1 /* $OpenBSD: kern_physio.c,v 1.49 2024/02/03 18:51:58 beck Exp $ */ 2 /* $NetBSD: kern_physio.c,v 1.28 1997/05/19 10:43:28 pk Exp $ */ 3 4 /*- 5 * Copyright (c) 1994 Christopher G. Demetriou 6 * Copyright (c) 1982, 1986, 1990, 1993 7 * The Regents of the University of California. All rights reserved. 8 * (c) UNIX System Laboratories, Inc. 9 * All or some portions of this file are derived from material licensed 10 * to the University of California by American Telephone and Telegraph 11 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 12 * the permission of UNIX System Laboratories, Inc. 13 * 14 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions 16 * are met: 17 * 1. Redistributions of source code must retain the above copyright 18 * notice, this list of conditions and the following disclaimer. 19 * 2. Redistributions in binary form must reproduce the above copyright 20 * notice, this list of conditions and the following disclaimer in the 21 * documentation and/or other materials provided with the distribution. 22 * 3. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)kern_physio.c 8.1 (Berkeley) 6/10/93 39 */ 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/buf.h> 44 #include <sys/pool.h> 45 46 #include <uvm/uvm_extern.h> 47 48 /* 49 * The routines implemented in this file are described in: 50 * Leffler, et al.: The Design and Implementation of the 4.3BSD 51 * UNIX Operating System (Addison Welley, 1989) 52 * on pages 231-233. 53 */ 54 55 /* 56 * Do "physical I/O" on behalf of a user. "Physical I/O" is I/O directly 57 * from the raw device to user buffers, and bypasses the buffer cache. 58 * 59 * Comments in brackets are from Leffler, et al.'s pseudo-code implementation. 60 */ 61 int 62 physio(void (*strategy)(struct buf *), dev_t dev, int flags, 63 void (*minphys)(struct buf *), struct uio *uio) 64 { 65 struct iovec *iovp; 66 struct proc *p = curproc; 67 long done, todo; 68 int error, i, s; 69 struct buf *bp; 70 71 if ((uio->uio_offset % DEV_BSIZE) != 0) 72 return (EINVAL); 73 74 error = 0; 75 flags &= B_READ | B_WRITE; 76 77 /* Create a buffer. */ 78 s = splbio(); 79 bp = pool_get(&bufpool, PR_WAITOK | PR_ZERO); 80 81 /* [set up the fixed part of the buffer for a transfer] */ 82 bp->b_vnbufs.le_next = NOLIST; 83 bp->b_dev = dev; 84 bp->b_error = 0; 85 bp->b_proc = p; 86 bp->b_flags = B_BUSY; 87 splx(s); 88 89 /* 90 * [while there are data to transfer and no I/O error] 91 * Note that I/O errors are handled with a 'goto' at the bottom 92 * of the 'while' loop. 93 */ 94 for (i = 0; i < uio->uio_iovcnt; i++) { 95 iovp = &uio->uio_iov[i]; 96 while (iovp->iov_len > 0) { 97 void *map = NULL; 98 99 /* 100 * [mark the buffer busy for physical I/O] 101 * (i.e. set B_PHYS (because it's an I/O to user 102 * memory), and B_RAW, because B_RAW is to be 103 * "Set by physio for raw transfers.", in addition 104 * to the "busy" and read/write flag.) 105 */ 106 CLR(bp->b_flags, B_DONE | B_ERROR); 107 bp->b_flags |= (B_BUSY | B_PHYS | B_RAW | flags); 108 109 /* [set up the buffer for a maximum-sized transfer] */ 110 bp->b_blkno = btodb(uio->uio_offset); 111 112 /* 113 * Because iov_len is size_t (unsigned) but b_bcount is 114 * long (signed), an overflow is possible. Therefore 115 * limit b_bcount to LONG_MAX before calling the 116 * provided minphys. 117 */ 118 if (iovp->iov_len > LONG_MAX) 119 bp->b_bcount = LONG_MAX; 120 else 121 bp->b_bcount = iovp->iov_len; 122 123 /* 124 * [call minphys to bound the transfer size] 125 * and remember the amount of data to transfer, 126 * for later comparison. 127 */ 128 (*minphys)(bp); 129 todo = bp->b_bcount; 130 KASSERTMSG(todo >= 0, "minphys broken"); 131 132 /* 133 * [lock the part of the user address space involved 134 * in the transfer] 135 * Beware vmapbuf(); it clobbers b_data and 136 * saves it in b_saveaddr. However, vunmapbuf() 137 * restores it. 138 */ 139 error = uvm_vslock_device(p, iovp->iov_base, todo, 140 (flags & B_READ) ? 141 PROT_READ | PROT_WRITE : PROT_READ, &map); 142 if (error) 143 goto done; 144 if (map) { 145 bp->b_data = map; 146 } else { 147 bp->b_data = iovp->iov_base; 148 vmapbuf(bp, todo); 149 } 150 151 /* [call strategy to start the transfer] */ 152 (*strategy)(bp); 153 154 /* 155 * Note that the raise/wait/lower/get error 156 * steps below would be done by biowait(), but 157 * we want to unlock the address space before 158 * we lower the priority. 159 * 160 * [raise the priority level to splbio] 161 */ 162 s = splbio(); 163 164 /* [wait for the transfer to complete] */ 165 while ((bp->b_flags & B_DONE) == 0) 166 tsleep_nsec(bp, PRIBIO + 1, "physio", INFSLP); 167 168 /* Mark it busy again, so nobody else will use it. */ 169 bp->b_flags |= B_BUSY; 170 171 /* [lower the priority level] */ 172 splx(s); 173 174 /* 175 * [unlock the part of the address space previously 176 * locked] 177 */ 178 if (!map) 179 vunmapbuf(bp, todo); 180 uvm_vsunlock_device(p, iovp->iov_base, todo, map); 181 182 /* remember error value (save a splbio/splx pair) */ 183 if (bp->b_flags & B_ERROR) 184 error = (bp->b_error ? bp->b_error : EIO); 185 186 /* 187 * [deduct the transfer size from the total number 188 * of data to transfer] 189 */ 190 KASSERTMSG(bp->b_resid <= LONG_MAX, "strategy broken"); 191 done = bp->b_bcount - bp->b_resid; 192 KASSERTMSG(done >= 0, "strategy broken"); 193 KASSERTMSG(done <= todo, "strategy broken"); 194 iovp->iov_len -= done; 195 iovp->iov_base = (caddr_t)iovp->iov_base + done; 196 uio->uio_offset += done; 197 uio->uio_resid -= done; 198 199 /* 200 * Now, check for an error. 201 * Also, handle weird end-of-disk semantics. 202 */ 203 if (error || done < todo) 204 goto done; 205 } 206 } 207 208 done: 209 /* 210 * [clean up the state of the buffer] 211 */ 212 s = splbio(); 213 /* XXXCDC: is this necessary? */ 214 if (bp->b_vp) 215 brelvp(bp); 216 splx(s); 217 pool_put(&bufpool, bp); 218 219 return (error); 220 } 221 222 /* 223 * Leffler, et al., says on p. 231: 224 * "The minphys() routine is called by physio() to adjust the 225 * size of each I/O transfer before the latter is passed to 226 * the strategy routine..." 227 * 228 * so, just adjust the buffer's count accounting to MAXPHYS here, 229 * and return the new count; 230 */ 231 void 232 minphys(struct buf *bp) 233 { 234 235 if (bp->b_bcount > MAXPHYS) 236 bp->b_bcount = MAXPHYS; 237 } 238