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| author | OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> | 2021-03-12 21:07:37 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-03-13 11:27:30 -0800 |
| commit | 184cee516f3e24019a08ac8eb5c7cf04c00933cb (patch) | |
| tree | d9f5e41fdfdfdc86143d8ff60e58f1bb835ebdfe /mm/highmem.c | |
| parent | 4eae4efa2c299f85b7ebfbeeda56c19c5eba2768 (diff) | |
| download | lwn-184cee516f3e24019a08ac8eb5c7cf04c00933cb.tar.gz lwn-184cee516f3e24019a08ac8eb5c7cf04c00933cb.zip | |
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>
Diffstat (limited to 'mm/highmem.c')
| -rw-r--r-- | mm/highmem.c | 17 |
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; } |