From dbc7b01492371e4a54b92d2b6d968f9b863cc794 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Tue, 27 Oct 2020 00:05:55 -0500 Subject: nbd: Add 'qemu-nbd -A' to expose allocation depth Allow the server to expose an additional metacontext to be requested by savvy clients. qemu-nbd adds a new option -A to expose the qemu:allocation-depth metacontext through NBD_CMD_BLOCK_STATUS; this can also be set via QMP when using block-export-add. qemu as client is hacked into viewing the key aspects of this new context by abusing the already-experimental x-dirty-bitmap option to collapse all depths greater than 2, which results in a tri-state value visible in the output of 'qemu-img map --output=json' (yes, that means x-dirty-bitmap is now a bit of a misnomer, but I didn't feel like renaming it as it would introduce a needless break of back-compat, even though we make no compat guarantees with x- members): unallocated (depth 0) => "zero":false, "data":true local (depth 1) => "zero":false, "data":false backing (depth 2+) => "zero":true, "data":true libnbd as client is probably a nicer way to get at the information without having to decipher such hacks in qemu as client. ;) Signed-off-by: Eric Blake Message-Id: <20201027050556.269064-11-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy --- qemu-nbd.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'qemu-nbd.c') diff --git a/qemu-nbd.c b/qemu-nbd.c index 74e73a7465..75ced65030 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -100,6 +100,7 @@ static void usage(const char *name) "\n" "Exposing part of the image:\n" " -o, --offset=OFFSET offset into the image\n" +" -A, --allocation-depth expose the allocation depth\n" " -B, --bitmap=NAME expose a persistent dirty bitmap\n" "\n" "General purpose options:\n" @@ -524,7 +525,7 @@ int main(int argc, char **argv) char *device = NULL; QemuOpts *sn_opts = NULL; const char *sn_id_or_name = NULL; - const char *sopt = "hVb:o:p:rsnc:dvk:e:f:tl:x:T:D:B:L"; + const char *sopt = "hVb:o:p:rsnc:dvk:e:f:tl:x:T:D:AB:L"; struct option lopt[] = { { "help", no_argument, NULL, 'h' }, { "version", no_argument, NULL, 'V' }, @@ -533,6 +534,7 @@ int main(int argc, char **argv) { "socket", required_argument, NULL, 'k' }, { "offset", required_argument, NULL, 'o' }, { "read-only", no_argument, NULL, 'r' }, + { "allocation-depth", no_argument, NULL, 'A' }, { "bitmap", required_argument, NULL, 'B' }, { "connect", required_argument, NULL, 'c' }, { "disconnect", no_argument, NULL, 'd' }, @@ -575,6 +577,7 @@ int main(int argc, char **argv) const char *export_name = NULL; /* defaults to "" later for server mode */ const char *export_description = NULL; strList *bitmaps = NULL; + bool alloc_depth = false; const char *tlscredsid = NULL; bool imageOpts = false; bool writethrough = true; @@ -689,6 +692,9 @@ int main(int argc, char **argv) readonly = true; flags &= ~BDRV_O_RDWR; break; + case 'A': + alloc_depth = true; + break; case 'B': QAPI_LIST_PREPEND(bitmaps, g_strdup(optarg)); break; @@ -787,7 +793,7 @@ int main(int argc, char **argv) } if (export_name || export_description || dev_offset || device || disconnect || fmt || sn_id_or_name || bitmaps || - seen_aio || seen_discard || seen_cache) { + alloc_depth || seen_aio || seen_discard || seen_cache) { error_report("List mode is incompatible with per-device settings"); exit(EXIT_FAILURE); } @@ -1073,6 +1079,8 @@ int main(int argc, char **argv) .description = g_strdup(export_description), .has_bitmaps = !!bitmaps, .bitmaps = bitmaps, + .has_allocation_depth = alloc_depth, + .allocation_depth = alloc_depth, }, }; blk_exp_add(export_opts, &error_fatal); -- cgit v1.2.3