similar to: [nbdkit PATCH] connections: Extract common export flag computation code

# HG changeset patch # User Carl-Daniel Hailfinger <Carl-Daniel.Hailfinger@inf.h-brs.de> # Date 1474903734 -7200 # Mon Sep 26 17:28:54 2016 +0200 # Node ID dbd1ea0a401cedcfa426097a289d852971b14f1e # Parent d7d5078d08c711032837dcac79a4450226ec2ce5 nbdkit: Fix flags in old-style connection diff -r d7d5078d08c7 -r dbd1ea0a401c src/connections.c --- a/src/connections.c Sun Sep 25 05:04:02

Experimental and only very lightly tested so far. Rich.

The upstream protocol recently promoted NBD_CMD_WRITE_ZEROES from experimental to a documented extension. Exposing support for this allows plugin writers to create sparse files when driven by a client that knows how to use the extension; meanwhile, even if a plugin does not support this extension, the server benefits from less network traffic from the client. Eric Blake (5): protocol: Support

For mainly historical reasons we tended to use int to store boolean values. However using bool is probably safer in some corner cases (eg. ?v == true? can fail badly if v is an int, but works for bool). bool was added in C99 so let's use it. --- server/internal.h | 16 +++++------ server/connections.c | 28 +++++++++--------- server/crypto.c | 4 +-- server/main.c | 67

While our plugin code always advertises WRITE_ZEROES on writable connections (because we can emulate .zero by calling .pwrite), and FUA support when .flush exists (because we can emulate the persistence by calling .flush), it is conceivable that a filter may want to explicitly avoid advertising particular bits. (More to the point, I plan on writing a 'nozero' filter that hides

The code handling the NBD protocol was located in the same file as the code handling connections, for not really any reason except historical. This is quite a large code movement which splits out the protocol code into four new files: server/protocol-handshake.c initial handshake server/protocol-handshake-newstyle.c " " (newstyle)

Introduce the concept of a backend. Currently the only type of backend is a plugin, and there can only be one of them. Instead of calling functions like ‘plugin_pwrite’ you call the backend method ‘backend->pwrite (backend, ...)’. The change is largely mechanical. I was able to remove ‘assert (dl)’ statements throughout since we can now prove they will never be called. Note this does not

Introduce the concept of a backend. Currently the only type of backend is a plugin, and there can only be one of them. Instead of calling functions like ‘plugin_pwrite’ you call the backend method ‘backend->pwrite (backend, ...)’. The change is largely mechanical. I was able to remove ‘assert (dl)’ statements throughout since we can now prove they will never be called. Note this does not

Introduce the concept of a backend. Currently the only type of backend is a plugin, and there can only be one of them. Instead of calling functions like ‘plugin_pwrite’ you call the backend method ‘backend->pwrite (backend, ...)’. The change is largely mechanical. I was able to remove ‘assert (dl)’ statements throughout since we can now prove they will never be called. Note this does not

v1 -> v2: - Fixed everything mentioned in the review. Rich.

These are a couple of patches in preparation for the Block Status implementation. While the patches (especially the second one) are very large they are really just elementary code motion. Rich.

Somewhat invasive but mostly mechanical change to how plugins are called. This patch is in preparation for adding a second backend subtype for filters. Rich.

I still need to add testsuite coverage. Perhaps it might be easier if I create a new '--filter=log logfile=foo' filter that produces a log of which commands a client sent, then compare the log using a known client that uses write_zeroes (qemu-io works well) both with and without --filter=nozero to prove that the change in advertisement changes the commands sent over the wire (that would

Similar to the previous patch in caching size, we want to avoid calling into the plugin more than once per connection on any of the flag determination callbacks. The following script demonstrates the speedup, where we avoid repeated calls into a slow can_fua. Pre-patch: $ cat script case "$1" in get_size) echo 1m;; can_fua) sleep 1; echo native;; can_write | can_zero |

--- src/connections.c | 233 +++++++++++++++++++++++++++++++++++++--------- src/protocol.h | 27 ++++-- 2 files changed, 209 insertions(+), 51 deletions(-) diff --git a/src/connections.c b/src/connections.c index ba6e91d..4e9b191 100644 --- a/src/connections.c +++ b/src/connections.c @@ -75,7 +75,9 @@ struct connection { void **handles; size_t nr_handles; + uint32_t cflags;

This conversion should be feature compatible with the standalone nbd code. Note that the use of libnbd makes the binary for this particular plugin fall under an LGPLv2+ license rather than BSD; but the source code in nbd.c remains BSD. A lot of code simply disappears, now that I'm no longer directly utilizing the NBD protocol files but relying on libnbd. Coordination between threads from

This conversion should be feature compatible with the standalone nbd code. Note that the use of libnbd makes the binary for this particular plugin fall under an LGPLv2+ license rather than BSD; but the source code in nbd.c remains BSD. A lot of code simply disappears, now that I'm no longer directly utilizing the NBD protocol files but relying on libnbd. Coordination between threads from

Since commit 86fdb48c6a5362d66865493d9d2172166f99722e we have stored the connection object in thread-local storage. In this very large, but mostly mechanical change we stop passing the connection pointer around everywhere, and instead use the value stored in thread-local storage. This assumes a 1-1 mapping between the connection and the current thread which is true in *most* places.

When we first used libnbd (nbdkit 1.14), it was brand new, so we left in the ability to build a limited nbd plugin without the use of libnbd for comparison. But now that libnbd has had more time under its belt, and we have learned that our nbd-standalone code is not getting much testing, it's time to follow through with our plan to finish off the old code, and now build the nbd plugin only

There's no substantial difference over v1, I simply fixed a few whitespace issues, moved one struct around and tidied up the comments. Rich.