From 75d34eb98ca0bb2f49d607fcaefd9c482e56b15d Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Sat, 30 Mar 2019 11:53:49 -0500 Subject: [PATCH] nbd/client: Trace server noncompliance on structured reads Just as we recently added a trace for a server sending block status that doesn't match the server's advertised minimum block alignment, let's do the same for read chunks. But since qemu 3.1 is such a server (because it advertised 512-byte alignment, but when serving a file that ends in data but is not sector-aligned, NBD_CMD_READ would detect a mid-sector change between data and hole at EOF and the resulting read chunks are unaligned), we don't want to change our behavior of otherwise tolerating unaligned reads. Note that even though we fixed the server for 4.0 to advertise an actual block alignment (which gets rid of the unaligned reads at EOF for posix files), we can still trigger it via other means: $ qemu-nbd --image-opts driver=blkdebug,align=512,image.driver=file,image.filename=/path/to/non-aligned-file Arguably, that is a bug in the blkdebug block status function, for leaking a block status that is not aligned. It may also be possible to observe issues with a backing layer with smaller alignment than the active layer, although so far I have been unable to write a reliable iotest for that scenario. Signed-off-by: Eric Blake Message-Id: <20190330165349.32256-1-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy --- block/nbd-client.c | 12 ++++++++++-- block/trace-events | 1 + 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/block/nbd-client.c b/block/nbd-client.c index 409c2171bc..790ecc1ee1 100644 --- a/block/nbd-client.c +++ b/block/nbd-client.c @@ -211,7 +211,8 @@ static inline uint64_t payload_advance64(uint8_t **payload) return ldq_be_p(*payload - 8); } -static int nbd_parse_offset_hole_payload(NBDStructuredReplyChunk *chunk, +static int nbd_parse_offset_hole_payload(NBDClientSession *client, + NBDStructuredReplyChunk *chunk, uint8_t *payload, uint64_t orig_offset, QEMUIOVector *qiov, Error **errp) { @@ -233,6 +234,10 @@ static int nbd_parse_offset_hole_payload(NBDStructuredReplyChunk *chunk, " region"); return -EINVAL; } + if (client->info.min_block && + !QEMU_IS_ALIGNED(hole_size, client->info.min_block)) { + trace_nbd_structured_read_compliance("hole"); + } qemu_iovec_memset(qiov, offset - orig_offset, 0, hole_size); @@ -390,6 +395,9 @@ static int nbd_co_receive_offset_data_payload(NBDClientSession *s, " region"); return -EINVAL; } + if (s->info.min_block && !QEMU_IS_ALIGNED(data_size, s->info.min_block)) { + trace_nbd_structured_read_compliance("data"); + } qemu_iovec_init(&sub_qiov, qiov->niov); qemu_iovec_concat(&sub_qiov, qiov, offset - orig_offset, data_size); @@ -712,7 +720,7 @@ static int nbd_co_receive_cmdread_reply(NBDClientSession *s, uint64_t handle, * in qiov */ break; case NBD_REPLY_TYPE_OFFSET_HOLE: - ret = nbd_parse_offset_hole_payload(&reply.structured, payload, + ret = nbd_parse_offset_hole_payload(s, &reply.structured, payload, offset, qiov, &local_err); if (ret < 0) { s->quit = true; diff --git a/block/trace-events b/block/trace-events index debb25c0ac..7335a42540 100644 --- a/block/trace-events +++ b/block/trace-events @@ -158,6 +158,7 @@ iscsi_xcopy(void *src_lun, uint64_t src_off, void *dst_lun, uint64_t dst_off, ui # nbd-client.c nbd_parse_blockstatus_compliance(const char *err) "ignoring extra data from non-compliant server: %s" +nbd_structured_read_compliance(const char *type) "server sent non-compliant unaligned read %s chunk" nbd_read_reply_entry_fail(int ret, const char *err) "ret = %d, err: %s" nbd_co_request_fail(uint64_t from, uint32_t len, uint64_t handle, uint16_t flags, uint16_t type, const char *name, int ret, const char *err) "Request failed { .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64 ", .flags = 0x%" PRIx16 ", .type = %" PRIu16 " (%s) } ret = %d, err: %s"