ping
On 28.09.2017 10:06, Nikolay Shirokovskiy wrote:
> One of the usecases of iohelper is to read from pipe and write
> to file with O_DIRECT. As we read from pipe we can have partial
> read and then we fail to write this data because output file
> is open with O_DIRECT and buffer size is not aligned.
> ---
> src/util/iohelper.c | 16 ++++++++++++++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/src/util/iohelper.c b/src/util/iohelper.c
> index 5416d45..bb8a8dd 100644
> --- a/src/util/iohelper.c
> +++ b/src/util/iohelper.c
> @@ -109,9 +109,21 @@ runIO(const char *path, int fd, int oflags)
> while (1) {
> ssize_t got;
>
> - if ((got = read(fdin, buf, buflen)) < 0) {
> - if (errno == EINTR)
> + /* If we read with O_DIRECT from file we can't use saferead as
> + * it can lead to unaligned read after reading last bytes.
> + * If we write with O_DIRECT use should use saferead so that
> + * writes will be aligned.
> + * In other cases using saferead reduces number of syscalls.
> + */
> + if (fdin == fd && direct) {
> + if ((got = read(fdin, buf, buflen)) < 0 &&
> + errno == EINTR)
> continue;
> + } else {
> + got = saferead(fdin, buf, buflen);
> + }
> +
> + if (got < 0) {
> virReportSystemError(errno, _("Unable to read %s"), fdinname);
> goto cleanup;
> }
>
--
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