kernel/syscall/pathconf.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 /*
  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 <sys/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 = fop_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 = fop_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 = fop_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 }