win: fs: fix `FILE_FLAG_NO_BUFFERING` for writes

On Windows, `fs__open()` maps `UV_FS_O_DIRECT` to
`FILE_FLAG_NO_BUFFERING`.

When `access` is only `FILE_GENERIC_READ` this succeeds, but when
`access` is `FILE_GENERIC_WRITE` this returns an error:

```
0x00000057, ERROR_INVALID_PARAMETER, The parameter is incorrect.
```

The reason is that `FILE_GENERIC_WRITE` includes `FILE_APPEND_DATA`,
but `FILE_APPEND_DATA` and `FILE_FLAG_NO_BUFFERING` are mutually
exclusive:

```
FILE_GENERIC_WRITE = STANDARD_RIGHTS_WRITE |
                     FILE_WRITE_DATA |
                     FILE_WRITE_ATTRIBUTES |
                     FILE_WRITE_EA |
                     FILE_APPEND_DATA |
                     SYNCHRONIZE
```

This incompatibility between access and attribute flags does not appear
to be documented by Microsoft for `FILE_FLAG_NO_BUFFERING` but it is
indirectly documented under [NtCreateFile](https://bit.ly/2rm5wRT):

```
FILE_NO_INTERMEDIATE_BUFFERING
The file cannot be cached or buffered in a driver's internal buffers.
This flag is incompatible with the DesiredAccess FILE_APPEND_DATA flag.
```

The solution is to remove `FILE_APPEND_DATA` from the access flags when
`FILE_FLAG_NO_BUFFERING` is set. Note that this does not prevent
appends, since `FILE_GENERIC_WRITE` also includes `FILE_WRITE_DATA`,
which in turn allows appends.

PR-URL: https://github.com/libuv/libuv/pull/2102
Reviewed-By: Bartosz Sosnowski <bartosz@janeasystems.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

0 files changed, 0 insertions, 0 deletions