On Wed, Apr 10, 2013 at 04:15:07PM -0700, Andrew Morton wrote: > On Tue, 9 Apr 2013 21:39:24 -0500 Robin Holt <[email protected]> wrote: > > > Trying to run an application which was trying to put data into half > > of memory using shmget(), we found that having a shmall value below > > 8EiB-8TiB would prevent us from using anything more than 8TiB. By setting > > kernel.shmall greater that 8EiB-8TiB would make the job work. > > > > In the newseg() function, ns->shm_tot which, at 8TiB is INT_MAX. > > You have way too much memory. > > > ipc/shm.c: > > 458 static int newseg(struct ipc_namespace *ns, struct ipc_params *params) > > 459 { > > ... > > 465 int numpages = (size + PAGE_SIZE -1) >> PAGE_SHIFT; > > ... > > 474 if (ns->shm_tot + numpages > ns->shm_ctlall) > > 475 return -ENOSPC; > > > > ... > > > > --- a/include/linux/ipc_namespace.h > > +++ b/include/linux/ipc_namespace.h > > @@ -43,8 +43,8 @@ struct ipc_namespace { > > > > size_t shm_ctlmax; > > size_t shm_ctlall; > > + unsigned long shm_tot; > > int shm_ctlmni; > > - int shm_tot; > > /* > > * Defines whether IPC_RMID is forced for _all_ shm segments regardless > > * of shmctl() > > I reviewed everything for fallout from this and don't see any obvious > issues. > > I do wonder about the appropriateness of the unsigned long type. Most > (but by no means all) code in this area uses size_t, and the > above-quoted ns->shm_ctlall is size_t.
The only reason I went with unsigned long instead of size_t was most places in the kernel track stuff I recalled that was tracking stuff in pages used unsigned longs. Also, I found shm_tot field in shm_info structure was an unsigned long so this felt like a natural fit. I would happily changed to size_t. Whatever you feel is right. > And the above-quoted num_pages is `int'. Both the size and signedness > of `int' make no sense - what happens if the incoming ipc_params.u.size > is >2G? > > So I'll add this, and ask whether ipc_namespace.shm_tot should be size_t? > > --- a/ipc/shm.c~ipc-sysv-shared-memory-limited-to-8tib-fix > +++ a/ipc/shm.c > @@ -462,7 +462,7 @@ static int newseg(struct ipc_namespace * > size_t size = params->u.size; > int error; > struct shmid_kernel *shp; > - int numpages = (size + PAGE_SIZE -1) >> PAGE_SHIFT; > + size_t numpages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; I was holding off from that change only because I was asking for this to go to stable and this doubles the size of the patch. ;) > struct file * file; > char name[13]; > int id; > _ Thank you, Robin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
