From 701270fa193aadf00bdcf607738f64997275d4c7 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Fri, 30 Nov 2018 14:10:25 -0800 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 Reviewed-by: Matthew Wilcox Cc: Kirill A. Shutemov Cc: Jerome Glisse Cc: Konstantin Khlebnikov Cc: [4.8+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/khugepaged.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'mm/khugepaged.c') 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; -- cgit v1.2.3-55-g7522