| Commit message (Collapse) | Author | Age | Files | Lines |
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When establishing a new connection on a disconnected device, the old
list of alt-servers was retained. This would lead to us connecting to
the wrong server, as the number of newly passed servers was used when
looping over the list of alt-servers to actually connect.
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Incoming requests from clients might actually be prefetch jobs from
another downstream proxy. Don't do prefetching for those, as this would
cascade upwars in the proxy chain (prefetch for a prefetch of a prefetch)
Incoming requests might also be background replication. Don't relay
those if we're not configured for background replication as well.
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This will send all (block) requests immediately at sometimes more
overhead, but slighly less delays. Since the outgoing connection on a
client is only used very lightly, this tradeoff should always make
sense.
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There is a race condition where we process the next request from the
same client faster than the OS will schedule the async prefetch job,
rendering it a NOOP in the best case (request ranges match) or fetching
redundant data from the upstream server (prefetch range is larger than
actual request by client). Make prefetching synchronous to prevent this
race condition.
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If you need daemon mode, run as root with --daemon, normal users can
then request devices to be connected using the same binary WITHOUT
havind the suid bit set on it.
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- Remove the ugly timeout hack that apparently isn't required after all.
- Set a few socket options that appear to make sense in out use case (no
linger, only one SYN retry, NODELAY).
- Adapt socket timeout in panic mode, in case we're on a very bad
connection.
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Remove superflous, reduntant or otherwise useless
information. Use space as separator instead of comma
for better readability and easier parsing in shell etc.
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Similar logic already exists in the fuse client:
Count how many times in a row a server was fastest when
measuring RTTs, and lower the switching threshold
more the higher the count gets.
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Convert dnbd3_host_t to struct sockaddr immediately when
adding alt servers, so we don't have to convert it every time
we establish a connection. Additionally we can now use %pISpc
in printf-like functions instead of having if/else constructs
whenever we want to print an address.
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This avoids automatically switching back right after adding
and switching to a server.
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This change prevents the dnbd3-client to print the help text twice if
the help parameter is submitted. In addition to that, correct exit codes
are set after the help text is printed and the program terminates.
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Formerly, the request that was about to be received was looked up in
the receive queue without removing it, then the request payload was
received from the socket while the lock was not being held, and finally,
the lock was required again and the request removed from the queue.
This is dangrous as another thread can concurrently take the request
from the queue while the receive thread reads the payload from the
socket, leading to a double-free by calling blk_mq_end_request twice.
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This change links the dnbd3-server with 'libatomic' to add support for
atomic operations not supported by hardware (especially 32-bit hardware
architectures, such as ARM). Thus the dnbd3-server can also run on a
Raspberry Pi 1 running Rasperry Pi OS.
Note that the dnbd3-server is still linked to the libatomic, even if the
hardware supports atomic operations. In this case, the compiler resolves
atomic operations and replaces them automatically with specific built-in
functions. This unnecessary linkage can be removed in the future if the
GCC supports an upcoming option called automatic linking of libatomic
(--enable-autolink-libatomic).
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Previously disconnect was protected against concurrent calls, but connect
wasn't. It was easy to crash the kernel when calling connect and
disconnect IOCTLs in a tight loop concurrently.
A global lock was introduced to make sure only one caller can change the
connection state at a time. dev->connection_lock needs to be aquired
when calling dnbd3_net_connect or _disconnect.
This atomic_t based locking mechanism should be turned into a mutex in a
next step, relying on mutex_trylock for cases where we don't have the
cmpxchg-schedule() loop.
Along the way it was noticed that the send/receive timeouts don't apply
to kernel_connect, which might have been the case in older 3.x kernel
versions. A crude workaround using nonblocking connect has been
introduced to emulate this, but a clean solution for this is welcomed.
Also, devices are now properly closed on module unload.
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This patch replaces the __VA_OPT__ varadic macro for the C preprocessor
with a builtin GCC extension for optional varadic arguments. Based on
this change, the dnbd3 Linux kernel module can be also built with GCC
7.5 on a fresh Ubuntu 18.04 with Linux kernel version 4.19.x.
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With this change, the dnbd3-client is able to display the selected
server (choosen by the Linux kernel module) after successful probing.
Therefore, the ioctl call OPEN returns the selected server host as
index of the specified dnbd3-server hosts after successful probing.
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This patch adds the feature to manually switch the dnbd3-server to a
specified server. The switching is implemented by the use of the ioctl
call SWITCH.
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This patch completes the changes from the last commit [1] and protects
in addition the read-only access to the alternative list of new servers.
Otherwise a race condition between ioctl ADD_SRV/REM_SRV (process
context) and dnbd3 discover thread would be possible since the
'new_servers_num' field is changed in both contexts.
[1] - DNBD3 commit db5a93a43fea2aa3c3bbaf8c48d238e60d834676
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This patch locks the protecting spinlock of the DNBD3 device's new
server list. Otherwise a race condition between ioctl ADD_SRV/REM_SRV
(process context) and dnbd3 discover thread would be possible.
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This patch changes the probing logic to select the first available
dnbd3-server submitted by the ioctl OPEN call. All other specified
dnbd3-servers are added to the alternative server list and do not have
to be available.
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The ioctl OPEN call for DNBD3 devices exposed by the dnbd3 Linux kernel
module, is extended with a fixed array of dnbd3 hosts. The fixed array
allows the dnbd3-client to submit host information (IP address and port)
of multiple dnbd3-servers. This information is used to probe all
submitted dnbd3-servers and add them to the alternative dnbd3-server
list. If at least one dnbd3-server is not reachable, the OPEN ioctl call
will abort with an error code.
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