Commit ff792584 authored Mar 09, 2016 by Will Deacon

arm64: hugetlb: partial revert of 66b3923a



Commit 66b3923a ("arm64: hugetlb: add support for PTE contiguous bit")
introduced support for huge pages using the contiguous bit in the PTE
as opposed to block mappings, which may be slightly unwieldy (512M) in
64k page configurations.

Unfortunately, this support has resulted in some late regressions when
running the libhugetlbfs test suite with 64k pages and CONFIG_DEBUG_VM
as a result of a BUG:

 | readback (2M: 64):	------------[ cut here ]------------
 | kernel BUG at fs/hugetlbfs/inode.c:446!
 | Internal error: Oops - BUG: 0 [#1] SMP
 | Modules linked in:
 | CPU: 7 PID: 1448 Comm: readback Not tainted 4.5.0-rc7 #148
 | Hardware name: linux,dummy-virt (DT)
 | task: fffffe0040964b00 ti: fffffe00c2668000 task.ti: fffffe00c2668000
 | PC is at remove_inode_hugepages+0x44c/0x480
 | LR is at remove_inode_hugepages+0x264/0x480

Rather than revert the entire patch, simply avoid advertising the
contiguous huge page sizes for now while people are actively working on
a fix. This patch can then be reverted once things have been sorted out.

Cc: David Woods <dwoods@ezchip.com>
Reported-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

parent 36e5cd6b

arch/arm64/mm/hugetlbpage.c

+0 −14

Original line number	Diff line number	Diff line
		@@ -306,10 +306,6 @@ static __init int setup_hugepagesz(char *opt)
		hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
		} else if (ps == PUD_SIZE) {
		hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
		} else if (ps == (PAGE_SIZE * CONT_PTES)) {
		hugetlb_add_hstate(CONT_PTE_SHIFT);
		} else if (ps == (PMD_SIZE * CONT_PMDS)) {
		hugetlb_add_hstate((PMD_SHIFT + CONT_PMD_SHIFT) - PAGE_SHIFT);
		} else {
		pr_err("hugepagesz: Unsupported page size %lu K\n", ps >> 10);
		return 0;
		@@ -317,13 +313,3 @@ static __init int setup_hugepagesz(char *opt)
		return 1;
		}
		__setup("hugepagesz=", setup_hugepagesz);

		#ifdef CONFIG_ARM64_64K_PAGES
		static __init int add_default_hugepagesz(void)
		{
		if (size_to_hstate(CONT_PTES * PAGE_SIZE) == NULL)
		hugetlb_add_hstate(CONT_PMD_SHIFT);
		return 0;
		}
		arch_initcall(add_default_hugepagesz);
		#endif

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