| Message ID | 20201001145608.GA10204@embeddedor (mailing list archive) |
|---|---|
| State | Deferred, archived |
| Headers | show |
| Series | [v2,next] x86/uv/time: Replace one-element array and save heap space | expand |
On Thu, 2020-10-01 at 09:56 -0500, Gustavo A. R. Silva wrote: > There is a regular need in the kernel to provide a way to declare having > a dynamically sized set of trailing elements in a structure. Kernel code > should always use “flexible array members”[1] for these cases. The older > style of one-element or zero-length arrays should no longer be used[2]. > > struct uv_rtc_timer_head contains a one-element array cpu[1]. > > Switch it to a flexible array and use the struct_size() helper to > calculate the allocation size. Also, save some heap space in the > process[3]. trivia: > diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c [] > @@ -148,9 +148,8 @@ static __init int uv_rtc_allocate_timers(void) > struct uv_rtc_timer_head *head = blade_info[bid]; > > if (!head) { > - head = kmalloc_node(sizeof(struct uv_rtc_timer_head) + > - (uv_blade_nr_possible_cpus(bid) * > - 2 * sizeof(u64)), > + head = kmalloc_node(struct_size(head, cpu, > + uv_blade_nr_possible_cpus(bid)), > GFP_KERNEL, nid); > if (!head) { > uv_rtc_deallocate_timers(); Maybe save the value of uv_blade_nr_possible_cpus(bid) to reduce duplication and make the sizeof_struct more readable? if (!head) { int ncpus = uv_blade_nr_possible_cpus(bid); head = kmalloc_node(struct_size(head, cpu, ncpus), GFP_KERNEL, nid); if (!head) { uv_rtc_deallocate_timers(); return -ENOMEM; } spin_lock_init(&head->lock); head->ncpus = ncpus; head->next_cpu = -1; blade_info[bid] = head; }
On Thu, Oct 01, 2020 at 09:56:08AM -0500, Gustavo A. R. Silva wrote: > There is a regular need in the kernel to provide a way to declare having > a dynamically sized set of trailing elements in a structure. Kernel code > should always use “flexible array members”[1] for these cases. The older > style of one-element or zero-length arrays should no longer be used[2]. I see this has already gone in, so I'm late. But for whatever it's worth, it's a good change. Thank you. Reviewed-by: Steve Wahl <steve.wahl@hpe.com> --> Steve wahl > struct uv_rtc_timer_head contains a one-element array cpu[1]. > > Switch it to a flexible array and use the struct_size() helper to > calculate the allocation size. Also, save some heap space in the > process[3]. > > [1] https://en.wikipedia.org/wiki/Flexible_array_member > [2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays > [3] https://lore.kernel.org/lkml/20200518190114.GA7757@embeddedor/ > > Reviewed-by: Kees Cook <keescook@chromium.org> > Build-tested-by: kernel test robot <lkp@intel.com> > Link: https://lore.kernel.org/lkml/5f75bc0a.rQcNS6620b2eA74S%25lkp@intel.com/ > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> > --- > Changes in v2: > - Modify changelog text (Thomas). > - Add Reviewed-by and Build-tested-by tags. > - Add a public link to the build-test results. > > arch/x86/platform/uv/uv_time.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c > index f82a1337a608..6c348c2d0def 100644 > --- a/arch/x86/platform/uv/uv_time.c > +++ b/arch/x86/platform/uv/uv_time.c > @@ -52,7 +52,7 @@ struct uv_rtc_timer_head { > struct { > int lcpu; /* systemwide logical cpu number */ > u64 expires; /* next timer expiration for this cpu */ > - } cpu[1]; > + } cpu[]; > }; > > /* > @@ -148,9 +148,8 @@ static __init int uv_rtc_allocate_timers(void) > struct uv_rtc_timer_head *head = blade_info[bid]; > > if (!head) { > - head = kmalloc_node(sizeof(struct uv_rtc_timer_head) + > - (uv_blade_nr_possible_cpus(bid) * > - 2 * sizeof(u64)), > + head = kmalloc_node(struct_size(head, cpu, > + uv_blade_nr_possible_cpus(bid)), > GFP_KERNEL, nid); > if (!head) { > uv_rtc_deallocate_timers(); > -- > 2.27.0 >
diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c index f82a1337a608..6c348c2d0def 100644 --- a/arch/x86/platform/uv/uv_time.c +++ b/arch/x86/platform/uv/uv_time.c @@ -52,7 +52,7 @@ struct uv_rtc_timer_head { struct { int lcpu; /* systemwide logical cpu number */ u64 expires; /* next timer expiration for this cpu */ - } cpu[1]; + } cpu[]; }; /* @@ -148,9 +148,8 @@ static __init int uv_rtc_allocate_timers(void) struct uv_rtc_timer_head *head = blade_info[bid]; if (!head) { - head = kmalloc_node(sizeof(struct uv_rtc_timer_head) + - (uv_blade_nr_possible_cpus(bid) * - 2 * sizeof(u64)), + head = kmalloc_node(struct_size(head, cpu, + uv_blade_nr_possible_cpus(bid)), GFP_KERNEL, nid); if (!head) { uv_rtc_deallocate_timers();