By adding a 'write_ready' interface following the lines of the existing
'read_ready', VFS plugins become able to propagate the (de-)saturation
of I/O buffers to the VFS user. This information is important when using
a non-blocking file descriptor for writing into a TCP socket. Once the
application observes EAGAIN, it expects a subsequent 'select' call to
return as soon as new I/O buffer space becomes available.
Before this patch, the select call would always return under this
condition, causing an unnecessarily busy write loop.
Issue #4697
This patch removes the 'Insufficient_buffer' exception by returning the
WRITE_ERR_WOULD_BLOCK result value instead. It also eliminates the
superfluous WRITE_ERR_AGAIN and WRITE_ERR_INTERRUPT codes.
Issue #4697
This patch facilitates the batching of I/O operations in the VFS library
by replacing the implicit wakeup of remote peer (via the traditional
packet-stream interface like 'submit_packet') by explicit wakeup
signalling.
The wakeup signalling is triggered not before the VFS user settles down.
E.g., for libc-based applications, this is the case if the libc goes
idle, waiting for external I/O.
In the case of a busy writer to a non-blocking file descriptor or socket
(e.g., lighttpd), the remote peers are woken up once a write operation
yields an out-count of 0.
The deferring of wakeup signals is accommodated by the new 'Remote_io'
mechanism (vfs/remote_io.h) that is designated to be used by all VFS
plugins that interact with asynchronous Genode services for I/O.
Issue #4697
With the increase of MAXPHYS, the rump kernel requests a contiguous
allocation of 2101248 bytes, which exceeds the allocator's block size of
2 MiB.
Error: backend allocator: Unable to allocate memory (size: 2101248 align: 12)
The patch avoids this corner case by increasing the allocator's block
size to 4 MiB.
Fixes#4613
Instead of having a generic "virt_qemu" board use "virt_qemu_<arch>" in
order to have a clean distinction between boards. Current supported
boards are "virt_qemu_arm_v7a", "virt_qemu_arm_v8a", and
"virt_qemu_riscv".
issue #4034
This patch fixes a potential data corruption issue that could occur when
issuing large I/O requests to vfs/rump, which don't fit into the default
block I/O buffer of 128 KiB. Note that we haven't observed the problem
in practice (Sculpt hosts vfs/rump in a dedicated vfs server, which
fragments requests) but spotted the issue while reviewing the code. We
could trigger problem by explicitly changing the I/O buffer size to 32
KiB.
Issue #4474
As it stands, the implementation requires minimal reflection measures to
implement correct cleanup procedure. static_cast<> cannot be used as it
does not implement runtime type casting as dynamic_cast<> does.
This patch replaces the direct interaction with the packet stream of
the block session by the use of the 'Block::Connection::Job' API,
removing the reliance on blocking packet-stream semantics.
Since I/O signals can now occur during 'Backend::submit', the patch
conditions the periodic calls of 'rump_sys_sync' by taking the backend
state into account.
Issue #4390
This patch changes the 'Allocator' interface to the use of 'Attempt'
return values instead of using exceptions for propagating errors.
To largely uphold compatibility with components using the original
exception-based interface - in particluar use cases where an 'Allocator'
is passed to the 'new' operator - the traditional 'alloc' is still
supported. But it existes merely as a wrapper around the new
'try_alloc'.
Issue #4324
