+ mm-page_alloc-revert-pahole-zero-sized-workaround.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm/page_alloc: Revert pahole zero-sized workaround
has been added to the -mm tree.  Its filename is
     mm-page_alloc-revert-pahole-zero-sized-workaround.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-revert-pahole-zero-sized-workaround.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-revert-pahole-zero-sized-workaround.patch

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------------------------------------------------------
From: Mel Gorman <mgorman@techsingularity.net>
Subject: mm/page_alloc: Revert pahole zero-sized workaround

Commit dbbee9d5cd83 ("mm/page_alloc: convert per-cpu list protection to
local_lock") folded in a workaround patch for pahole that was unable to
deal with zero-sized percpu structures.  A superior workaround is achieved
with commit a0b8200d06ad ("kbuild: skip per-CPU BTF generation for pahole
v1.18-v1.21").  This patch reverts the dummy field and the pahole version
check.

Link: https://lkml.kernel.org/r/20210705095117.GM3840@techsingularity.net
Fixes: dbbee9d5cd83 ("mm/page_alloc: convert per-cpu list protection to local_lock")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Chuck Lever III <chuck.lever@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/Kconfig.debug |    3 ---
 mm/page_alloc.c   |   11 -----------
 2 files changed, 14 deletions(-)

--- a/lib/Kconfig.debug~mm-page_alloc-revert-pahole-zero-sized-workaround
+++ a/lib/Kconfig.debug
@@ -313,9 +313,6 @@ config DEBUG_INFO_BTF
 config PAHOLE_HAS_SPLIT_BTF
 	def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119")
 
-config PAHOLE_HAS_ZEROSIZE_PERCPU_SUPPORT
-	def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "122")
-
 config DEBUG_INFO_BTF_MODULES
 	def_bool y
 	depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF
--- a/mm/page_alloc.c~mm-page_alloc-revert-pahole-zero-sized-workaround
+++ a/mm/page_alloc.c
@@ -124,17 +124,6 @@ static DEFINE_MUTEX(pcp_batch_high_lock)
 
 struct pagesets {
 	local_lock_t lock;
-#if defined(CONFIG_DEBUG_INFO_BTF) &&				\
-	!defined(CONFIG_DEBUG_LOCK_ALLOC) &&			\
-	!defined(CONFIG_PAHOLE_HAS_ZEROSIZE_PERCPU_SUPPORT)
-	/*
-	 * pahole 1.21 and earlier gets confused by zero-sized per-CPU
-	 * variables and produces invalid BTF. Ensure that
-	 * sizeof(struct pagesets) != 0 for older versions of pahole.
-	 */
-	char __pahole_hack;
-	#warning "pahole too old to support zero-sized struct pagesets"
-#endif
 };
 static DEFINE_PER_CPU(struct pagesets, pagesets) = {
 	.lock = INIT_LOCAL_LOCK(lock),
_

Patches currently in -mm which might be from mgorman@techsingularity.net are

mm-page_alloc-revert-pahole-zero-sized-workaround.patch