* [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
@ 2015-08-07 11:53 ` Kirill A. Shutemov
0 siblings, 0 replies; 13+ messages in thread
From: Kirill A. Shutemov @ 2015-08-07 11:53 UTC (permalink / raw)
To: Andrew Morton, Matthew Wilcox
Cc: linux-mm, linux-fsdevel, linux-kernel, Kirill A. Shutemov
DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
__dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
Re-aquiring the lock should be fine since we check i_size after the
point.
Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
fs/dax.c | 35 +++++++++++++++++++----------------
mm/memory.c | 11 ++---------
2 files changed, 21 insertions(+), 25 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 9ef9b80cc132..ed54efedade6 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
goto fallback;
+ if (buffer_unwritten(&bh) || buffer_new(&bh)) {
+ int i;
+ for (i = 0; i < PTRS_PER_PMD; i++)
+ clear_page(kaddr + i * PAGE_SIZE);
+ count_vm_event(PGMAJFAULT);
+ mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
+ result |= VM_FAULT_MAJOR;
+ }
+
+ /*
+ * If we allocated new storage, make sure no process has any
+ * zero pages covering this hole
+ */
+ if (buffer_new(&bh)) {
+ i_mmap_unlock_write(mapping);
+ unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0);
+ i_mmap_lock_write(mapping);
+ }
+
/*
* If a truncate happened while we were allocating blocks, we may
* leave blocks allocated to the file that are beyond EOF. We can't
@@ -568,13 +587,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if ((pgoff | PG_PMD_COLOUR) >= size)
goto fallback;
- /*
- * If we allocated new storage, make sure no process has any
- * zero pages covering this hole
- */
- if (buffer_new(&bh))
- unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0);
-
if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
spinlock_t *ptl;
pmd_t entry;
@@ -605,15 +617,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR))
goto fallback;
- if (buffer_unwritten(&bh) || buffer_new(&bh)) {
- int i;
- for (i = 0; i < PTRS_PER_PMD; i++)
- clear_page(kaddr + i * PAGE_SIZE);
- count_vm_event(PGMAJFAULT);
- mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
- result |= VM_FAULT_MAJOR;
- }
-
result |= vmf_insert_pfn_pmd(vma, address, pmd, pfn, write);
}
diff --git a/mm/memory.c b/mm/memory.c
index 5a3427bb3f32..670cdfa9f33e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2426,17 +2426,10 @@ void unmap_mapping_range(struct address_space *mapping,
if (details.last_index < details.first_index)
details.last_index = ULONG_MAX;
-
- /*
- * DAX already holds i_mmap_lock to serialise file truncate vs
- * page fault and page fault vs page fault.
- */
- if (!IS_DAX(mapping->host))
- i_mmap_lock_write(mapping);
+ i_mmap_lock_write(mapping);
if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
unmap_mapping_range_tree(&mapping->i_mmap, &details);
- if (!IS_DAX(mapping->host))
- i_mmap_unlock_write(mapping);
+ i_mmap_unlock_write(mapping);
}
EXPORT_SYMBOL(unmap_mapping_range);
--
2.4.6
^ permalink raw reply related [flat|nested] 13+ messages in thread
* [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
@ 2015-08-07 11:53 ` Kirill A. Shutemov
0 siblings, 0 replies; 13+ messages in thread
From: Kirill A. Shutemov @ 2015-08-07 11:53 UTC (permalink / raw)
To: Andrew Morton, Matthew Wilcox
Cc: linux-mm, linux-fsdevel, linux-kernel, Kirill A. Shutemov
DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
__dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
Re-aquiring the lock should be fine since we check i_size after the
point.
Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
fs/dax.c | 35 +++++++++++++++++++----------------
mm/memory.c | 11 ++---------
2 files changed, 21 insertions(+), 25 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 9ef9b80cc132..ed54efedade6 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
goto fallback;
+ if (buffer_unwritten(&bh) || buffer_new(&bh)) {
+ int i;
+ for (i = 0; i < PTRS_PER_PMD; i++)
+ clear_page(kaddr + i * PAGE_SIZE);
+ count_vm_event(PGMAJFAULT);
+ mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
+ result |= VM_FAULT_MAJOR;
+ }
+
+ /*
+ * If we allocated new storage, make sure no process has any
+ * zero pages covering this hole
+ */
+ if (buffer_new(&bh)) {
+ i_mmap_unlock_write(mapping);
+ unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0);
+ i_mmap_lock_write(mapping);
+ }
+
/*
* If a truncate happened while we were allocating blocks, we may
* leave blocks allocated to the file that are beyond EOF. We can't
@@ -568,13 +587,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if ((pgoff | PG_PMD_COLOUR) >= size)
goto fallback;
- /*
- * If we allocated new storage, make sure no process has any
- * zero pages covering this hole
- */
- if (buffer_new(&bh))
- unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0);
-
if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
spinlock_t *ptl;
pmd_t entry;
@@ -605,15 +617,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR))
goto fallback;
- if (buffer_unwritten(&bh) || buffer_new(&bh)) {
- int i;
- for (i = 0; i < PTRS_PER_PMD; i++)
- clear_page(kaddr + i * PAGE_SIZE);
- count_vm_event(PGMAJFAULT);
- mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
- result |= VM_FAULT_MAJOR;
- }
-
result |= vmf_insert_pfn_pmd(vma, address, pmd, pfn, write);
}
diff --git a/mm/memory.c b/mm/memory.c
index 5a3427bb3f32..670cdfa9f33e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2426,17 +2426,10 @@ void unmap_mapping_range(struct address_space *mapping,
if (details.last_index < details.first_index)
details.last_index = ULONG_MAX;
-
- /*
- * DAX already holds i_mmap_lock to serialise file truncate vs
- * page fault and page fault vs page fault.
- */
- if (!IS_DAX(mapping->host))
- i_mmap_lock_write(mapping);
+ i_mmap_lock_write(mapping);
if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
unmap_mapping_range_tree(&mapping->i_mmap, &details);
- if (!IS_DAX(mapping->host))
- i_mmap_unlock_write(mapping);
+ i_mmap_unlock_write(mapping);
}
EXPORT_SYMBOL(unmap_mapping_range);
--
2.4.6
--
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^ permalink raw reply related [flat|nested] 13+ messages in thread
* Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
2015-08-07 11:53 ` Kirill A. Shutemov
@ 2015-09-15 23:52 ` Dan Williams
-1 siblings, 0 replies; 13+ messages in thread
From: Dan Williams @ 2015-09-15 23:52 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: Andrew Morton, Matthew Wilcox, linux-mm, linux-fsdevel,
Linux Kernel Mailing List, linux-nvdimm@lists.01.org,
ross.zwisler
Hi Kirill,
On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
> DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
>
> __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
> all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
>
> Re-aquiring the lock should be fine since we check i_size after the
> point.
>
> Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
> fs/dax.c | 35 +++++++++++++++++++----------------
> mm/memory.c | 11 ++---------
> 2 files changed, 21 insertions(+), 25 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 9ef9b80cc132..ed54efedade6 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
> goto fallback;
>
> + if (buffer_unwritten(&bh) || buffer_new(&bh)) {
> + int i;
> + for (i = 0; i < PTRS_PER_PMD; i++)
> + clear_page(kaddr + i * PAGE_SIZE);
This patch, now upstream as commit 46c043ede471, moves the call to
clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not
set at this point, so I'm not sure this path was ever tested. I'm
also not sure why the compiler is not complaining about an
uninitialized variable?
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
@ 2015-09-15 23:52 ` Dan Williams
0 siblings, 0 replies; 13+ messages in thread
From: Dan Williams @ 2015-09-15 23:52 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: Andrew Morton, Matthew Wilcox, linux-mm, linux-fsdevel,
Linux Kernel Mailing List, linux-nvdimm@lists.01.org,
ross.zwisler
Hi Kirill,
On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
> DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
>
> __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
> all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
>
> Re-aquiring the lock should be fine since we check i_size after the
> point.
>
> Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
> fs/dax.c | 35 +++++++++++++++++++----------------
> mm/memory.c | 11 ++---------
> 2 files changed, 21 insertions(+), 25 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 9ef9b80cc132..ed54efedade6 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
> goto fallback;
>
> + if (buffer_unwritten(&bh) || buffer_new(&bh)) {
> + int i;
> + for (i = 0; i < PTRS_PER_PMD; i++)
> + clear_page(kaddr + i * PAGE_SIZE);
This patch, now upstream as commit 46c043ede471, moves the call to
clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not
set at this point, so I'm not sure this path was ever tested. I'm
also not sure why the compiler is not complaining about an
uninitialized variable?
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
2015-09-15 23:52 ` Dan Williams
@ 2015-09-16 11:12 ` Kirill A. Shutemov
-1 siblings, 0 replies; 13+ messages in thread
From: Kirill A. Shutemov @ 2015-09-16 11:12 UTC (permalink / raw)
To: Matthew Wilcox, Dan Williams
Cc: Kirill A. Shutemov, Andrew Morton, linux-mm, linux-fsdevel,
Linux Kernel Mailing List, linux-nvdimm@lists.01.org,
ross.zwisler
On Tue, Sep 15, 2015 at 04:52:42PM -0700, Dan Williams wrote:
> Hi Kirill,
>
> On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov
> <kirill.shutemov@linux.intel.com> wrote:
> > DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
> >
> > __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
> > all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
> >
> > Re-aquiring the lock should be fine since we check i_size after the
> > point.
> >
> > Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > ---
> > fs/dax.c | 35 +++++++++++++++++++----------------
> > mm/memory.c | 11 ++---------
> > 2 files changed, 21 insertions(+), 25 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 9ef9b80cc132..ed54efedade6 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> > if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
> > goto fallback;
> >
> > + if (buffer_unwritten(&bh) || buffer_new(&bh)) {
> > + int i;
> > + for (i = 0; i < PTRS_PER_PMD; i++)
> > + clear_page(kaddr + i * PAGE_SIZE);
>
> This patch, now upstream as commit 46c043ede471, moves the call to
> clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not
> set at this point, so I'm not sure this path was ever tested.
Ughh. It's obviously broken.
I took fs/dax.c part of the patch from Matthew. And I'm not sure now we
would need to move this "if (buffer_unwritten(&bh) || buffer_new(&bh)) {"
block around. It should work fine where it was before. Right?
Matthew?
> I'm also not sure why the compiler is not complaining about an
> uninitialized variable?
No idea.
--
Kirill A. Shutemov
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
@ 2015-09-16 11:12 ` Kirill A. Shutemov
0 siblings, 0 replies; 13+ messages in thread
From: Kirill A. Shutemov @ 2015-09-16 11:12 UTC (permalink / raw)
To: Matthew Wilcox, Dan Williams
Cc: Kirill A. Shutemov, Andrew Morton, linux-mm, linux-fsdevel,
Linux Kernel Mailing List, linux-nvdimm@lists.01.org,
ross.zwisler
On Tue, Sep 15, 2015 at 04:52:42PM -0700, Dan Williams wrote:
> Hi Kirill,
>
> On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov
> <kirill.shutemov@linux.intel.com> wrote:
> > DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
> >
> > __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
> > all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
> >
> > Re-aquiring the lock should be fine since we check i_size after the
> > point.
> >
> > Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > ---
> > fs/dax.c | 35 +++++++++++++++++++----------------
> > mm/memory.c | 11 ++---------
> > 2 files changed, 21 insertions(+), 25 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 9ef9b80cc132..ed54efedade6 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> > if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
> > goto fallback;
> >
> > + if (buffer_unwritten(&bh) || buffer_new(&bh)) {
> > + int i;
> > + for (i = 0; i < PTRS_PER_PMD; i++)
> > + clear_page(kaddr + i * PAGE_SIZE);
>
> This patch, now upstream as commit 46c043ede471, moves the call to
> clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not
> set at this point, so I'm not sure this path was ever tested.
Ughh. It's obviously broken.
I took fs/dax.c part of the patch from Matthew. And I'm not sure now we
would need to move this "if (buffer_unwritten(&bh) || buffer_new(&bh)) {"
block around. It should work fine where it was before. Right?
Matthew?
> I'm also not sure why the compiler is not complaining about an
> uninitialized variable?
No idea.
--
Kirill A. Shutemov
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
2015-09-16 11:12 ` Kirill A. Shutemov
@ 2015-09-17 15:41 ` Ross Zwisler
-1 siblings, 0 replies; 13+ messages in thread
From: Ross Zwisler @ 2015-09-17 15:41 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: Matthew Wilcox, Dan Williams, Kirill A. Shutemov, Andrew Morton,
linux-mm, linux-fsdevel, Linux Kernel Mailing List,
linux-nvdimm@lists.01.org, ross.zwisler
On Wed, Sep 16, 2015 at 02:12:18PM +0300, Kirill A. Shutemov wrote:
> On Tue, Sep 15, 2015 at 04:52:42PM -0700, Dan Williams wrote:
> > Hi Kirill,
> >
> > On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov
> > <kirill.shutemov@linux.intel.com> wrote:
> > > DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
> > >
> > > __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
> > > all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
> > >
> > > Re-aquiring the lock should be fine since we check i_size after the
> > > point.
> > >
> > > Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
> > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > > ---
> > > fs/dax.c | 35 +++++++++++++++++++----------------
> > > mm/memory.c | 11 ++---------
> > > 2 files changed, 21 insertions(+), 25 deletions(-)
> > >
> > > diff --git a/fs/dax.c b/fs/dax.c
> > > index 9ef9b80cc132..ed54efedade6 100644
> > > --- a/fs/dax.c
> > > +++ b/fs/dax.c
> > > @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> > > if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
> > > goto fallback;
> > >
> > > + if (buffer_unwritten(&bh) || buffer_new(&bh)) {
> > > + int i;
> > > + for (i = 0; i < PTRS_PER_PMD; i++)
> > > + clear_page(kaddr + i * PAGE_SIZE);
> >
> > This patch, now upstream as commit 46c043ede471, moves the call to
> > clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not
> > set at this point, so I'm not sure this path was ever tested.
>
> Ughh. It's obviously broken.
>
> I took fs/dax.c part of the patch from Matthew. And I'm not sure now we
> would need to move this "if (buffer_unwritten(&bh) || buffer_new(&bh)) {"
> block around. It should work fine where it was before. Right?
> Matthew?
Moving the "if (buffer_unwritten(&bh) || buffer_new(&bh)) {" block back seems
correct to me. Matthew is out for a while, so we should probably take care of
this without him.
Kirill, do you want to whip up a quick patch? I'm happy to do it if you're
busy.
--
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^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
@ 2015-09-17 15:41 ` Ross Zwisler
0 siblings, 0 replies; 13+ messages in thread
From: Ross Zwisler @ 2015-09-17 15:41 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: Matthew Wilcox, Dan Williams, Kirill A. Shutemov, Andrew Morton,
linux-mm, linux-fsdevel, Linux Kernel Mailing List,
linux-nvdimm@lists.01.org, ross.zwisler
On Wed, Sep 16, 2015 at 02:12:18PM +0300, Kirill A. Shutemov wrote:
> On Tue, Sep 15, 2015 at 04:52:42PM -0700, Dan Williams wrote:
> > Hi Kirill,
> >
> > On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov
> > <kirill.shutemov@linux.intel.com> wrote:
> > > DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
> > >
> > > __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
> > > all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
> > >
> > > Re-aquiring the lock should be fine since we check i_size after the
> > > point.
> > >
> > > Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
> > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > > ---
> > > fs/dax.c | 35 +++++++++++++++++++----------------
> > > mm/memory.c | 11 ++---------
> > > 2 files changed, 21 insertions(+), 25 deletions(-)
> > >
> > > diff --git a/fs/dax.c b/fs/dax.c
> > > index 9ef9b80cc132..ed54efedade6 100644
> > > --- a/fs/dax.c
> > > +++ b/fs/dax.c
> > > @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> > > if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
> > > goto fallback;
> > >
> > > + if (buffer_unwritten(&bh) || buffer_new(&bh)) {
> > > + int i;
> > > + for (i = 0; i < PTRS_PER_PMD; i++)
> > > + clear_page(kaddr + i * PAGE_SIZE);
> >
> > This patch, now upstream as commit 46c043ede471, moves the call to
> > clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not
> > set at this point, so I'm not sure this path was ever tested.
>
> Ughh. It's obviously broken.
>
> I took fs/dax.c part of the patch from Matthew. And I'm not sure now we
> would need to move this "if (buffer_unwritten(&bh) || buffer_new(&bh)) {"
> block around. It should work fine where it was before. Right?
> Matthew?
Moving the "if (buffer_unwritten(&bh) || buffer_new(&bh)) {" block back seems
correct to me. Matthew is out for a while, so we should probably take care of
this without him.
Kirill, do you want to whip up a quick patch? I'm happy to do it if you're
busy.
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
2015-09-17 15:41 ` Ross Zwisler
@ 2015-09-17 15:46 ` Dan Williams
-1 siblings, 0 replies; 13+ messages in thread
From: Dan Williams @ 2015-09-17 15:46 UTC (permalink / raw)
To: Ross Zwisler, Kirill A. Shutemov, Matthew Wilcox, Dan Williams,
Kirill A. Shutemov, Andrew Morton, Linux MM, linux-fsdevel,
Linux Kernel Mailing List, linux-nvdimm@lists.01.org
On Thu, Sep 17, 2015 at 8:41 AM, Ross Zwisler
<ross.zwisler@linux.intel.com> wrote:
> On Wed, Sep 16, 2015 at 02:12:18PM +0300, Kirill A. Shutemov wrote:
>> On Tue, Sep 15, 2015 at 04:52:42PM -0700, Dan Williams wrote:
>> > Hi Kirill,
>> >
>> > On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov
>> > <kirill.shutemov@linux.intel.com> wrote:
>> > > DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
>> > >
>> > > __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
>> > > all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
>> > >
>> > > Re-aquiring the lock should be fine since we check i_size after the
>> > > point.
>> > >
>> > > Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
>> > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>> > > ---
>> > > fs/dax.c | 35 +++++++++++++++++++----------------
>> > > mm/memory.c | 11 ++---------
>> > > 2 files changed, 21 insertions(+), 25 deletions(-)
>> > >
>> > > diff --git a/fs/dax.c b/fs/dax.c
>> > > index 9ef9b80cc132..ed54efedade6 100644
>> > > --- a/fs/dax.c
>> > > +++ b/fs/dax.c
>> > > @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
>> > > if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
>> > > goto fallback;
>> > >
>> > > + if (buffer_unwritten(&bh) || buffer_new(&bh)) {
>> > > + int i;
>> > > + for (i = 0; i < PTRS_PER_PMD; i++)
>> > > + clear_page(kaddr + i * PAGE_SIZE);
>> >
>> > This patch, now upstream as commit 46c043ede471, moves the call to
>> > clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not
>> > set at this point, so I'm not sure this path was ever tested.
>>
>> Ughh. It's obviously broken.
>>
>> I took fs/dax.c part of the patch from Matthew. And I'm not sure now we
>> would need to move this "if (buffer_unwritten(&bh) || buffer_new(&bh)) {"
>> block around. It should work fine where it was before. Right?
>> Matthew?
>
> Moving the "if (buffer_unwritten(&bh) || buffer_new(&bh)) {" block back seems
> correct to me. Matthew is out for a while, so we should probably take care of
> this without him.
I'd say leave it at its current location and add a local call to
bdev_direct_access() as I'm not sure you'd want to trigger one of the
failure conditions without having zeroed the page. I.e. right before
vmf_insert_pfn_pmd() is probably too late.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
@ 2015-09-17 15:46 ` Dan Williams
0 siblings, 0 replies; 13+ messages in thread
From: Dan Williams @ 2015-09-17 15:46 UTC (permalink / raw)
To: Ross Zwisler, Kirill A. Shutemov, Matthew Wilcox, Dan Williams,
Kirill A. Shutemov, Andrew Morton, Linux MM, linux-fsdevel,
Linux Kernel Mailing List, linux-nvdimm@lists.01.org
On Thu, Sep 17, 2015 at 8:41 AM, Ross Zwisler
<ross.zwisler@linux.intel.com> wrote:
> On Wed, Sep 16, 2015 at 02:12:18PM +0300, Kirill A. Shutemov wrote:
>> On Tue, Sep 15, 2015 at 04:52:42PM -0700, Dan Williams wrote:
>> > Hi Kirill,
>> >
>> > On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov
>> > <kirill.shutemov@linux.intel.com> wrote:
>> > > DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
>> > >
>> > > __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
>> > > all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
>> > >
>> > > Re-aquiring the lock should be fine since we check i_size after the
>> > > point.
>> > >
>> > > Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
>> > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>> > > ---
>> > > fs/dax.c | 35 +++++++++++++++++++----------------
>> > > mm/memory.c | 11 ++---------
>> > > 2 files changed, 21 insertions(+), 25 deletions(-)
>> > >
>> > > diff --git a/fs/dax.c b/fs/dax.c
>> > > index 9ef9b80cc132..ed54efedade6 100644
>> > > --- a/fs/dax.c
>> > > +++ b/fs/dax.c
>> > > @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
>> > > if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
>> > > goto fallback;
>> > >
>> > > + if (buffer_unwritten(&bh) || buffer_new(&bh)) {
>> > > + int i;
>> > > + for (i = 0; i < PTRS_PER_PMD; i++)
>> > > + clear_page(kaddr + i * PAGE_SIZE);
>> >
>> > This patch, now upstream as commit 46c043ede471, moves the call to
>> > clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not
>> > set at this point, so I'm not sure this path was ever tested.
>>
>> Ughh. It's obviously broken.
>>
>> I took fs/dax.c part of the patch from Matthew. And I'm not sure now we
>> would need to move this "if (buffer_unwritten(&bh) || buffer_new(&bh)) {"
>> block around. It should work fine where it was before. Right?
>> Matthew?
>
> Moving the "if (buffer_unwritten(&bh) || buffer_new(&bh)) {" block back seems
> correct to me. Matthew is out for a while, so we should probably take care of
> this without him.
I'd say leave it at its current location and add a local call to
bdev_direct_access() as I'm not sure you'd want to trigger one of the
failure conditions without having zeroed the page. I.e. right before
vmf_insert_pfn_pmd() is probably too late.
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
2015-09-17 15:41 ` Ross Zwisler
(?)
@ 2015-09-17 15:47 ` Kirill A. Shutemov
-1 siblings, 0 replies; 13+ messages in thread
From: Kirill A. Shutemov @ 2015-09-17 15:47 UTC (permalink / raw)
To: Ross Zwisler
Cc: Kirill A. Shutemov, Matthew Wilcox, Dan Williams,
Kirill A. Shutemov, Andrew Morton, linux-mm, linux-fsdevel,
Linux Kernel Mailing List, linux-nvdimm@lists.01.org
Ross Zwisler wrote:
> On Wed, Sep 16, 2015 at 02:12:18PM +0300, Kirill A. Shutemov wrote:
> > On Tue, Sep 15, 2015 at 04:52:42PM -0700, Dan Williams wrote:
> > > Hi Kirill,
> > >
> > > On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov
> > > <kirill.shutemov@linux.intel.com> wrote:
> > > > DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
> > > >
> > > > __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
> > > > all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
> > > >
> > > > Re-aquiring the lock should be fine since we check i_size after the
> > > > point.
> > > >
> > > > Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
> > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > > > ---
> > > > fs/dax.c | 35 +++++++++++++++++++----------------
> > > > mm/memory.c | 11 ++---------
> > > > 2 files changed, 21 insertions(+), 25 deletions(-)
> > > >
> > > > diff --git a/fs/dax.c b/fs/dax.c
> > > > index 9ef9b80cc132..ed54efedade6 100644
> > > > --- a/fs/dax.c
> > > > +++ b/fs/dax.c
> > > > @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> > > > if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
> > > > goto fallback;
> > > >
> > > > + if (buffer_unwritten(&bh) || buffer_new(&bh)) {
> > > > + int i;
> > > > + for (i = 0; i < PTRS_PER_PMD; i++)
> > > > + clear_page(kaddr + i * PAGE_SIZE);
> > >
> > > This patch, now upstream as commit 46c043ede471, moves the call to
> > > clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not
> > > set at this point, so I'm not sure this path was ever tested.
> >
> > Ughh. It's obviously broken.
> >
> > I took fs/dax.c part of the patch from Matthew. And I'm not sure now we
> > would need to move this "if (buffer_unwritten(&bh) || buffer_new(&bh)) {"
> > block around. It should work fine where it was before. Right?
> > Matthew?
>
> Moving the "if (buffer_unwritten(&bh) || buffer_new(&bh)) {" block back seems
> correct to me. Matthew is out for a while, so we should probably take care of
> this without him.
>
> Kirill, do you want to whip up a quick patch? I'm happy to do it if you're
> busy.
I would be better if you'll prepare the patch. Thanks.
--
Kirill
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
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^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
@ 2015-09-17 15:47 ` Kirill A. Shutemov
0 siblings, 0 replies; 13+ messages in thread
From: Kirill A. Shutemov @ 2015-09-17 15:47 UTC (permalink / raw)
To: Ross Zwisler
Cc: Kirill A. Shutemov, Matthew Wilcox, Dan Williams,
Kirill A. Shutemov, Andrew Morton, linux-mm, linux-fsdevel,
Linux Kernel Mailing List, linux-nvdimm@lists.01.org,
ross.zwisler
Ross Zwisler wrote:
> On Wed, Sep 16, 2015 at 02:12:18PM +0300, Kirill A. Shutemov wrote:
> > On Tue, Sep 15, 2015 at 04:52:42PM -0700, Dan Williams wrote:
> > > Hi Kirill,
> > >
> > > On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov
> > > <kirill.shutemov@linux.intel.com> wrote:
> > > > DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
> > > >
> > > > __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
> > > > all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
> > > >
> > > > Re-aquiring the lock should be fine since we check i_size after the
> > > > point.
> > > >
> > > > Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
> > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > > > ---
> > > > fs/dax.c | 35 +++++++++++++++++++----------------
> > > > mm/memory.c | 11 ++---------
> > > > 2 files changed, 21 insertions(+), 25 deletions(-)
> > > >
> > > > diff --git a/fs/dax.c b/fs/dax.c
> > > > index 9ef9b80cc132..ed54efedade6 100644
> > > > --- a/fs/dax.c
> > > > +++ b/fs/dax.c
> > > > @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> > > > if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
> > > > goto fallback;
> > > >
> > > > + if (buffer_unwritten(&bh) || buffer_new(&bh)) {
> > > > + int i;
> > > > + for (i = 0; i < PTRS_PER_PMD; i++)
> > > > + clear_page(kaddr + i * PAGE_SIZE);
> > >
> > > This patch, now upstream as commit 46c043ede471, moves the call to
> > > clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not
> > > set at this point, so I'm not sure this path was ever tested.
> >
> > Ughh. It's obviously broken.
> >
> > I took fs/dax.c part of the patch from Matthew. And I'm not sure now we
> > would need to move this "if (buffer_unwritten(&bh) || buffer_new(&bh)) {"
> > block around. It should work fine where it was before. Right?
> > Matthew?
>
> Moving the "if (buffer_unwritten(&bh) || buffer_new(&bh)) {" block back seems
> correct to me. Matthew is out for a while, so we should probably take care of
> this without him.
>
> Kirill, do you want to whip up a quick patch? I'm happy to do it if you're
> busy.
I would be better if you'll prepare the patch. Thanks.
--
Kirill
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX
@ 2015-09-17 15:47 ` Kirill A. Shutemov
0 siblings, 0 replies; 13+ messages in thread
From: Kirill A. Shutemov @ 2015-09-17 15:47 UTC (permalink / raw)
To: Ross Zwisler
Cc: Kirill A. Shutemov, Matthew Wilcox, Dan Williams,
Kirill A. Shutemov, Andrew Morton, linux-mm, linux-fsdevel,
Linux Kernel Mailing List, linux-nvdimm@lists.01.org,
ross.zwisler
Ross Zwisler wrote:
> On Wed, Sep 16, 2015 at 02:12:18PM +0300, Kirill A. Shutemov wrote:
> > On Tue, Sep 15, 2015 at 04:52:42PM -0700, Dan Williams wrote:
> > > Hi Kirill,
> > >
> > > On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov
> > > <kirill.shutemov@linux.intel.com> wrote:
> > > > DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.
> > > >
> > > > __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
> > > > all mappings. We need to drop i_mmap_lock there to avoid lock deadlock.
> > > >
> > > > Re-aquiring the lock should be fine since we check i_size after the
> > > > point.
> > > >
> > > > Not-yet-signed-off-by: Matthew Wilcox <willy@linux.intel.com>
> > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > > > ---
> > > > fs/dax.c | 35 +++++++++++++++++++----------------
> > > > mm/memory.c | 11 ++---------
> > > > 2 files changed, 21 insertions(+), 25 deletions(-)
> > > >
> > > > diff --git a/fs/dax.c b/fs/dax.c
> > > > index 9ef9b80cc132..ed54efedade6 100644
> > > > --- a/fs/dax.c
> > > > +++ b/fs/dax.c
> > > > @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> > > > if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
> > > > goto fallback;
> > > >
> > > > + if (buffer_unwritten(&bh) || buffer_new(&bh)) {
> > > > + int i;
> > > > + for (i = 0; i < PTRS_PER_PMD; i++)
> > > > + clear_page(kaddr + i * PAGE_SIZE);
> > >
> > > This patch, now upstream as commit 46c043ede471, moves the call to
> > > clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not
> > > set at this point, so I'm not sure this path was ever tested.
> >
> > Ughh. It's obviously broken.
> >
> > I took fs/dax.c part of the patch from Matthew. And I'm not sure now we
> > would need to move this "if (buffer_unwritten(&bh) || buffer_new(&bh)) {"
> > block around. It should work fine where it was before. Right?
> > Matthew?
>
> Moving the "if (buffer_unwritten(&bh) || buffer_new(&bh)) {" block back seems
> correct to me. Matthew is out for a while, so we should probably take care of
> this without him.
>
> Kirill, do you want to whip up a quick patch? I'm happy to do it if you're
> busy.
I would be better if you'll prepare the patch. Thanks.
--
Kirill
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 13+ messages in thread
end of thread, other threads:[~2015-09-17 15:47 UTC | newest]
Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-08-07 11:53 [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX Kirill A. Shutemov
2015-08-07 11:53 ` Kirill A. Shutemov
2015-09-15 23:52 ` Dan Williams
2015-09-15 23:52 ` Dan Williams
2015-09-16 11:12 ` Kirill A. Shutemov
2015-09-16 11:12 ` Kirill A. Shutemov
2015-09-17 15:41 ` Ross Zwisler
2015-09-17 15:41 ` Ross Zwisler
2015-09-17 15:46 ` Dan Williams
2015-09-17 15:46 ` Dan Williams
2015-09-17 15:47 ` Kirill A. Shutemov
2015-09-17 15:47 ` Kirill A. Shutemov
2015-09-17 15:47 ` Kirill A. Shutemov
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