kern_physio.c revision 255032 
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 255032 2013-08-29 16:41:40Z 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 || uio->uio_resid > MAXPHYS ||
63	    uio->uio_iovcnt > 1)) {
64		/*
65		 * Tell the user why his I/O was rejected.
66		 */
67		if (uio->uio_resid > dev->si_iosize_max)
68			uprintf("%s: request size=%zd > si_iosize_max=%d; "
69			    "cannot split request\n", devtoname(dev),
70			    uio->uio_resid, dev->si_iosize_max);
71		if (uio->uio_resid > MAXPHYS)
72			uprintf("%s: request size=%zd > MAXPHYS=%d; "
73			    "cannot split request\n", devtoname(dev),
74			    uio->uio_resid, MAXPHYS);
75		if (uio->uio_iovcnt > 1)
76			uprintf("%s: request vectors=%d > 1; "
77			    "cannot split request\n", devtoname(dev),
78			    uio->uio_iovcnt);
79
80		error = EFBIG;
81		goto doerror;
82	}
83
84	for (i = 0; i < uio->uio_iovcnt; i++) {
85		while (uio->uio_iov[i].iov_len) {
86			bp->b_flags = 0;
87			if (uio->uio_rw == UIO_READ) {
88				bp->b_iocmd = BIO_READ;
89				curthread->td_ru.ru_inblock++;
90			} else {
91				bp->b_iocmd = BIO_WRITE;
92				curthread->td_ru.ru_oublock++;
93			}
94			bp->b_iodone = bdone;
95			bp->b_data = uio->uio_iov[i].iov_base;
96			bp->b_bcount = uio->uio_iov[i].iov_len;
97			bp->b_offset = uio->uio_offset;
98			bp->b_iooffset = uio->uio_offset;
99			bp->b_saveaddr = sa;
100
101			/* Don't exceed drivers iosize limit */
102			if (bp->b_bcount > dev->si_iosize_max)
103				bp->b_bcount = dev->si_iosize_max;
104
105			/*
106			 * Make sure the pbuf can map the request
107			 * XXX: The pbuf has kvasize = MAXPHYS so a request
108			 * XXX: larger than MAXPHYS - PAGE_SIZE must be
109			 * XXX: page aligned or it will be fragmented.
110			 */
111			iolen = ((vm_offset_t) bp->b_data) & PAGE_MASK;
112			if ((bp->b_bcount + iolen) > bp->b_kvasize) {
113				/*
114				 * This device does not want I/O to be split.
115				 */
116				if (dev->si_flags & SI_NOSPLIT) {
117					uprintf("%s: request ptr %p is not "
118					    "on a page boundary; cannot split "
119					    "request\n", devtoname(dev),
120					    bp->b_data);
121					error = EFBIG;
122					goto doerror;
123				}
124				bp->b_bcount = bp->b_kvasize;
125				if (iolen != 0)
126					bp->b_bcount -= PAGE_SIZE;
127			}
128			bp->b_bufsize = bp->b_bcount;
129
130			bp->b_blkno = btodb(bp->b_offset);
131
132			csw = dev->si_devsw;
133			if (uio->uio_segflg == UIO_USERSPACE) {
134				if (dev->si_flags & SI_UNMAPPED)
135					mapped = 0;
136				else
137					mapped = 1;
138				if (vmapbuf(bp, mapped) < 0) {
139					error = EFAULT;
140					goto doerror;
141				}
142			}
143
144			dev_strategy_csw(dev, csw, bp);
145			if (uio->uio_rw == UIO_READ)
146				bwait(bp, PRIBIO, "physrd");
147			else
148				bwait(bp, PRIBIO, "physwr");
149
150			if (uio->uio_segflg == UIO_USERSPACE)
151				vunmapbuf(bp);
152			iolen = bp->b_bcount - bp->b_resid;
153			if (iolen == 0 && !(bp->b_ioflags & BIO_ERROR))
154				goto doerror;	/* EOF */
155			uio->uio_iov[i].iov_len -= iolen;
156			uio->uio_iov[i].iov_base =
157			    (char *)uio->uio_iov[i].iov_base + iolen;
158			uio->uio_resid -= iolen;
159			uio->uio_offset += iolen;
160			if( bp->b_ioflags & BIO_ERROR) {
161				error = bp->b_error;
162				goto doerror;
163			}
164		}
165	}
166doerror:
167	relpbuf(bp, NULL);
168	PRELE(curproc);
169	return (error);
170}
171