The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/fs/fdescfs/fdesc_vfsops.c

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    1 /*-
    2  * Copyright (c) 1992, 1993, 1995
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software donated to Berkeley by
    6  * Jan-Simon Pendry.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  *      @(#)fdesc_vfsops.c      8.4 (Berkeley) 1/21/94
   33  *
   34  * $FreeBSD: releng/8.4/sys/fs/fdescfs/fdesc_vfsops.c 191990 2009-05-11 15:33:26Z attilio $
   35  */
   36 
   37 /*
   38  * /dev/fd Filesystem
   39  */
   40 
   41 #include <sys/param.h>
   42 #include <sys/systm.h>
   43 #include <sys/filedesc.h>
   44 #include <sys/kernel.h>
   45 #include <sys/lock.h>
   46 #include <sys/mutex.h>
   47 #include <sys/malloc.h>
   48 #include <sys/mount.h>
   49 #include <sys/proc.h>
   50 #include <sys/resourcevar.h>
   51 #include <sys/vnode.h>
   52 
   53 #include <fs/fdescfs/fdesc.h>
   54 
   55 static MALLOC_DEFINE(M_FDESCMNT, "fdesc_mount", "FDESC mount structure");
   56 
   57 static vfs_cmount_t     fdesc_cmount;
   58 static vfs_mount_t      fdesc_mount;
   59 static vfs_unmount_t    fdesc_unmount;
   60 static vfs_statfs_t     fdesc_statfs;
   61 static vfs_root_t       fdesc_root;
   62 
   63 /*
   64  * Compatibility shim for old mount(2) system call.
   65  */
   66 int
   67 fdesc_cmount(struct mntarg *ma, void *data, int flags)
   68 {
   69         return kernel_mount(ma, flags);
   70 }
   71 
   72 /*
   73  * Mount the per-process file descriptors (/dev/fd)
   74  */
   75 static int
   76 fdesc_mount(struct mount *mp)
   77 {
   78         int error = 0;
   79         struct fdescmount *fmp;
   80         struct vnode *rvp;
   81 
   82         /*
   83          * Update is a no-op
   84          */
   85         if (mp->mnt_flag & (MNT_UPDATE | MNT_ROOTFS))
   86                 return (EOPNOTSUPP);
   87 
   88         fmp = malloc(sizeof(struct fdescmount),
   89                                 M_FDESCMNT, M_WAITOK);  /* XXX */
   90 
   91         /*
   92          * We need to initialize a few bits of our local mount point struct to
   93          * avoid confusion in allocvp.
   94          */
   95         mp->mnt_data = (qaddr_t) fmp;
   96         fmp->flags = 0;
   97         error = fdesc_allocvp(Froot, -1, FD_ROOT, mp, &rvp);
   98         if (error) {
   99                 free(fmp, M_FDESCMNT);
  100                 mp->mnt_data = 0;
  101                 return (error);
  102         }
  103         rvp->v_type = VDIR;
  104         rvp->v_vflag |= VV_ROOT;
  105         fmp->f_root = rvp;
  106         VOP_UNLOCK(rvp, 0);
  107         /* XXX -- don't mark as local to work around fts() problems */
  108         /*mp->mnt_flag |= MNT_LOCAL;*/
  109         MNT_ILOCK(mp);
  110         mp->mnt_kern_flag |= MNTK_MPSAFE;
  111         MNT_IUNLOCK(mp);
  112         vfs_getnewfsid(mp);
  113 
  114         vfs_mountedfrom(mp, "fdescfs");
  115         return (0);
  116 }
  117 
  118 static int
  119 fdesc_unmount(mp, mntflags)
  120         struct mount *mp;
  121         int mntflags;
  122 {
  123         struct fdescmount *fmp;
  124         caddr_t data;
  125         int error;
  126         int flags = 0;
  127 
  128         fmp = (struct fdescmount *)mp->mnt_data;
  129         if (mntflags & MNT_FORCE) {
  130                 /* The hash mutex protects the private mount flags. */
  131                 mtx_lock(&fdesc_hashmtx);
  132                 fmp->flags |= FMNT_UNMOUNTF;
  133                 mtx_unlock(&fdesc_hashmtx);
  134                 flags |= FORCECLOSE;
  135         }
  136 
  137         /*
  138          * Clear out buffer cache.  I don't think we
  139          * ever get anything cached at this level at the
  140          * moment, but who knows...
  141          *
  142          * There is 1 extra root vnode reference corresponding
  143          * to f_root.
  144          */
  145         if ((error = vflush(mp, 1, flags, curthread)) != 0)
  146                 return (error);
  147 
  148         /*
  149          * Finally, throw away the fdescmount structure. Hold the hashmtx to
  150          * protect the fdescmount structure.
  151          */
  152         mtx_lock(&fdesc_hashmtx);
  153         data = mp->mnt_data;
  154         mp->mnt_data = 0;
  155         mtx_unlock(&fdesc_hashmtx);
  156         free(data, M_FDESCMNT); /* XXX */
  157 
  158         return (0);
  159 }
  160 
  161 static int
  162 fdesc_root(mp, flags, vpp)
  163         struct mount *mp;
  164         int flags;
  165         struct vnode **vpp;
  166 {
  167         struct vnode *vp;
  168 
  169         /*
  170          * Return locked reference to root.
  171          */
  172         vp = VFSTOFDESC(mp)->f_root;
  173         vget(vp, LK_EXCLUSIVE | LK_RETRY, curthread);
  174         *vpp = vp;
  175         return (0);
  176 }
  177 
  178 static int
  179 fdesc_statfs(mp, sbp)
  180         struct mount *mp;
  181         struct statfs *sbp;
  182 {
  183         struct thread *td;
  184         struct filedesc *fdp;
  185         int lim;
  186         int i;
  187         int last;
  188         int freefd;
  189 
  190         td = curthread;
  191 
  192         /*
  193          * Compute number of free file descriptors.
  194          * [ Strange results will ensue if the open file
  195          * limit is ever reduced below the current number
  196          * of open files... ]
  197          */
  198         PROC_LOCK(td->td_proc);
  199         lim = lim_cur(td->td_proc, RLIMIT_NOFILE);
  200         PROC_UNLOCK(td->td_proc);
  201         fdp = td->td_proc->p_fd;
  202         FILEDESC_SLOCK(fdp);
  203         last = min(fdp->fd_nfiles, lim);
  204         freefd = 0;
  205         for (i = fdp->fd_freefile; i < last; i++)
  206                 if (fdp->fd_ofiles[i] == NULL)
  207                         freefd++;
  208 
  209         /*
  210          * Adjust for the fact that the fdesc array may not
  211          * have been fully allocated yet.
  212          */
  213         if (fdp->fd_nfiles < lim)
  214                 freefd += (lim - fdp->fd_nfiles);
  215         FILEDESC_SUNLOCK(fdp);
  216 
  217         sbp->f_flags = 0;
  218         sbp->f_bsize = DEV_BSIZE;
  219         sbp->f_iosize = DEV_BSIZE;
  220         sbp->f_blocks = 2;              /* 1K to keep df happy */
  221         sbp->f_bfree = 0;
  222         sbp->f_bavail = 0;
  223         sbp->f_files = lim + 1;         /* Allow for "." */
  224         sbp->f_ffree = freefd;          /* See comments above */
  225         return (0);
  226 }
  227 
  228 static struct vfsops fdesc_vfsops = {
  229         .vfs_cmount =           fdesc_cmount,
  230         .vfs_init =             fdesc_init,
  231         .vfs_mount =            fdesc_mount,
  232         .vfs_root =             fdesc_root,
  233         .vfs_statfs =           fdesc_statfs,
  234         .vfs_uninit =           fdesc_uninit,
  235         .vfs_unmount =          fdesc_unmount,
  236 };
  237 
  238 VFS_SET(fdesc_vfsops, fdescfs, VFCF_SYNTHETIC);

Cache object: a63d992a5c7239b7ad202e63da70b8a5


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