| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.10 105/111] device-dax: fix pmd/pte fault fallback handling | Date | Tue, 28 Mar 2017 14:31:31 +0200 |
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4.10-stable review patch. If anyone has any objections, please let me know.
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From: Dave Jiang <dave.jiang@intel.com>
commit 0134ed4fb9e78672ee9f7b18007114404c81e63f upstream.
Jeff Moyer reports:
With a device dax alignment of 4KB or 2MB, I get sigbus when running the attached fio job file for the current kernel (4.11.0-rc1+). If I specify an alignment of 1GB, it works.
I turned on debug output, and saw that it was failing in the huge fault code.
dax dax1.0: dax_open dax dax1.0: dax_mmap dax dax1.0: dax_dev_huge_fault: fio: write (0x7f08f0a00000 - dax dax1.0: __dax_dev_pud_fault: phys_to_pgoff(0xffffffffcf60 dax dax1.0: dax_release
fio config for reproduce: [global] ioengine=dev-dax direct=0 filename=/dev/dax0.0 bs=2m
[write] rw=write
[read] stonewall rw=read
The driver fails to fallback when taking a fault that is larger than the device alignment, or handling a larger fault when a smaller mapping is already established. While we could support larger mappings for a device with a smaller alignment, that change is too large for the immediate fix. The simplest change is to force fallback until the fault size matches the alignment.
Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap") Cc: <stable@vger.kernel.org> Reported-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Dave Jiang <dave.jiang@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/dax/dax.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
--- a/drivers/dax/dax.c +++ b/drivers/dax/dax.c @@ -427,6 +427,7 @@ static int __dax_dev_fault(struct dax_de int rc = VM_FAULT_SIGBUS; phys_addr_t phys; pfn_t pfn; + unsigned int fault_size = PAGE_SIZE; if (check_vma(dax_dev, vma, __func__)) return VM_FAULT_SIGBUS; @@ -437,6 +438,9 @@ static int __dax_dev_fault(struct dax_de return VM_FAULT_SIGBUS; } + if (fault_size != dax_region->align) + return VM_FAULT_SIGBUS; + phys = pgoff_to_phys(dax_dev, vmf->pgoff, PAGE_SIZE); if (phys == -1) { dev_dbg(dev, "%s: phys_to_pgoff(%#lx) failed\n", __func__, @@ -482,6 +486,7 @@ static int __dax_dev_pmd_fault(struct da phys_addr_t phys; pgoff_t pgoff; pfn_t pfn; + unsigned int fault_size = PMD_SIZE; if (check_vma(dax_dev, vma, __func__)) return VM_FAULT_SIGBUS; @@ -498,6 +503,16 @@ static int __dax_dev_pmd_fault(struct da return VM_FAULT_SIGBUS; } + if (fault_size < dax_region->align) + return VM_FAULT_SIGBUS; + else if (fault_size > dax_region->align) + return VM_FAULT_FALLBACK; + + /* if we are outside of the VMA */ + if (pmd_addr < vma->vm_start || + (pmd_addr + PMD_SIZE) > vma->vm_end) + return VM_FAULT_SIGBUS; + pgoff = linear_page_index(vma, pmd_addr); phys = pgoff_to_phys(dax_dev, pgoff, PMD_SIZE); if (phys == -1) {
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