[patch 048/114] dax: use pfn_mkwrite to update c/mtime + freeze protection

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From: Boaz Harrosh <boaz@xxxxxxxxxxxxx>
Subject: dax: use pfn_mkwrite to update c/mtime + freeze protection

From: Yigal Korman <yigal@xxxxxxxxxxxxx>

[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@xxxxxxxxxxxxx>
Signed-off-by: Boaz Harrosh <boaz@xxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 fs/dax.c           |   17 +++++++++++++++++
 fs/ext2/file.c     |    1 +
 fs/ext4/file.c     |    1 +
 include/linux/fs.h |    1 +
 4 files changed, 20 insertions(+)

diff -puN fs/dax.c~dax-use-pfn_mkwrite-to-update-c-mtime-freeze-protection fs/dax.c
--- a/fs/dax.c~dax-use-pfn_mkwrite-to-update-c-mtime-freeze-protection
+++ a/fs/dax.c
@@ -464,6 +464,23 @@ int dax_fault(struct vm_area_struct *vma
 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 -puN fs/ext2/file.c~dax-use-pfn_mkwrite-to-update-c-mtime-freeze-protection fs/ext2/file.c
--- a/fs/ext2/file.c~dax-use-pfn_mkwrite-to-update-c-mtime-freeze-protection
+++ a/fs/ext2/file.c
@@ -39,6 +39,7 @@ static int ext2_dax_mkwrite(struct vm_ar
 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 -puN fs/ext4/file.c~dax-use-pfn_mkwrite-to-update-c-mtime-freeze-protection fs/ext4/file.c
--- a/fs/ext4/file.c~dax-use-pfn_mkwrite-to-update-c-mtime-freeze-protection
+++ a/fs/ext4/file.c
@@ -206,6 +206,7 @@ static int ext4_dax_mkwrite(struct vm_ar
 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 -puN include/linux/fs.h~dax-use-pfn_mkwrite-to-update-c-mtime-freeze-protection include/linux/fs.h
--- a/include/linux/fs.h~dax-use-pfn_mkwrite-to-update-c-mtime-freeze-protection
+++ a/include/linux/fs.h
@@ -2620,6 +2620,7 @@ int dax_clear_blocks(struct inode *, sec
 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
_
--
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