Re: [libvirt] [PATCH v2 1/3] virfile: Refactor safezero, introduce virFileFdPosixFallocate

On Mon, Aug 11, 2014 at 04:30:19PM -0400, John Ferlan wrote: > Currently the safezero() function uses build conditionals to choose either > the posix_fallocate() or mmap() with a fallback to safewrite() in order to > preallocate a file. > > This patch will modify the logic in order to allow fallbacks in the > event that posix_fallocate() or the ftruncate()and mmap() doesn't work > properly. The fallback will be to use the slow safewrite of zero filled > buffers to the file. Have you actually encountered failing of posix_fallocate() in the real world ? It is supposed to automatically fallback to the equivalent of writing zeros if the filesystem / kernel does not support it, so we should not have todo runtime fallback ourselves. The existance of fallback is the main distinction between the posix_fallocate() and fallocate() system calls.