5.10-stable review patch. If anyone has any objections, please let me know.
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From: Eliav Farber farbere@amazon.com
Fix compilation warning:
In file included from ./include/linux/kernel.h:15, from ./include/linux/list.h:9, from ./include/linux/module.h:12, from net/ipv4/inet_hashtables.c:12: net/ipv4/inet_hashtables.c: In function ‘inet_ehash_locks_alloc’: ./include/linux/minmax.h:20:35: warning: comparison of distinct pointer types lacks a cast 20 | (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1))) | ^~ ./include/linux/minmax.h:26:18: note: in expansion of macro ‘__typecheck’ 26 | (__typecheck(x, y) && __no_side_effects(x, y)) | ^~~~~~~~~~~ ./include/linux/minmax.h:36:31: note: in expansion of macro ‘__safe_cmp’ 36 | __builtin_choose_expr(__safe_cmp(x, y), \ | ^~~~~~~~~~ ./include/linux/minmax.h:52:25: note: in expansion of macro ‘__careful_cmp’ 52 | #define max(x, y) __careful_cmp(x, y, >) | ^~~~~~~~~~~~~ net/ipv4/inet_hashtables.c:946:19: note: in expansion of macro ‘max’ 946 | nblocks = max(nblocks, num_online_nodes() * PAGE_SIZE / locksz); | ^~~ CC block/badblocks.o
When warnings are treated as errors, this causes the build to fail.
The issue is a type mismatch between the operands passed to the max() macro. Here, nblocks is an unsigned int, while the expression num_online_nodes() * PAGE_SIZE / locksz is promoted to unsigned long.
This happens because: - num_online_nodes() returns int - PAGE_SIZE is typically defined as an unsigned long (depending on the architecture) - locksz is unsigned int
The resulting arithmetic expression is promoted to unsigned long.
Thus, the max() macro compares values of different types: unsigned int vs unsigned long.
This issue was introduced in commit f8ece40786c9 ("tcp: bring back NUMA dispersion in inet_ehash_locks_alloc()") during the update from kernel v5.10.237 to v5.10.238.
It does not exist in newer kernel branches (e.g., v5.15.185 and all 6.x branches), because they include commit d03eba99f5bf ("minmax: allow min()/max()/clamp() if the arguments have the same signedness.")
Fix the issue by using max_t(unsigned int, ...) to explicitly cast both operands to the same type, avoiding the type mismatch and ensuring correctness.
Fixes: f8ece40786c9 ("tcp: bring back NUMA dispersion in inet_ehash_locks_alloc()") Signed-off-by: Eliav Farber farbere@amazon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/inet_hashtables.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -943,7 +943,7 @@ int inet_ehash_locks_alloc(struct inet_h nblocks = max(2U * L1_CACHE_BYTES / locksz, 1U) * num_possible_cpus();
/* At least one page per NUMA node. */ - nblocks = max(nblocks, num_online_nodes() * PAGE_SIZE / locksz); + nblocks = max_t(unsigned int, nblocks, num_online_nodes() * PAGE_SIZE / locksz);
nblocks = roundup_pow_of_two(nblocks);