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Merge tag 'dax-locking-for-4.7' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

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Pull DAX locking updates from Ross Zwisler:
 "Filesystem DAX locking for 4.7

   - We use a bit in an exceptional radix tree entry as a lock bit and
     use it similarly to how page lock is used for normal faults.  This
     fixes races between hole instantiation and read faults of the same
     index.

   - Filesystem DAX PMD faults are disabled, and will be re-enabled when
     PMD locking is implemented"

* tag 'dax-locking-for-4.7' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  dax: Remove i_mmap_lock protection
  dax: Use radix tree entry lock to protect cow faults
  dax: New fault locking
  dax: Allow DAX code to replace exceptional entries
  dax: Define DAX lock bit for radix tree exceptional entry
  dax: Make huge page handling depend of CONFIG_BROKEN
  dax: Fix condition for filling of PMD holes
This commit is contained in:
Linus Torvalds
2016-05-26 20:00:28 -07:00
parent 315227f6da 4d9a2c8746
commit 478a1469a7
7 changed files with 514 additions and 236 deletions
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40
mm/memory.c
View File

@@ -63,6 +63,7 @@
#include <linux/dma-debug.h>
#include <linux/debugfs.h>
#include <linux/userfaultfd_k.h>
#include <linux/dax.h>
#include <asm/io.h>
#include <asm/mmu_context.h>
@@ -2492,8 +2493,6 @@ void unmap_mapping_range(struct address_space *mapping,
if (details.last_index < details.first_index)
details.last_index = ULONG_MAX;
/* DAX uses i_mmap_lock to serialise file truncate vs page fault */
i_mmap_lock_write(mapping);
if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
unmap_mapping_range_tree(&mapping->i_mmap, &details);
@@ -2825,7 +2824,8 @@ oom:
*/
static int __do_fault(struct vm_area_struct *vma, unsigned long address,
pgoff_t pgoff, unsigned int flags,
struct page *cow_page, struct page **page)
struct page *cow_page, struct page **page,
void **entry)
{
struct vm_fault vmf;
int ret;
@@ -2840,8 +2840,10 @@ static int __do_fault(struct vm_area_struct *vma, unsigned long address,
ret = vma->vm_ops->fault(vma, &vmf);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
return ret;
if (!vmf.page)
goto out;
if (ret & VM_FAULT_DAX_LOCKED) {
*entry = vmf.entry;
return ret;
}
if (unlikely(PageHWPoison(vmf.page))) {
if (ret & VM_FAULT_LOCKED)
@@ -2855,7 +2857,6 @@ static int __do_fault(struct vm_area_struct *vma, unsigned long address,
else
VM_BUG_ON_PAGE(!PageLocked(vmf.page), vmf.page);
out:
*page = vmf.page;
return ret;
}
@@ -3048,7 +3049,7 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
pte_unmap_unlock(pte, ptl);
}
ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page);
ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page, NULL);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
return ret;
@@ -3071,6 +3072,7 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma,
pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
{
struct page *fault_page, *new_page;
void *fault_entry;
struct mem_cgroup *memcg;
spinlock_t *ptl;
pte_t *pte;
@@ -3088,26 +3090,24 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma,
return VM_FAULT_OOM;
}
ret = __do_fault(vma, address, pgoff, flags, new_page, &fault_page);
ret = __do_fault(vma, address, pgoff, flags, new_page, &fault_page,
&fault_entry);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
goto uncharge_out;
if (fault_page)
if (!(ret & VM_FAULT_DAX_LOCKED))
copy_user_highpage(new_page, fault_page, address, vma);
__SetPageUptodate(new_page);
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
if (unlikely(!pte_same(*pte, orig_pte))) {
pte_unmap_unlock(pte, ptl);
if (fault_page) {
if (!(ret & VM_FAULT_DAX_LOCKED)) {
unlock_page(fault_page);
put_page(fault_page);
} else {
/*
* The fault handler has no page to lock, so it holds
* i_mmap_lock for read to protect against truncate.
*/
i_mmap_unlock_read(vma->vm_file->f_mapping);
dax_unlock_mapping_entry(vma->vm_file->f_mapping,
pgoff);
}
goto uncharge_out;
}
@@ -3115,15 +3115,11 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma,
mem_cgroup_commit_charge(new_page, memcg, false, false);
lru_cache_add_active_or_unevictable(new_page, vma);
pte_unmap_unlock(pte, ptl);
if (fault_page) {
if (!(ret & VM_FAULT_DAX_LOCKED)) {
unlock_page(fault_page);
put_page(fault_page);
} else {
/*
* The fault handler has no page to lock, so it holds
* i_mmap_lock for read to protect against truncate.
*/
i_mmap_unlock_read(vma->vm_file->f_mapping);
dax_unlock_mapping_entry(vma->vm_file->f_mapping, pgoff);
}
return ret;
uncharge_out:
@@ -3143,7 +3139,7 @@ static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma,
int dirtied = 0;
int ret, tmp;
ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page);
ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page, NULL);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
return ret;