1 /* $NetBSD: kern_physio.c,v 1.43 2000/06/27 17:41:24 mrg 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, todo; 84 85 error = 0; 86 flags &= B_READ | B_WRITE | B_ORDERED; 87 88 /* 89 * [check user read/write access to the data buffer] 90 * 91 * Check each iov one by one. Note that we know if we're reading or 92 * writing, so we ignore the uio's rw parameter. Also note that if 93 * we're doing a read, that's a *write* to user-space. 94 */ 95 if (uio->uio_segflg == UIO_USERSPACE) { 96 for (i = 0; i < uio->uio_iovcnt; i++) { 97 /* XXXCDC: map not locked, rethink */ 98 if (__predict_false(!uvm_useracc(uio->uio_iov[i].iov_base, 99 uio->uio_iov[i].iov_len, 100 (flags == B_READ) ? B_WRITE : B_READ))) 101 return (EFAULT); 102 } 103 } 104 105 /* Make sure we have a buffer, creating one if necessary. */ 106 if ((nobuf = (bp == NULL)) != 0) { 107 108 bp = getphysbuf(); 109 /* bp was just malloc'd so can't already be busy */ 110 bp->b_flags |= B_BUSY; 111 112 } else { 113 114 /* [raise the processor priority level to splbio;] */ 115 s = splbio(); 116 117 /* [while the buffer is marked busy] */ 118 while (bp->b_flags & B_BUSY) { 119 /* [mark the buffer wanted] */ 120 bp->b_flags |= B_WANTED; 121 /* [wait until the buffer is available] */ 122 tsleep((caddr_t)bp, PRIBIO+1, "physbuf", 0); 123 } 124 125 /* Mark it busy, so nobody else will use it. */ 126 bp->b_flags |= B_BUSY; 127 128 /* [lower the priority level] */ 129 splx(s); 130 131 } 132 133 /* [set up the fixed part of the buffer for a transfer] */ 134 bp->b_dev = dev; 135 bp->b_error = 0; 136 bp->b_proc = p; 137 LIST_INIT(&bp->b_dep); 138 139 /* 140 * [while there are data to transfer and no I/O error] 141 * Note that I/O errors are handled with a 'goto' at the bottom 142 * of the 'while' loop. 143 */ 144 for (i = 0; i < uio->uio_iovcnt; i++) { 145 iovp = &uio->uio_iov[i]; 146 while (iovp->iov_len > 0) { 147 /* 148 * [mark the buffer busy for physical I/O] 149 * (i.e. set B_PHYS (because it's an I/O to user 150 * memory, and B_RAW, because B_RAW is to be 151 * "Set by physio for raw transfers.", in addition 152 * to the "busy" and read/write flag.) 153 */ 154 bp->b_flags = B_BUSY | B_PHYS | B_RAW | flags; 155 156 /* [set up the buffer for a maximum-sized transfer] */ 157 bp->b_blkno = btodb(uio->uio_offset); 158 bp->b_bcount = iovp->iov_len; 159 bp->b_data = iovp->iov_base; 160 161 /* 162 * [call minphys to bound the tranfer size] 163 * and remember the amount of data to transfer, 164 * for later comparison. 165 */ 166 (*minphys)(bp); 167 todo = bp->b_bcount; 168 #ifdef DIAGNOSTIC 169 if (todo < 0) 170 panic("todo < 0; minphys broken"); 171 if (todo > MAXPHYS) 172 panic("todo > MAXPHYS; minphys broken"); 173 #endif 174 175 /* 176 * [lock the part of the user address space involved 177 * in the transfer] 178 * Beware vmapbuf(); it clobbers b_data and 179 * saves it in b_saveaddr. However, vunmapbuf() 180 * restores it. 181 */ 182 PHOLD(p); 183 if (__predict_false(uvm_vslock(p, bp->b_data, todo, 184 (flags & B_READ) ? 185 VM_PROT_READ | VM_PROT_WRITE : VM_PROT_READ) 186 != KERN_SUCCESS)) { 187 bp->b_flags |= B_ERROR; 188 bp->b_error = EFAULT; 189 goto after_vsunlock; 190 } 191 vmapbuf(bp, todo); 192 193 /* [call strategy to start the transfer] */ 194 (*strategy)(bp); 195 196 /* 197 * Note that the raise/wait/lower/get error 198 * steps below would be done by biowait(), but 199 * we want to unlock the address space before 200 * we lower the priority. 201 * 202 * [raise the priority level to splbio] 203 */ 204 s = splbio(); 205 206 /* [wait for the transfer to complete] */ 207 while ((bp->b_flags & B_DONE) == 0) 208 tsleep((caddr_t) bp, PRIBIO + 1, "physio", 0); 209 210 /* Mark it busy again, so nobody else will use it. */ 211 bp->b_flags |= B_BUSY; 212 213 /* [lower the priority level] */ 214 splx(s); 215 216 /* 217 * [unlock the part of the address space previously 218 * locked] 219 */ 220 vunmapbuf(bp, todo); 221 uvm_vsunlock(p, bp->b_data, todo); 222 after_vsunlock: 223 PRELE(p); 224 225 /* remember error value (save a splbio/splx pair) */ 226 if (bp->b_flags & B_ERROR) 227 error = (bp->b_error ? bp->b_error : EIO); 228 229 /* 230 * [deduct the transfer size from the total number 231 * of data to transfer] 232 */ 233 done = bp->b_bcount - bp->b_resid; 234 #ifdef DIAGNOSTIC 235 if (__predict_false(done < 0)) 236 panic("done < 0; strategy broken"); 237 if (__predict_false(done > todo)) 238 panic("done > todo; strategy broken"); 239 #endif 240 iovp->iov_len -= done; 241 iovp->iov_base = (caddr_t)iovp->iov_base + done; 242 uio->uio_offset += done; 243 uio->uio_resid -= done; 244 245 /* 246 * Now, check for an error. 247 * Also, handle weird end-of-disk semantics. 248 */ 249 if (error || done < todo) 250 goto done; 251 } 252 } 253 254 done: 255 /* 256 * [clean up the state of the buffer] 257 * Remember if somebody wants it, so we can wake them up below. 258 * Also, if we had to steal it, give it back. 259 */ 260 s = splbio(); 261 bp->b_flags &= ~(B_BUSY | B_PHYS | B_RAW); 262 if (nobuf) 263 putphysbuf(bp); 264 else { 265 /* 266 * [if another process is waiting for the raw I/O buffer, 267 * wake up processes waiting to do physical I/O; 268 */ 269 if (bp->b_flags & B_WANTED) { 270 bp->b_flags &= ~B_WANTED; 271 wakeup(bp); 272 } 273 } 274 splx(s); 275 276 return (error); 277 } 278 279 /* 280 * allocate a buffer structure for use in physical I/O. 281 */ 282 struct buf * 283 getphysbuf() 284 { 285 struct buf *bp; 286 int s; 287 288 s = splbio(); 289 bp = pool_get(&bufpool, PR_WAITOK); 290 splx(s); 291 memset(bp, 0, sizeof(*bp)); 292 293 /* XXXCDC: are the following two lines necessary? */ 294 bp->b_rcred = bp->b_wcred = NOCRED; 295 bp->b_vnbufs.le_next = NOLIST; 296 297 return(bp); 298 } 299 300 /* 301 * get rid of a swap buffer structure which has been used in physical I/O. 302 */ 303 void 304 putphysbuf(bp) 305 struct buf *bp; 306 { 307 int s; 308 309 /* XXXCDC: is this necesary? */ 310 if (bp->b_vp) 311 brelvp(bp); 312 313 if (__predict_false(bp->b_flags & B_WANTED)) 314 panic("putphysbuf: private buf B_WANTED"); 315 s = splbio(); 316 pool_put(&bufpool, bp); 317 splx(s); 318 } 319 320 /* 321 * Leffler, et al., says on p. 231: 322 * "The minphys() routine is called by physio() to adjust the 323 * size of each I/O transfer before the latter is passed to 324 * the strategy routine..." 325 * 326 * so, just adjust the buffer's count accounting to MAXPHYS here, 327 * and return the new count; 328 */ 329 void 330 minphys(bp) 331 struct buf *bp; 332 { 333 334 if (bp->b_bcount > MAXPHYS) 335 bp->b_bcount = MAXPHYS; 336 } 337