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authorZi Yan <zi.yan@cs.rutgers.edu>2017-09-08 16:11:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-09-08 18:26:45 -0700
commit84c3fc4e9c563d8fb91cfdf5948da48fe1af34d3 (patch)
treefc028524f9272c5ba1690d18937ebfc0bf0a0f9e /include/asm-generic/pgtable.h
parent616b8371539a6c487404c3b8fb04078016dab4ba (diff)
mm: thp: check pmd migration entry in common path
When THP migration is being used, memory management code needs to handle pmd migration entries properly. This patch uses !pmd_present() or is_swap_pmd() (depending on whether pmd_none() needs separate code or not) to check pmd migration entries at the places where a pmd entry is present. Since pmd-related code uses split_huge_page(), split_huge_pmd(), pmd_trans_huge(), pmd_trans_unstable(), or pmd_none_or_trans_huge_or_clear_bad(), this patch: 1. adds pmd migration entry split code in split_huge_pmd(), 2. takes care of pmd migration entries whenever pmd_trans_huge() is present, 3. makes pmd_none_or_trans_huge_or_clear_bad() pmd migration entry aware. Since split_huge_page() uses split_huge_pmd() and pmd_trans_unstable() is equivalent to pmd_none_or_trans_huge_or_clear_bad(), we do not change them. Until this commit, a pmd entry should be: 1. pointing to a pte page, 2. is_swap_pmd(), 3. pmd_trans_huge(), 4. pmd_devmap(), or 5. pmd_none(). Signed-off-by: Zi Yan <zi.yan@cs.rutgers.edu> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: David Nellans <dnellans@nvidia.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Minchan Kim <minchan@kernel.org> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/asm-generic/pgtable.h')
-rw-r--r--include/asm-generic/pgtable.h18
1 files changed, 17 insertions, 1 deletions
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 4d7bb98f4134..4f93a6d10a47 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -846,7 +846,23 @@ static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd)
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
barrier();
#endif
- if (pmd_none(pmdval) || pmd_trans_huge(pmdval))
+ /*
+ * !pmd_present() checks for pmd migration entries
+ *
+ * The complete check uses is_pmd_migration_entry() in linux/swapops.h
+ * But using that requires moving current function and pmd_trans_unstable()
+ * to linux/swapops.h to resovle dependency, which is too much code move.
+ *
+ * !pmd_present() is equivalent to is_pmd_migration_entry() currently,
+ * because !pmd_present() pages can only be under migration not swapped
+ * out.
+ *
+ * pmd_none() is preseved for future condition checks on pmd migration
+ * entries and not confusing with this function name, although it is
+ * redundant with !pmd_present().
+ */
+ if (pmd_none(pmdval) || pmd_trans_huge(pmdval) ||
+ (IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION) && !pmd_present(pmdval)))
return 1;
if (unlikely(pmd_bad(pmdval))) {
pmd_clear_bad(pmd);