1 /* $NetBSD: kern_physio.c,v 1.49 2001/07/24 16:43:03 wiz Exp $ */ 2 3 /*- 4 * Copyright (c) 1994 Christopher G. Demetriou 5 * Copyright (c) 1982, 1986, 1990, 1993 6 * The Regents of the University of California. All rights reserved. 7 * (c) UNIX System Laboratories, Inc. 8 * All or some portions of this file are derived from material licensed 9 * to the University of California by American Telephone and Telegraph 10 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 11 * the permission of UNIX System Laboratories, Inc. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * @(#)kern_physio.c 8.1 (Berkeley) 6/10/93 42 */ 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/buf.h> 47 #include <sys/malloc.h> 48 #include <sys/proc.h> 49 50 #include <uvm/uvm_extern.h> 51 52 /* 53 * The routines implemented in this file are described in: 54 * Leffler, et al.: The Design and Implementation of the 4.3BSD 55 * UNIX Operating System (Addison Welley, 1989) 56 * on pages 231-233. 57 * 58 * The routines "getphysbuf" and "putphysbuf" steal and return a swap 59 * buffer. Leffler, et al., says that swap buffers are used to do the 60 * I/O, so raw I/O requests don't have to be single-threaded. 61 */ 62 63 struct buf *getphysbuf __P((void)); 64 void putphysbuf __P((struct buf *bp)); 65 66 /* 67 * Do "physical I/O" on behalf of a user. "Physical I/O" is I/O directly 68 * from the raw device to user buffers, and bypasses the buffer cache. 69 * 70 * Comments in brackets are from Leffler, et al.'s pseudo-code implementation. 71 */ 72 int 73 physio(strategy, bp, dev, flags, minphys, uio) 74 void (*strategy) __P((struct buf *)); 75 struct buf *bp; 76 dev_t dev; 77 int flags; 78 void (*minphys) __P((struct buf *)); 79 struct uio *uio; 80 { 81 struct iovec *iovp; 82 struct proc *p = curproc; 83 int error, done, i, nobuf, s; 84 long todo; 85 86 error = 0; 87 flags &= B_READ | B_WRITE | B_ORDERED; 88 89 /* Make sure we have a buffer, creating one if necessary. */ 90 if ((nobuf = (bp == NULL)) != 0) { 91 92 bp = getphysbuf(); 93 /* bp was just malloc'd so can't already be busy */ 94 bp->b_flags |= B_BUSY; 95 96 } else { 97 98 /* [raise the processor priority level to splbio;] */ 99 s = splbio(); 100 101 /* [while the buffer is marked busy] */ 102 while (bp->b_flags & B_BUSY) { 103 /* [mark the buffer wanted] */ 104 bp->b_flags |= B_WANTED; 105 /* [wait until the buffer is available] */ 106 tsleep((caddr_t)bp, PRIBIO+1, "physbuf", 0); 107 } 108 109 /* Mark it busy, so nobody else will use it. */ 110 bp->b_flags |= B_BUSY; 111 112 /* [lower the priority level] */ 113 splx(s); 114 } 115 116 /* [set up the fixed part of the buffer for a transfer] */ 117 bp->b_dev = dev; 118 bp->b_error = 0; 119 bp->b_proc = p; 120 LIST_INIT(&bp->b_dep); 121 122 /* 123 * [while there are data to transfer and no I/O error] 124 * Note that I/O errors are handled with a 'goto' at the bottom 125 * of the 'while' loop. 126 */ 127 for (i = 0; i < uio->uio_iovcnt; i++) { 128 iovp = &uio->uio_iov[i]; 129 while (iovp->iov_len > 0) { 130 131 /* 132 * [mark the buffer busy for physical I/O] 133 * (i.e. set B_PHYS (because it's an I/O to user 134 * memory, and B_RAW, because B_RAW is to be 135 * "Set by physio for raw transfers.", in addition 136 * to the "busy" and read/write flag.) 137 */ 138 bp->b_flags = B_BUSY | B_PHYS | B_RAW | flags; 139 140 /* [set up the buffer for a maximum-sized transfer] */ 141 bp->b_blkno = btodb(uio->uio_offset); 142 bp->b_bcount = iovp->iov_len; 143 bp->b_data = iovp->iov_base; 144 145 /* 146 * [call minphys to bound the transfer size] 147 * and remember the amount of data to transfer, 148 * for later comparison. 149 */ 150 (*minphys)(bp); 151 todo = bp->b_bcount; 152 #ifdef DIAGNOSTIC 153 if (todo <= 0) 154 panic("todo(%ld) <= 0; minphys broken", todo); 155 if (todo > MAXPHYS) 156 panic("todo(%ld) > MAXPHYS; minphys broken", 157 todo); 158 #endif 159 160 /* 161 * [lock the part of the user address space involved 162 * in the transfer] 163 * Beware vmapbuf(); it clobbers b_data and 164 * saves it in b_saveaddr. However, vunmapbuf() 165 * restores it. 166 */ 167 PHOLD(p); 168 error = uvm_vslock(p, bp->b_data, todo, 169 (flags & B_READ) ? 170 VM_PROT_READ | VM_PROT_WRITE : 171 VM_PROT_READ); 172 if (error) { 173 bp->b_flags |= B_ERROR; 174 bp->b_error = error; 175 goto after_vsunlock; 176 } 177 vmapbuf(bp, todo); 178 179 /* [call strategy to start the transfer] */ 180 (*strategy)(bp); 181 182 /* 183 * Note that the raise/wait/lower/get error 184 * steps below would be done by biowait(), but 185 * we want to unlock the address space before 186 * we lower the priority. 187 * 188 * [raise the priority level to splbio] 189 */ 190 s = splbio(); 191 192 /* [wait for the transfer to complete] */ 193 while ((bp->b_flags & B_DONE) == 0) 194 tsleep((caddr_t) bp, PRIBIO + 1, "physio", 0); 195 196 /* Mark it busy again, so nobody else will use it. */ 197 bp->b_flags |= B_BUSY; 198 199 /* [lower the priority level] */ 200 splx(s); 201 202 /* 203 * [unlock the part of the address space previously 204 * locked] 205 */ 206 vunmapbuf(bp, todo); 207 uvm_vsunlock(p, bp->b_data, todo); 208 after_vsunlock: 209 PRELE(p); 210 211 /* remember error value (save a splbio/splx pair) */ 212 if (bp->b_flags & B_ERROR) 213 error = (bp->b_error ? bp->b_error : EIO); 214 215 /* 216 * [deduct the transfer size from the total number 217 * of data to transfer] 218 */ 219 done = bp->b_bcount - bp->b_resid; 220 KASSERT(done >= 0); 221 KASSERT(done <= todo); 222 223 iovp->iov_len -= done; 224 iovp->iov_base = (caddr_t)iovp->iov_base + done; 225 uio->uio_offset += done; 226 uio->uio_resid -= done; 227 228 /* 229 * Now, check for an error. 230 * Also, handle weird end-of-disk semantics. 231 */ 232 if (error || done < todo) 233 goto done; 234 } 235 } 236 237 done: 238 /* 239 * [clean up the state of the buffer] 240 * Remember if somebody wants it, so we can wake them up below. 241 * Also, if we had to steal it, give it back. 242 */ 243 s = splbio(); 244 bp->b_flags &= ~(B_BUSY | B_PHYS | B_RAW); 245 if (nobuf) 246 putphysbuf(bp); 247 else { 248 /* 249 * [if another process is waiting for the raw I/O buffer, 250 * wake up processes waiting to do physical I/O; 251 */ 252 if (bp->b_flags & B_WANTED) { 253 bp->b_flags &= ~B_WANTED; 254 wakeup(bp); 255 } 256 } 257 splx(s); 258 259 return (error); 260 } 261 262 /* 263 * allocate a buffer structure for use in physical I/O. 264 */ 265 struct buf * 266 getphysbuf() 267 { 268 struct buf *bp; 269 int s; 270 271 s = splbio(); 272 bp = pool_get(&bufpool, PR_WAITOK); 273 splx(s); 274 memset(bp, 0, sizeof(*bp)); 275 276 /* XXXCDC: is the following line necessary? */ 277 bp->b_vnbufs.le_next = NOLIST; 278 279 return(bp); 280 } 281 282 /* 283 * get rid of a swap buffer structure which has been used in physical I/O. 284 */ 285 void 286 putphysbuf(bp) 287 struct buf *bp; 288 { 289 int s; 290 291 /* XXXCDC: is this necessary? */ 292 if (bp->b_vp) 293 brelvp(bp); 294 295 if (__predict_false(bp->b_flags & B_WANTED)) 296 panic("putphysbuf: private buf B_WANTED"); 297 s = splbio(); 298 pool_put(&bufpool, bp); 299 splx(s); 300 } 301 302 /* 303 * Leffler, et al., says on p. 231: 304 * "The minphys() routine is called by physio() to adjust the 305 * size of each I/O transfer before the latter is passed to 306 * the strategy routine..." 307 * 308 * so, just adjust the buffer's count accounting to MAXPHYS here, 309 * and return the new count; 310 */ 311 void 312 minphys(bp) 313 struct buf *bp; 314 { 315 316 if (bp->b_bcount > MAXPHYS) 317 bp->b_bcount = MAXPHYS; 318 } 319