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[Qemu-block] [PULL 15/71] nbd: Use low-level QIOChannel API in nbd_read_
From: |
Kevin Wolf |
Subject: |
[Qemu-block] [PULL 15/71] nbd: Use low-level QIOChannel API in nbd_read_eof() |
Date: |
Mon, 25 Feb 2019 16:19:57 +0100 |
Instead of using the convenience wrapper qio_channel_read_all_eof(), use
the lower level QIOChannel API. This means duplicating some code, but
we'll need this because this coroutine yield is special: We want it to
be interruptible so that nbd_client_attach_aio_context() can correctly
reenter the coroutine.
This moves the bdrv_dec/inc_in_flight() pair into nbd_read_eof(), so
that connection_co will always sit in this exact qio_channel_yield()
call when bdrv_drain() returns.
Signed-off-by: Kevin Wolf <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
---
include/block/nbd.h | 4 ++--
block/nbd-client.c | 8 +-------
nbd/client.c | 46 ++++++++++++++++++++++++++++++++++++---------
3 files changed, 40 insertions(+), 18 deletions(-)
diff --git a/include/block/nbd.h b/include/block/nbd.h
index cad975e00c..c6ef1ef42e 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -300,8 +300,8 @@ int nbd_receive_export_list(QIOChannel *ioc,
QCryptoTLSCreds *tlscreds,
int nbd_init(int fd, QIOChannelSocket *sioc, NBDExportInfo *info,
Error **errp);
int nbd_send_request(QIOChannel *ioc, NBDRequest *request);
-int coroutine_fn nbd_receive_reply(QIOChannel *ioc, NBDReply *reply,
- Error **errp);
+int coroutine_fn nbd_receive_reply(BlockDriverState *bs, QIOChannel *ioc,
+ NBDReply *reply, Error **errp);
int nbd_client(int fd);
int nbd_disconnect(int fd);
int nbd_errno_to_system_errno(int err);
diff --git a/block/nbd-client.c b/block/nbd-client.c
index 5ce4aa9520..60f38f0320 100644
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -84,15 +84,9 @@ static coroutine_fn void nbd_connection_entry(void *opaque)
*
* Therefore we keep an additional in_flight reference all the time and
* only drop it temporarily here.
- *
- * FIXME This is not safe because the QIOChannel could wake up the
- * coroutine for a second time; it is not prepared for coroutine
- * resumption from external code.
*/
- bdrv_dec_in_flight(s->bs);
assert(s->reply.handle == 0);
- ret = nbd_receive_reply(s->ioc, &s->reply, &local_err);
- bdrv_inc_in_flight(s->bs);
+ ret = nbd_receive_reply(s->bs, s->ioc, &s->reply, &local_err);
if (local_err) {
trace_nbd_read_reply_entry_fail(ret, error_get_pretty(local_err));
diff --git a/nbd/client.c b/nbd/client.c
index 28d174c0f3..de7da48246 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -1394,30 +1394,58 @@ static int
nbd_receive_structured_reply_chunk(QIOChannel *ioc,
* negative errno on failure (errp is set)
*/
static inline int coroutine_fn
-nbd_read_eof(QIOChannel *ioc, void *buffer, size_t size, Error **errp)
+nbd_read_eof(BlockDriverState *bs, QIOChannel *ioc, void *buffer, size_t size,
+ Error **errp)
{
- int ret;
+ bool partial = false;
assert(size);
- ret = qio_channel_read_all_eof(ioc, buffer, size, errp);
- if (ret < 0) {
- ret = -EIO;
+ while (size > 0) {
+ struct iovec iov = { .iov_base = buffer, .iov_len = size };
+ ssize_t len;
+
+ len = qio_channel_readv(ioc, &iov, 1, errp);
+ if (len == QIO_CHANNEL_ERR_BLOCK) {
+ bdrv_dec_in_flight(bs);
+ qio_channel_yield(ioc, G_IO_IN);
+ bdrv_inc_in_flight(bs);
+ continue;
+ } else if (len < 0) {
+ return -EIO;
+ } else if (len == 0) {
+ if (partial) {
+ error_setg(errp,
+ "Unexpected end-of-file before all bytes were
read");
+ return -EIO;
+ } else {
+ return 0;
+ }
+ }
+
+ partial = true;
+ size -= len;
+ buffer = (uint8_t*) buffer + len;
}
- return ret;
+ return 1;
}
/* nbd_receive_reply
+ *
+ * Decreases bs->in_flight while waiting for a new reply. This yield is where
+ * we wait indefinitely and the coroutine must be able to be safely reentered
+ * for nbd_client_attach_aio_context().
+ *
* Returns 1 on success
* 0 on eof, when no data was read (errp is not set)
* negative errno on failure (errp is set)
*/
-int coroutine_fn nbd_receive_reply(QIOChannel *ioc, NBDReply *reply,
- Error **errp)
+int coroutine_fn nbd_receive_reply(BlockDriverState *bs, QIOChannel *ioc,
+ NBDReply *reply, Error **errp)
{
int ret;
const char *type;
- ret = nbd_read_eof(ioc, &reply->magic, sizeof(reply->magic), errp);
+ ret = nbd_read_eof(bs, ioc, &reply->magic, sizeof(reply->magic), errp);
if (ret <= 0) {
return ret;
}
--
2.20.1
- [Qemu-block] [PULL 09/71] block-backend: Make blk_inc/dec_in_flight public, (continued)
- [Qemu-block] [PULL 09/71] block-backend: Make blk_inc/dec_in_flight public, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 10/71] virtio-blk: Increase in_flight for request restart BH, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 11/71] nbd: Restrict connection_co reentrance, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 12/71] io: Make qio_channel_yield() interruptible, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 13/71] io: Remove redundant read/write_coroutine assignments, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 14/71] nbd: Move nbd_read_eof() to nbd/client.c, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 18/71] block: Fix AioContext switch for drained node, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 20/71] block: Use normal drain for bdrv_set_aio_context(), Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 16/71] nbd: Increase bs->in_flight during AioContext switch, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 17/71] block: Don't poll in bdrv_set_aio_context(), Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 15/71] nbd: Use low-level QIOChannel API in nbd_read_eof(),
Kevin Wolf <=
- [Qemu-block] [PULL 19/71] test-bdrv-drain: AioContext switch in drained section, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 21/71] aio-posix: Assert that aio_poll() is always called in home thread, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 22/71] block: improve should_update_child, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 23/71] block: fix bdrv_check_perm for non-tree subgraph, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 24/71] tests: add test-bdrv-graph-mod, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 25/71] qcow2: Assert that L2 table offsets fit in the L1 table, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 32/71] iotests.py: Add filter_imgfmt(), Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 29/71] block: Skip implicit nodes for filename info, Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 36/71] block: bdrv_get_full_backing_filename_from_...'s ret. val., Kevin Wolf, 2019/02/25
- [Qemu-block] [PULL 38/71] block: Add bdrv_make_absolute_filename(), Kevin Wolf, 2019/02/25