kern_physio.c revision 1.87.16.2
1 /* $NetBSD: kern_physio.c,v 1.87.16.2 2008/12/13 01:15:08 haad 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 1.87.16.2 2008/12/13 01:15:08 haad 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 #include <sys/kmem.h> 83 84 #include <uvm/uvm_extern.h> 85 86 ONCE_DECL(physio_initialized); 87 struct workqueue *physio_workqueue; 88 89 /* 90 * The routines implemented in this file are described in: 91 * Leffler, et al.: The Design and Implementation of the 4.3BSD 92 * UNIX Operating System (Addison Welley, 1989) 93 * on pages 231-233. 94 */ 95 96 /* #define PHYSIO_DEBUG */ 97 #if defined(PHYSIO_DEBUG) 98 #define DPRINTF(a) printf a 99 #else /* defined(PHYSIO_DEBUG) */ 100 #define DPRINTF(a) /* nothing */ 101 #endif /* defined(PHYSIO_DEBUG) */ 102 103 struct physio_stat { 104 int ps_running; 105 int ps_error; 106 int ps_failed; 107 off_t ps_endoffset; 108 buf_t *ps_orig_bp; 109 kmutex_t ps_lock; 110 kcondvar_t ps_cv; 111 }; 112 113 static void 114 physio_done(struct work *wk, void *dummy) 115 { 116 struct buf *bp = (void *)wk; 117 size_t todo = bp->b_bufsize; 118 size_t done = bp->b_bcount - bp->b_resid; 119 struct physio_stat *ps = bp->b_private; 120 121 KASSERT(&bp->b_work == wk); 122 KASSERT(bp->b_bcount <= todo); 123 KASSERT(bp->b_resid <= bp->b_bcount); 124 KASSERT((bp->b_flags & B_PHYS) != 0); 125 KASSERT(dummy == NULL); 126 127 vunmapbuf(bp, todo); 128 uvm_vsunlock(bp->b_proc->p_vmspace, bp->b_data, todo); 129 130 mutex_enter(&ps->ps_lock); 131 if (__predict_false(done != todo)) { 132 off_t endoffset = dbtob(bp->b_blkno) + done; 133 134 /* 135 * we got an error or hit EOM. 136 * 137 * we only care about the first one. 138 * ie. the one at the lowest offset. 139 */ 140 141 KASSERT(ps->ps_endoffset != endoffset); 142 DPRINTF(("%s: error=%d at %" PRIu64 " - %" PRIu64 143 ", blkno=%" PRIu64 ", bcount=%d, flags=0x%x\n", 144 __func__, bp->b_error, dbtob(bp->b_blkno), endoffset, 145 bp->b_blkno, bp->b_bcount, bp->b_flags)); 146 147 if (ps->ps_endoffset == -1 || endoffset < ps->ps_endoffset) { 148 DPRINTF(("%s: ps=%p, error %d -> %d, endoff %" PRIu64 149 " -> %" PRIu64 "\n", 150 __func__, ps, 151 ps->ps_error, bp->b_error, 152 ps->ps_endoffset, endoffset)); 153 154 ps->ps_endoffset = endoffset; 155 ps->ps_error = bp->b_error; 156 } 157 ps->ps_failed++; 158 } else { 159 KASSERT(bp->b_error == 0); 160 } 161 162 ps->ps_running--; 163 cv_signal(&ps->ps_cv); 164 mutex_exit(&ps->ps_lock); 165 166 if (bp != ps->ps_orig_bp) 167 putiobuf(bp); 168 } 169 170 static void 171 physio_biodone(struct buf *bp) 172 { 173 #if defined(DIAGNOSTIC) 174 struct physio_stat *ps = bp->b_private; 175 size_t todo = bp->b_bufsize; 176 size_t done = bp->b_bcount - bp->b_resid; 177 178 KASSERT(ps->ps_running > 0); 179 KASSERT(bp->b_bcount <= todo); 180 KASSERT(bp->b_resid <= bp->b_bcount); 181 if (done == todo) 182 KASSERT(bp->b_error == 0); 183 #endif /* defined(DIAGNOSTIC) */ 184 185 workqueue_enqueue(physio_workqueue, &bp->b_work, NULL); 186 } 187 188 static void 189 physio_wait(struct physio_stat *ps, int n) 190 { 191 192 KASSERT(mutex_owned(&ps->ps_lock)); 193 194 while (ps->ps_running > n) 195 cv_wait(&ps->ps_cv, &ps->ps_lock); 196 } 197 198 static int 199 physio_init(void) 200 { 201 int error; 202 203 KASSERT(physio_workqueue == NULL); 204 205 error = workqueue_create(&physio_workqueue, "physiod", 206 physio_done, NULL, PRI_BIO, IPL_BIO, WQ_MPSAFE); 207 208 return error; 209 } 210 211 #define PHYSIO_CONCURRENCY 16 /* XXX tune */ 212 213 /* 214 * Do "physical I/O" on behalf of a user. "Physical I/O" is I/O directly 215 * from the raw device to user buffers, and bypasses the buffer cache. 216 * 217 * Comments in brackets are from Leffler, et al.'s pseudo-code implementation. 218 */ 219 int 220 physio(void (*strategy)(struct buf *), struct buf *obp, dev_t dev, int flags, 221 void (*min_phys)(struct buf *), struct uio *uio) 222 { 223 struct iovec *iovp; 224 struct lwp *l = curlwp; 225 struct proc *p = l->l_proc; 226 int i, error; 227 struct buf *bp = NULL; 228 struct physio_stat *ps; 229 int concurrency = PHYSIO_CONCURRENCY - 1; 230 231 error = RUN_ONCE(&physio_initialized, physio_init); 232 if (__predict_false(error != 0)) { 233 return error; 234 } 235 236 DPRINTF(("%s: called: off=%" PRIu64 ", resid=%zu\n", 237 __func__, uio->uio_offset, uio->uio_resid)); 238 239 flags &= B_READ | B_WRITE; 240 241 if ((ps = kmem_zalloc(sizeof(*ps), KM_SLEEP)) == NULL) 242 return ENOMEM; 243 /* ps->ps_running = 0; */ 244 /* ps->ps_error = 0; */ 245 /* ps->ps_failed = 0; */ 246 ps->ps_orig_bp = obp; 247 ps->ps_endoffset = -1; 248 mutex_init(&ps->ps_lock, MUTEX_DEFAULT, IPL_NONE); 249 cv_init(&ps->ps_cv, "physio"); 250 251 /* Make sure we have a buffer, creating one if necessary. */ 252 if (obp != NULL) { 253 /* [raise the processor priority level to splbio;] */ 254 mutex_enter(&bufcache_lock); 255 /* Mark it busy, so nobody else will use it. */ 256 while (bbusy(obp, false, 0, NULL) == EPASSTHROUGH) 257 ; 258 mutex_exit(&bufcache_lock); 259 concurrency = 0; /* see "XXXkludge" comment below */ 260 } 261 262 uvm_lwp_hold(l); 263 264 for (i = 0; i < uio->uio_iovcnt; i++) { 265 bool sync = true; 266 267 iovp = &uio->uio_iov[i]; 268 while (iovp->iov_len > 0) { 269 size_t todo; 270 vaddr_t endp; 271 272 mutex_enter(&ps->ps_lock); 273 if (ps->ps_failed != 0) { 274 goto done_locked; 275 } 276 physio_wait(ps, sync ? 0 : concurrency); 277 mutex_exit(&ps->ps_lock); 278 if (obp != NULL) { 279 /* 280 * XXXkludge 281 * some drivers use "obp" as an identifier. 282 */ 283 bp = obp; 284 } else { 285 bp = getiobuf(NULL, true); 286 bp->b_cflags = BC_BUSY; 287 } 288 bp->b_dev = dev; 289 bp->b_proc = p; 290 bp->b_private = ps; 291 292 /* 293 * [mark the buffer busy for physical I/O] 294 * (i.e. set B_PHYS (because it's an I/O to user 295 * memory, and B_RAW, because B_RAW is to be 296 * "Set by physio for raw transfers.", in addition 297 * to the "busy" and read/write flag.) 298 */ 299 bp->b_oflags = 0; 300 bp->b_cflags = BC_BUSY; 301 bp->b_flags = flags | B_PHYS | B_RAW; 302 bp->b_iodone = physio_biodone; 303 304 /* [set up the buffer for a maximum-sized transfer] */ 305 bp->b_blkno = btodb(uio->uio_offset); 306 if (dbtob(bp->b_blkno) != uio->uio_offset) { 307 error = EINVAL; 308 goto done; 309 } 310 bp->b_bcount = MIN(MAXPHYS, iovp->iov_len); 311 bp->b_data = iovp->iov_base; 312 313 /* 314 * [call minphys to bound the transfer size] 315 * and remember the amount of data to transfer, 316 * for later comparison. 317 */ 318 (*min_phys)(bp); 319 todo = bp->b_bufsize = bp->b_bcount; 320 #if defined(DIAGNOSTIC) 321 if (todo > MAXPHYS) 322 panic("todo(%zu) > MAXPHYS; minphys broken", 323 todo); 324 #endif /* defined(DIAGNOSTIC) */ 325 326 sync = false; 327 endp = (vaddr_t)bp->b_data + todo; 328 if (trunc_page(endp) != endp) { 329 /* 330 * following requests can overlap. 331 * note that uvm_vslock does round_page. 332 */ 333 sync = true; 334 } 335 336 /* 337 * [lock the part of the user address space involved 338 * in the transfer] 339 * Beware vmapbuf(); it clobbers b_data and 340 * saves it in b_saveaddr. However, vunmapbuf() 341 * restores it. 342 */ 343 error = uvm_vslock(p->p_vmspace, bp->b_data, todo, 344 (flags & B_READ) ? VM_PROT_WRITE : VM_PROT_READ); 345 if (error) { 346 goto done; 347 } 348 vmapbuf(bp, todo); 349 350 BIO_SETPRIO(bp, BPRIO_TIMECRITICAL); 351 352 mutex_enter(&ps->ps_lock); 353 ps->ps_running++; 354 mutex_exit(&ps->ps_lock); 355 356 /* [call strategy to start the transfer] */ 357 (*strategy)(bp); 358 bp = NULL; 359 360 iovp->iov_len -= todo; 361 iovp->iov_base = (char *)iovp->iov_base + todo; 362 uio->uio_offset += todo; 363 uio->uio_resid -= todo; 364 } 365 } 366 367 done: 368 mutex_enter(&ps->ps_lock); 369 done_locked: 370 physio_wait(ps, 0); 371 mutex_exit(&ps->ps_lock); 372 373 if (ps->ps_failed != 0) { 374 off_t delta; 375 376 delta = uio->uio_offset - ps->ps_endoffset; 377 KASSERT(delta > 0); 378 uio->uio_resid += delta; 379 /* uio->uio_offset = ps->ps_endoffset; */ 380 } else { 381 KASSERT(ps->ps_endoffset == -1); 382 } 383 if (bp != NULL && bp != obp) { 384 putiobuf(bp); 385 } 386 if (error == 0) { 387 error = ps->ps_error; 388 } 389 mutex_destroy(&ps->ps_lock); 390 cv_destroy(&ps->ps_cv); 391 kmem_free(ps, sizeof(*ps)); 392 393 /* 394 * [clean up the state of the buffer] 395 * Remember if somebody wants it, so we can wake them up below. 396 * Also, if we had to steal it, give it back. 397 */ 398 if (obp != NULL) { 399 KASSERT((obp->b_cflags & BC_BUSY) != 0); 400 401 /* 402 * [if another process is waiting for the raw I/O buffer, 403 * wake up processes waiting to do physical I/O; 404 */ 405 mutex_enter(&bufcache_lock); 406 obp->b_cflags &= ~(BC_BUSY | BC_WANTED); 407 obp->b_flags &= ~(B_PHYS | B_RAW); 408 obp->b_iodone = NULL; 409 cv_broadcast(&obp->b_busy); 410 mutex_exit(&bufcache_lock); 411 } 412 uvm_lwp_rele(l); 413 414 DPRINTF(("%s: done: off=%" PRIu64 ", resid=%zu\n", 415 __func__, uio->uio_offset, uio->uio_resid)); 416 417 return error; 418 } 419 420 /* 421 * Leffler, et al., says on p. 231: 422 * "The minphys() routine is called by physio() to adjust the 423 * size of each I/O transfer before the latter is passed to 424 * the strategy routine..." 425 * 426 * so, just adjust the buffer's count accounting to MAXPHYS here, 427 * and return the new count; 428 */ 429 void 430 minphys(struct buf *bp) 431 { 432 433 if (bp->b_bcount > MAXPHYS) 434 bp->b_bcount = MAXPHYS; 435 } 436
Indexes created Mon Sep 29 21:09:56 GMT 2025