module/zcommon/zfs_uio.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25
  26 /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
  27 /*        All Rights Reserved   */
  28
  29 /*
  30  * University Copyright- Copyright (c) 1982, 1986, 1988
  31  * The Regents of the University of California
  32  * All Rights Reserved
  33  *
  34  * University Acknowledgment- Portions of this document are derived from
  35  * software developed by the University of California, Berkeley, and its
  36  * contributors.
  37  */
  38 /*
  39  * Copyright (c) 2015 by Chunwei Chen. All rights reserved.
  40  */
  41
  42 /*
  43  * The uio support from OpenSolaris has been added as a short term
  44  * work around.  The hope is to adopt native Linux type and drop the
  45  * use of uio's entirely.  Under Linux they only add overhead and
  46  * when possible we want to use native APIs for the ZPL layer.
  47  */
  48 #ifdef _KERNEL
  49
  50 #include <sys/types.h>
  51 #include <sys/uio_impl.h>
  52 #include <linux/kmap_compat.h>
  53
  54 /*
  55  * Move "n" bytes at byte address "p"; "rw" indicates the direction
  56  * of the move, and the I/O parameters are provided in "uio", which is
  57  * update to reflect the data which was moved.  Returns 0 on success or
  58  * a non-zero errno on failure.
  59  */
  60 static int
  61 uiomove_iov(void *p, size_t n, enum uio_rw rw, struct uio *uio)
  62 {
  63         const struct iovec *iov = uio->uio_iov;
  64         size_t skip = uio->uio_skip;
  65         ulong_t cnt;
  66
  67         while (n && uio->uio_resid) {
  68                 cnt = MIN(iov->iov_len - skip, n);
  69                 switch (uio->uio_segflg) {
  70                 case UIO_USERSPACE:
  71                 case UIO_USERISPACE:
  72                         /*
  73                          * p = kernel data pointer
  74                          * iov->iov_base = user data pointer
  75                          */
  76                         if (rw == UIO_READ) {
  77                                 if (copy_to_user(iov->iov_base+skip, p, cnt))
  78                                         return (EFAULT);
  79                         } else {
  80                                 if (copy_from_user(p, iov->iov_base+skip, cnt))
  81                                         return (EFAULT);
  82                         }
  83                         break;
  84                 case UIO_SYSSPACE:
  85                         if (rw == UIO_READ)
  86                                 bcopy(p, iov->iov_base + skip, cnt);
  87                         else
  88                                 bcopy(iov->iov_base + skip, p, cnt);
  89                         break;
  90                 default:
  91                         ASSERT(0);
  92                 }
  93                 skip += cnt;
  94                 if (skip == iov->iov_len) {
  95                         skip = 0;
  96                         uio->uio_iov = (++iov);
  97                         uio->uio_iovcnt--;
  98                 }
  99                 uio->uio_skip = skip;
 100                 uio->uio_resid -= cnt;
 101                 uio->uio_loffset += cnt;
 102                 p = (caddr_t)p + cnt;
 103                 n -= cnt;
 104         }
 105         return (0);
 106 }
 107
 108 static int
 109 uiomove_bvec(void *p, size_t n, enum uio_rw rw, struct uio *uio)
 110 {
 111         const struct bio_vec *bv = uio->uio_bvec;
 112         size_t skip = uio->uio_skip;
 113         ulong_t cnt;
 114
 115         while (n && uio->uio_resid) {
 116                 void *paddr;
 117                 cnt = MIN(bv->bv_len - skip, n);
 118
 119                 paddr = zfs_kmap_atomic(bv->bv_page, KM_USER1);
 120                 if (rw == UIO_READ)
 121                         bcopy(p, paddr + bv->bv_offset + skip, cnt);
 122                 else
 123                         bcopy(paddr + bv->bv_offset + skip, p, cnt);
 124                 zfs_kunmap_atomic(paddr, KM_USER1);
 125
 126                 skip += cnt;
 127                 if (skip == bv->bv_len) {
 128                         skip = 0;
 129                         uio->uio_bvec = (++bv);
 130                         uio->uio_iovcnt--;
 131                 }
 132                 uio->uio_skip = skip;
 133                 uio->uio_resid -= cnt;
 134                 uio->uio_loffset += cnt;
 135                 p = (caddr_t)p + cnt;
 136                 n -= cnt;
 137         }
 138         return (0);
 139 }
 140
 141 int
 142 uiomove(void *p, size_t n, enum uio_rw rw, struct uio *uio)
 143 {
 144         if (uio->uio_segflg != UIO_BVEC)
 145                 return (uiomove_iov(p, n, rw, uio));
 146         else
 147                 return (uiomove_bvec(p, n, rw, uio));
 148 }
 149 EXPORT_SYMBOL(uiomove);
 150
 151 #define fuword8(uptr, vptr)     get_user((*vptr), (uptr))
 152
 153 /*
 154  * Fault in the pages of the first n bytes specified by the uio structure.
 155  * 1 byte in each page is touched and the uio struct is unmodified. Any
 156  * error will terminate the process as this is only a best attempt to get
 157  * the pages resident.
 158  */
 159 void
 160 uio_prefaultpages(ssize_t n, struct uio *uio)
 161 {
 162         const struct iovec *iov;
 163         ulong_t cnt, incr;
 164         caddr_t p;
 165         uint8_t tmp;
 166         int iovcnt;
 167         size_t skip;
 168
 169         /* no need to fault in kernel pages */
 170         switch (uio->uio_segflg) {
 171                 case UIO_SYSSPACE:
 172                 case UIO_BVEC:
 173                         return;
 174                 case UIO_USERSPACE:
 175                 case UIO_USERISPACE:
 176                         break;
 177                 default:
 178                         ASSERT(0);
 179         }
 180
 181         iov = uio->uio_iov;
 182         iovcnt = uio->uio_iovcnt;
 183         skip = uio->uio_skip;
 184
 185         for (; n > 0 && iovcnt > 0; iov++, iovcnt--, skip = 0) {
 186                 cnt = MIN(iov->iov_len - skip, n);
 187                 /* empty iov */
 188                 if (cnt == 0)
 189                         continue;
 190                 n -= cnt;
 191                 /*
 192                  * touch each page in this segment.
 193                  */
 194                 p = iov->iov_base + skip;
 195                 while (cnt) {
 196                         if (fuword8((uint8_t *)p, &tmp))
 197                                 return;
 198                         incr = MIN(cnt, PAGESIZE);
 199                         p += incr;
 200                         cnt -= incr;
 201                 }
 202                 /*
 203                  * touch the last byte in case it straddles a page.
 204                  */
 205                 p--;
 206                 if (fuword8((uint8_t *)p, &tmp))
 207                         return;
 208         }
 209 }
 210 EXPORT_SYMBOL(uio_prefaultpages);
 211
 212 /*
 213  * same as uiomove() but doesn't modify uio structure.
 214  * return in cbytes how many bytes were copied.
 215  */
 216 int
 217 uiocopy(void *p, size_t n, enum uio_rw rw, struct uio *uio, size_t *cbytes)
 218 {
 219         struct uio uio_copy;
 220         int ret;
 221
 222         bcopy(uio, &uio_copy, sizeof (struct uio));
 223         ret = uiomove(p, n, rw, &uio_copy);
 224         *cbytes = uio->uio_resid - uio_copy.uio_resid;
 225         return (ret);
 226 }
 227 EXPORT_SYMBOL(uiocopy);
 228
 229 /*
 230  * Drop the next n chars out of *uiop.
 231  */
 232 void
 233 uioskip(uio_t *uiop, size_t n)
 234 {
 235         if (n > uiop->uio_resid)
 236                 return;
 237
 238         uiop->uio_skip += n;
 239         if (uiop->uio_segflg != UIO_BVEC) {
 240                 while (uiop->uio_iovcnt &&
 241                     uiop->uio_skip >= uiop->uio_iov->iov_len) {
 242                         uiop->uio_skip -= uiop->uio_iov->iov_len;
 243                         uiop->uio_iov++;
 244                         uiop->uio_iovcnt--;
 245                 }
 246         } else {
 247                 while (uiop->uio_iovcnt &&
 248                     uiop->uio_skip >= uiop->uio_bvec->bv_len) {
 249                         uiop->uio_skip -= uiop->uio_bvec->bv_len;
 250                         uiop->uio_bvec++;
 251                         uiop->uio_iovcnt--;
 252                 }
 253         }
 254         uiop->uio_loffset += n;
 255         uiop->uio_resid -= n;
 256 }
 257 EXPORT_SYMBOL(uioskip);
 258 #endif /* _KERNEL */