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Implement DIOCBSDBB ioctl which overwrites first BBSIZE bytes of BSD

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labeled disk.

This is complicated by the fact that BBSIZE is greater than the
PAGE_SIZE limit ioctl inflicts on arguments which are automatically
copied in.

As long as we don't need access to userland memory (copyin/out) we
can deal with the ioctl using g_callme() which executes it from the
GEOM event thread.

Once we need copyin/out, we need to return the bio with EDIRIOCTL
in order to make geom_dev call us back in the original process context
where copyin will work.

Unfortunately, that results in us getting called with Giant, so
we have to DROP_GIANT/PICKUP_GIANT around the code where we diddle
GEOMs internals.

Sometimes you just can't win...

... But it does make geom_bsd.c an almost complete example of the
GEOM beastiarium.
This commit is contained in:
Poul-Henning Kamp 2003-01-26 21:54:36 +00:00
parent afdc2f6786
commit 7253da9c05
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=109900
1 changed files with 62 additions and 0 deletions
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62
sys/geom/geom_bsd.c
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@ -546,6 +546,63 @@ g_bsd_ioctl(void *arg)
g_io_deliver(bp, error);
}
/*
* Rewrite the bootblock, which is BBSIZE bytes from the start of the disk.
* We punch down the disklabel where we expect it to be before writing.
*/
static int
g_bsd_diocbsdbb(dev_t dev, u_long cmd, caddr_t data, int fflag, struct thread *td)
{
struct g_geom *gp;
struct g_slicer *gsp;
struct g_bsd_softc *ms;
struct disklabel *dl;
struct g_consumer *cp;
u_char *buf;
void *p;
u_int secsize;
int error, i;
uint64_t sum;
/* Get hold of the interesting bits from the bio. */
gp = (void *)dev;
gsp = gp->softc;
ms = gsp->softc;
/* The disklabel to set is the ioctl argument. */
buf = g_malloc(BBSIZE, 0);
p = *(void **)data;
error = copyin(p, buf, BBSIZE);
if (error) {
g_free(buf);
return (error);
}
/* The disklabel to set is the ioctl argument. */
dl = (void *)(buf + ms->labeloffset);
DROP_GIANT();
/* Validate and modify our slice instance to match. */
error = g_bsd_modify(gp, dl); /* Picks up topology lock on success. */
if (!error) {
cp = LIST_FIRST(&gp->consumer);
secsize = cp->provider->sectorsize;
dl = &ms->ondisk;
g_bsd_leenc_disklabel(buf + ms->labeloffset, dl);
if (ms->labeloffset == ALPHA_LABEL_OFFSET) {
sum = 0;
for (i = 0; i < 63; i++)
sum += g_dec_le8(buf + i * 8);
g_enc_le8(buf + 504, sum);
}
error = g_write_data(cp, 0, buf, BBSIZE);
g_topology_unlock();
}
g_free(buf);
PICKUP_GIANT();
return (error);
}
/*
* If the user tries to overwrite our disklabel through an open partition
* or via a magicwrite config call, we end up here and try to prevent
@ -655,6 +712,11 @@ g_bsd_start(struct bio *bp)
bcopy(&ms->inram, gio->data, sizeof(ms->inram));
g_io_deliver(bp, 0);
return (1);
case DIOCBSDBB:
gio->func = g_bsd_diocbsdbb;
gio->dev = (void *)gp;
g_io_deliver(bp, EDIRIOCTL);
return (1);
case DIOCSDINFO:
case DIOCWDINFO:
/*