xref: /titanic_52/usr/src/uts/common/syscall/pathconf.c (revision 269e59f9a28bf47e0f463e64fc5af4a408b73b21)
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 /*
23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 /*	Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T	*/
28 /*	  All Rights Reserved  	*/
29 
30 /*
31  * Portions of this source code were derived from Berkeley 4.3 BSD
32  * under license from the Regents of the University of California.
33  */
34 
35 #pragma ident	"%Z%%M%	%I%	%E% SMI"
36 
37 #include <sys/param.h>
38 #include <sys/isa_defs.h>
39 #include <sys/types.h>
40 #include <sys/sysmacros.h>
41 #include <sys/cred.h>
42 #include <sys/systm.h>
43 #include <sys/errno.h>
44 #include <sys/pathname.h>
45 #include <sys/vnode.h>
46 #include <sys/vfs.h>
47 #include <sys/file.h>
48 #include <sys/uio.h>
49 #include <sys/debug.h>
50 #include <fs/fs_subr.h>
51 
52 /*
53  * Common code for pathconf(), fpathconf() system calls
54  */
55 static long
56 cpathconf(register vnode_t *vp, int cmd, struct cred *cr)
57 {
58 	struct statvfs64 sb;
59 	int error;
60 	ulong_t val;
61 
62 	switch (cmd) {
63 	case _PC_2_SYMLINKS:
64 		if (error = VOP_PATHCONF(vp, _PC_SYMLINK_MAX, &val, cr, NULL))
65 			return ((long)set_errno(error));
66 		return ((long)(val > 0));
67 
68 	case _PC_ALLOC_SIZE_MIN:
69 	case _PC_REC_INCR_XFER_SIZE:
70 	case _PC_REC_MAX_XFER_SIZE:
71 	case _PC_REC_MIN_XFER_SIZE:
72 	case _PC_REC_XFER_ALIGN:
73 		if ((error = VFS_STATVFS(vp->v_vfsp, &sb)) != 0)
74 			return ((long)set_errno(error));
75 
76 		/*
77 		 * There is generally no harm in doing larger transfers, but
78 		 * there's a point of diminishing returns.  With 1MB transfers,
79 		 * even if they're random, you get very close to platter speed.
80 		 * Se we return 1MB as the maximum transfer size.
81 		 */
82 		if (cmd == _PC_REC_MAX_XFER_SIZE)
83 			return ((long)MAX(sb.f_bsize, 1UL << 20));
84 
85 		/*
86 		 * By definition, f_frsize is the smallest filesystem block.
87 		 * However, _PC_ALLOC_SIZE_MIN is intended to define the
88 		 * threshold for direct I/O.  This implies two requirements:
89 		 * the VM and I/O subsystems must be able to create mappings
90 		 * for DMA, which requires at least page alignment; and the
91 		 * filesystem must avoid read/modify/write, which generally
92 		 * requires multiples of its 'preferred' blocksize, f_bsize.
93 		 *
94 		 * PAGESIZE alignment is sufficient for DMA and block copy.
95 		 * Rounding up to the filesystem 'preferred' blocksize
96 		 * works just as well.
97 		 *
98 		 * All together, this means that the remaining parameters
99 		 * map into the same value.
100 		 */
101 		return ((long)MAX(sb.f_bsize, PAGESIZE));
102 
103 	case _PC_ASYNC_IO:
104 		return (1l);
105 
106 	case _PC_PRIO_IO:
107 		return ((long)set_errno(EINVAL));
108 
109 	case _PC_SYNC_IO:
110 		if (!(error = VOP_FSYNC(vp, FSYNC, cr, NULL)))
111 			return (1l);
112 		return ((long)set_errno(error));
113 
114 	case _PC_XATTR_ENABLED:
115 		return ((vp->v_vfsp->vfs_flag & VFS_XATTR) ? 1 : 0);
116 
117 	default:
118 		if (error = VOP_PATHCONF(vp, cmd, &val, cr, NULL))
119 			return ((long)set_errno(error));
120 		return (val);
121 	}
122 	/* NOTREACHED */
123 }
124 
125 /* fpathconf/pathconf interfaces */
126 
127 long
128 fpathconf(int fdes, int name)
129 {
130 	file_t *fp;
131 	long retval;
132 
133 	if ((fp = getf(fdes)) == NULL)
134 		return (set_errno(EBADF));
135 	retval = cpathconf(fp->f_vnode, name, fp->f_cred);
136 	releasef(fdes);
137 	return (retval);
138 }
139 
140 long
141 pathconf(char *fname, int name)
142 {
143 	vnode_t *vp;
144 	long	retval;
145 	int	error;
146 	int 	estale_retry = 0;
147 
148 lookup:
149 	if (error = lookupname(fname, UIO_USERSPACE, FOLLOW, NULLVPP, &vp)) {
150 		if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
151 			goto lookup;
152 		return ((long)set_errno(error));
153 	}
154 
155 	retval = cpathconf(vp, name, CRED());
156 	VN_RELE(vp);
157 	return (retval);
158 }
159