Re: [Libguestfs] [PATCH nbdkit 4/7] cache, cow: Use full pread/pwrite operations

On Wed, Aug 04, 2021 at 10:45:36AM +0200, Martin Kletzander wrote: > On Mon, Jul 26, 2021 at 06:28:57PM +0100, Richard W.M. Jones wrote: > >Although it probably cannot happen on Linux, POSIX allows pread/pwrite > >to return or write fewer bytes than requested. The cache and cow > >filters didn't handle this situation. Replace the raw > >pread(2)/pwrite(2) syscalls with alternate versions which can handle > >this.

> >+ssize_t > >+full_pwrite (int fd, const void *buf, size_t count, off_t offset) > >+{ > >+ ssize_t ret = 0, r; > >+ > >+ while (count > 0) { > >+ r = pwrite (fd, buf, count, offset); > >+ if (r == -1) return -1; > >+ ret += r; > >+ offset += r; > >+ count -= r; > >+ } > >+ > > Shouldn't these continue on EINTR? I'm not sure .. Eric? The documentation for read(2) says this so it seems likely: EINTR The call was interrupted by a signal before any data was read; see signal(7).