The patch titled
Subject: mm/khugepaged: collapse_shmem() stop if punched or truncated
has been added to the -mm tree. Its filename is
mm-khugepaged-collapse_shmem-stop-if-punched-or-truncated.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-khugepaged-collapse_shmem-stop-if-punched-or-truncated.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-khugepaged-collapse_shmem-stop-if-punched-or-truncated.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm/khugepaged: collapse_shmem() stop if punched or truncated
Huge tmpfs testing showed that although collapse_shmem() recognizes a
concurrently truncated or hole-punched page correctly, its handling of
holes was liable to refill an emptied extent. Add check to stop that.
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261522040.2275@eggly.anvils
Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reviewed-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [4.8+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/khugepaged.c~mm-khugepaged-collapse_shmem-stop-if-punched-or-truncated
+++ a/mm/khugepaged.c
@@ -1359,6 +1359,17 @@ static void collapse_shmem(struct mm_str
VM_BUG_ON(index != xas.xa_index);
if (!page) {
+ /*
+ * Stop if extent has been truncated or hole-punched,
+ * and is now completely empty.
+ */
+ if (index == start) {
+ if (!xas_next_entry(&xas, end - 1)) {
+ result = SCAN_TRUNCATED;
+ break;
+ }
+ xas_set(&xas, index);
+ }
if (!shmem_charge(mapping->host, 1)) {
result = SCAN_FAIL;
break;
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-huge_memory-rename-freeze_page-to-unmap_page.patch
mm-huge_memory-splitting-set-mappingindex-before-unfreeze.patch
mm-huge_memory-fix-lockdep-complaint-on-32-bit-i_size_read.patch
mm-khugepaged-collapse_shmem-stop-if-punched-or-truncated.patch
mm-khugepaged-fix-crashes-due-to-misaccounted-holes.patch
mm-khugepaged-collapse_shmem-remember-to-clear-holes.patch
mm-khugepaged-minor-reorderings-in-collapse_shmem.patch
mm-khugepaged-collapse_shmem-without-freezing-new_page.patch
mm-khugepaged-collapse_shmem-do-not-crash-on-compound.patch
mm-khugepaged-fix-the-xas_create_range-error-path.patch
mm-put_and_wait_on_page_locked-while-page-is-migrated.patch
