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Groups > linux.kernel > #1239942
| From | Ross Zwisler <ross.zwisler@linux.intel.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v3 3/3] dax: temporarily disable DAX PMD fault path |
| Date | 2015-10-05 22:40 +0200 |
| Message-ID | <qgkIb-1ks-23@gated-at.bofh.it> (permalink) |
| References | <qgkIa-1ks-7@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
There is currently a deadlock in the DAX PMD fault path because it ends up taking the same mapping->i_mmap_rwsem twice. The first take is a i_mmap_lock_read() near the beginning of __dax_pmd_fault(), and the second is __dax_pmd_fault() -> unmap_mapping_range() -> i_mmap_lock_write(). We are re-working the way that DAX does its locking for v4.4, so for now just disable DAX PMD faults and fall back to PAGE_SIZE faults to make sure we don't hit this deadlock. Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> --- fs/dax.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/dax.c b/fs/dax.c index f364c90..d42217d 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -534,6 +534,13 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, unsigned long pfn; int result = 0; + /* + * There is currently a deadlock in the DAX PMD fault path. Disable + * this path and fall back to the normal dax_fault() path for now + * while we rework locking. + */ + return VM_FAULT_FALLBACK; + /* Fall back to PTEs if we're going to COW */ if (write && !(vma->vm_flags & VM_SHARED)) return VM_FAULT_FALLBACK; -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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[PATCH v3 0/3] Revert locking changes in DAX for v4.3 Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-10-05 22:40 +0200 [PATCH v3 1/3] Revert "mm: take i_mmap_lock in unmap_mapping_range() for DAX" Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-10-05 22:40 +0200 [PATCH v3 2/3] Revert "dax: fix race between simultaneous faults" Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-10-05 22:40 +0200 [PATCH v3 3/3] dax: temporarily disable DAX PMD fault path Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-10-05 22:40 +0200
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