On Thu, Apr 4, 2019 at 4:09 PM Christian Brauner <christian@xxxxxxxxxx> wrote: > > On Wed, Apr 03, 2019 at 07:08:47PM +0200, Matteo Croce wrote: > > On Wed, Apr 3, 2019 at 6:40 PM Matteo Croce <mcroce@xxxxxxxxxx> wrote: > > > > > > On Wed, Apr 3, 2019 at 5:51 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > > > > > > On Wed, Apr 03, 2019 at 05:24:26PM +0200, Matteo Croce wrote: > > > > > On Wed, Apr 3, 2019 at 4:02 PM Christian Brauner <christian@xxxxxxxxxx> wrote: > > > > > > Yeah, maybe but it still feels cleaner and more obvious to just add: > > > > > > > > > > > > static long long_zero; > > > > > > > > > > > > given that most callers actually seem to want an (unsigned) int. > > > > > > > > > > > > I don't have a strong opinion though so if others feel that it's just a > > > > > > waste of space consider it acked. > > > > > > > > > > > > > > > > Well, given that the value is zero, in this expectional case we could > > > > > avoid duplicating the symbol and save 4 bytes. > > > > > What the maintainers think? > > > > > > > > If we care about saving four bytes, we could just pass the address of > > > > ZERO_PAGE(0). > > > > > > That would work, work too, maybe it's a bit overkill. > > > int zero is always there and it's static, so enlarging it to long > > > should be a straightforward fix. > > > Obviously we can't do it for other numbers, but we can alias it just > > > for the zero case.. > > > > > > Regards, > > > > > > -- > > > Matteo Croce > > > per aspera ad upstream > > > > Anyway, I'm fine with both solutions, as I have other patches in the > > I think Matthew's idea gets us best of both worlds so I'd suggest to use > it and resend the patch. You likely want to Cc stable@xxxxxxxxxxxxxxx > since the original patch this fixes got backported by Greg quite a bit > since this was a rather long-standing issue. Please also Cc Andrew this > time since he's likely going to pick it up. > > Thanks for the patch! > Christian So you mean using page_address(ZERO_PAGE(0)) ? The idea is nice, but since struct ctl_table kern_table is declared as global variable, how can I assign it to the structure? GCC complains about 'initializer element is not constant', and ZERO_PAGE(0)->virtual only works if WANT_PAGE_VIRTUAL. Anyway, I'm preparing a treewide patch to move all "zero", "one" and "int_max" to three single, const variables in fs/proc/proc_sysctl.c as there are 200+ occourrences of them, so I'd rather keep this simple to have it easily backported to stable. -- Matteo Croce per aspera ad upstream
