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/9.0/sys/fs/fdescfs/fdesc_vfsops.c 220400 2011-04-06 19:13:04Z trasz $
   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/racct.h>
   51 #include <sys/resourcevar.h>
   52 #include <sys/vnode.h>
   53 
   54 #include <fs/fdescfs/fdesc.h>
   55 
   56 static MALLOC_DEFINE(M_FDESCMNT, "fdesc_mount", "FDESC mount structure");
   57 
   58 static vfs_cmount_t     fdesc_cmount;
   59 static vfs_mount_t      fdesc_mount;
   60 static vfs_unmount_t    fdesc_unmount;
   61 static vfs_statfs_t     fdesc_statfs;
   62 static vfs_root_t       fdesc_root;
   63 
   64 /*
   65  * Compatibility shim for old mount(2) system call.
   66  */
   67 int
   68 fdesc_cmount(struct mntarg *ma, void *data, int flags)
   69 {
   70         return kernel_mount(ma, flags);
   71 }
   72 
   73 /*
   74  * Mount the per-process file descriptors (/dev/fd)
   75  */
   76 static int
   77 fdesc_mount(struct mount *mp)
   78 {
   79         int error = 0;
   80         struct fdescmount *fmp;
   81         struct vnode *rvp;
   82 
   83         /*
   84          * Update is a no-op
   85          */
   86         if (mp->mnt_flag & (MNT_UPDATE | MNT_ROOTFS))
   87                 return (EOPNOTSUPP);
   88 
   89         fmp = malloc(sizeof(struct fdescmount),
   90                                 M_FDESCMNT, M_WAITOK);  /* XXX */
   91 
   92         /*
   93          * We need to initialize a few bits of our local mount point struct to
   94          * avoid confusion in allocvp.
   95          */
   96         mp->mnt_data = (qaddr_t) fmp;
   97         fmp->flags = 0;
   98         error = fdesc_allocvp(Froot, -1, FD_ROOT, mp, &rvp);
   99         if (error) {
  100                 free(fmp, M_FDESCMNT);
  101                 mp->mnt_data = 0;
  102                 return (error);
  103         }
  104         rvp->v_type = VDIR;
  105         rvp->v_vflag |= VV_ROOT;
  106         fmp->f_root = rvp;
  107         VOP_UNLOCK(rvp, 0);
  108         /* XXX -- don't mark as local to work around fts() problems */
  109         /*mp->mnt_flag |= MNT_LOCAL;*/
  110         MNT_ILOCK(mp);
  111         mp->mnt_kern_flag |= MNTK_MPSAFE;
  112         MNT_IUNLOCK(mp);
  113         vfs_getnewfsid(mp);
  114 
  115         vfs_mountedfrom(mp, "fdescfs");
  116         return (0);
  117 }
  118 
  119 static int
  120 fdesc_unmount(mp, mntflags)
  121         struct mount *mp;
  122         int mntflags;
  123 {
  124         struct fdescmount *fmp;
  125         caddr_t data;
  126         int error;
  127         int flags = 0;
  128 
  129         fmp = (struct fdescmount *)mp->mnt_data;
  130         if (mntflags & MNT_FORCE) {
  131                 /* The hash mutex protects the private mount flags. */
  132                 mtx_lock(&fdesc_hashmtx);
  133                 fmp->flags |= FMNT_UNMOUNTF;
  134                 mtx_unlock(&fdesc_hashmtx);
  135                 flags |= FORCECLOSE;
  136         }
  137 
  138         /*
  139          * Clear out buffer cache.  I don't think we
  140          * ever get anything cached at this level at the
  141          * moment, but who knows...
  142          *
  143          * There is 1 extra root vnode reference corresponding
  144          * to f_root.
  145          */
  146         if ((error = vflush(mp, 1, flags, curthread)) != 0)
  147                 return (error);
  148 
  149         /*
  150          * Finally, throw away the fdescmount structure. Hold the hashmtx to
  151          * protect the fdescmount structure.
  152          */
  153         mtx_lock(&fdesc_hashmtx);
  154         data = mp->mnt_data;
  155         mp->mnt_data = 0;
  156         mtx_unlock(&fdesc_hashmtx);
  157         free(data, M_FDESCMNT); /* XXX */
  158 
  159         return (0);
  160 }
  161 
  162 static int
  163 fdesc_root(mp, flags, vpp)
  164         struct mount *mp;
  165         int flags;
  166         struct vnode **vpp;
  167 {
  168         struct vnode *vp;
  169 
  170         /*
  171          * Return locked reference to root.
  172          */
  173         vp = VFSTOFDESC(mp)->f_root;
  174         vget(vp, LK_EXCLUSIVE | LK_RETRY, curthread);
  175         *vpp = vp;
  176         return (0);
  177 }
  178 
  179 static int
  180 fdesc_statfs(mp, sbp)
  181         struct mount *mp;
  182         struct statfs *sbp;
  183 {
  184         struct thread *td;
  185         struct filedesc *fdp;
  186         int lim;
  187         int i;
  188         int last;
  189         int freefd;
  190         uint64_t limit;
  191 
  192         td = curthread;
  193 
  194         /*
  195          * Compute number of free file descriptors.
  196          * [ Strange results will ensue if the open file
  197          * limit is ever reduced below the current number
  198          * of open files... ]
  199          */
  200         PROC_LOCK(td->td_proc);
  201         lim = lim_cur(td->td_proc, RLIMIT_NOFILE);
  202         PROC_UNLOCK(td->td_proc);
  203         fdp = td->td_proc->p_fd;
  204         FILEDESC_SLOCK(fdp);
  205         limit = racct_get_limit(td->td_proc, RACCT_NOFILE);
  206         if (lim > limit)
  207                 lim = limit;
  208         last = min(fdp->fd_nfiles, lim);
  209         freefd = 0;
  210         for (i = fdp->fd_freefile; i < last; i++)
  211                 if (fdp->fd_ofiles[i] == NULL)
  212                         freefd++;
  213 
  214         /*
  215          * Adjust for the fact that the fdesc array may not
  216          * have been fully allocated yet.
  217          */
  218         if (fdp->fd_nfiles < lim)
  219                 freefd += (lim - fdp->fd_nfiles);
  220         FILEDESC_SUNLOCK(fdp);
  221 
  222         sbp->f_flags = 0;
  223         sbp->f_bsize = DEV_BSIZE;
  224         sbp->f_iosize = DEV_BSIZE;
  225         sbp->f_blocks = 2;              /* 1K to keep df happy */
  226         sbp->f_bfree = 0;
  227         sbp->f_bavail = 0;
  228         sbp->f_files = lim + 1;         /* Allow for "." */
  229         sbp->f_ffree = freefd;          /* See comments above */
  230         return (0);
  231 }
  232 
  233 static struct vfsops fdesc_vfsops = {
  234         .vfs_cmount =           fdesc_cmount,
  235         .vfs_init =             fdesc_init,
  236         .vfs_mount =            fdesc_mount,
  237         .vfs_root =             fdesc_root,
  238         .vfs_statfs =           fdesc_statfs,
  239         .vfs_uninit =           fdesc_uninit,
  240         .vfs_unmount =          fdesc_unmount,
  241 };
  242 
  243 VFS_SET(fdesc_vfsops, fdescfs, VFCF_SYNTHETIC);

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

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sys/fs/fdescfs/fdesc_vfsops.c