NAME

       free_mntarg,  kernel_mount,  kernel_vmount,  mount_arg,  mount_argb,  mount_argf, mount_argsu — functions
       provided as part of the kernel mount interface

SYNOPSIS

       void
       free_mntarg(struct mntarg *ma);

       int
       kernel_mount(struct mntarg *ma, int flags);

       int
       kernel_vmount(int flags, ...);

       struct mntarg *
       mount_arg(struct mntarg *ma, const char *name, const void *val, int len);

       struct mntarg *
       mount_argb(struct mntarg *ma, int flag, const char *name);

       struct mntarg *
       mount_argf(struct mntarg *ma, const char *name, const char *fmt, ...);

       struct mntarg *
       mount_argsu(struct mntarg *ma, const char *name, const void *val, int len);

DESCRIPTION

       The kernel_mount() family of functions are provided as an API for building  a  list  of  mount  arguments
       which  will  be  used to mount file systems from inside the kernel.  By accumulating a list of arguments,
       the API takes shape and provides the information  necessary  for  the  kernel  to  control  the  mount(8)
       utility.  When an error occurs, the process will stop.  This will not cause a panic(9).

       The  header  of  the  structure  is  stored in src/sys/kern/vfs_mount.c which permits automatic structure
       creation to ease the mount process.  Memory allocation must always be freed when the  entire  process  is
       complete, it is an error otherwise.

       The free_mntarg() function is used to free or clear the mntarg structure.

       The  kernel_mount() function pulls information from the structure to perform the mount request on a given
       file system.  Additionally, the kernel_mount() function always calls the free_mntarg() function.   If  ma
       contains  any  error code generated during the construction, that code will be called and the file system
       mount will not be attempted.

       The kernel_vmount() is a function similar to printf(9) which is used to mount a file system.

       The mount_arg() function takes a plain argument and crafts parts of the structure with regards to various
       mount options.  If the length is a value  less  than  0,  strlen(3)  is  used.   This  argument  will  be
       referenced until either free_mntarg() or kernel_mount() is called.

       The  mount_argb()  function  is  used to add boolean arguments to the structure.  The flag is the boolean
       value and name must start with "no", otherwise a panic will occur.

       The mount_argf() function adds printf(9) style arguments to the current structure.

       The mount_argsu() function will add arguments to the structure from a userland string.

EXAMPLES

       An example of the *_cmount() function:

       static int
       msdosfs_cmount(struct mntarg *ma, void *data, int flags, struct thread *td)
       {
               struct msdosfs_args args;
               int error;

               if (data == NULL)
                       return (EINVAL);
               error = copyin(data, &args, sizeof(args));
               if (error)
                       return (error);

               ma = mount_argsu(ma, "from", args.fspec, MAXPATHLEN);
               ma = mount_arg(ma, "export", &args.export, sizeof(args.export));
               ma = mount_argf(ma, "uid", "%d", args.uid);
               ma = mount_argf(ma, "gid", "%d", args.gid);
               ma = mount_argf(ma, "mask", "%d", args.mask);
               ma = mount_argf(ma, "dirmask", "%d", args.dirmask);

               ma = mount_argb(ma, args.flags & MSDOSFSMNT_SHORTNAME, "noshortname");
               ma = mount_argb(ma, args.flags & MSDOSFSMNT_LONGNAME, "nolongname");
               ma = mount_argb(ma, !(args.flags & MSDOSFSMNT_NOWIN95), "nowin95");
               ma = mount_argb(ma, args.flags & MSDOSFSMNT_KICONV, "nokiconv");

               ma = mount_argsu(ma, "cs_win", args.cs_win, MAXCSLEN);
               ma = mount_argsu(ma, "cs_dos", args.cs_dos, MAXCSLEN);
               ma = mount_argsu(ma, "cs_local", args.cs_local, MAXCSLEN);

               error = kernel_mount(ma, flags);

               return (error);
       }

       When working with kernel_vmount(), varargs must come in pairs, e.g., {name, value}.

               error = kernel_vmount(
                   MNT_RDONLY,
                   "fstype", vfsname,
                   "fspath", "/",
                   "from", path,
                   NULL);

SEE ALSO

       VFS(9), VFS_MOUNT(9)

HISTORY

       The kernel_mount() family of functions and this manual page first appeared in FreeBSD 6.0.

AUTHORS

       The kernel_mount() family of functions and API was  developed  by  Poul-Henning  Kamp  <phk@FreeBSD.org>.
       This manual page was written by Tom Rhodes <trhodes@FreeBSD.org>.

Debian                                          December 13, 2004                                KERNEL_MOUNT(9)