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

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * Copyright (c) 1992, 1993, 1995
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code is derived from software donated to Berkeley by
      * Jan-Simon Pendry.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)fdesc_vfsops.c      8.4 (Berkeley) 1/21/94
     *
     * $FreeBSD: releng/12.0/sys/fs/fdescfs/fdesc_vfsops.c 333263 2018-05-04 20:54:27Z jamie $
     */
    
    /*
     * /dev/fd Filesystem
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/filedesc.h>
    #include <sys/kernel.h>
    #include <sys/jail.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/malloc.h>
    #include <sys/mount.h>
    #include <sys/proc.h>
    #include <sys/racct.h>
    #include <sys/resourcevar.h>
    #include <sys/vnode.h>
    
    #include <fs/fdescfs/fdesc.h>
    
    static MALLOC_DEFINE(M_FDESCMNT, "fdesc_mount", "FDESC mount structure");
    
    static vfs_cmount_t     fdesc_cmount;
    static vfs_mount_t      fdesc_mount;
    static vfs_unmount_t    fdesc_unmount;
    static vfs_statfs_t     fdesc_statfs;
    static vfs_root_t       fdesc_root;
    
    /*
     * Compatibility shim for old mount(2) system call.
     */
    int
    fdesc_cmount(struct mntarg *ma, void *data, uint64_t flags)
    {
    
            return kernel_mount(ma, flags);
    }
    
    /*
     * Mount the per-process file descriptors (/dev/fd)
     */
    static int
    fdesc_mount(struct mount *mp)
    {
            struct fdescmount *fmp;
            struct vnode *rvp;
            int error;
    
            /*
             * Update is a no-op
             */
            if (mp->mnt_flag & (MNT_UPDATE | MNT_ROOTFS))
                    return (EOPNOTSUPP);
    
            fmp = malloc(sizeof(struct fdescmount),
                                    M_FDESCMNT, M_WAITOK);  /* XXX */
    
            /*
             * We need to initialize a few bits of our local mount point struct to
             * avoid confusion in allocvp.
             */
           mp->mnt_data = fmp;
           fmp->flags = 0;
           if (vfs_getopt(mp->mnt_optnew, "linrdlnk", NULL, NULL) == 0)
                   fmp->flags |= FMNT_LINRDLNKF;
           error = fdesc_allocvp(Froot, -1, FD_ROOT, mp, &rvp);
           if (error) {
                   free(fmp, M_FDESCMNT);
                   mp->mnt_data = NULL;
                   return (error);
           }
           rvp->v_type = VDIR;
           rvp->v_vflag |= VV_ROOT;
           fmp->f_root = rvp;
           VOP_UNLOCK(rvp, 0);
           /* XXX -- don't mark as local to work around fts() problems */
           /*mp->mnt_flag |= MNT_LOCAL;*/
           vfs_getnewfsid(mp);
   
           vfs_mountedfrom(mp, "fdescfs");
           return (0);
   }
   
   static int
   fdesc_unmount(struct mount *mp, int mntflags)
   {
           struct fdescmount *fmp;
           int error, flags;
   
           flags = 0;
           fmp = mp->mnt_data;
           if (mntflags & MNT_FORCE) {
                   /* The hash mutex protects the private mount flags. */
                   mtx_lock(&fdesc_hashmtx);
                   fmp->flags |= FMNT_UNMOUNTF;
                   mtx_unlock(&fdesc_hashmtx);
                   flags |= FORCECLOSE;
           }
   
           /*
            * Clear out buffer cache.  I don't think we
            * ever get anything cached at this level at the
            * moment, but who knows...
            *
            * There is 1 extra root vnode reference corresponding
            * to f_root.
            */
           if ((error = vflush(mp, 1, flags, curthread)) != 0)
                   return (error);
   
           /*
            * Finally, throw away the fdescmount structure.
            */
           mp->mnt_data = NULL;
           free(fmp, M_FDESCMNT);
           return (0);
   }
   
   static int
   fdesc_root(struct mount *mp, int flags, struct vnode **vpp)
   {
           struct vnode *vp;
   
           /*
            * Return locked reference to root.
            */
           vp = VFSTOFDESC(mp)->f_root;
           vget(vp, LK_EXCLUSIVE | LK_RETRY, curthread);
           *vpp = vp;
           return (0);
   }
   
   static int
   fdesc_statfs(struct mount *mp, struct statfs *sbp)
   {
           struct thread *td;
           struct filedesc *fdp;
           int lim;
           int i;
           int last;
           int freefd;
           uint64_t limit;
   
           td = curthread;
   
           /*
            * Compute number of free file descriptors.
            * [ Strange results will ensue if the open file
            * limit is ever reduced below the current number
            * of open files... ]
            */
           lim = lim_cur(td, RLIMIT_NOFILE);
           fdp = td->td_proc->p_fd;
           FILEDESC_SLOCK(fdp);
           limit = racct_get_limit(td->td_proc, RACCT_NOFILE);
           if (lim > limit)
                   lim = limit;
           last = min(fdp->fd_nfiles, lim);
           freefd = 0;
           for (i = fdp->fd_freefile; i < last; i++)
                   if (fdp->fd_ofiles[i].fde_file == NULL)
                           freefd++;
   
           /*
            * Adjust for the fact that the fdesc array may not
            * have been fully allocated yet.
            */
           if (fdp->fd_nfiles < lim)
                   freefd += (lim - fdp->fd_nfiles);
           FILEDESC_SUNLOCK(fdp);
   
           sbp->f_flags = 0;
           sbp->f_bsize = DEV_BSIZE;
           sbp->f_iosize = DEV_BSIZE;
           sbp->f_blocks = 2;              /* 1K to keep df happy */
           sbp->f_bfree = 0;
           sbp->f_bavail = 0;
           sbp->f_files = lim + 1;         /* Allow for "." */
           sbp->f_ffree = freefd;          /* See comments above */
           return (0);
   }
   
   static struct vfsops fdesc_vfsops = {
           .vfs_cmount =           fdesc_cmount,
           .vfs_init =             fdesc_init,
           .vfs_mount =            fdesc_mount,
           .vfs_root =             fdesc_root,
           .vfs_statfs =           fdesc_statfs,
           .vfs_uninit =           fdesc_uninit,
           .vfs_unmount =          fdesc_unmount,
   };
   
   VFS_SET(fdesc_vfsops, fdescfs, VFCF_SYNTHETIC | VFCF_JAIL);

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