This is my counter-proposal to Nir's request [1] to revert a 6.0
behavior change. It does not expose any new information over NBD, but
does make it easier to collect necessary information from a single
context rather than requiring the client to have to request two
contexts in parallel, then cross-correlate what may be different
extent lengths between those contexts. Furthermore, this is easy to
backport to downstream based on qemu 6.0, at which point clients could
use the existence or absence of qemu:joint-allocation as a witness of
whether it can get away with trusting base:allocation when trying to
recreate a qcow2 backing chain.
[1] https://lists.gnu.org/archive/html/qemu-devel/2021-06/msg01796.html
Things I still want to do:
- a followup patch to libnbd to teach 'nbdinfo
--map=qemu:joint-allocation' to decode the bits
- teach 'nbdinfo --map' to read all available contexts, instead of
having to manually type each map besides base:allocation
- potential followup patches to qemu to automatically feed this
information through qemu-img map:
- add a new BDRV_BLOCK_BACKING bit for bdrv_block_status(), with
opposite semantics from BDRV_BLOCK_ALLOCATED, but where the only
thing known is that the data is not local (not how deep it is)
- teach qemu to favor qemu:joint-allocation over base:allocation
when available, and use it to drive BDRV_BLOCK_BACKING
- teach qemu-img map to recognize BDRV_BLOCK_BACKING
Eric Blake (2):
iotests: Improve and rename test 309 to nbd-qemu-allocation
nbd: Add new qemu:joint-allocation metadata context
docs/interop/nbd.txt | 31 ++++++-
docs/tools/qemu-nbd.rst | 4 +-
qapi/block-export.json | 4 +-
include/block/nbd.h | 10 ++-
nbd/server.c | 87 +++++++++++++++++--
.../{309 => tests/nbd-qemu-allocation} | 5 +-
.../nbd-qemu-allocation.out} | 13 ++-
7 files changed, 139 insertions(+), 15 deletions(-)
rename tests/qemu-iotests/{309 => tests/nbd-qemu-allocation} (95%)
rename tests/qemu-iotests/{309.out => tests/nbd-qemu-allocation.out} (79%)
--
2.31.1
Eric Blake
2021-Jun-09 18:01 UTC
[Libguestfs] [PATCH 1/2] iotests: Improve and rename test 309 to nbd-qemu-allocation
Enhance the test to inspect what qemu-nbd is advertising during
handshake, and rename it now that we support useful iotest names.
Signed-off-by: Eric Blake <eblake at redhat.com>
---
.../qemu-iotests/{309 => tests/nbd-qemu-allocation} | 5 ++++-
.../{309.out => tests/nbd-qemu-allocation.out} | 12 +++++++++++-
2 files changed, 15 insertions(+), 2 deletions(-)
rename tests/qemu-iotests/{309 => tests/nbd-qemu-allocation} (95%)
rename tests/qemu-iotests/{309.out => tests/nbd-qemu-allocation.out} (81%)
diff --git a/tests/qemu-iotests/309
b/tests/qemu-iotests/tests/nbd-qemu-allocation
similarity index 95%
rename from tests/qemu-iotests/309
rename to tests/qemu-iotests/tests/nbd-qemu-allocation
index b90b279994c9..4ee73db8033b 100755
--- a/tests/qemu-iotests/309
+++ b/tests/qemu-iotests/tests/nbd-qemu-allocation
@@ -3,7 +3,7 @@
#
# Test qemu-nbd -A
#
-# Copyright (C) 2018-2020 Red Hat, Inc.
+# Copyright (C) 2018-2021 Red Hat, Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
@@ -32,6 +32,7 @@ _cleanup()
trap "_cleanup; exit \$status" 0 1 2 3 15
# get standard environment, filters and checks
+cd ..
. ./common.rc
. ./common.filter
. ./common.nbd
@@ -57,6 +58,8 @@ echo
$QEMU_IMG map --output=json -f qcow2 "$TEST_IMG"
IMG="driver=nbd,server.type=unix,server.path=$nbd_unix_socket"
nbd_server_start_unix_socket -r -f qcow2 -A "$TEST_IMG"
+# Inspect what the server is exposing
+$QEMU_NBD --list -k $nbd_unix_socket
# Normal -f raw NBD block status loses access to allocation information
$QEMU_IMG map --output=json --image-opts \
"$IMG" | _filter_qemu_img_map
diff --git a/tests/qemu-iotests/309.out
b/tests/qemu-iotests/tests/nbd-qemu-allocation.out
similarity index 81%
rename from tests/qemu-iotests/309.out
rename to tests/qemu-iotests/tests/nbd-qemu-allocation.out
index db75bb6b0df9..c51022b2a38d 100644
--- a/tests/qemu-iotests/309.out
+++ b/tests/qemu-iotests/tests/nbd-qemu-allocation.out
@@ -1,4 +1,4 @@
-QA output created by 309
+QA output created by nbd-qemu-allocation
=== Initial image setup ==
@@ -14,6 +14,16 @@ wrote 2097152/2097152 bytes at offset 1048576
[{ "start": 0, "length": 1048576, "depth": 1,
"zero": false, "data": true, "offset": 327680},
{ "start": 1048576, "length": 2097152, "depth":
0, "zero": false, "data": true, "offset": 327680},
{ "start": 3145728, "length": 1048576, "depth":
1, "zero": true, "data": false}]
+exports available: 1
+ export: ''
+ size: 4194304
+ flags: 0x58f ( readonly flush fua df multi cache )
+ min block: 1
+ opt block: 4096
+ max block: 33554432
+ available meta contexts: 2
+ base:allocation
+ qemu:allocation-depth
[{ "start": 0, "length": 3145728, "depth": 0,
"zero": false, "data": true, "offset": OFFSET},
{ "start": 3145728, "length": 1048576, "depth":
0, "zero": true, "data": false, "offset": OFFSET}]
[{ "start": 0, "length": 1048576, "depth": 0,
"zero": true, "data": true, "offset": OFFSET},
--
2.31.1
Eric Blake
2021-Jun-09 18:01 UTC
[Libguestfs] [PATCH 2/2] nbd: Add new qemu:joint-allocation metadata context
When trying to reconstruct a qcow2 chain using information provided
over NBD, ovirt had been relying on an unsafe assumption that any
portion of the qcow2 file advertised as sparse would defer to the
backing image; this worked with what qemu 5.2 reports for a qcow2 BSD
loaded with "backing":null. However, in 6.0, commit 0da9856851 (nbd:
server: Report holes for raw images) also had a side-effect of
reporting unallocated zero clusters in qcow2 files as sparse. This
change is correct from the NBD spec perspective (advertising bits has
always been optional based on how much information the server has
available, and should only be used to optimize behavior when a bit is
set, while not assuming semantics merely because a bit is clear), but
means that a qcow2 file that uses an unallocated zero cluster to
override a backing file now shows up as sparse over NBD, and causes
ovirt to fail to reproduce that cluster (ie. ovirt was assuming it
only had to write clusters where the bit was clear, and the 6.0
behavior change shows the flaw in that assumption).
The correct fix is for ovirt to additionally use the
qemu:allocation-depth metadata context added in 5.2: after all, the
actual determination for what is needed to recreate a qcow2 file is
not whether a cluster is sparse, but whether the allocation-depth
shows the cluster to be local. But reproducing an image is more
efficient when handling known-zero clusters, which means that ovirt
has to track both base:allocation and qemu:allocation-depth metadata
contexts simultaneously. While NBD_CMD_BLOCK_STATUS is just fine
sending back information for two contexts in parallel, it comes with
some bookkeeping overhead at the client side: the two contexts need
not report the same length of replies, and it involves more network
traffic.
So, as a convenience, we can provide yet another metadata context,
"qemu:joint-allocation", which provides the bulk of the same
information already available from using "base:allocation" and
"qemu:allocation-depth" in parallel; the only difference is that an
allocation depth larger than one is collapsed to a single bit, rather
than remaining an integer representing actual depth. By connecting to
just this context, a client has less work to perform while still
getting at all pieces of information needed to recreate a qcow2
backing chain.
With regards to exposing this new feature from qemu as NBD server, it
is sufficient to reuse the existing 'qemu-nbd -A': since that already
exposes allocation depth, it does not hurt to advertise two separate
qemu:XXX metadata contexts at once for two different views of
allocation depth. And just because the server supports multiple
contexts does not mean a client will want or need to connect to
everything available. On the other hand, the existing hack of using
the qemu NBD client option of x-dirty-bitmap to select an alternative
context from the client does NOT make it possible to read the extra
information exposed by the new metadata context. For now, you MUST
use something like libnbd's 'nbdinfo --map=qemu:joint-allocation' in
order to properly see all four bits in action:
# Create a qcow2 image with a raw backing file:
$ qemu-img create base.raw $((4*64*1024))
$ qemu-img create -f qcow2 -b base.raw -F raw top.qcow2
# Write to first 3 clusters of base:
$ qemu-io -f raw -c "w -P 65 0 64k" -c "w -P 66 64k 64k"
\
-c "w -P 67 128k 64k" base.raw
# Write to second and third clusters of top, hiding base:
$ qemu-io -f qcow2 -c "w -P 69 64k 64k" -c "w -z 128k
64k" top.qcow2
# Expose top.qcow2 without backing file over NBD
$ ./qemu-nbd -r -t -f qcow2 -A
'json:{"driver":"qcow2", "backing":null, \
"file":{"driver":"file",
"filename":"top.qcow2"}}'
$ nbdinfo --map=qemu:joint-allocation nbd://localhost
0 65536 3
65536 65536 4
131072 65536 7
196608 65536 3
[This was output from nbdinfo 1.8.0; a later version will also add a
column to decode the bits into human-readable strings]
Additionally, later qemu patches may try to improve qemu-img to
automatically take advantage of additional NBD context information,
without having to use x-dirty-bitmap.
Reported-by: Nir Soffer <nsoffer at redhat.com>
Resolves: https://bugzilla.redhat.com/1968693
Signed-off-by: Eric Blake <eblake at redhat.com>
---
docs/interop/nbd.txt | 31 ++++++-
docs/tools/qemu-nbd.rst | 4 +-
qapi/block-export.json | 4 +-
include/block/nbd.h | 10 ++-
nbd/server.c | 87 +++++++++++++++++--
.../tests/nbd-qemu-allocation.out | 3 +-
6 files changed, 125 insertions(+), 14 deletions(-)
diff --git a/docs/interop/nbd.txt b/docs/interop/nbd.txt
index 10ce098a29bf..cc8ce2d5389f 100644
--- a/docs/interop/nbd.txt
+++ b/docs/interop/nbd.txt
@@ -17,7 +17,7 @@ namespace "qemu".
== "qemu" namespace =
-The "qemu" namespace currently contains two available metadata
context
+The "qemu" namespace currently contains three available metadata
context
types. The first is related to exposing the contents of a dirty
bitmap alongside the associated disk contents. That metadata context
is named with the following form:
@@ -39,8 +39,32 @@ depth of which layer in a thin-provisioned backing chain
provided the
data (0 for unallocated, 1 for the active layer, 2 for the first
backing layer, and so forth).
-For NBD_OPT_LIST_META_CONTEXT the following queries are supported
-in addition to the specific "qemu:allocation-depth" and
+The third is for convenience in querying the results of
+base:allocation and qemu:allocation-depth in one go, under the
+metadata context named
+
+ qemu:joint-allocation
+
+In this context, bits 0 and 1 reflect the same information as
+base:allocation, and bits 2 and 3 provide a summary of
+qemu:allocation-depth (although this context is not able to convey
+how deep in the backing chain data comes from).
+
+ bit 0: NBD_STATE_HOLE, set when the extent is sparse
+ bit 1: NBD_STATE_ZERO, set when the extent reads as zero
+ bit 2: NBD_STATE_LOCAL, set when the extent contents come from the
+ local layer
+ bit 3: NBD_STATE_BACKING, set when the extent contents come from a
+ backing layer of unspecified depth
+
+This context does not provide any unique information, but does make it
+easier to reconstruct backing chains without having to piece together
+what might other be disparate-length returns of two separate metadata
+contexts.
+
+For NBD_OPT_LIST_META_CONTEXT the following queries are supported in
+addition to the specific "qemu:allocation-depth",
+"qemu:joint-allocation", and
"qemu:dirty-bitmap:<dirty-bitmap-export-name>":
* "qemu:" - returns list of all available metadata contexts in the
@@ -68,3 +92,4 @@ NBD_CMD_BLOCK_STATUS for "qemu:dirty-bitmap:",
NBD_CMD_CACHE
* 4.2: NBD_FLAG_CAN_MULTI_CONN for shareable read-only exports,
NBD_CMD_FLAG_FAST_ZERO
* 5.2: NBD_CMD_BLOCK_STATUS for "qemu:allocation-depth"
+* 6.1: NBD_CMD_BLOCK_STATUS for "qemu:joint-allocation"
diff --git a/docs/tools/qemu-nbd.rst b/docs/tools/qemu-nbd.rst
index ee862fa0bc02..975ef5cedd14 100644
--- a/docs/tools/qemu-nbd.rst
+++ b/docs/tools/qemu-nbd.rst
@@ -75,8 +75,8 @@ driver options if ``--image-opts`` is specified.
.. option:: -A, --allocation-depth
Expose allocation depth information via the
- ``qemu:allocation-depth`` metadata context accessible through
- NBD_OPT_SET_META_CONTEXT.
+ ``qemu:allocation-depth`` and ``qemu:joint-allocation`` metadata
+ contexts accessible through NBD_OPT_SET_META_CONTEXT.
.. option:: -B, --bitmap=NAME
diff --git a/qapi/block-export.json b/qapi/block-export.json
index e819e70cac0d..1bd315b7958d 100644
--- a/qapi/block-export.json
+++ b/qapi/block-export.json
@@ -92,8 +92,8 @@
#
# @allocation-depth: Also export the allocation depth map for @device, so
# the NBD client can use NBD_OPT_SET_META_CONTEXT with
-# the metadata context name
"qemu:allocation-depth" to
-# inspect allocation details. (since 5.2)
+# the metadata context name
"qemu:allocation-depth" or
+# "qemu:joint-allocation" to inspect allocation
details.
#
# Since: 5.2
##
diff --git a/include/block/nbd.h b/include/block/nbd.h
index 5f34d23bb037..7f411dc59e57 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -1,5 +1,5 @@
/*
- * Copyright (C) 2016-2020 Red Hat, Inc.
+ * Copyright (C) 2016-2021 Red Hat, Inc.
* Copyright (C) 2005 Anthony Liguori <anthony at codemonkey.ws>
*
* Network Block Device
@@ -261,6 +261,14 @@ enum {
/* No flags needed for qemu:allocation-depth in NBD_REPLY_TYPE_BLOCK_STATUS */
+/*
+ * Extent flags for qemu:joint-allocation in NBD_REPLY_TYPE_BLOCK_STATUS,
+ * reusing the two flags already in base:allocation, and compressing the
+ * results of qemu:allocation-depth into two bits
+ */
+#define NBD_STATE_LOCAL (1 << 2)
+#define NBD_STATE_BACKING (1 << 3)
+
static inline bool nbd_reply_type_is_error(int type)
{
return type & (1 << 15);
diff --git a/nbd/server.c b/nbd/server.c
index b60ebc3ab6ac..8b825ccaf2ac 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -28,8 +28,9 @@
#define NBD_META_ID_BASE_ALLOCATION 0
#define NBD_META_ID_ALLOCATION_DEPTH 1
+#define NBD_META_ID_JOINT_ALLOCATION 2
/* Dirty bitmaps use 'NBD_META_ID_DIRTY_BITMAP + i', so keep this id
last. */
-#define NBD_META_ID_DIRTY_BITMAP 2
+#define NBD_META_ID_DIRTY_BITMAP 3
/*
* NBD_MAX_BLOCK_STATUS_EXTENTS: 1 MiB of extents data. An empirical
@@ -97,6 +98,7 @@ struct NBDExport {
Notifier eject_notifier;
bool allocation_depth;
+ bool joint_allocation;
BdrvDirtyBitmap **export_bitmaps;
size_t nr_export_bitmaps;
};
@@ -111,6 +113,7 @@ typedef struct NBDExportMetaContexts {
size_t count; /* number of negotiated contexts */
bool base_allocation; /* export base:allocation context (block status) */
bool allocation_depth; /* export qemu:allocation-depth */
+ bool joint_allocation; /* export qemu:joint-allocation */
bool *bitmaps; /*
* export qemu:dirty-bitmap:<export bitmap name>,
* sized by exp->nr_export_bitmaps
@@ -862,9 +865,9 @@ static bool nbd_meta_base_query(NBDClient *client,
NBDExportMetaContexts *meta,
/* nbd_meta_qemu_query
*
- * Handle queries to 'qemu' namespace. For now, only the
qemu:dirty-bitmap:
- * and qemu:allocation-depth contexts are available. Return true if @query
- * has been handled.
+ * Handle queries to 'qemu' namespace. For now, only the
qemu:dirty-bitmap:,
+ * qemu:joint-allocation, and qemu:allocation-depth contexts are available.
+ * Return true if @query has been handled.
*/
static bool nbd_meta_qemu_query(NBDClient *client, NBDExportMetaContexts *meta,
const char *query)
@@ -891,6 +894,12 @@ static bool nbd_meta_qemu_query(NBDClient *client,
NBDExportMetaContexts *meta,
return true;
}
+ if (strcmp(query, "joint-allocation") == 0) {
+ trace_nbd_negotiate_meta_query_parse("joint-allocation");
+ meta->joint_allocation = meta->exp->joint_allocation;
+ return true;
+ }
+
if (nbd_strshift(&query, "dirty-bitmap:")) {
trace_nbd_negotiate_meta_query_parse("dirty-bitmap:");
if (!*query) {
@@ -1023,6 +1032,7 @@ static int nbd_negotiate_meta_queries(NBDClient *client,
/* enable all known contexts */
meta->base_allocation = true;
meta->allocation_depth = meta->exp->allocation_depth;
+ meta->joint_allocation = meta->exp->joint_allocation;
memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps);
} else {
for (i = 0; i < nb_queries; ++i) {
@@ -1053,6 +1063,16 @@ static int nbd_negotiate_meta_queries(NBDClient *client,
count++;
}
+ if (meta->joint_allocation) {
+ ret = nbd_negotiate_send_meta_context(client,
"qemu:joint-allocation",
+ NBD_META_ID_JOINT_ALLOCATION,
+ errp);
+ if (ret < 0) {
+ return ret;
+ }
+ count++;
+ }
+
for (i = 0; i < meta->exp->nr_export_bitmaps; i++) {
const char *bm_name;
g_autofree char *context = NULL;
@@ -1743,7 +1763,8 @@ static int nbd_export_create(BlockExport *blk_exp,
BlockExportOptions *exp_args,
bdrv_dirty_bitmap_set_busy(exp->export_bitmaps[i], true);
}
- exp->allocation_depth = arg->allocation_depth;
+ /* QMP allocation_depth flag controls export of both metadata contexts. */
+ exp->allocation_depth = exp->joint_allocation =
arg->allocation_depth;
/*
* We need to inhibit request queuing in the block layer to ensure we can
@@ -2164,6 +2185,47 @@ static int blockalloc_to_extents(BlockDriverState *bs,
uint64_t offset,
return 0;
}
+static int blockjoint_to_extents(BlockDriverState *bs, uint64_t offset,
+ uint64_t bytes, NBDExtentArray *ea)
+{
+ while (bytes) {
+ uint32_t flags = 0;
+ int64_t num, num1, num2;
+ int ret1 = bdrv_block_status_above(bs, NULL, offset, bytes, &num1,
+ NULL, NULL);
+ int ret2 = bdrv_is_allocated_above(bs, NULL, false, offset, bytes,
+ &num2);
+
+ if (ret1 < 0) {
+ return ret1;
+ }
+ if (ret2 < 0) {
+ return ret2;
+ }
+ num = MIN(num1, num2);
+
+ if (!(ret1 & BDRV_BLOCK_DATA)) {
+ flags |= NBD_STATE_HOLE;
+ }
+ if (ret1 & BDRV_BLOCK_ZERO) {
+ flags |= NBD_STATE_ZERO;
+ }
+ if (ret2 == 1) {
+ flags |= NBD_STATE_LOCAL;
+ } else if (ret2 > 1) {
+ flags |= NBD_STATE_BACKING;
+ }
+ if (nbd_extent_array_add(ea, num, flags) < 0) {
+ return 0;
+ }
+
+ offset += num;
+ bytes -= num;
+ }
+
+ return 0;
+}
+
/*
* nbd_co_send_extents
*
@@ -2205,6 +2267,8 @@ static int nbd_co_send_block_status(NBDClient *client,
uint64_t handle,
if (context_id == NBD_META_ID_BASE_ALLOCATION) {
ret = blockstatus_to_extents(bs, offset, length, ea);
+ } else if (context_id == NBD_META_ID_JOINT_ALLOCATION) {
+ ret = blockjoint_to_extents(bs, offset, length, ea);
} else {
ret = blockalloc_to_extents(bs, offset, length, ea);
}
@@ -2574,6 +2638,19 @@ static coroutine_fn int nbd_handle_request(NBDClient
*client,
}
}
+ if (client->export_meta.joint_allocation) {
+ ret = nbd_co_send_block_status(client, request->handle,
+ blk_bs(exp->common.blk),
+ request->from,
request->len,
+ dont_fragment,
+ !--contexts_remaining,
+ NBD_META_ID_JOINT_ALLOCATION,
+ errp);
+ if (ret < 0) {
+ return ret;
+ }
+ }
+
for (i = 0; i < client->exp->nr_export_bitmaps; i++) {
if (!client->export_meta.bitmaps[i]) {
continue;
diff --git a/tests/qemu-iotests/tests/nbd-qemu-allocation.out
b/tests/qemu-iotests/tests/nbd-qemu-allocation.out
index c51022b2a38d..b9e469efc58e 100644
--- a/tests/qemu-iotests/tests/nbd-qemu-allocation.out
+++ b/tests/qemu-iotests/tests/nbd-qemu-allocation.out
@@ -21,9 +21,10 @@ exports available: 1
min block: 1
opt block: 4096
max block: 33554432
- available meta contexts: 2
+ available meta contexts: 3
base:allocation
qemu:allocation-depth
+ qemu:joint-allocation
[{ "start": 0, "length": 3145728, "depth": 0,
"zero": false, "data": true, "offset": OFFSET},
{ "start": 3145728, "length": 1048576, "depth":
0, "zero": true, "data": false, "offset": OFFSET}]
[{ "start": 0, "length": 1048576, "depth": 0,
"zero": true, "data": true, "offset": OFFSET},
--
2.31.1
Eric Blake
2021-Jun-09 21:31 UTC
[Libguestfs] [RFC libnbd PATCH] info: Add support for new qemu:joint-allocation
Qemu is adding qemu:joint-allocation as a single context combining the
two bits of base:allocation and a compression of qemu:allocation-depth
into two bits [1]. Decoding the bits makes it easier for humans to
see the result of that context.
[1] https://lists.gnu.org/archive/html/qemu-devel/2021-06/msg02446.html
---
Obviously, this libnbd patch should only go in if the qemu RFC is
accepted favorably. With this patch applied, the example listed in my
qemu patch 2/2 commit message [2] becomes
$ ~/libnbd/run nbdinfo --map=qemu:joint-allocation nbd://localhost
0 65536 3 hole,zero,unallocated
65536 65536 4 allocated,local
131072 65536 7 hole,zero,local
196608 65536 3 hole,zero,unallocated
[2] https://lists.gnu.org/archive/html/qemu-devel/2021-06/msg02448.html
For what it's worth, you can also play with the qemu+libnbd patches at:
https://repo.or.cz/qemu/ericb.git/ master
https://repo.or.cz/libnbd/ericb.git/ master
(I sometimes rewind those branches, but they'll be stable for at least
a few days after this email)
info/map.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/info/map.c b/info/map.c
index ae6d4fe..21e8657 100644
--- a/info/map.c
+++ b/info/map.c
@@ -226,6 +226,27 @@ extent_description (const char *metacontext, uint32_t type)
return ret;
}
}
+ else if (strcmp (metacontext, "qemu:joint-allocation") == 0) {
+ /* Combo of base:allocation and stripped-down qemu:allocation-depth */
+ const char *base, *depth;
+ switch (type & 3) {
+ case 0: base = "allocated"; break;
+ case 1: base = "hole"; break;
+ case 2: base = "zero"; break;
+ case 3: base = "hole,zero"; break;
+ }
+ switch (type & 0xc) {
+ case 0: depth = "unallocated"; break;
+ case 4: depth = "local"; break;
+ case 8: depth = "backing"; break;
+ case 12: depth = "<unexpected depth>"; break;
+ }
+ if (asprintf (&ret, "%s,%s", base, depth) == -1) {
+ perror ("asprintf");
+ exit (EXIT_FAILURE);
+ }
+ return ret;
+ }
return NULL; /* Don't know - description field will be omitted. */
}
--
2.31.1