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authorKees Cook <keescook@chromium.org>2020-04-06 20:07:51 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-04-07 10:43:41 -0700
commit27d80fa24326b7b33c8ee7527843776e5df808a7 (patch)
treeaba58ff81aff6d5c68eee6266218b1f4c8b67387 /mm/shmem.c
parent104049017b774036fa971722a202a17e6585a200 (diff)
mm/shmem.c: distribute switch variables for initialization
Variables declared in a switch statement before any case statements cannot be automatically initialized with compiler instrumentation (as they are not part of any execution flow). With GCC's proposed automatic stack variable initialization feature, this triggers a warning (and they don't get initialized). Clang's automatic stack variable initialization (via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also doesn't initialize such variables[1]. Note that these warnings (or silent skipping) happen before the dead-store elimination optimization phase, so even when the automatic initializations are later elided in favor of direct initializations, the warnings remain. To avoid these problems, move such variables into the "case" where they're used or lift them up into the main function body. mm/shmem.c: In function `shmem_getpage_gfp': mm/shmem.c:1816:10: warning: statement will never be executed [-Wswitch-unreachable] 1816 | loff_t i_size; | ^~~~~~ [1] https://bugs.llvm.org/show_bug.cgi?id=44916 Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Hugh Dickins <hughd@google.com> Cc: Alexander Potapenko <glider@google.com> Link: http://lkml.kernel.org/r/20200220062312.69165-1-keescook@chromium.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/shmem.c')
-rw-r--r--mm/shmem.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index 2c255f383608..97448a46a4dc 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1812,17 +1812,20 @@ repeat:
if (shmem_huge == SHMEM_HUGE_FORCE)
goto alloc_huge;
switch (sbinfo->huge) {
- loff_t i_size;
- pgoff_t off;
case SHMEM_HUGE_NEVER:
goto alloc_nohuge;
- case SHMEM_HUGE_WITHIN_SIZE:
+ case SHMEM_HUGE_WITHIN_SIZE: {
+ loff_t i_size;
+ pgoff_t off;
+
off = round_up(index, HPAGE_PMD_NR);
i_size = round_up(i_size_read(inode), PAGE_SIZE);
if (i_size >= HPAGE_PMD_SIZE &&
i_size >> PAGE_SHIFT >= off)
goto alloc_huge;
- /* fallthrough */
+
+ fallthrough;
+ }
case SHMEM_HUGE_ADVISE:
if (sgp_huge == SGP_HUGE)
goto alloc_huge;