Re: [libvirt RFCv4 04/20] runio: add arguments to extend use beyond just stdin and stdout

On 4/28/22 2:54 PM, Daniel P. Berrangé wrote: > On Wed, Apr 27, 2022 at 11:13:23PM +0200, Claudio Fontana wrote: >> add arguments to runio to allow read/write from/to arbitrary >> file descriptors, as opposed to just stdin and stdout. >> >> Signed-off-by: Claudio Fontana <cfontana(a)suse.de&gt; >> --- >> src/util/iohelper.c | 2 +- >> src/util/runio.c | 10 +++++----- >> src/util/runio.h | 17 ++++++++++++++++- >> 3 files changed, 22 insertions(+), 7 deletions(-) >> >> diff --git a/src/util/iohelper.c b/src/util/iohelper.c >> index 5a0098542e..93674c1e2f 100644 >> --- a/src/util/iohelper.c >> +++ b/src/util/iohelper.c >> @@ -96,7 +96,7 @@ main(int argc, char **argv) >> usage(EXIT_FAILURE); >> } >> >> - if (fd < 0 || runIO(path, fd, oflags) < 0) >> + if (fd < 0 || runIO(path, fd, oflags, STDIN_FILENO, STDOUT_FILENO) < 0) >> goto error; >> >> return 0; >> diff --git a/src/util/runio.c b/src/util/runio.c >> index a7b902af7e..f42acddae9 100644 >> --- a/src/util/runio.c >> +++ b/src/util/runio.c >> @@ -134,7 +134,7 @@ runIOCopy(const struct runIOParams p) >> >> >> off_t >> -runIO(const char *path, int fd, int oflags) >> +runIO(const char *path, int fd, int oflags, int in_fd, int out_fd) > > This is getting rather wierd as a signature. > > If O_RDONLY, then in_fd is ignored, 'fd' is input. > > If O_WRONLY, then out_fd is ignored, 'fd' is output > > What about instead simply : > > runIO(const char *srcpath, int srcfd, > const char *dstpath, int dstfd) > > so there's no read vs write distinction at all. maybe I am a bit confused/tired, but I don't see how this would work, which side one of those is the disk, where we want to check for S_ISBLK and O_DIRECT, and buffer accordingly?