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iohelper: use saferead if later write with O_DIRECT 

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.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
This commit is contained in:
Nikolay Shirokovskiy 2017-09-28 10:06:47 +03:00 committed by Jiri Denemark
parent 55ac6a5d44
commit 05021e727d
1 changed files with 14 additions and 2 deletions
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16
src/util/iohelper.c
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@ -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;
}