FreeBSD/Linux Kernel Cross Reference
sys/geom/zero/g_zero.c

     /*-
      * Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
      * All rights reserved.
      *
      * 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.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHORS 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 AUTHORS 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.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/10.0/sys/geom/zero/g_zero.c 254936 2013-08-26 20:39:02Z mav $");
    
    #include <sys/param.h>
    #include <sys/bio.h>
    #include <sys/kernel.h>
    #include <sys/limits.h>
    #include <sys/malloc.h>
    #include <sys/queue.h>
    #include <sys/sysctl.h>
    #include <sys/systm.h>
    
    #include <geom/geom.h>
    
    
    #define G_ZERO_CLASS_NAME       "ZERO"
    
    static int      g_zero_clear_sysctl(SYSCTL_HANDLER_ARGS);
    
    SYSCTL_DECL(_kern_geom);
    static SYSCTL_NODE(_kern_geom, OID_AUTO, zero, CTLFLAG_RW, 0,
        "GEOM_ZERO stuff");
    static int g_zero_clear = 1;
    SYSCTL_PROC(_kern_geom_zero, OID_AUTO, clear, CTLTYPE_INT|CTLFLAG_RW,
        &g_zero_clear, 0, g_zero_clear_sysctl, "I", "Clear read data buffer");
    static int g_zero_byte = 0;
    SYSCTL_INT(_kern_geom_zero, OID_AUTO, byte, CTLFLAG_RW, &g_zero_byte, 0,
        "Byte (octet) value to clear the buffers with");
    
    static struct g_provider *gpp;
    
    static int
    g_zero_clear_sysctl(SYSCTL_HANDLER_ARGS)
    {
            int error;
    
            error = sysctl_handle_int(oidp, &g_zero_clear, 0, req);
            if (error != 0 || req->newptr == NULL)
                    return (error);
            if (gpp == NULL)
                    return (ENXIO);
            if (g_zero_clear)
                    gpp->flags &= ~G_PF_ACCEPT_UNMAPPED;
            else
                    gpp->flags |= G_PF_ACCEPT_UNMAPPED;
            return (0);
    }
    
    static void
    g_zero_start(struct bio *bp)
    {
            int error = ENXIO;
    
            switch (bp->bio_cmd) {
            case BIO_READ:
                    if (g_zero_clear && (bp->bio_flags & BIO_UNMAPPED) == 0)
                            memset(bp->bio_data, g_zero_byte, bp->bio_length);
                    /* FALLTHROUGH */
            case BIO_DELETE:
            case BIO_WRITE:
                    bp->bio_completed = bp->bio_length;
                    error = 0;
                    break;
            case BIO_GETATTR:
            default:
                    error = EOPNOTSUPP;
                    break;
            }
            g_io_deliver(bp, error);
    }
    
    static void
    g_zero_init(struct g_class *mp)
   {
           struct g_geom *gp;
           struct g_provider *pp;
   
           g_topology_assert();
           gp = g_new_geomf(mp, "gzero");
           gp->start = g_zero_start;
           gp->access = g_std_access;
           gpp = pp = g_new_providerf(gp, "%s", gp->name);
           if (!g_zero_clear)
                   pp->flags |= G_PF_ACCEPT_UNMAPPED;
           pp->mediasize = 1152921504606846976LLU;
           pp->sectorsize = 512;
           g_error_provider(pp, 0);
   }
   
   static int
   g_zero_destroy_geom(struct gctl_req *req __unused, struct g_class *mp __unused,
       struct g_geom *gp)
   {
           struct g_provider *pp;
   
           g_topology_assert();
           if (gp == NULL)
                   return (0);
           pp = LIST_FIRST(&gp->provider);
           if (pp == NULL)
                   return (0);
           if (pp->acr > 0 || pp->acw > 0 || pp->ace > 0)
                   return (EBUSY);
           gpp = NULL;
           g_wither_geom(gp, ENXIO);
           return (0);
   }
   
   static struct g_class g_zero_class = {
           .name = G_ZERO_CLASS_NAME,
           .version = G_VERSION,
           .init = g_zero_init,
           .destroy_geom = g_zero_destroy_geom
   };
   
   DECLARE_GEOM_CLASS(g_zero_class, g_zero);

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