Re: FAILED: patch "[PATCH] dax: use pfn_mkwrite to update c/mtime + freeze protection" failed to apply to 4.0-stable tree

[Boaz Harrosh <boaz@plexistor.com>]

On 05/02/2015 05:15 PM, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 4.0-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
> 
> thanks,
> 
> greg k-h
> 

Hi Greg

I think it is safe to ignore this patch for 4.0 . It is for
DAX that went into 4.0. But DAX is very experimental in 4.0
so it is not worth the trouble.

[This is the patch, that I sent the mm preliminary patch for, which we talk about...]

Ye dropping it should be fine, thanks.
Boaz

> ------------------ original commit in Linus's tree ------------------
> 
> From 0e3b210ce1722168227cb3bc7746256d0c0afece Mon Sep 17 00:00:00 2001
> From: Boaz Harrosh <boaz@plexistor.com>
> Date: Wed, 15 Apr 2015 16:15:14 -0700
> Subject: [PATCH] dax: use pfn_mkwrite to update c/mtime + freeze protection
> 
> From: Yigal Korman <yigal@plexistor.com>
> 
> [v1]
> Without this patch, c/mtime is not updated correctly when mmap'ed page is
> first read from and then written to.
> 
> A new xfstest is submitted for testing this (generic/080)
> 
> [v2]
> Jan Kara has pointed out that if we add the
> sb_start/end_pagefault pair in the new pfn_mkwrite we
> are then fixing another bug where: A user could start
> writing to the page while filesystem is frozen.
> 
> Signed-off-by: Yigal Korman <yigal@plexistor.com>
> Signed-off-by: Boaz Harrosh <boaz@plexistor.com>
> Reviewed-by: Jan Kara <jack@suse.cz>
> Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index ed1619ec6537..d0bd1f4f81b3 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -464,6 +464,23 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
>  EXPORT_SYMBOL_GPL(dax_fault);
>  
>  /**
> + * dax_pfn_mkwrite - handle first write to DAX page
> + * @vma: The virtual memory area where the fault occurred
> + * @vmf: The description of the fault
> + *
> + */
> +int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> +{
> +	struct super_block *sb = file_inode(vma->vm_file)->i_sb;
> +
> +	sb_start_pagefault(sb);
> +	file_update_time(vma->vm_file);
> +	sb_end_pagefault(sb);
> +	return VM_FAULT_NOPAGE;
> +}
> +EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
> +
> +/**
>   * dax_zero_page_range - zero a range within a page of a DAX file
>   * @inode: The file being truncated
>   * @from: The file offset that is being truncated to
> diff --git a/fs/ext2/file.c b/fs/ext2/file.c
> index e31701713516..866a3ce3f864 100644
> --- a/fs/ext2/file.c
> +++ b/fs/ext2/file.c
> @@ -39,6 +39,7 @@ static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
>  static const struct vm_operations_struct ext2_dax_vm_ops = {
>  	.fault		= ext2_dax_fault,
>  	.page_mkwrite	= ext2_dax_mkwrite,
> +	.pfn_mkwrite	= dax_pfn_mkwrite,
>  };
>  
>  static int ext2_file_mmap(struct file *file, struct vm_area_struct *vma)
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 598abbbe6786..aa78c70553f4 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -206,6 +206,7 @@ static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
>  static const struct vm_operations_struct ext4_dax_vm_ops = {
>  	.fault		= ext4_dax_fault,
>  	.page_mkwrite	= ext4_dax_mkwrite,
> +	.pfn_mkwrite	= dax_pfn_mkwrite,
>  };
>  #else
>  #define ext4_dax_vm_ops	ext4_file_vm_ops
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 60733bdc74b4..0f696328f218 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2620,6 +2620,7 @@ int dax_clear_blocks(struct inode *, sector_t block, long size);
>  int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
>  int dax_truncate_page(struct inode *, loff_t from, get_block_t);
>  int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
> +int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
>  #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
>  
>  #ifdef CONFIG_BLOCK
>