This is a note to let you know that I've just added the patch titled
device-dax: fix pmd/pte fault fallback handling
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
device-dax-fix-pmd-pte-fault-fallback-handling.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0134ed4fb9e78672ee9f7b18007114404c81e63f Mon Sep 17 00:00:00 2001
From: Dave Jiang <dave.jiang@xxxxxxxxx>
Date: Fri, 10 Mar 2017 13:24:22 -0700
Subject: device-dax: fix pmd/pte fault fallback handling
From: Dave Jiang <dave.jiang@xxxxxxxxx>
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@xxxxxxxxxxxxxxx>
Reported-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/dax/dax.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
--- a/drivers/dax/dax.c
+++ b/drivers/dax/dax.c
@@ -334,6 +334,7 @@ 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;
@@ -344,6 +345,9 @@ 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__,
@@ -389,6 +393,7 @@ 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;
@@ -405,6 +410,16 @@ 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) {
Patches currently in stable-queue which might be from dave.jiang@xxxxxxxxx are
queue-4.9/device-dax-fix-pmd-pte-fault-fallback-handling.patch