1 /* $NetBSD: kern_physio.c,v 1.51 2001/11/12 15:25:13 lukem 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/cdefs.h> 45 __KERNEL_RCSID(0, "$NetBSD: kern_physio.c,v 1.51 2001/11/12 15:25:13 lukem Exp $"); 46 47 #include <sys/param.h> 48 #include <sys/systm.h> 49 #include <sys/buf.h> 50 #include <sys/malloc.h> 51 #include <sys/proc.h> 52 53 #include <uvm/uvm_extern.h> 54 55 /* 56 * The routines implemented in this file are described in: 57 * Leffler, et al.: The Design and Implementation of the 4.3BSD 58 * UNIX Operating System (Addison Welley, 1989) 59 * on pages 231-233. 60 * 61 * The routines "getphysbuf" and "putphysbuf" steal and return a swap 62 * buffer. Leffler, et al., says that swap buffers are used to do the 63 * I/O, so raw I/O requests don't have to be single-threaded. 64 */ 65 66 struct buf *getphysbuf __P((void)); 67 void putphysbuf __P((struct buf *bp)); 68 69 /* 70 * Do "physical I/O" on behalf of a user. "Physical I/O" is I/O directly 71 * from the raw device to user buffers, and bypasses the buffer cache. 72 * 73 * Comments in brackets are from Leffler, et al.'s pseudo-code implementation. 74 */ 75 int 76 physio(strategy, bp, dev, flags, minphys, uio) 77 void (*strategy) __P((struct buf *)); 78 struct buf *bp; 79 dev_t dev; 80 int flags; 81 void (*minphys) __P((struct buf *)); 82 struct uio *uio; 83 { 84 struct iovec *iovp; 85 struct proc *p = curproc; 86 int error, done, i, nobuf, s; 87 long todo; 88 89 error = 0; 90 flags &= B_READ | B_WRITE | B_ORDERED; 91 92 /* Make sure we have a buffer, creating one if necessary. */ 93 if ((nobuf = (bp == NULL)) != 0) { 94 95 bp = getphysbuf(); 96 /* bp was just malloc'd so can't already be busy */ 97 bp->b_flags |= B_BUSY; 98 99 } else { 100 101 /* [raise the processor priority level to splbio;] */ 102 s = splbio(); 103 104 /* [while the buffer is marked busy] */ 105 while (bp->b_flags & B_BUSY) { 106 /* [mark the buffer wanted] */ 107 bp->b_flags |= B_WANTED; 108 /* [wait until the buffer is available] */ 109 tsleep((caddr_t)bp, PRIBIO+1, "physbuf", 0); 110 } 111 112 /* Mark it busy, so nobody else will use it. */ 113 bp->b_flags |= B_BUSY; 114 115 /* [lower the priority level] */ 116 splx(s); 117 } 118 119 /* [set up the fixed part of the buffer for a transfer] */ 120 bp->b_dev = dev; 121 bp->b_error = 0; 122 bp->b_proc = p; 123 LIST_INIT(&bp->b_dep); 124 125 /* 126 * [while there are data to transfer and no I/O error] 127 * Note that I/O errors are handled with a 'goto' at the bottom 128 * of the 'while' loop. 129 */ 130 for (i = 0; i < uio->uio_iovcnt; i++) { 131 iovp = &uio->uio_iov[i]; 132 while (iovp->iov_len > 0) { 133 134 /* 135 * [mark the buffer busy for physical I/O] 136 * (i.e. set B_PHYS (because it's an I/O to user 137 * memory, and B_RAW, because B_RAW is to be 138 * "Set by physio for raw transfers.", in addition 139 * to the "busy" and read/write flag.) 140 */ 141 bp->b_flags = B_BUSY | B_PHYS | B_RAW | flags; 142 143 /* [set up the buffer for a maximum-sized transfer] */ 144 bp->b_blkno = btodb(uio->uio_offset); 145 bp->b_bcount = iovp->iov_len; 146 bp->b_data = iovp->iov_base; 147 148 /* 149 * [call minphys to bound the transfer size] 150 * and remember the amount of data to transfer, 151 * for later comparison. 152 */ 153 (*minphys)(bp); 154 todo = bp->b_bcount; 155 #ifdef DIAGNOSTIC 156 if (todo <= 0) 157 panic("todo(%ld) <= 0; minphys broken", todo); 158 if (todo > MAXPHYS) 159 panic("todo(%ld) > MAXPHYS; minphys broken", 160 todo); 161 #endif 162 163 /* 164 * [lock the part of the user address space involved 165 * in the transfer] 166 * Beware vmapbuf(); it clobbers b_data and 167 * saves it in b_saveaddr. However, vunmapbuf() 168 * restores it. 169 */ 170 PHOLD(p); 171 error = uvm_vslock(p, bp->b_data, todo, 172 (flags & B_READ) ? 173 VM_PROT_READ | VM_PROT_WRITE : 174 VM_PROT_READ); 175 if (error) { 176 bp->b_flags |= B_ERROR; 177 bp->b_error = error; 178 goto after_vsunlock; 179 } 180 vmapbuf(bp, todo); 181 182 /* [call strategy to start the transfer] */ 183 (*strategy)(bp); 184 185 /* 186 * Note that the raise/wait/lower/get error 187 * steps below would be done by biowait(), but 188 * we want to unlock the address space before 189 * we lower the priority. 190 * 191 * [raise the priority level to splbio] 192 */ 193 s = splbio(); 194 195 /* [wait for the transfer to complete] */ 196 while ((bp->b_flags & B_DONE) == 0) 197 tsleep((caddr_t) bp, PRIBIO + 1, "physio", 0); 198 199 /* Mark it busy again, so nobody else will use it. */ 200 bp->b_flags |= B_BUSY; 201 202 /* [lower the priority level] */ 203 splx(s); 204 205 /* 206 * [unlock the part of the address space previously 207 * locked] 208 */ 209 vunmapbuf(bp, todo); 210 uvm_vsunlock(p, bp->b_data, todo); 211 after_vsunlock: 212 PRELE(p); 213 214 /* remember error value (save a splbio/splx pair) */ 215 if (bp->b_flags & B_ERROR) 216 error = (bp->b_error ? bp->b_error : EIO); 217 218 /* 219 * [deduct the transfer size from the total number 220 * of data to transfer] 221 */ 222 done = bp->b_bcount - bp->b_resid; 223 KASSERT(done >= 0); 224 KASSERT(done <= todo); 225 226 iovp->iov_len -= done; 227 iovp->iov_base = (caddr_t)iovp->iov_base + done; 228 uio->uio_offset += done; 229 uio->uio_resid -= done; 230 231 /* 232 * Now, check for an error. 233 * Also, handle weird end-of-disk semantics. 234 */ 235 if (error || done < todo) 236 goto done; 237 } 238 } 239 240 done: 241 /* 242 * [clean up the state of the buffer] 243 * Remember if somebody wants it, so we can wake them up below. 244 * Also, if we had to steal it, give it back. 245 */ 246 s = splbio(); 247 bp->b_flags &= ~(B_BUSY | B_PHYS | B_RAW); 248 if (nobuf) 249 putphysbuf(bp); 250 else { 251 /* 252 * [if another process is waiting for the raw I/O buffer, 253 * wake up processes waiting to do physical I/O; 254 */ 255 if (bp->b_flags & B_WANTED) { 256 bp->b_flags &= ~B_WANTED; 257 wakeup(bp); 258 } 259 } 260 splx(s); 261 262 return (error); 263 } 264 265 /* 266 * allocate a buffer structure for use in physical I/O. 267 */ 268 struct buf * 269 getphysbuf() 270 { 271 struct buf *bp; 272 int s; 273 274 s = splbio(); 275 bp = pool_get(&bufpool, PR_WAITOK); 276 splx(s); 277 memset(bp, 0, sizeof(*bp)); 278 return(bp); 279 } 280 281 /* 282 * get rid of a swap buffer structure which has been used in physical I/O. 283 */ 284 void 285 putphysbuf(bp) 286 struct buf *bp; 287 { 288 int s; 289 290 if (__predict_false(bp->b_flags & B_WANTED)) 291 panic("putphysbuf: private buf B_WANTED"); 292 s = splbio(); 293 pool_put(&bufpool, bp); 294 splx(s); 295 } 296 297 /* 298 * Leffler, et al., says on p. 231: 299 * "The minphys() routine is called by physio() to adjust the 300 * size of each I/O transfer before the latter is passed to 301 * the strategy routine..." 302 * 303 * so, just adjust the buffer's count accounting to MAXPHYS here, 304 * and return the new count; 305 */ 306 void 307 minphys(bp) 308 struct buf *bp; 309 { 310 311 if (bp->b_bcount > MAXPHYS) 312 bp->b_bcount = MAXPHYS; 313 } 314