1 /* $NetBSD: kern_physio.c,v 1.61 2005/06/23 23:15:12 thorpej 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 1.61 2005/06/23 23:15:12 thorpej Exp $"); 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/buf.h> 79 #include <sys/malloc.h> 80 #include <sys/proc.h> 81 82 #include <uvm/uvm_extern.h> 83 84 /* 85 * The routines implemented in this file are described in: 86 * Leffler, et al.: The Design and Implementation of the 4.3BSD 87 * UNIX Operating System (Addison Welley, 1989) 88 * on pages 231-233. 89 * 90 * The routines "getphysbuf" and "putphysbuf" steal and return a swap 91 * buffer. Leffler, et al., says that swap buffers are used to do the 92 * I/O, so raw I/O requests don't have to be single-threaded. Of course, 93 * NetBSD doesn't use "swap buffers" -- we have our own memory pool for 94 * buffer descriptors. 95 */ 96 97 /* 98 * allocate a buffer structure for use in physical I/O. 99 */ 100 static struct buf * 101 getphysbuf(void) 102 { 103 struct buf *bp; 104 int s; 105 106 s = splbio(); 107 bp = pool_get(&bufpool, PR_WAITOK); 108 splx(s); 109 memset(bp, 0, sizeof(*bp)); 110 BUF_INIT(bp); 111 return(bp); 112 } 113 114 /* 115 * get rid of a swap buffer structure which has been used in physical I/O. 116 */ 117 static void 118 putphysbuf(struct buf *bp) 119 { 120 int s; 121 122 if (__predict_false(bp->b_flags & B_WANTED)) 123 panic("putphysbuf: private buf B_WANTED"); 124 s = splbio(); 125 pool_put(&bufpool, bp); 126 splx(s); 127 } 128 129 /* 130 * Do "physical I/O" on behalf of a user. "Physical I/O" is I/O directly 131 * from the raw device to user buffers, and bypasses the buffer cache. 132 * 133 * Comments in brackets are from Leffler, et al.'s pseudo-code implementation. 134 */ 135 int 136 physio(void (*strategy)(struct buf *), struct buf *bp, dev_t dev, int flags, 137 void (*min_phys)(struct buf *), struct uio *uio) 138 { 139 struct iovec *iovp; 140 struct lwp *l = curlwp; 141 struct proc *p = l->l_proc; 142 int error, done, i, nobuf, s; 143 long todo; 144 145 error = 0; 146 flags &= B_READ | B_WRITE; 147 148 /* Make sure we have a buffer, creating one if necessary. */ 149 if ((nobuf = (bp == NULL)) != 0) { 150 151 bp = getphysbuf(); 152 /* bp was just malloc'd so can't already be busy */ 153 bp->b_flags |= B_BUSY; 154 155 } else { 156 157 /* [raise the processor priority level to splbio;] */ 158 s = splbio(); 159 160 /* [while the buffer is marked busy] */ 161 while (bp->b_flags & B_BUSY) { 162 /* [mark the buffer wanted] */ 163 bp->b_flags |= B_WANTED; 164 /* [wait until the buffer is available] */ 165 tsleep((caddr_t)bp, PRIBIO+1, "physbuf", 0); 166 } 167 168 /* Mark it busy, so nobody else will use it. */ 169 bp->b_flags |= B_BUSY; 170 171 /* [lower the priority level] */ 172 splx(s); 173 } 174 175 /* [set up the fixed part of the buffer for a transfer] */ 176 bp->b_dev = dev; 177 bp->b_error = 0; 178 bp->b_proc = p; 179 LIST_INIT(&bp->b_dep); 180 181 /* 182 * [while there are data to transfer and no I/O error] 183 * Note that I/O errors are handled with a 'goto' at the bottom 184 * of the 'while' loop. 185 */ 186 for (i = 0; i < uio->uio_iovcnt; i++) { 187 iovp = &uio->uio_iov[i]; 188 while (iovp->iov_len > 0) { 189 190 /* 191 * [mark the buffer busy for physical I/O] 192 * (i.e. set B_PHYS (because it's an I/O to user 193 * memory, and B_RAW, because B_RAW is to be 194 * "Set by physio for raw transfers.", in addition 195 * to the "busy" and read/write flag.) 196 */ 197 bp->b_flags = B_BUSY | B_PHYS | B_RAW | flags; 198 199 /* [set up the buffer for a maximum-sized transfer] */ 200 bp->b_blkno = btodb(uio->uio_offset); 201 bp->b_bcount = iovp->iov_len; 202 bp->b_data = iovp->iov_base; 203 204 /* 205 * [call minphys to bound the transfer size] 206 * and remember the amount of data to transfer, 207 * for later comparison. 208 */ 209 (*min_phys)(bp); 210 todo = bp->b_bcount; 211 #ifdef DIAGNOSTIC 212 if (todo <= 0) 213 panic("todo(%ld) <= 0; minphys broken", todo); 214 if (todo > MAXPHYS) 215 panic("todo(%ld) > MAXPHYS; minphys broken", 216 todo); 217 #endif 218 219 /* 220 * [lock the part of the user address space involved 221 * in the transfer] 222 * Beware vmapbuf(); it clobbers b_data and 223 * saves it in b_saveaddr. However, vunmapbuf() 224 * restores it. 225 */ 226 PHOLD(l); 227 error = uvm_vslock(p, bp->b_data, todo, 228 (flags & B_READ) ? 229 VM_PROT_WRITE : VM_PROT_READ); 230 if (error) { 231 bp->b_flags |= B_ERROR; 232 bp->b_error = error; 233 goto after_vsunlock; 234 } 235 vmapbuf(bp, todo); 236 237 BIO_SETPRIO(bp, BPRIO_TIMECRITICAL); 238 239 /* [call strategy to start the transfer] */ 240 (*strategy)(bp); 241 242 /* 243 * Note that the raise/wait/lower/get error 244 * steps below would be done by biowait(), but 245 * we want to unlock the address space before 246 * we lower the priority. 247 * 248 * [raise the priority level to splbio] 249 */ 250 s = splbio(); 251 252 /* [wait for the transfer to complete] */ 253 while ((bp->b_flags & B_DONE) == 0) 254 tsleep((caddr_t) bp, PRIBIO + 1, "physio", 0); 255 256 /* Mark it busy again, so nobody else will use it. */ 257 bp->b_flags |= B_BUSY; 258 259 /* [lower the priority level] */ 260 splx(s); 261 262 /* 263 * [unlock the part of the address space previously 264 * locked] 265 */ 266 vunmapbuf(bp, todo); 267 uvm_vsunlock(p, bp->b_data, todo); 268 after_vsunlock: 269 PRELE(l); 270 271 /* remember error value (save a splbio/splx pair) */ 272 if (bp->b_flags & B_ERROR) 273 error = (bp->b_error ? bp->b_error : EIO); 274 275 /* 276 * [deduct the transfer size from the total number 277 * of data to transfer] 278 */ 279 done = bp->b_bcount - bp->b_resid; 280 KASSERT(done >= 0); 281 KASSERT(done <= todo); 282 283 iovp->iov_len -= done; 284 iovp->iov_base = (caddr_t)iovp->iov_base + done; 285 uio->uio_offset += done; 286 uio->uio_resid -= done; 287 288 /* 289 * Now, check for an error. 290 * Also, handle weird end-of-disk semantics. 291 */ 292 if (error || done < todo) 293 goto done; 294 } 295 } 296 297 done: 298 /* 299 * [clean up the state of the buffer] 300 * Remember if somebody wants it, so we can wake them up below. 301 * Also, if we had to steal it, give it back. 302 */ 303 s = splbio(); 304 bp->b_flags &= ~(B_BUSY | B_PHYS | B_RAW); 305 if (nobuf) 306 putphysbuf(bp); 307 else { 308 /* 309 * [if another process is waiting for the raw I/O buffer, 310 * wake up processes waiting to do physical I/O; 311 */ 312 if (bp->b_flags & B_WANTED) { 313 bp->b_flags &= ~B_WANTED; 314 wakeup(bp); 315 } 316 } 317 splx(s); 318 319 return (error); 320 } 321 322 /* 323 * Leffler, et al., says on p. 231: 324 * "The minphys() routine is called by physio() to adjust the 325 * size of each I/O transfer before the latter is passed to 326 * the strategy routine..." 327 * 328 * so, just adjust the buffer's count accounting to MAXPHYS here, 329 * and return the new count; 330 */ 331 void 332 minphys(struct buf *bp) 333 { 334 335 if (bp->b_bcount > MAXPHYS) 336 bp->b_bcount = MAXPHYS; 337 } 338