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authorHugh Dickins <hughd@google.com>2018-12-01 01:10:25 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-12-01 01:56:15 +0300
commit701270fa193aadf00bdcf607738f64997275d4c7 (patch)
tree6f9a0bd6ab13d9213050c0ff4e739953dd5c7570
parent006d3ff27e884f80bd7d306b041afc415f63598f (diff)
downloadlinux-701270fa193aadf00bdcf607738f64997275d4c7.tar.xz
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@google.com> Reviewed-by: Matthew Wilcox <willy@infradead.org> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: <stable@vger.kernel.org> [4.8+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/khugepaged.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index c13625c1ad5e..2070c316f06e 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1359,6 +1359,17 @@ static void collapse_shmem(struct mm_struct *mm,
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;