 482 __func__, uio->uio_offset, uio->uio_resid)); 483 484 return error; 485 } 486 487 /* 488 * Leffler, et al., says on p. 231: 489 * "The minphys() routine is called by physio() to adjust the 490 * size of each I/O transfer before the latter is passed to 491 * the strategy routine..." 492 * 493 * so, just adjust the buffer's count accounting to MAXPHYS here, 494 * and return the new count; 495 */ 496 void 497 minphys(struct buf *bp) 498 { 499 500 if (bp->b_bcount > MAXPHYS) 501 bp->b_bcount = MAXPHYS; 502 }
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