path: root/mm/page-writeback.c
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authorVlastimil Babka <>2020-01-13 16:29:20 -0800
committerLinus Torvalds <>2020-01-13 18:19:02 -0800
commit8e57f8acbbd121ecfb0c9dc13b8b030f86c6bd3b (patch)
tree91516d1faa0be5ed78a8919e0fc6a0b1da1d2a8d /mm/page-writeback.c
parent4a87e2a25dc27131c3cce5e94421622193305638 (diff)
mm, debug_pagealloc: don't rely on static keys too early
Commit 96a2b03f281d ("mm, debug_pagelloc: use static keys to enable debugging") has introduced a static key to reduce overhead when debug_pagealloc is compiled in but not enabled. It relied on the assumption that jump_label_init() is called before parse_early_param() as in start_kernel(), so when the "debug_pagealloc=on" option is parsed, it is safe to enable the static key. However, it turns out multiple architectures call parse_early_param() earlier from their setup_arch(). x86 also calls jump_label_init() even earlier, so no issue was found while testing the commit, but same is not true for e.g. ppc64 and s390 where the kernel would not boot with debug_pagealloc=on as found by our QA. To fix this without tricky changes to init code of multiple architectures, this patch partially reverts the static key conversion from 96a2b03f281d. Init-time and non-fastpath calls (such as in arch code) of debug_pagealloc_enabled() will again test a simple bool variable. Fastpath mm code is converted to a new debug_pagealloc_enabled_static() variant that relies on the static key, which is enabled in a well-defined point in mm_init() where it's guaranteed that jump_label_init() has been called, regardless of architecture. [ export _debug_pagealloc_enabled_early] Link: Link: Fixes: 96a2b03f281d ("mm, debug_pagelloc: use static keys to enable debugging") Signed-off-by: Vlastimil Babka <> Signed-off-by: Stephen Rothwell <> Cc: Joonsoo Kim <> Cc: "Kirill A. Shutemov" <> Cc: Michal Hocko <> Cc: Vlastimil Babka <> Cc: Matthew Wilcox <> Cc: Mel Gorman <> Cc: Peter Zijlstra <> Cc: Borislav Petkov <> Cc: Qian Cai <> Cc: <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm/page-writeback.c')
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