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authorOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>2021-03-12 21:07:37 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-03-13 11:27:30 -0800
commit184cee516f3e24019a08ac8eb5c7cf04c00933cb (patch)
treed9f5e41fdfdfdc86143d8ff60e58f1bb835ebdfe
parent4eae4efa2c299f85b7ebfbeeda56c19c5eba2768 (diff)
mm/highmem.c: fix zero_user_segments() with start > end
zero_user_segments() is used from __block_write_begin_int(), for example like the following zero_user_segments(page, 4096, 1024, 512, 918) But new the zero_user_segments() implementation for for HIGHMEM + TRANSPARENT_HUGEPAGE doesn't handle "start > end" case correctly, and hits BUG_ON(). (we can fix __block_write_begin_int() instead though, it is the old and multiple usage) Also it calls kmap_atomic() unnecessarily while start == end == 0. Link: https://lkml.kernel.org/r/87v9ab60r4.fsf@mail.parknet.co.jp Fixes: 0060ef3b4e6d ("mm: support THPs in zero_user_segments") Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Cc: Matthew Wilcox <willy@infradead.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/highmem.c17
1 files changed, 12 insertions, 5 deletions
diff --git a/mm/highmem.c b/mm/highmem.c
index 874b732b120c..86f2b9495f9c 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -368,20 +368,24 @@ void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
BUG_ON(end1 > page_size(page) || end2 > page_size(page));
+ if (start1 >= end1)
+ start1 = end1 = 0;
+ if (start2 >= end2)
+ start2 = end2 = 0;
+
for (i = 0; i < compound_nr(page); i++) {
void *kaddr = NULL;
- if (start1 < PAGE_SIZE || start2 < PAGE_SIZE)
- kaddr = kmap_atomic(page + i);
-
if (start1 >= PAGE_SIZE) {
start1 -= PAGE_SIZE;
end1 -= PAGE_SIZE;
} else {
unsigned this_end = min_t(unsigned, end1, PAGE_SIZE);
- if (end1 > start1)
+ if (end1 > start1) {
+ kaddr = kmap_atomic(page + i);
memset(kaddr + start1, 0, this_end - start1);
+ }
end1 -= this_end;
start1 = 0;
}
@@ -392,8 +396,11 @@ void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
} else {
unsigned this_end = min_t(unsigned, end2, PAGE_SIZE);
- if (end2 > start2)
+ if (end2 > start2) {
+ if (!kaddr)
+ kaddr = kmap_atomic(page + i);
memset(kaddr + start2, 0, this_end - start2);
+ }
end2 -= this_end;
start2 = 0;
}

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