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* [PATCH v4] mm: pmd dirty emulation in page fault handler
@ 2016-12-23 15:14 ` Minchan Kim
  0 siblings, 0 replies; 6+ messages in thread
From: Minchan Kim @ 2016-12-23 15:14 UTC (permalink / raw)
  To: Andrew Morton
  Cc: linux-mm, linux-kernel, Andreas Schwab, Minchan Kim, Jason Evans,
	Michal Hocko, Will Deacon, Catalin Marinas, linux-arch,
	linux-arm-kernel, [4.5+],
	Kirill A. Shutemov

Andreas reported [1] made a test in jemalloc hang in THP mode in arm64.
http://lkml.kernel.org/r/mvmmvfy37g1.fsf@hawking.suse.de

The problem is currently page fault handler doesn't supports dirty bit
emulation of pmd for non-HW dirty-bit architecture so that application
stucks until VM marked the pmd dirty.

How the emulation work depends on the architecture. In case of arm64,
when it set up pte firstly, it sets pte PTE_RDONLY to get a chance to
mark the pte dirty via triggering page fault when store access happens.
Once the page fault occurs, VM marks the pmd dirty and arch code for
setting pmd will clear PTE_RDONLY for application to proceed.

IOW, if VM doesn't mark the pmd dirty, application hangs forever by
repeated fault(i.e., store op but the pmd is PTE_RDONLY).

This patch enables pmd dirty-bit emulation for those architectures.

[1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called

Cc: Jason Evans <je@fb.com>
Cc: Michal Hocko <mhocko@suse.com> 
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: <stable@vger.kernel.org> [4.5+]
Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called")
Reported-and-Tested-by: Andreas Schwab <schwab@suse.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
  Merry Xmas!

* from v3
  * Elaborate description
* from v2
  * Add acked-by/tested-by
* from v1
  * Remove __handle_mm_fault part - Kirill
 mm/huge_memory.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 10eedbf..29ec8a4 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -883,15 +883,17 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
 {
 	pmd_t entry;
 	unsigned long haddr;
+	bool write = vmf->flags & FAULT_FLAG_WRITE;
 
 	vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
 	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
 		goto unlock;
 
 	entry = pmd_mkyoung(orig_pmd);
+	if (write)
+		entry = pmd_mkdirty(entry);
 	haddr = vmf->address & HPAGE_PMD_MASK;
-	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry,
-				vmf->flags & FAULT_FLAG_WRITE))
+	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
 		update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
 
 unlock:
-- 
2.7.4

^ permalink raw reply	[flat|nested] 6+ messages in thread

* [PATCH v4] mm: pmd dirty emulation in page fault handler
@ 2016-12-23 15:14 ` Minchan Kim
  0 siblings, 0 replies; 6+ messages in thread
From: Minchan Kim @ 2016-12-23 15:14 UTC (permalink / raw)
  To: Andrew Morton
  Cc: linux-mm, linux-kernel, Andreas Schwab, Minchan Kim, Jason Evans,
	Michal Hocko, Will Deacon, Catalin Marinas, linux-arch,
	linux-arm-kernel, [4.5+],
	Kirill A. Shutemov

Andreas reported [1] made a test in jemalloc hang in THP mode in arm64.
http://lkml.kernel.org/r/mvmmvfy37g1.fsf@hawking.suse.de

The problem is currently page fault handler doesn't supports dirty bit
emulation of pmd for non-HW dirty-bit architecture so that application
stucks until VM marked the pmd dirty.

How the emulation work depends on the architecture. In case of arm64,
when it set up pte firstly, it sets pte PTE_RDONLY to get a chance to
mark the pte dirty via triggering page fault when store access happens.
Once the page fault occurs, VM marks the pmd dirty and arch code for
setting pmd will clear PTE_RDONLY for application to proceed.

IOW, if VM doesn't mark the pmd dirty, application hangs forever by
repeated fault(i.e., store op but the pmd is PTE_RDONLY).

This patch enables pmd dirty-bit emulation for those architectures.

[1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called

Cc: Jason Evans <je@fb.com>
Cc: Michal Hocko <mhocko@suse.com> 
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: <stable@vger.kernel.org> [4.5+]
Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called")
Reported-and-Tested-by: Andreas Schwab <schwab@suse.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
  Merry Xmas!

* from v3
  * Elaborate description
* from v2
  * Add acked-by/tested-by
* from v1
  * Remove __handle_mm_fault part - Kirill
 mm/huge_memory.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 10eedbf..29ec8a4 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -883,15 +883,17 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
 {
 	pmd_t entry;
 	unsigned long haddr;
+	bool write = vmf->flags & FAULT_FLAG_WRITE;
 
 	vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
 	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
 		goto unlock;
 
 	entry = pmd_mkyoung(orig_pmd);
+	if (write)
+		entry = pmd_mkdirty(entry);
 	haddr = vmf->address & HPAGE_PMD_MASK;
-	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry,
-				vmf->flags & FAULT_FLAG_WRITE))
+	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
 		update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
 
 unlock:
-- 
2.7.4

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply	[flat|nested] 6+ messages in thread

* [PATCH v4] mm: pmd dirty emulation in page fault handler
@ 2016-12-23 15:14 ` Minchan Kim
  0 siblings, 0 replies; 6+ messages in thread
From: Minchan Kim @ 2016-12-23 15:14 UTC (permalink / raw)
  To: linux-arm-kernel

Andreas reported [1] made a test in jemalloc hang in THP mode in arm64.
http://lkml.kernel.org/r/mvmmvfy37g1.fsf at hawking.suse.de

The problem is currently page fault handler doesn't supports dirty bit
emulation of pmd for non-HW dirty-bit architecture so that application
stucks until VM marked the pmd dirty.

How the emulation work depends on the architecture. In case of arm64,
when it set up pte firstly, it sets pte PTE_RDONLY to get a chance to
mark the pte dirty via triggering page fault when store access happens.
Once the page fault occurs, VM marks the pmd dirty and arch code for
setting pmd will clear PTE_RDONLY for application to proceed.

IOW, if VM doesn't mark the pmd dirty, application hangs forever by
repeated fault(i.e., store op but the pmd is PTE_RDONLY).

This patch enables pmd dirty-bit emulation for those architectures.

[1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called

Cc: Jason Evans <je@fb.com>
Cc: Michal Hocko <mhocko@suse.com> 
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-arch at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: <stable@vger.kernel.org> [4.5+]
Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called")
Reported-and-Tested-by: Andreas Schwab <schwab@suse.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
  Merry Xmas!

* from v3
  * Elaborate description
* from v2
  * Add acked-by/tested-by
* from v1
  * Remove __handle_mm_fault part - Kirill
 mm/huge_memory.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 10eedbf..29ec8a4 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -883,15 +883,17 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
 {
 	pmd_t entry;
 	unsigned long haddr;
+	bool write = vmf->flags & FAULT_FLAG_WRITE;
 
 	vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
 	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
 		goto unlock;
 
 	entry = pmd_mkyoung(orig_pmd);
+	if (write)
+		entry = pmd_mkdirty(entry);
 	haddr = vmf->address & HPAGE_PMD_MASK;
-	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry,
-				vmf->flags & FAULT_FLAG_WRITE))
+	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
 		update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
 
 unlock:
-- 
2.7.4

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH v4] mm: pmd dirty emulation in page fault handler
  2016-12-23 15:14 ` Minchan Kim
  (?)
@ 2016-12-27 10:17   ` Michal Hocko
  -1 siblings, 0 replies; 6+ messages in thread
From: Michal Hocko @ 2016-12-27 10:17 UTC (permalink / raw)
  To: Minchan Kim
  Cc: Andrew Morton, linux-mm, linux-kernel, Andreas Schwab,
	Jason Evans, Will Deacon, Catalin Marinas, linux-arch,
	linux-arm-kernel, [4.5+],
	Kirill A. Shutemov

On Sat 24-12-16 00:14:58, Minchan Kim wrote:
> Andreas reported [1] made a test in jemalloc hang in THP mode in arm64.
> http://lkml.kernel.org/r/mvmmvfy37g1.fsf@hawking.suse.de
> 
> The problem is currently page fault handler doesn't supports dirty bit
> emulation of pmd for non-HW dirty-bit architecture so that application
> stucks until VM marked the pmd dirty.
> 
> How the emulation work depends on the architecture. In case of arm64,
> when it set up pte firstly, it sets pte PTE_RDONLY to get a chance to
> mark the pte dirty via triggering page fault when store access happens.
> Once the page fault occurs, VM marks the pmd dirty and arch code for
> setting pmd will clear PTE_RDONLY for application to proceed.
> 
> IOW, if VM doesn't mark the pmd dirty, application hangs forever by
> repeated fault(i.e., store op but the pmd is PTE_RDONLY).
> 
> This patch enables pmd dirty-bit emulation for those architectures.

Thanks for extending the patch description again!

> [1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called
> 
> Cc: Jason Evans <je@fb.com>
> Cc: Michal Hocko <mhocko@suse.com> 
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: linux-arch@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: <stable@vger.kernel.org> [4.5+]
> Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called")
> Reported-and-Tested-by: Andreas Schwab <schwab@suse.de>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>   Merry Xmas!
> 
> * from v3
>   * Elaborate description
> * from v2
>   * Add acked-by/tested-by
> * from v1
>   * Remove __handle_mm_fault part - Kirill
>  mm/huge_memory.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 10eedbf..29ec8a4 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -883,15 +883,17 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
>  {
>  	pmd_t entry;
>  	unsigned long haddr;
> +	bool write = vmf->flags & FAULT_FLAG_WRITE;
>  
>  	vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
>  	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
>  		goto unlock;
>  
>  	entry = pmd_mkyoung(orig_pmd);
> +	if (write)
> +		entry = pmd_mkdirty(entry);
>  	haddr = vmf->address & HPAGE_PMD_MASK;
> -	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry,
> -				vmf->flags & FAULT_FLAG_WRITE))
> +	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
>  		update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
>  
>  unlock:
> -- 
> 2.7.4
> 

-- 
Michal Hocko
SUSE Labs

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH v4] mm: pmd dirty emulation in page fault handler
@ 2016-12-27 10:17   ` Michal Hocko
  0 siblings, 0 replies; 6+ messages in thread
From: Michal Hocko @ 2016-12-27 10:17 UTC (permalink / raw)
  To: Minchan Kim
  Cc: Andrew Morton, linux-mm, linux-kernel, Andreas Schwab,
	Jason Evans, Will Deacon, Catalin Marinas, linux-arch,
	linux-arm-kernel, [4.5+],
	Kirill A. Shutemov

On Sat 24-12-16 00:14:58, Minchan Kim wrote:
> Andreas reported [1] made a test in jemalloc hang in THP mode in arm64.
> http://lkml.kernel.org/r/mvmmvfy37g1.fsf@hawking.suse.de
> 
> The problem is currently page fault handler doesn't supports dirty bit
> emulation of pmd for non-HW dirty-bit architecture so that application
> stucks until VM marked the pmd dirty.
> 
> How the emulation work depends on the architecture. In case of arm64,
> when it set up pte firstly, it sets pte PTE_RDONLY to get a chance to
> mark the pte dirty via triggering page fault when store access happens.
> Once the page fault occurs, VM marks the pmd dirty and arch code for
> setting pmd will clear PTE_RDONLY for application to proceed.
> 
> IOW, if VM doesn't mark the pmd dirty, application hangs forever by
> repeated fault(i.e., store op but the pmd is PTE_RDONLY).
> 
> This patch enables pmd dirty-bit emulation for those architectures.

Thanks for extending the patch description again!

> [1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called
> 
> Cc: Jason Evans <je@fb.com>
> Cc: Michal Hocko <mhocko@suse.com> 
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: linux-arch@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: <stable@vger.kernel.org> [4.5+]
> Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called")
> Reported-and-Tested-by: Andreas Schwab <schwab@suse.de>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>   Merry Xmas!
> 
> * from v3
>   * Elaborate description
> * from v2
>   * Add acked-by/tested-by
> * from v1
>   * Remove __handle_mm_fault part - Kirill
>  mm/huge_memory.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 10eedbf..29ec8a4 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -883,15 +883,17 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
>  {
>  	pmd_t entry;
>  	unsigned long haddr;
> +	bool write = vmf->flags & FAULT_FLAG_WRITE;
>  
>  	vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
>  	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
>  		goto unlock;
>  
>  	entry = pmd_mkyoung(orig_pmd);
> +	if (write)
> +		entry = pmd_mkdirty(entry);
>  	haddr = vmf->address & HPAGE_PMD_MASK;
> -	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry,
> -				vmf->flags & FAULT_FLAG_WRITE))
> +	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
>  		update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
>  
>  unlock:
> -- 
> 2.7.4
> 

-- 
Michal Hocko
SUSE Labs

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply	[flat|nested] 6+ messages in thread

* [PATCH v4] mm: pmd dirty emulation in page fault handler
@ 2016-12-27 10:17   ` Michal Hocko
  0 siblings, 0 replies; 6+ messages in thread
From: Michal Hocko @ 2016-12-27 10:17 UTC (permalink / raw)
  To: linux-arm-kernel

On Sat 24-12-16 00:14:58, Minchan Kim wrote:
> Andreas reported [1] made a test in jemalloc hang in THP mode in arm64.
> http://lkml.kernel.org/r/mvmmvfy37g1.fsf at hawking.suse.de
> 
> The problem is currently page fault handler doesn't supports dirty bit
> emulation of pmd for non-HW dirty-bit architecture so that application
> stucks until VM marked the pmd dirty.
> 
> How the emulation work depends on the architecture. In case of arm64,
> when it set up pte firstly, it sets pte PTE_RDONLY to get a chance to
> mark the pte dirty via triggering page fault when store access happens.
> Once the page fault occurs, VM marks the pmd dirty and arch code for
> setting pmd will clear PTE_RDONLY for application to proceed.
> 
> IOW, if VM doesn't mark the pmd dirty, application hangs forever by
> repeated fault(i.e., store op but the pmd is PTE_RDONLY).
> 
> This patch enables pmd dirty-bit emulation for those architectures.

Thanks for extending the patch description again!

> [1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called
> 
> Cc: Jason Evans <je@fb.com>
> Cc: Michal Hocko <mhocko@suse.com> 
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: linux-arch at vger.kernel.org
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: <stable@vger.kernel.org> [4.5+]
> Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called")
> Reported-and-Tested-by: Andreas Schwab <schwab@suse.de>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>   Merry Xmas!
> 
> * from v3
>   * Elaborate description
> * from v2
>   * Add acked-by/tested-by
> * from v1
>   * Remove __handle_mm_fault part - Kirill
>  mm/huge_memory.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 10eedbf..29ec8a4 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -883,15 +883,17 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
>  {
>  	pmd_t entry;
>  	unsigned long haddr;
> +	bool write = vmf->flags & FAULT_FLAG_WRITE;
>  
>  	vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
>  	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
>  		goto unlock;
>  
>  	entry = pmd_mkyoung(orig_pmd);
> +	if (write)
> +		entry = pmd_mkdirty(entry);
>  	haddr = vmf->address & HPAGE_PMD_MASK;
> -	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry,
> -				vmf->flags & FAULT_FLAG_WRITE))
> +	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
>  		update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
>  
>  unlock:
> -- 
> 2.7.4
> 

-- 
Michal Hocko
SUSE Labs

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2016-12-27 10:18 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-12-23 15:14 [PATCH v4] mm: pmd dirty emulation in page fault handler Minchan Kim
2016-12-23 15:14 ` Minchan Kim
2016-12-23 15:14 ` Minchan Kim
2016-12-27 10:17 ` Michal Hocko
2016-12-27 10:17   ` Michal Hocko
2016-12-27 10:17   ` Michal Hocko

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