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Subject[PATCH v2] powerpc/mm: Fix growth direction for hugepages mmaps with slice
Date
An application running with libhugetlbfs fails to allocate
additional pages to HEAP due to the hugemap being done
inconditionally as topdown mapping:

mmap(0x10080000, 1572864, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x40000, -1, 0) = 0x73e80000
[...]
mmap(0x74000000, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x40000, -1, 0x180000) = 0x73d80000
munmap(0x73d80000, 1048576) = 0
[...]
mmap(0x74000000, 1572864, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x40000, -1, 0x180000) = 0x73d00000
munmap(0x73d00000, 1572864) = 0
[...]
mmap(0x74000000, 1572864, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x40000, -1, 0x180000) = 0x73d00000
munmap(0x73d00000, 1572864) = 0
[...]

As one can see from the above strace log, mmap() allocates further
pages below the initial one.

This patch fixes it by taking into account MAP_GROWSDOWN flag.

Fixes: d0f13e3c20b6f ("[POWERPC] Introduce address space "slices" ")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
v2: Added missing include

arch/powerpc/mm/hugetlbpage.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 79e1378ee303..0eadf9f199de 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -19,6 +19,7 @@
#include <linux/moduleparam.h>
#include <linux/swap.h>
#include <linux/swapops.h>
+#include <linux/mman.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>
@@ -558,7 +559,8 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
return radix__hugetlb_get_unmapped_area(file, addr, len,
pgoff, flags);
#endif
- return slice_get_unmapped_area(addr, len, flags, mmu_psize, 1);
+ return slice_get_unmapped_area(addr, len, flags, mmu_psize,
+ flags & MAP_GROWSDOWN);
}
#endif

--
2.13.3
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