Re: [PATCH] mm/mremap: fix BUILD_BUG_ON() error in get_extent
From: Nathan Chancellor <hidden>
Date: 2021-01-04 23:37:52
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On Wed, Dec 30, 2020 at 04:40:40PM +0100, Arnd Bergmann wrote:
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From: Arnd Bergmann <arnd@arndb.de> clang cannt evaluate this function argument at compile time when the function is not inlined, which leads to a link time failure: ld.lld: error: undefined symbol: __compiletime_assert_414quoted
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referenced by mremap.c mremap.o:(get_extent) in archive mm/built-in.aMark the function as __always_inline to avoid it. Fixes: 9ad9718bfa41 ("mm/mremap: calculate extent in one place") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- mm/mremap.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)diff --git a/mm/mremap.c b/mm/mremap.c index c5590afe7165..1cb464a07184 100644 --- a/mm/mremap.c +++ b/mm/mremap.c@@ -336,8 +336,9 @@ enum pgt_entry { * valid. Else returns a smaller extent bounded by the end of the source and * destination pgt_entry. */ -static unsigned long get_extent(enum pgt_entry entry, unsigned long old_addr, - unsigned long old_end, unsigned long new_addr) +static __always_inline unsigned long get_extent(enum pgt_entry entry, + unsigned long old_addr, unsigned long old_end, + unsigned long new_addr) { unsigned long next, extent, mask, size;-- 2.29.2
I am in agreement with Vlastimil, I would rather see the BUILD_BUG() dropped or converted into BUG() instead of papering over with __always_inline. For what it's worth, I only see this build failure with CONFIG_UBSAN_UNSIGNED_OVERFLOW, which you proposed disabling: https://lore.kernel.org/lkml/20201230154749.746641-1-arnd@kernel.org/ (local) Cheers, Nathan