Re: [PATCH v1 3/5] treewide: use get_random_u32() when possible
Andy Shevchenko <[email protected]>
| Newsgroups | org.kernel.vger.dccp,dev.linux.lists.drbd-dev,net.sourceforge.lists.linux-f2fs-devel,org.freedesktop.lists.dri-devel,org.infradead.lists.linux-arm-kernel,org.infradead.lists.linux-mtd,org.infradead.lists.linux-nvme,org.kernel.vger.ceph-devel,org.kernel.vger.dmaengine,org.kernel.vger.linux-block,org.kernel.vger.linux-crypto,org.kernel.vger.linux-doc,org.kernel.vger.linux-ext4,org.kernel.vger.linux-fbdev,org.kernel.vger.linux-fsdevel,org.kernel.vger.linux-hams,org.kernel.vger.linux-kernel,org.kernel.vger.linux-media,org.kernel.vger.linux-mmc,org.kernel.vger.linux-nfs,org.kernel.vger.linux-raid,org.kernel.vger.linux-rdma,org.kernel.vger.linux-scsi,org.kernel.vger.linux-sctp,org.kernel.vger.linux-usb,org.kernel.vger.linux-wireless,org.kernel.vger.linux-xfs,org.kernel.vger.lvs-devel,org.kernel.vger.netdev,org.kernel.vger.netfilter-devel,org.kernel.vger.target-devel,org.kvack.linux-mm,org.ozlabs.lists.linuxppc-dev |
|---|---|
| Message-ID | <[email protected]> |
On Thu, Oct 06, 2022 at 07:05:48AM -0600, Jason A. Donenfeld wrote: > On Thu, Oct 6, 2022 at 6:47 AM Jason Gunthorpe <[email protected]> wrote: > > On Wed, Oct 05, 2022 at 11:48:42PM +0200, Jason A. Donenfeld wrote: ... > > > - u32 isn = (prandom_u32() & ~7UL) - 1; > > > + u32 isn = (get_random_u32() & ~7UL) - 1; > > > > Maybe this wants to be written as > > > > (prandom_max(U32_MAX >> 7) << 7) | 7 > > ? > > Holy smokes. Yea I guess maybe? It doesn't exactly gain anything or > make the code clearer though, and is a little bit more magical than > I'd like on a first pass. Shouldn't the two first 7s to be 3s? ... > > > - psn = prandom_u32() & 0xffffff; > > > + psn = get_random_u32() & 0xffffff; > > > > prandom_max(0xffffff + 1) > > That'd work, but again it's not more clear. Authors here are going for > a 24-bit number, and masking seems like a clear way to express that. We have some 24-bit APIs (and 48-bit) already in kernel, why not to have get_random_u24() ? -- With Best Regards, Andy Shevchenko