kern_physio.c revision 254802 
1/*-
2 * Copyright (c) 1994 John S. Dyson
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice immediately at the beginning of the file, without modification,
10 *    this list of conditions, and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. Absolutely no warranty of function or purpose is made by the author
15 *    John S. Dyson.
16 * 4. Modifications may be freely made to this file if the above conditions
17 *    are met.
18 */
19
20#include <sys/cdefs.h>
21__FBSDID("$FreeBSD: head/sys/kern/kern_physio.c 254802 2013-08-24 19:02:36Z ken $");
22
23#include <sys/param.h>
24#include <sys/systm.h>
25#include <sys/bio.h>
26#include <sys/buf.h>
27#include <sys/conf.h>
28#include <sys/proc.h>
29#include <sys/uio.h>
30
31#include <vm/vm.h>
32#include <vm/vm_extern.h>
33
34int
35physio(struct cdev *dev, struct uio *uio, int ioflag)
36{
37	struct buf *bp;
38	struct cdevsw *csw;
39	caddr_t sa;
40	u_int iolen;
41	int error, i, mapped;
42
43	/* Keep the process UPAGES from being swapped. XXX: why ? */
44	PHOLD(curproc);
45
46	bp = getpbuf(NULL);
47	sa = bp->b_data;
48	error = 0;
49
50	/* XXX: sanity check */
51	if(dev->si_iosize_max < PAGE_SIZE) {
52		printf("WARNING: %s si_iosize_max=%d, using DFLTPHYS.\n",
53		    devtoname(dev), dev->si_iosize_max);
54		dev->si_iosize_max = DFLTPHYS;
55	}
56
57	/*
58	 * If the driver does not want I/O to be split, that means that we
59	 * need to reject any requests that will not fit into one buffer.
60	 */
61	if ((dev->si_flags & SI_NOSPLIT) &&
62	    ((uio->uio_resid > dev->si_iosize_max) ||
63	     (uio->uio_resid > MAXPHYS) ||
64	     (uio->uio_iovcnt > 1))) {
65		/*
66		 * Tell the user why his I/O was rejected.
67		 */
68		if (uio->uio_resid > dev->si_iosize_max)
69			printf("%s: request size %zd > si_iosize_max=%d, "
70			    "cannot split request\n", devtoname(dev),
71			    uio->uio_resid, dev->si_iosize_max);
72
73		if (uio->uio_resid > MAXPHYS)
74			printf("%s: request size %zd > MAXPHYS=%d, "
75			    "cannot split request\n", devtoname(dev),
76			    uio->uio_resid, MAXPHYS);
77
78		if (uio->uio_iovcnt > 1)
79			printf("%s: request vectors=%d > 1, "
80			    "cannot split request\n", devtoname(dev),
81			    uio->uio_iovcnt);
82
83		error = EFBIG;
84		goto doerror;
85	}
86
87	for (i = 0; i < uio->uio_iovcnt; i++) {
88		while (uio->uio_iov[i].iov_len) {
89			bp->b_flags = 0;
90			if (uio->uio_rw == UIO_READ) {
91				bp->b_iocmd = BIO_READ;
92				curthread->td_ru.ru_inblock++;
93			} else {
94				bp->b_iocmd = BIO_WRITE;
95				curthread->td_ru.ru_oublock++;
96			}
97			bp->b_iodone = bdone;
98			bp->b_data = uio->uio_iov[i].iov_base;
99			bp->b_bcount = uio->uio_iov[i].iov_len;
100			bp->b_offset = uio->uio_offset;
101			bp->b_iooffset = uio->uio_offset;
102			bp->b_saveaddr = sa;
103
104			/* Don't exceed drivers iosize limit */
105			if (bp->b_bcount > dev->si_iosize_max)
106				bp->b_bcount = dev->si_iosize_max;
107
108			/*
109			 * Make sure the pbuf can map the request
110			 * XXX: The pbuf has kvasize = MAXPHYS so a request
111			 * XXX: larger than MAXPHYS - PAGE_SIZE must be
112			 * XXX: page aligned or it will be fragmented.
113			 */
114			iolen = ((vm_offset_t) bp->b_data) & PAGE_MASK;
115			if ((bp->b_bcount + iolen) > bp->b_kvasize) {
116				/*
117				 * This device does not want I/O to be split.
118				 */
119				if (dev->si_flags & SI_NOSPLIT) {
120					printf("%s: request ptr %p is not "
121					    "on a page boundary, cannot split "
122					    "request\n", devtoname(dev),
123					    bp->b_data);
124					error = EFBIG;
125					goto doerror;
126				}
127				bp->b_bcount = bp->b_kvasize;
128				if (iolen != 0)
129					bp->b_bcount -= PAGE_SIZE;
130			}
131			bp->b_bufsize = bp->b_bcount;
132
133			bp->b_blkno = btodb(bp->b_offset);
134
135			csw = dev->si_devsw;
136			if (uio->uio_segflg == UIO_USERSPACE) {
137				if (dev->si_flags & SI_UNMAPPED)
138					mapped = 0;
139				else
140					mapped = 1;
141				if (vmapbuf(bp, mapped) < 0) {
142					error = EFAULT;
143					goto doerror;
144				}
145			}
146
147			dev_strategy_csw(dev, csw, bp);
148			if (uio->uio_rw == UIO_READ)
149				bwait(bp, PRIBIO, "physrd");
150			else
151				bwait(bp, PRIBIO, "physwr");
152
153			if (uio->uio_segflg == UIO_USERSPACE)
154				vunmapbuf(bp);
155			iolen = bp->b_bcount - bp->b_resid;
156			if (iolen == 0 && !(bp->b_ioflags & BIO_ERROR))
157				goto doerror;	/* EOF */
158			uio->uio_iov[i].iov_len -= iolen;
159			uio->uio_iov[i].iov_base =
160			    (char *)uio->uio_iov[i].iov_base + iolen;
161			uio->uio_resid -= iolen;
162			uio->uio_offset += iolen;
163			if( bp->b_ioflags & BIO_ERROR) {
164				error = bp->b_error;
165				goto doerror;
166			}
167		}
168	}
169doerror:
170	relpbuf(bp, NULL);
171	PRELE(curproc);
172	return (error);
173}
174