[PATCH] ext2, ext4: Fix issue with missing journal entry

[PATCH] ext2, ext4: Fix issue with missing journal entry

[Ross Zwisler]

As it is currently written ext4_dax_mkwrite() assumes that the call into
__dax_mkwrite() will not have to do a block allocation so it doesn't create
a journal entry.  For a read that creates a zero page to cover a hole
followed by a write that actually allocates storage this is incorrect.  The
ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
get_blocks() to allocate storage.

Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
as this function already has all the logic needed to allocate a journal
entry and call __dax_fault().

Also update the ext2 fault handlers in this same way to remove duplicate
code and keep the logic between ext2 and ext4 the same.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/ext2/file.c | 19 +------------------
 fs/ext4/file.c | 19 ++-----------------
 2 files changed, 3 insertions(+), 35 deletions(-)

diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 2c88d68..c1400b1 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -80,23 +80,6 @@ static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return ret;
 }
 
-static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
-{
-	struct inode *inode = file_inode(vma->vm_file);
-	struct ext2_inode_info *ei = EXT2_I(inode);
-	int ret;
-
-	sb_start_pagefault(inode->i_sb);
-	file_update_time(vma->vm_file);
-	down_read(&ei->dax_sem);
-
-	ret = __dax_mkwrite(vma, vmf, ext2_get_block, NULL);
-
-	up_read(&ei->dax_sem);
-	sb_end_pagefault(inode->i_sb);
-	return ret;
-}
-
 static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 		struct vm_fault *vmf)
 {
@@ -124,7 +107,7 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 static const struct vm_operations_struct ext2_dax_vm_ops = {
 	.fault		= ext2_dax_fault,
 	.pmd_fault	= ext2_dax_pmd_fault,
-	.page_mkwrite	= ext2_dax_mkwrite,
+	.page_mkwrite	= ext2_dax_fault,
 	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
 };
 
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 1126436..d2e8500 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -262,23 +262,8 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return result;
 }
 
-static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
-{
-	int err;
-	struct inode *inode = file_inode(vma->vm_file);
-
-	sb_start_pagefault(inode->i_sb);
-	file_update_time(vma->vm_file);
-	down_read(&EXT4_I(inode)->i_mmap_sem);
-	err = __dax_mkwrite(vma, vmf, ext4_dax_mmap_get_block, NULL);
-	up_read(&EXT4_I(inode)->i_mmap_sem);
-	sb_end_pagefault(inode->i_sb);
-
-	return err;
-}
-
 /*
- * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_mkwrite()
+ * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_fault()
  * handler we check for races agaist truncate. Note that since we cycle through
  * i_mmap_sem, we are sure that also any hole punching that began before we
  * were called is finished by now and so if it included part of the file we
@@ -311,7 +296,7 @@ static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma,
 static const struct vm_operations_struct ext4_dax_vm_ops = {
 	.fault		= ext4_dax_fault,
 	.pmd_fault	= ext4_dax_pmd_fault,
-	.page_mkwrite	= ext4_dax_mkwrite,
+	.page_mkwrite	= ext4_dax_fault,
 	.pfn_mkwrite	= ext4_dax_pfn_mkwrite,
 };
 #else
-- 
2.5.0

[PATCH] ext2, ext4: Fix issue with missing journal entry

[Ross Zwisler]

As it is currently written ext4_dax_mkwrite() assumes that the call into
__dax_mkwrite() will not have to do a block allocation so it doesn't create
a journal entry.  For a read that creates a zero page to cover a hole
followed by a write that actually allocates storage this is incorrect.  The
ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
get_blocks() to allocate storage.

Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
as this function already has all the logic needed to allocate a journal
entry and call __dax_fault().

Also update the ext2 fault handlers in this same way to remove duplicate
code and keep the logic between ext2 and ext4 the same.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/ext2/file.c | 19 +------------------
 fs/ext4/file.c | 19 ++-----------------
 2 files changed, 3 insertions(+), 35 deletions(-)

diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 2c88d68..c1400b1 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -80,23 +80,6 @@ static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return ret;
 }
 
-static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
-{
-	struct inode *inode = file_inode(vma->vm_file);
-	struct ext2_inode_info *ei = EXT2_I(inode);
-	int ret;
-
-	sb_start_pagefault(inode->i_sb);
-	file_update_time(vma->vm_file);
-	down_read(&ei->dax_sem);
-
-	ret = __dax_mkwrite(vma, vmf, ext2_get_block, NULL);
-
-	up_read(&ei->dax_sem);
-	sb_end_pagefault(inode->i_sb);
-	return ret;
-}
-
 static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 		struct vm_fault *vmf)
 {
@@ -124,7 +107,7 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 static const struct vm_operations_struct ext2_dax_vm_ops = {
 	.fault		= ext2_dax_fault,
 	.pmd_fault	= ext2_dax_pmd_fault,
-	.page_mkwrite	= ext2_dax_mkwrite,
+	.page_mkwrite	= ext2_dax_fault,
 	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
 };
 
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 1126436..d2e8500 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -262,23 +262,8 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return result;
 }
 
-static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
-{
-	int err;
-	struct inode *inode = file_inode(vma->vm_file);
-
-	sb_start_pagefault(inode->i_sb);
-	file_update_time(vma->vm_file);
-	down_read(&EXT4_I(inode)->i_mmap_sem);
-	err = __dax_mkwrite(vma, vmf, ext4_dax_mmap_get_block, NULL);
-	up_read(&EXT4_I(inode)->i_mmap_sem);
-	sb_end_pagefault(inode->i_sb);
-
-	return err;
-}
-
 /*
- * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_mkwrite()
+ * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_fault()
  * handler we check for races agaist truncate. Note that since we cycle through
  * i_mmap_sem, we are sure that also any hole punching that began before we
  * were called is finished by now and so if it included part of the file we
@@ -311,7 +296,7 @@ static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma,
 static const struct vm_operations_struct ext4_dax_vm_ops = {
 	.fault		= ext4_dax_fault,
 	.pmd_fault	= ext4_dax_pmd_fault,
-	.page_mkwrite	= ext4_dax_mkwrite,
+	.page_mkwrite	= ext4_dax_fault,
 	.pfn_mkwrite	= ext4_dax_pfn_mkwrite,
 };
 #else
-- 
2.5.0

[PATCH] ext2, ext4: Fix issue with missing journal entry

[Ross Zwisler]

As it is currently written ext4_dax_mkwrite() assumes that the call into
__dax_mkwrite() will not have to do a block allocation so it doesn't create
a journal entry.  For a read that creates a zero page to cover a hole
followed by a write that actually allocates storage this is incorrect.  The
ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
get_blocks() to allocate storage.

Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
as this function already has all the logic needed to allocate a journal
entry and call __dax_fault().

Also update the ext2 fault handlers in this same way to remove duplicate
code and keep the logic between ext2 and ext4 the same.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/ext2/file.c | 19 +------------------
 fs/ext4/file.c | 19 ++-----------------
 2 files changed, 3 insertions(+), 35 deletions(-)

diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 2c88d68..c1400b1 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -80,23 +80,6 @@ static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return ret;
 }
 
-static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
-{
-	struct inode *inode = file_inode(vma->vm_file);
-	struct ext2_inode_info *ei = EXT2_I(inode);
-	int ret;
-
-	sb_start_pagefault(inode->i_sb);
-	file_update_time(vma->vm_file);
-	down_read(&ei->dax_sem);
-
-	ret = __dax_mkwrite(vma, vmf, ext2_get_block, NULL);
-
-	up_read(&ei->dax_sem);
-	sb_end_pagefault(inode->i_sb);
-	return ret;
-}
-
 static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 		struct vm_fault *vmf)
 {
@@ -124,7 +107,7 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 static const struct vm_operations_struct ext2_dax_vm_ops = {
 	.fault		= ext2_dax_fault,
 	.pmd_fault	= ext2_dax_pmd_fault,
-	.page_mkwrite	= ext2_dax_mkwrite,
+	.page_mkwrite	= ext2_dax_fault,
 	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
 };
 
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 1126436..d2e8500 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -262,23 +262,8 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return result;
 }
 
-static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
-{
-	int err;
-	struct inode *inode = file_inode(vma->vm_file);
-
-	sb_start_pagefault(inode->i_sb);
-	file_update_time(vma->vm_file);
-	down_read(&EXT4_I(inode)->i_mmap_sem);
-	err = __dax_mkwrite(vma, vmf, ext4_dax_mmap_get_block, NULL);
-	up_read(&EXT4_I(inode)->i_mmap_sem);
-	sb_end_pagefault(inode->i_sb);
-
-	return err;
-}

Re: [PATCH] ext2, ext4: Fix issue with missing journal entry

[Jan Kara]

On Wed 27-01-16 12:01:48, Ross Zwisler wrote:
> As it is currently written ext4_dax_mkwrite() assumes that the call into
> __dax_mkwrite() will not have to do a block allocation so it doesn't create
> a journal entry.  For a read that creates a zero page to cover a hole
> followed by a write that actually allocates storage this is incorrect.  The
> ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
> get_blocks() to allocate storage.
> 
> Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
> as this function already has all the logic needed to allocate a journal
> entry and call __dax_fault().
> 
> Also update the ext2 fault handlers in this same way to remove duplicate
> code and keep the logic between ext2 and ext4 the same.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Ah, ok, you are right. The patch looks good but Matthew is reworking the
area more (so ext4_da_mkwrite() is likely to return) so it this worth it?
Or do you expect Matthew's patches to land much later?

								Honza

> ---
>  fs/ext2/file.c | 19 +------------------
>  fs/ext4/file.c | 19 ++-----------------
>  2 files changed, 3 insertions(+), 35 deletions(-)
> 
> diff --git a/fs/ext2/file.c b/fs/ext2/file.c
> index 2c88d68..c1400b1 100644
> --- a/fs/ext2/file.c
> +++ b/fs/ext2/file.c
> @@ -80,23 +80,6 @@ static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
>  	return ret;
>  }
>  
> -static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> -{
> -	struct inode *inode = file_inode(vma->vm_file);
> -	struct ext2_inode_info *ei = EXT2_I(inode);
> -	int ret;
> -
> -	sb_start_pagefault(inode->i_sb);
> -	file_update_time(vma->vm_file);
> -	down_read(&ei->dax_sem);
> -
> -	ret = __dax_mkwrite(vma, vmf, ext2_get_block, NULL);
> -
> -	up_read(&ei->dax_sem);
> -	sb_end_pagefault(inode->i_sb);
> -	return ret;
> -}
> -
>  static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
>  		struct vm_fault *vmf)
>  {
> @@ -124,7 +107,7 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
>  static const struct vm_operations_struct ext2_dax_vm_ops = {
>  	.fault		= ext2_dax_fault,
>  	.pmd_fault	= ext2_dax_pmd_fault,
> -	.page_mkwrite	= ext2_dax_mkwrite,
> +	.page_mkwrite	= ext2_dax_fault,
>  	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
>  };
>  
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 1126436..d2e8500 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -262,23 +262,8 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
>  	return result;
>  }
>  
> -static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> -{
> -	int err;
> -	struct inode *inode = file_inode(vma->vm_file);
> -
> -	sb_start_pagefault(inode->i_sb);
> -	file_update_time(vma->vm_file);
> -	down_read(&EXT4_I(inode)->i_mmap_sem);
> -	err = __dax_mkwrite(vma, vmf, ext4_dax_mmap_get_block, NULL);
> -	up_read(&EXT4_I(inode)->i_mmap_sem);
> -	sb_end_pagefault(inode->i_sb);
> -
> -	return err;
> -}
> -
>  /*
> - * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_mkwrite()
> + * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_fault()
>   * handler we check for races agaist truncate. Note that since we cycle through
>   * i_mmap_sem, we are sure that also any hole punching that began before we
>   * were called is finished by now and so if it included part of the file we
> @@ -311,7 +296,7 @@ static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma,
>  static const struct vm_operations_struct ext4_dax_vm_ops = {
>  	.fault		= ext4_dax_fault,
>  	.pmd_fault	= ext4_dax_pmd_fault,
> -	.page_mkwrite	= ext4_dax_mkwrite,
> +	.page_mkwrite	= ext4_dax_fault,
>  	.pfn_mkwrite	= ext4_dax_pfn_mkwrite,
>  };
>  #else
> -- 
> 2.5.0
> 
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] ext2, ext4: Fix issue with missing journal entry

[Jan Kara]

On Wed 27-01-16 12:01:48, Ross Zwisler wrote:
> As it is currently written ext4_dax_mkwrite() assumes that the call into
> __dax_mkwrite() will not have to do a block allocation so it doesn't create
> a journal entry.  For a read that creates a zero page to cover a hole
> followed by a write that actually allocates storage this is incorrect.  The
> ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
> get_blocks() to allocate storage.
> 
> Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
> as this function already has all the logic needed to allocate a journal
> entry and call __dax_fault().
> 
> Also update the ext2 fault handlers in this same way to remove duplicate
> code and keep the logic between ext2 and ext4 the same.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Ah, ok, you are right. The patch looks good but Matthew is reworking the
area more (so ext4_da_mkwrite() is likely to return) so it this worth it?
Or do you expect Matthew's patches to land much later?

								Honza

> ---
>  fs/ext2/file.c | 19 +------------------
>  fs/ext4/file.c | 19 ++-----------------
>  2 files changed, 3 insertions(+), 35 deletions(-)
> 
> diff --git a/fs/ext2/file.c b/fs/ext2/file.c
> index 2c88d68..c1400b1 100644
> --- a/fs/ext2/file.c
> +++ b/fs/ext2/file.c
> @@ -80,23 +80,6 @@ static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
>  	return ret;
>  }
>  
> -static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> -{
> -	struct inode *inode = file_inode(vma->vm_file);
> -	struct ext2_inode_info *ei = EXT2_I(inode);
> -	int ret;
> -
> -	sb_start_pagefault(inode->i_sb);
> -	file_update_time(vma->vm_file);
> -	down_read(&ei->dax_sem);
> -
> -	ret = __dax_mkwrite(vma, vmf, ext2_get_block, NULL);
> -
> -	up_read(&ei->dax_sem);
> -	sb_end_pagefault(inode->i_sb);
> -	return ret;
> -}
> -
>  static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
>  		struct vm_fault *vmf)
>  {
> @@ -124,7 +107,7 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
>  static const struct vm_operations_struct ext2_dax_vm_ops = {
>  	.fault		= ext2_dax_fault,
>  	.pmd_fault	= ext2_dax_pmd_fault,
> -	.page_mkwrite	= ext2_dax_mkwrite,
> +	.page_mkwrite	= ext2_dax_fault,
>  	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
>  };
>  
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 1126436..d2e8500 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -262,23 +262,8 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
>  	return result;
>  }
>  
> -static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> -{
> -	int err;
> -	struct inode *inode = file_inode(vma->vm_file);
> -
> -	sb_start_pagefault(inode->i_sb);
> -	file_update_time(vma->vm_file);
> -	down_read(&EXT4_I(inode)->i_mmap_sem);
> -	err = __dax_mkwrite(vma, vmf, ext4_dax_mmap_get_block, NULL);
> -	up_read(&EXT4_I(inode)->i_mmap_sem);
> -	sb_end_pagefault(inode->i_sb);
> -
> -	return err;
> -}
> -
>  /*
> - * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_mkwrite()
> + * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_fault()
>   * handler we check for races agaist truncate. Note that since we cycle through
>   * i_mmap_sem, we are sure that also any hole punching that began before we
>   * were called is finished by now and so if it included part of the file we
> @@ -311,7 +296,7 @@ static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma,
>  static const struct vm_operations_struct ext4_dax_vm_ops = {
>  	.fault		= ext4_dax_fault,
>  	.pmd_fault	= ext4_dax_pmd_fault,
> -	.page_mkwrite	= ext4_dax_mkwrite,
> +	.page_mkwrite	= ext4_dax_fault,
>  	.pfn_mkwrite	= ext4_dax_pfn_mkwrite,
>  };
>  #else
> -- 
> 2.5.0
> 
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] ext2, ext4: Fix issue with missing journal entry

[Ross Zwisler]

On Thu, Jan 28, 2016 at 02:16:30PM +0100, Jan Kara wrote:
> On Wed 27-01-16 12:01:48, Ross Zwisler wrote:
> > As it is currently written ext4_dax_mkwrite() assumes that the call into
> > __dax_mkwrite() will not have to do a block allocation so it doesn't create
> > a journal entry.  For a read that creates a zero page to cover a hole
> > followed by a write that actually allocates storage this is incorrect.  The
> > ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
> > get_blocks() to allocate storage.
> > 
> > Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
> > as this function already has all the logic needed to allocate a journal
> > entry and call __dax_fault().
> > 
> > Also update the ext2 fault handlers in this same way to remove duplicate
> > code and keep the logic between ext2 and ext4 the same.
> > 
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> 
> Ah, ok, you are right. The patch looks good but Matthew is reworking the
> area more (so ext4_da_mkwrite() is likely to return) so it this worth it?
> Or do you expect Matthew's patches to land much later?

Yep, Matthew is in the process of reworking all of the DAX fault handling.

I was thinking that we might want to take this patch for v4.5, since it fixes
a bug that I'm guessing could lead to some sort of corruption (lack of a
journal entry entry for an allocating write), and then Matthew's reworks would
land in v4.6?

> > ---
> >  fs/ext2/file.c | 19 +------------------
> >  fs/ext4/file.c | 19 ++-----------------
> >  2 files changed, 3 insertions(+), 35 deletions(-)
> > 
> > diff --git a/fs/ext2/file.c b/fs/ext2/file.c
> > index 2c88d68..c1400b1 100644
> > --- a/fs/ext2/file.c
> > +++ b/fs/ext2/file.c
> > @@ -80,23 +80,6 @@ static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
> >  	return ret;
> >  }
> >  
> > -static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> > -{
> > -	struct inode *inode = file_inode(vma->vm_file);
> > -	struct ext2_inode_info *ei = EXT2_I(inode);
> > -	int ret;
> > -
> > -	sb_start_pagefault(inode->i_sb);
> > -	file_update_time(vma->vm_file);
> > -	down_read(&ei->dax_sem);
> > -
> > -	ret = __dax_mkwrite(vma, vmf, ext2_get_block, NULL);
> > -
> > -	up_read(&ei->dax_sem);
> > -	sb_end_pagefault(inode->i_sb);
> > -	return ret;
> > -}
> > -
> >  static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
> >  		struct vm_fault *vmf)
> >  {
> > @@ -124,7 +107,7 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
> >  static const struct vm_operations_struct ext2_dax_vm_ops = {
> >  	.fault		= ext2_dax_fault,
> >  	.pmd_fault	= ext2_dax_pmd_fault,
> > -	.page_mkwrite	= ext2_dax_mkwrite,
> > +	.page_mkwrite	= ext2_dax_fault,
> >  	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
> >  };
> >  
> > diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> > index 1126436..d2e8500 100644
> > --- a/fs/ext4/file.c
> > +++ b/fs/ext4/file.c
> > @@ -262,23 +262,8 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
> >  	return result;
> >  }
> >  
> > -static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> > -{
> > -	int err;
> > -	struct inode *inode = file_inode(vma->vm_file);
> > -
> > -	sb_start_pagefault(inode->i_sb);
> > -	file_update_time(vma->vm_file);
> > -	down_read(&EXT4_I(inode)->i_mmap_sem);
> > -	err = __dax_mkwrite(vma, vmf, ext4_dax_mmap_get_block, NULL);
> > -	up_read(&EXT4_I(inode)->i_mmap_sem);
> > -	sb_end_pagefault(inode->i_sb);
> > -
> > -	return err;
> > -}
> > -
> >  /*
> > - * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_mkwrite()
> > + * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_fault()
> >   * handler we check for races agaist truncate. Note that since we cycle through
> >   * i_mmap_sem, we are sure that also any hole punching that began before we
> >   * were called is finished by now and so if it included part of the file we
> > @@ -311,7 +296,7 @@ static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma,
> >  static const struct vm_operations_struct ext4_dax_vm_ops = {
> >  	.fault		= ext4_dax_fault,
> >  	.pmd_fault	= ext4_dax_pmd_fault,
> > -	.page_mkwrite	= ext4_dax_mkwrite,
> > +	.page_mkwrite	= ext4_dax_fault,
> >  	.pfn_mkwrite	= ext4_dax_pfn_mkwrite,
> >  };
> >  #else
> > -- 
> > 2.5.0
> > 
> > 
> -- 
> Jan Kara <jack@suse.com>
> SUSE Labs, CR

Re: [PATCH] ext2, ext4: Fix issue with missing journal entry

[Ross Zwisler]

On Thu, Jan 28, 2016 at 02:16:30PM +0100, Jan Kara wrote:
> On Wed 27-01-16 12:01:48, Ross Zwisler wrote:
> > As it is currently written ext4_dax_mkwrite() assumes that the call into
> > __dax_mkwrite() will not have to do a block allocation so it doesn't create
> > a journal entry.  For a read that creates a zero page to cover a hole
> > followed by a write that actually allocates storage this is incorrect.  The
> > ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
> > get_blocks() to allocate storage.
> > 
> > Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
> > as this function already has all the logic needed to allocate a journal
> > entry and call __dax_fault().
> > 
> > Also update the ext2 fault handlers in this same way to remove duplicate
> > code and keep the logic between ext2 and ext4 the same.
> > 
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> 
> Ah, ok, you are right. The patch looks good but Matthew is reworking the
> area more (so ext4_da_mkwrite() is likely to return) so it this worth it?
> Or do you expect Matthew's patches to land much later?

Yep, Matthew is in the process of reworking all of the DAX fault handling.

I was thinking that we might want to take this patch for v4.5, since it fixes
a bug that I'm guessing could lead to some sort of corruption (lack of a
journal entry entry for an allocating write), and then Matthew's reworks would
land in v4.6?

> > ---
> >  fs/ext2/file.c | 19 +------------------
> >  fs/ext4/file.c | 19 ++-----------------
> >  2 files changed, 3 insertions(+), 35 deletions(-)
> > 
> > diff --git a/fs/ext2/file.c b/fs/ext2/file.c
> > index 2c88d68..c1400b1 100644
> > --- a/fs/ext2/file.c
> > +++ b/fs/ext2/file.c
> > @@ -80,23 +80,6 @@ static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
> >  	return ret;
> >  }
> >  
> > -static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> > -{
> > -	struct inode *inode = file_inode(vma->vm_file);
> > -	struct ext2_inode_info *ei = EXT2_I(inode);
> > -	int ret;
> > -
> > -	sb_start_pagefault(inode->i_sb);
> > -	file_update_time(vma->vm_file);
> > -	down_read(&ei->dax_sem);
> > -
> > -	ret = __dax_mkwrite(vma, vmf, ext2_get_block, NULL);
> > -
> > -	up_read(&ei->dax_sem);
> > -	sb_end_pagefault(inode->i_sb);
> > -	return ret;
> > -}
> > -
> >  static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
> >  		struct vm_fault *vmf)
> >  {
> > @@ -124,7 +107,7 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
> >  static const struct vm_operations_struct ext2_dax_vm_ops = {
> >  	.fault		= ext2_dax_fault,
> >  	.pmd_fault	= ext2_dax_pmd_fault,
> > -	.page_mkwrite	= ext2_dax_mkwrite,
> > +	.page_mkwrite	= ext2_dax_fault,
> >  	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
> >  };
> >  
> > diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> > index 1126436..d2e8500 100644
> > --- a/fs/ext4/file.c
> > +++ b/fs/ext4/file.c
> > @@ -262,23 +262,8 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
> >  	return result;
> >  }
> >  
> > -static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> > -{
> > -	int err;
> > -	struct inode *inode = file_inode(vma->vm_file);
> > -
> > -	sb_start_pagefault(inode->i_sb);
> > -	file_update_time(vma->vm_file);
> > -	down_read(&EXT4_I(inode)->i_mmap_sem);
> > -	err = __dax_mkwrite(vma, vmf, ext4_dax_mmap_get_block, NULL);
> > -	up_read(&EXT4_I(inode)->i_mmap_sem);
> > -	sb_end_pagefault(inode->i_sb);
> > -
> > -	return err;
> > -}
> > -
> >  /*
> > - * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_mkwrite()
> > + * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_fault()
> >   * handler we check for races agaist truncate. Note that since we cycle through
> >   * i_mmap_sem, we are sure that also any hole punching that began before we
> >   * were called is finished by now and so if it included part of the file we
> > @@ -311,7 +296,7 @@ static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma,
> >  static const struct vm_operations_struct ext4_dax_vm_ops = {
> >  	.fault		= ext4_dax_fault,
> >  	.pmd_fault	= ext4_dax_pmd_fault,
> > -	.page_mkwrite	= ext4_dax_mkwrite,
> > +	.page_mkwrite	= ext4_dax_fault,
> >  	.pfn_mkwrite	= ext4_dax_pfn_mkwrite,
> >  };
> >  #else
> > -- 
> > 2.5.0
> > 
> > 
> -- 
> Jan Kara <jack@suse.com>
> SUSE Labs, CR

Re: [PATCH] ext2, ext4: Fix issue with missing journal entry

[Ross Zwisler]

On Thu, Jan 28, 2016 at 09:32:11AM -0700, Ross Zwisler wrote:
> On Thu, Jan 28, 2016 at 02:16:30PM +0100, Jan Kara wrote:
> > On Wed 27-01-16 12:01:48, Ross Zwisler wrote:
> > > As it is currently written ext4_dax_mkwrite() assumes that the call into
> > > __dax_mkwrite() will not have to do a block allocation so it doesn't create
> > > a journal entry.  For a read that creates a zero page to cover a hole
> > > followed by a write that actually allocates storage this is incorrect.  The
> > > ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
> > > get_blocks() to allocate storage.
> > > 
> > > Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
> > > as this function already has all the logic needed to allocate a journal
> > > entry and call __dax_fault().
> > > 
> > > Also update the ext2 fault handlers in this same way to remove duplicate
> > > code and keep the logic between ext2 and ext4 the same.
> > > 
> > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > 
> > Ah, ok, you are right. The patch looks good but Matthew is reworking the
> > area more (so ext4_da_mkwrite() is likely to return) so it this worth it?
> > Or do you expect Matthew's patches to land much later?
> 
> Yep, Matthew is in the process of reworking all of the DAX fault handling.
> 
> I was thinking that we might want to take this patch for v4.5, since it fixes
> a bug that I'm guessing could lead to some sort of corruption (lack of a
> journal entry entry for an allocating write), and then Matthew's reworks would
> land in v4.6?

Hey Jan,

Looks like this patch didn't ever get merged for v4.5?  Is it still queued for
v4.6?

Thanks,
- Ross

Re: [PATCH] ext2, ext4: Fix issue with missing journal entry

[Ross Zwisler]

On Thu, Jan 28, 2016 at 09:32:11AM -0700, Ross Zwisler wrote:
> On Thu, Jan 28, 2016 at 02:16:30PM +0100, Jan Kara wrote:
> > On Wed 27-01-16 12:01:48, Ross Zwisler wrote:
> > > As it is currently written ext4_dax_mkwrite() assumes that the call into
> > > __dax_mkwrite() will not have to do a block allocation so it doesn't create
> > > a journal entry.  For a read that creates a zero page to cover a hole
> > > followed by a write that actually allocates storage this is incorrect.  The
> > > ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
> > > get_blocks() to allocate storage.
> > > 
> > > Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
> > > as this function already has all the logic needed to allocate a journal
> > > entry and call __dax_fault().
> > > 
> > > Also update the ext2 fault handlers in this same way to remove duplicate
> > > code and keep the logic between ext2 and ext4 the same.
> > > 
> > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > 
> > Ah, ok, you are right. The patch looks good but Matthew is reworking the
> > area more (so ext4_da_mkwrite() is likely to return) so it this worth it?
> > Or do you expect Matthew's patches to land much later?
> 
> Yep, Matthew is in the process of reworking all of the DAX fault handling.
> 
> I was thinking that we might want to take this patch for v4.5, since it fixes
> a bug that I'm guessing could lead to some sort of corruption (lack of a
> journal entry entry for an allocating write), and then Matthew's reworks would
> land in v4.6?

Hey Jan,

Looks like this patch didn't ever get merged for v4.5?  Is it still queued for
v4.6?

Thanks,
- Ross

Re: [PATCH] ext2, ext4: Fix issue with missing journal entry

[Jan Kara]

On Wed 24-02-16 13:44:46, Ross Zwisler wrote:
> On Thu, Jan 28, 2016 at 09:32:11AM -0700, Ross Zwisler wrote:
> > On Thu, Jan 28, 2016 at 02:16:30PM +0100, Jan Kara wrote:
> > > On Wed 27-01-16 12:01:48, Ross Zwisler wrote:
> > > > As it is currently written ext4_dax_mkwrite() assumes that the call into
> > > > __dax_mkwrite() will not have to do a block allocation so it doesn't create
> > > > a journal entry.  For a read that creates a zero page to cover a hole
> > > > followed by a write that actually allocates storage this is incorrect.  The
> > > > ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
> > > > get_blocks() to allocate storage.
> > > > 
> > > > Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
> > > > as this function already has all the logic needed to allocate a journal
> > > > entry and call __dax_fault().
> > > > 
> > > > Also update the ext2 fault handlers in this same way to remove duplicate
> > > > code and keep the logic between ext2 and ext4 the same.
> > > > 
> > > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > > 
> > > Ah, ok, you are right. The patch looks good but Matthew is reworking the
> > > area more (so ext4_da_mkwrite() is likely to return) so it this worth it?
> > > Or do you expect Matthew's patches to land much later?
> > 
> > Yep, Matthew is in the process of reworking all of the DAX fault handling.
> > 
> > I was thinking that we might want to take this patch for v4.5, since it fixes
> > a bug that I'm guessing could lead to some sort of corruption (lack of a
> > journal entry entry for an allocating write), and then Matthew's reworks would
> > land in v4.6?
> 
> Hey Jan,
> 
> Looks like this patch didn't ever get merged for v4.5?  Is it still queued for
> v4.6?

Ted has been pretty busy lately and we probably didn't make it sufficiently
clear that he should pick up this patch. Ted, can you please pick up this
patch and push it to 4.5? Thanks. Feel free to add my:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] ext2, ext4: Fix issue with missing journal entry

[Jan Kara]

On Wed 24-02-16 13:44:46, Ross Zwisler wrote:
> On Thu, Jan 28, 2016 at 09:32:11AM -0700, Ross Zwisler wrote:
> > On Thu, Jan 28, 2016 at 02:16:30PM +0100, Jan Kara wrote:
> > > On Wed 27-01-16 12:01:48, Ross Zwisler wrote:
> > > > As it is currently written ext4_dax_mkwrite() assumes that the call into
> > > > __dax_mkwrite() will not have to do a block allocation so it doesn't create
> > > > a journal entry.  For a read that creates a zero page to cover a hole
> > > > followed by a write that actually allocates storage this is incorrect.  The
> > > > ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
> > > > get_blocks() to allocate storage.
> > > > 
> > > > Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
> > > > as this function already has all the logic needed to allocate a journal
> > > > entry and call __dax_fault().
> > > > 
> > > > Also update the ext2 fault handlers in this same way to remove duplicate
> > > > code and keep the logic between ext2 and ext4 the same.
> > > > 
> > > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > > 
> > > Ah, ok, you are right. The patch looks good but Matthew is reworking the
> > > area more (so ext4_da_mkwrite() is likely to return) so it this worth it?
> > > Or do you expect Matthew's patches to land much later?
> > 
> > Yep, Matthew is in the process of reworking all of the DAX fault handling.
> > 
> > I was thinking that we might want to take this patch for v4.5, since it fixes
> > a bug that I'm guessing could lead to some sort of corruption (lack of a
> > journal entry entry for an allocating write), and then Matthew's reworks would
> > land in v4.6?
> 
> Hey Jan,
> 
> Looks like this patch didn't ever get merged for v4.5?  Is it still queued for
> v4.6?

Ted has been pretty busy lately and we probably didn't make it sufficiently
clear that he should pick up this patch. Ted, can you please pick up this
patch and push it to 4.5? Thanks. Feel free to add my:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] ext2, ext4: Fix issue with missing journal entry

[Theodore Ts'o]

On Thu, Feb 25, 2016 at 09:37:28AM +0100, Jan Kara wrote:
> > Looks like this patch didn't ever get merged for v4.5?  Is it still queued for
> > v4.6?
> 
> Ted has been pretty busy lately and we probably didn't make it sufficiently
> clear that he should pick up this patch. Ted, can you please pick up this
> patch and push it to 4.5? Thanks. Feel free to add my:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>

Sorry, yes, I missed this one since most of the DAX patches have been
going through other trees.   I've just sent a pull request to Linus.

      	      	    	     	       - Ted