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Revert "PROPOSAL libc: implement read and write by async_read and asy…
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…nc_write"

See
genodelabs#5302 (comment)
for a discussion of the proposal.

This reverts commit 4ed972c.
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@atopia
atopia committed Sep 19, 2024
1 parent dbc8847 commit 81cf113
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Showing 2 changed files with 49 additions and 40 deletions.
22 changes: 9 additions & 13 deletions repos/libports/src/lib/libc/internal/plugin.h
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Original file line number Diff line number Diff line change
Expand Up @@ -79,22 +79,18 @@ namespace Libc {
virtual bool supports_mmap();

/*
* Asynchronous I/O
* Asynchronous helper methods
*/
struct Async_result
{
bool complete;

/* value that would be returned by the corresponding read() etc. */
ssize_t return_status;

/* errno value that would be set by the corresponding read() etc. */
int error_status;
struct Async_read_state {
bool complete_read { false };
};
virtual bool async_read(File_descriptor *, void *, ::size_t, ::off_t, ssize_t &, int &, Async_read_state &);

virtual Async_result async_read(File_descriptor *, void *, ::size_t, ::off_t);

virtual Async_result async_write(File_descriptor *, const void *, ::size_t, ::off_t);
struct Async_write_state {
bool first_run { true };
size_t bytes_written { 0 };
};
virtual bool async_write(File_descriptor *, const void *, ::size_t, ::off_t, ssize_t &, int &, Async_write_state &);

/*
* Should be overwritten for plugins that require the Genode environment
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67 changes: 40 additions & 27 deletions repos/libports/src/lib/libc/vfs_plugin.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -946,37 +946,38 @@ ssize_t Libc::Vfs_plugin::read(File_descriptor *fd, void *buf,
}


Libc::Vfs_plugin::Async_result
Libc::Vfs_plugin::async_write(File_descriptor *fd,
void const *buf,
::size_t count,
::off_t offset)
bool Libc::Vfs_plugin::async_write(File_descriptor *fd,
void const *buf,
::size_t count,
::off_t offset,
ssize_t &retval,
int &result_errno,
Async_write_state &write_state)
{
using Result = Vfs::File_io_service::Write_result;

if ((fd->flags & O_ACCMODE) == O_RDONLY)
return { true, -1, EBADF };
if ((fd->flags & O_ACCMODE) == O_RDONLY) {
result_errno = EBADF;
retval = -1;
return true;
}

Vfs::Vfs_handle *handle = vfs_handle(fd);

Result out_result = Result::WRITE_OK;

size_t bytes_written = 0;
if (offset && write_state.first_run)
handle->seek(offset);

/* FIXME seek is not relevant for aio - thus implement in ::write only */
// if (offset && write_state.first_run)
// handle->seek(offset);
//
// write_state.first_run = false;
write_state.first_run = false;

if (fd->flags & O_NONBLOCK) {
Const_byte_range_ptr const src { (char const *)buf, count };

out_result = handle->fs().write(handle, src, bytes_written);
out_result = handle->fs().write(handle, src, write_state.bytes_written);

/* FIXME seek is not relevant for aio - thus implement in ::write only */
// if (out_result == Result::WRITE_OK)
// handle->advance_seek(write_state.bytes_written);
if (out_result == Result::WRITE_OK)
handle->advance_seek(write_state.bytes_written);
} else {
auto _fd_refers_to_continuous_file = [&]
{
Expand All @@ -1001,9 +1002,9 @@ Libc::Vfs_plugin::async_write(File_descriptor *fd,
::size_t partial_out_count = 0;

/* Subtract already written bytes from count */
::size_t remaining_count = count - bytes_written;
::size_t remaining_count = count - write_state.bytes_written;

Const_byte_range_ptr const src { (char const *)buf + bytes_written,
Const_byte_range_ptr const src { (char const *)buf + write_state.bytes_written,
remaining_count };

out_result = handle->fs().write(handle, src, partial_out_count);
Expand All @@ -1021,7 +1022,7 @@ Libc::Vfs_plugin::async_write(File_descriptor *fd,
bool const write_complete = (partial_out_count == remaining_count);

if (!write_complete) {
bool const continuous_file = (bytes_written || _fd_refers_to_continuous_file());
bool const continuous_file = (write_state.bytes_written || _fd_refers_to_continuous_file());

if (!continuous_file) {
warning("partial write on transactional file");
Expand All @@ -1030,7 +1031,7 @@ Libc::Vfs_plugin::async_write(File_descriptor *fd,
}
}

bytes_written += partial_out_count;
write_state.bytes_written += partial_out_count;

handle->advance_seek(partial_out_count);

Expand All @@ -1041,13 +1042,25 @@ Libc::Vfs_plugin::async_write(File_descriptor *fd,

switch (out_result) {
/* Not reached */
case Result::WRITE_ERR_WOULD_BLOCK: return { true, -1, EWOULDBLOCK };
case Result::WRITE_ERR_INVALID: return { true, -1, EINVAL };
case Result::WRITE_ERR_IO: return { true, -1, EIO };
case Result::WRITE_OK: return { true, -1, bytes_written };
case Result::WRITE_ERR_WOULD_BLOCK:
result_errno = EWOULDBLOCK;
retval = -1;
break;
case Result::WRITE_ERR_INVALID:
result_errno = EINVAL;
retval = -1;
break;
case Result::WRITE_ERR_IO:
result_errno = EIO;
retval = -1;
break;
case Result::WRITE_OK:
retval = write_state.bytes_written;
result_errno = 0;
break;
}
//
// return true;

return true;
}


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