From 2178a569be16b18f04ed854d24fd2281b6a429c5 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Tue, 2 Apr 2019 22:05:20 -0500 Subject: [PATCH 1/4] nbd/server: Fix blockstatus trace Don't increment remaining_bytes until we know that we will actually be including the current block status extent in the reply; otherwise, the value traced will include a bytes value that is oversized by the length of the next block status extent which did not get sent because it instead ended the loop. Fixes: fb7afc79 Signed-off-by: Eric Blake Message-Id: <20190403030526.12258-2-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy --- nbd/server.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/nbd/server.c b/nbd/server.c index 218a2aa5e6..1b8c861989 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -1880,17 +1880,12 @@ static int blockstatus_to_extents(BlockDriverState *bs, uint64_t offset, flags = (ret & BDRV_BLOCK_ALLOCATED ? 0 : NBD_STATE_HOLE) | (ret & BDRV_BLOCK_ZERO ? NBD_STATE_ZERO : 0); - offset += num; - remaining_bytes -= num; if (first_extent) { extent->flags = flags; extent->length = num; first_extent = false; - continue; - } - - if (flags == extent->flags) { + } else if (flags == extent->flags) { /* extend current extent */ extent->length += num; } else { @@ -1903,6 +1898,8 @@ static int blockstatus_to_extents(BlockDriverState *bs, uint64_t offset, extent->flags = flags; extent->length = num; } + offset += num; + remaining_bytes -= num; } extents_end = extent + 1; From 6e280648d21d8c0aa8a101b62d0732cd1e608743 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Tue, 2 Apr 2019 22:05:21 -0500 Subject: [PATCH 2/4] nbd/server: Trace client noncompliance on unaligned requests We've recently added traces for clients to flag server non-compliance; let's do the same for servers to flag client non-compliance. According to the spec, if the client requests NBD_INFO_BLOCK_SIZE, it is promising to send all requests aligned to those boundaries. Of course, if the client does not request NBD_INFO_BLOCK_SIZE, then it made no promises so we shouldn't flag anything; and because we are willing to handle clients that made no promises (the spec allows us to use NBD_REP_ERR_BLOCK_SIZE_REQD if we had been unwilling), we already have to handle unaligned requests (which the block layer already does on our behalf). So even though the spec allows us to return EINVAL for clients that promised to behave, it's easier to always answer unaligned requests. Still, flagging non-compliance can be useful in debugging a client that is trying to be maximally portable. Qemu as client used to have one spot where it sent non-compliant requests: if the server sends an unaligned reply to NBD_CMD_BLOCK_STATUS, and the client was iterating over the entire disk, the next request would start at that unaligned point; this was fixed in commit a39286dd when the client was taught to work around server non-compliance; but is equally fixed if the server is patched to not send unaligned replies in the first place (yes, qemu 4.0 as server still has few such bugs, although they will be patched in 4.1). Fortunately, I did not find any more spots where qemu as client was non-compliant. I was able to test the patch by using the following hack to convince qemu-io to run various unaligned commands, coupled with serving 512-byte alignment by intentionally omitting '-f raw' on the server while viewing server traces. | diff --git i/nbd/client.c w/nbd/client.c | index 427980bdd22..1858b2aac35 100644 | --- i/nbd/client.c | +++ w/nbd/client.c | @@ -449,6 +449,7 @@ static int nbd_opt_info_or_go(QIOChannel *ioc, uint32_t opt, | nbd_send_opt_abort(ioc); | return -1; | } | + info->min_block = 1;//hack | if (!is_power_of_2(info->min_block)) { | error_setg(errp, "server minimum block size %" PRIu32 | " is not a power of two", info->min_block); Signed-off-by: Eric Blake Message-Id: <20190403030526.12258-3-eblake@redhat.com> [eblake: address minor review nits] Reviewed-by: Vladimir Sementsov-Ogievskiy --- nbd/server.c | 17 ++++++++++++++++- nbd/trace-events | 1 + 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/nbd/server.c b/nbd/server.c index 1b8c861989..1c4c5474ad 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -124,6 +124,8 @@ struct NBDClient { int nb_requests; bool closing; + uint32_t check_align; /* If non-zero, check for aligned client requests */ + bool structured_reply; NBDExportMetaContexts export_meta; @@ -533,6 +535,7 @@ static int nbd_negotiate_handle_info(NBDClient *client, uint16_t myflags, bool blocksize = false; uint32_t sizes[3]; char buf[sizeof(uint64_t) + sizeof(uint16_t)]; + uint32_t check_align = 0; /* Client sends: 4 bytes: L, name length (can be 0) @@ -609,7 +612,7 @@ static int nbd_negotiate_handle_info(NBDClient *client, uint16_t myflags, * whether this is OPT_INFO or OPT_GO. */ /* minimum - 1 for back-compat, or actual if client will obey it. */ if (client->opt == NBD_OPT_INFO || blocksize) { - sizes[0] = blk_get_request_alignment(exp->blk); + check_align = sizes[0] = blk_get_request_alignment(exp->blk); } else { sizes[0] = 1; } @@ -660,6 +663,7 @@ static int nbd_negotiate_handle_info(NBDClient *client, uint16_t myflags, if (client->opt == NBD_OPT_GO) { client->exp = exp; + client->check_align = check_align; QTAILQ_INSERT_TAIL(&client->exp->clients, client, next); nbd_export_get(client->exp); nbd_check_meta_export(client); @@ -2126,6 +2130,17 @@ static int nbd_co_receive_request(NBDRequestData *req, NBDRequest *request, return (request->type == NBD_CMD_WRITE || request->type == NBD_CMD_WRITE_ZEROES) ? -ENOSPC : -EINVAL; } + if (client->check_align && !QEMU_IS_ALIGNED(request->from | request->len, + client->check_align)) { + /* + * The block layer gracefully handles unaligned requests, but + * it's still worth tracing client non-compliance + */ + trace_nbd_co_receive_align_compliance(nbd_cmd_lookup(request->type), + request->from, + request->len, + client->check_align); + } valid_flags = NBD_CMD_FLAG_FUA; if (request->type == NBD_CMD_READ && client->structured_reply) { valid_flags |= NBD_CMD_FLAG_DF; diff --git a/nbd/trace-events b/nbd/trace-events index a6cca8fdf8..7ab6b3788c 100644 --- a/nbd/trace-events +++ b/nbd/trace-events @@ -71,4 +71,5 @@ nbd_co_send_extents(uint64_t handle, unsigned int extents, uint32_t id, uint64_t nbd_co_send_structured_error(uint64_t handle, int err, const char *errname, const char *msg) "Send structured error reply: handle = %" PRIu64 ", error = %d (%s), msg = '%s'" nbd_co_receive_request_decode_type(uint64_t handle, uint16_t type, const char *name) "Decoding type: handle = %" PRIu64 ", type = %" PRIu16 " (%s)" nbd_co_receive_request_payload_received(uint64_t handle, uint32_t len) "Payload received: handle = %" PRIu64 ", len = %" PRIu32 +nbd_co_receive_align_compliance(const char *op, uint64_t from, uint32_t len, uint32_t align) "client sent non-compliant unaligned %s request: from=0x%" PRIx64 ", len=0x%" PRIx32 ", align=0x%" PRIx32 nbd_trip(void) "Reading request" From 099fbcd65c2064a4ba8251e749bf600055027759 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Tue, 2 Apr 2019 22:05:22 -0500 Subject: [PATCH 3/4] nbd/server: Don't fail NBD_OPT_INFO for byte-aligned sources In commit 0c1d50bd, I added a couple of TODO comments about whether we consult bl.request_alignment when responding to NBD_OPT_INFO. At the time, qemu as server was hard-coding an advertised alignment of 512 to clients that promised to obey constraints, and there was no function for getting at a device's preferred alignment. But in hindsight, advertising 512 when the block device prefers 1 caused other compliance problems, and commit b0245d64 changed one of the two TODO comments to advertise a more accurate alignment. Time to fix the other TODO. Doesn't really impact qemu as client (our normal client doesn't use NBD_OPT_INFO, and qemu-nbd --list promises to obey block sizes), but it might prove useful to other clients. Fixes: b0245d64 Signed-off-by: Eric Blake Message-Id: <20190403030526.12258-4-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy --- nbd/server.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/nbd/server.c b/nbd/server.c index 1c4c5474ad..e21bd501dc 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -643,11 +643,14 @@ static int nbd_negotiate_handle_info(NBDClient *client, uint16_t myflags, return rc; } - /* If the client is just asking for NBD_OPT_INFO, but forgot to - * request block sizes, return an error. - * TODO: consult blk_bs(blk)->request_align, and only error if it - * is not 1? */ - if (client->opt == NBD_OPT_INFO && !blocksize) { + /* + * If the client is just asking for NBD_OPT_INFO, but forgot to + * request block sizes in a situation that would impact + * performance, then return an error. But for NBD_OPT_GO, we + * tolerate all clients, regardless of alignments. + */ + if (client->opt == NBD_OPT_INFO && !blocksize && + blk_get_request_alignment(exp->blk) > 1) { return nbd_negotiate_send_rep_err(client, NBD_REP_ERR_BLOCK_SIZE_REQD, errp, From e53f88df77e70350b0eda92a2e5e39f67792008f Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 4 Apr 2019 09:52:26 -0500 Subject: [PATCH 4/4] nbd/client: Fix error message for server with unusable sizing Add a missing space to the error message used when giving up on a server that insists on an alignment which renders the last few bytes of the export unreadable. Fixes: 3add3ab78 Signed-off-by: Eric Blake Message-Id: <20190404145226.32649-1-eblake@redhat.com> Reviewed-by: Kevin Wolf --- nbd/client.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/nbd/client.c b/nbd/client.c index 427980bdd2..4de30630c7 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -428,7 +428,7 @@ static int nbd_opt_info_or_go(QIOChannel *ioc, uint32_t opt, } if (info->min_block && !QEMU_IS_ALIGNED(info->size, info->min_block)) { - error_setg(errp, "export size %" PRIu64 "is not multiple of " + error_setg(errp, "export size %" PRIu64 " is not multiple of " "minimum block size %" PRIu32, info->size, info->min_block); nbd_send_opt_abort(ioc);