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Allow more nesting of GEOM partitioning schemes

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GEOM is supposed to be topology-agnostic, but the GPT and BSD partition code
has arbitrary restrictions on nesting that are annoying in cases such as
running VMs on raw partitions (since the VM's partitioning scheme is not
visible to the host).

This patch adds sysctls to disable the restrictions except in the case of
BSD label (and similar) partitions with offset 0 (where we need to avoid
recursively recognizing the label).

Submitted by:	Andrew Gierth
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D21350
This commit is contained in:
Kyle Evans 2019-09-03 20:57:20 +00:00
parent dca52ab480
commit ef03f57dd2
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=351797
3 changed files with 34 additions and 7 deletions
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13
lib/geom/part/gpart.8
View File

@ -24,7 +24,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd June 17, 2018
.Dd September 3, 2019
.Dt GPART 8
.Os
.Sh NAME
@ -1207,7 +1207,13 @@ variables can be used to control the behavior of the
GEOM class.
The default value is shown next to each variable.
.Bl -tag -width indent
.It Va kern.geom.part.auto_resize: No 1
.It Va kern.geom.part.allow_nesting : No 0
By default, some schemes (currently BSD, BSD64 and VTOC8) do not permit
further nested partitioning.
This variable overrides this restriction and allows arbitrary nesting (except
within partitions created at offset 0).
Some schemes have their own separate checks, for which see below.
.It Va kern.geom.part.auto_resize : No 1
This variable controls automatic resize behavior of
.Nm
GEOM class.
@ -1228,6 +1234,9 @@ disk metadata.
If some inconsistency is detected, the partition table will be
rejected with a diagnostic message:
.Sy "GEOM_PART: Integrity check failed (provider, scheme)" .
.It Va kern.geom.part.gpt.allow_nesting : No 0
By default the GPT scheme is allowed only at the outermost nesting level.
This variable allows this restriction to be removed.
.It Va kern.geom.part.ldm.debug : No 0
Debug level of the Logical Disk Manager (LDM) module.
This can be set to a number between 0 and 2 inclusive.

12
sys/geom/part/g_part.c
View File

@ -143,6 +143,10 @@ static u_int auto_resize = 1;
SYSCTL_UINT(_kern_geom_part, OID_AUTO, auto_resize,
CTLFLAG_RWTUN, &auto_resize, 1,
"Enable auto resize");
static u_int allow_nesting = 0;
SYSCTL_UINT(_kern_geom_part, OID_AUTO, allow_nesting,
CTLFLAG_RWTUN, &allow_nesting, 0,
"Allow additional levels of nesting");
/*
* The GEOM partitioning class.
@ -2271,7 +2275,13 @@ g_part_start(struct bio *bp)
return;
if (g_handleattr_int(bp, "GEOM::fwsectors", table->gpt_sectors))
return;
if (g_handleattr_int(bp, "PART::isleaf", table->gpt_isleaf))
/*
* allow_nesting overrides "isleaf" to false _unless_ the
* provider offset is zero, since otherwise we would recurse.
*/
if (g_handleattr_int(bp, "PART::isleaf",
table->gpt_isleaf &&
(allow_nesting == 0 || entry->gpe_offset == 0)))
return;
if (g_handleattr_int(bp, "PART::depth", table->gpt_depth))
return;

16
sys/geom/part/g_part_gpt.c
View File

@ -54,6 +54,14 @@ __FBSDID("$FreeBSD$");
FEATURE(geom_part_gpt, "GEOM partitioning class for GPT partitions support");
SYSCTL_DECL(_kern_geom_part);
static SYSCTL_NODE(_kern_geom_part, OID_AUTO, gpt, CTLFLAG_RW, 0,
"GEOM_PART_GPT GUID Partition Table");
static u_int allow_nesting = 0;
SYSCTL_UINT(_kern_geom_part_gpt, OID_AUTO, allow_nesting,
CTLFLAG_RWTUN, &allow_nesting, 0, "Allow GPT to be nested inside other schemes");
CTASSERT(offsetof(struct gpt_hdr, padding) == 92);
CTASSERT(sizeof(struct gpt_ent) == 128);
@ -652,8 +660,8 @@ g_part_gpt_create(struct g_part_table *basetable, struct g_part_parms *gpp)
struct g_part_gpt_table *table;
size_t tblsz;
/* We don't nest, which means that our depth should be 0. */
if (basetable->gpt_depth != 0)
/* Our depth should be 0 unless nesting was explicitly enabled. */
if (!allow_nesting && basetable->gpt_depth != 0)
return (ENXIO);
table = (struct g_part_gpt_table *)basetable;
@ -815,8 +823,8 @@ g_part_gpt_probe(struct g_part_table *table, struct g_consumer *cp)
u_char *buf;
int error, index, pri, res;
/* We don't nest, which means that our depth should be 0. */
if (table->gpt_depth != 0)
/* Our depth should be 0 unless nesting was explicitly enabled. */
if (!allow_nesting && table->gpt_depth != 0)
return (ENXIO);
pp = cp->provider;