| Message ID | 20180222155627.1800948-1-arnd@arndb.de |
|---|---|
| State | New |
| Headers | show |
| Series | dm-bufio: avoid false-positive Wmaybe-uninitialized warning | expand |
On Thu, Feb 22 2018 at 10:56am -0500, Arnd Bergmann <arnd@arndb.de> wrote: > gcc-6.3 and earlier show a new warning after a seemingly unrelated change > to the arm64 PAGE_KERNEL definition: > > In file included from drivers/md/dm-bufio.c:14:0: > drivers/md/dm-bufio.c: In function 'alloc_buffer': > include/linux/sched/mm.h:182:56: warning: 'noio_flag' may be used uninitialized in this function [-Wmaybe-uninitialized] > current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags; > ^ > > The same warning happened earlier on linux-3.18 for MIPS and I did a > workaround for that, but now it's come back. > > gcc-7 and newer are apparently smart enough to figure this out, and > other architectures don't show it, so the best I could come up with is > to rework the caller slightly in a way that makes it obvious enough to > all arm64 compilers what is happening here. > > Fixes: 41acec624087 ("arm64: kpti: Make use of nG dependent on arm64_kernel_unmapped_at_el0()") > Link: https://patchwork.kernel.org/patch/9692829/ > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > drivers/md/dm-bufio.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c > index 414c9af54ded..e7ad6fc6a5ea 100644 > --- a/drivers/md/dm-bufio.c > +++ b/drivers/md/dm-bufio.c > @@ -413,13 +413,13 @@ static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask, > * as if GFP_NOIO was specified. > */ > > - if (gfp_mask & __GFP_NORETRY) > + if (gfp_mask & __GFP_NORETRY) { > noio_flag = memalloc_noio_save(); > - > - ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); > - > - if (gfp_mask & __GFP_NORETRY) > + ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); > memalloc_noio_restore(noio_flag); > + } else { > + ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); > + } > > return ptr; > } Mikulas already sent a fix for this: https://patchwork.kernel.org/patch/10211631/ But I like yours a bit better, though I'll likely move the declaration of 'noio_flag' temporary inside the conditional. Anyway, I'll get this fixed up shortly, thanks. Mike
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c index 414c9af54ded..e7ad6fc6a5ea 100644 --- a/drivers/md/dm-bufio.c +++ b/drivers/md/dm-bufio.c @@ -413,13 +413,13 @@ static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask, * as if GFP_NOIO was specified. */ - if (gfp_mask & __GFP_NORETRY) + if (gfp_mask & __GFP_NORETRY) { noio_flag = memalloc_noio_save(); - - ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); - - if (gfp_mask & __GFP_NORETRY) + ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); memalloc_noio_restore(noio_flag); + } else { + ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); + } return ptr; }
gcc-6.3 and earlier show a new warning after a seemingly unrelated change to the arm64 PAGE_KERNEL definition: In file included from drivers/md/dm-bufio.c:14:0: drivers/md/dm-bufio.c: In function 'alloc_buffer': include/linux/sched/mm.h:182:56: warning: 'noio_flag' may be used uninitialized in this function [-Wmaybe-uninitialized] current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags; ^ The same warning happened earlier on linux-3.18 for MIPS and I did a workaround for that, but now it's come back. gcc-7 and newer are apparently smart enough to figure this out, and other architectures don't show it, so the best I could come up with is to rework the caller slightly in a way that makes it obvious enough to all arm64 compilers what is happening here. Fixes: 41acec624087 ("arm64: kpti: Make use of nG dependent on arm64_kernel_unmapped_at_el0()") Link: https://patchwork.kernel.org/patch/9692829/ Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- drivers/md/dm-bufio.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) -- 2.9.0