FAILED: patch "[PATCH] device-dax: fix pmd/pte fault fallback handling" failed to apply to 4.9-stable tree

PATCH [email protected] 1 participant 1 message Mar 24, 2017

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2017-03-24 14:38 UTC #0 lore raw

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From 0134ed4fb9e78672ee9f7b18007114404c81e63f Mon Sep 17 00:00:00 2001

From: Dave Jiang <[email protected]>
Date: Fri, 10 Mar 2017 13:24:22 -0700
Subject: [PATCH] device-dax: fix pmd/pte fault fallback handling

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 <[email protected]>

Reported-by Jeff Moyer <[email protected]>

Signed-off-by Dave Jiang <[email protected]>

Signed-off-by Dan Williams <[email protected]>

drivers/dax/dax.c +15 -0

index 8d9829ff2a78..a284dc532e46 100644
@@ -427,6 +427,7 @@ static int __dax_dev_pte_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
 	int rc = VM_FAULT_SIGBUS;
 	phys_addr_t phys;
 	pfn_t pfn;
+	unsigned int fault_size = PAGE_SIZE;
 
 	if (check_vma(dax_dev, vmf->vma, __func__))
 		return VM_FAULT_SIGBUS;

@@ -437,6 +438,9 @@ static int __dax_dev_pte_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
 		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__,

@@ -464,6 +468,7 @@ static int __dax_dev_pmd_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
 	phys_addr_t phys;
 	pgoff_t pgoff;
 	pfn_t pfn;
+	unsigned int fault_size = PMD_SIZE;
 
 	if (check_vma(dax_dev, vmf->vma, __func__))
 		return VM_FAULT_SIGBUS;

@@ -480,6 +485,16 @@ static int __dax_dev_pmd_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
 		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 < vmf->vma->vm_start ||
+			(pmd_addr + PMD_SIZE) > vmf->vma->vm_end)
+		return VM_FAULT_SIGBUS;
+
 	pgoff = linear_page_index(vmf->vma, pmd_addr);
 	phys = pgoff_to_phys(dax_dev, pgoff, PMD_SIZE);
 	if (phys == -1) {