[PATCH 02/10] fs: Introduce filemap_range_has_page()

2017-06-20 Thread Goldwyn Rodrigues 
From: Goldwyn Rodrigues 

filemap_range_has_page() return true if the file's mapping has
a page within the range mentioned. This function will be used
to check if a write() call will cause a writeback of previous
writes.

Reviewed-by: Christoph Hellwig 
Reviewed-by: Jan Kara 
Signed-off-by: Goldwyn Rodrigues 
---
 include/linux/fs.h |  2 ++
 mm/filemap.c   | 32 
 2 files changed, 34 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 96a1a1fa54a9..0d34f5b5a6b0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2518,6 +2518,8 @@ extern int filemap_fdatawait(struct address_space *);
 extern void filemap_fdatawait_keep_errors(struct address_space *);
 extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
   loff_t lend);
+extern bool filemap_range_has_page(struct address_space *, loff_t lstart,
+ loff_t lend);
 extern int filemap_write_and_wait(struct address_space *mapping);
 extern int filemap_write_and_wait_range(struct address_space *mapping,
loff_t lstart, loff_t lend);
diff --git a/mm/filemap.c b/mm/filemap.c
index 6f1be573a5e6..9b39a2390b9e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -376,6 +376,38 @@ int filemap_flush(struct address_space *mapping)
 }
 EXPORT_SYMBOL(filemap_flush);
 
+/**
+ * filemap_range_has_page - check if a page exists in range.
+ * @mapping:   address space within which to check
+ * @start_byte:offset in bytes where the range starts
+ * @end_byte:  offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback.
+ */
+bool filemap_range_has_page(struct address_space *mapping,
+  loff_t start_byte, loff_t end_byte)
+{
+   pgoff_t index = start_byte >> PAGE_SHIFT;
+   pgoff_t end = end_byte >> PAGE_SHIFT;
+   struct pagevec pvec;
+   bool ret;
+
+   if (end_byte < start_byte)
+   return false;
+
+   if (mapping->nrpages == 0)
+   return false;
+
+   pagevec_init(, 0);
+   if (!pagevec_lookup(, mapping, index, 1))
+   return false;
+   ret = (pvec.pages[0]->index <= end);
+   pagevec_release();
+   return ret;
+}
+EXPORT_SYMBOL(filemap_range_has_page);
+
 static int __filemap_fdatawait_range(struct address_space *mapping,
 loff_t start_byte, loff_t end_byte)
 {
-- 
2.12.0

[PATCH 02/10] fs: Introduce filemap_range_has_page()

2017-06-19 Thread Goldwyn Rodrigues 
From: Goldwyn Rodrigues 

filemap_range_has_page() return true if the file's mapping has
a page within the range mentioned. This function will be used
to check if a write() call will cause a writeback of previous
writes.

Reviewed-by: Christoph Hellwig 
Reviewed-by: Jan Kara 
Signed-off-by: Goldwyn Rodrigues 
---
 include/linux/fs.h |  2 ++
 mm/filemap.c   | 32 
 2 files changed, 34 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 96a1a1fa54a9..0d34f5b5a6b0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2518,6 +2518,8 @@ extern int filemap_fdatawait(struct address_space *);
 extern void filemap_fdatawait_keep_errors(struct address_space *);
 extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
   loff_t lend);
+extern bool filemap_range_has_page(struct address_space *, loff_t lstart,
+ loff_t lend);
 extern int filemap_write_and_wait(struct address_space *mapping);
 extern int filemap_write_and_wait_range(struct address_space *mapping,
loff_t lstart, loff_t lend);
diff --git a/mm/filemap.c b/mm/filemap.c
index 6f1be573a5e6..9b39a2390b9e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -376,6 +376,38 @@ int filemap_flush(struct address_space *mapping)
 }
 EXPORT_SYMBOL(filemap_flush);
 
+/**
+ * filemap_range_has_page - check if a page exists in range.
+ * @mapping:   address space within which to check
+ * @start_byte:offset in bytes where the range starts
+ * @end_byte:  offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback.
+ */
+bool filemap_range_has_page(struct address_space *mapping,
+  loff_t start_byte, loff_t end_byte)
+{
+   pgoff_t index = start_byte >> PAGE_SHIFT;
+   pgoff_t end = end_byte >> PAGE_SHIFT;
+   struct pagevec pvec;
+   bool ret;
+
+   if (end_byte < start_byte)
+   return false;
+
+   if (mapping->nrpages == 0)
+   return false;
+
+   pagevec_init(, 0);
+   if (!pagevec_lookup(, mapping, index, 1))
+   return false;
+   ret = (pvec.pages[0]->index <= end);
+   pagevec_release();
+   return ret;
+}
+EXPORT_SYMBOL(filemap_range_has_page);
+
 static int __filemap_fdatawait_range(struct address_space *mapping,
 loff_t start_byte, loff_t end_byte)
 {
-- 
2.12.0

Re: [PATCH 02/10] fs: Introduce filemap_range_has_page()

2017-06-15 Thread Andrew Morton 
On Thu, 15 Jun 2017 10:59:54 -0500 Goldwyn Rodrigues  wrote:

> From: Goldwyn Rodrigues 
> 
> filemap_range_has_page() return true if the file's mapping has
> a page within the range mentioned. This function will be used
> to check if a write() call will cause a writeback of previous
> writes.
> 
> ...
>
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2517,6 +2517,8 @@ extern int filemap_fdatawait(struct address_space *);
>  extern void filemap_fdatawait_keep_errors(struct address_space *);
>  extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
>  loff_t lend);
> +extern int filemap_range_has_page(struct address_space *, loff_t lstart,
> +   loff_t lend);
>  extern int filemap_write_and_wait(struct address_space *mapping);
>  extern int filemap_write_and_wait_range(struct address_space *mapping,
>   loff_t lstart, loff_t lend);
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 6f1be573a5e6..87aba7698584 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -376,6 +376,39 @@ int filemap_flush(struct address_space *mapping)
>  }
>  EXPORT_SYMBOL(filemap_flush);
>  
> +/**
> + * filemap_range_has_page - check if a page exists in range.
> + * @mapping:   address space structure to wait for

"to wait for" seems wrong.

> + * @start_byte:offset in bytes where the range starts
> + * @end_byte:  offset in bytes where the range ends (inclusive)
> + *
> + * Find at least one page in the range supplied, usually used to check if
> + * direct writing in this range will trigger a writeback.
> + */
> +int filemap_range_has_page(struct address_space *mapping,
> +loff_t start_byte, loff_t end_byte)

Would a bool return type be better?

> +{
> + pgoff_t index = start_byte >> PAGE_SHIFT;
> + pgoff_t end = end_byte >> PAGE_SHIFT;
> + struct pagevec pvec;
> + int ret;
> +
> + if (end_byte < start_byte)
> + return 0;
> +
> + if (mapping->nrpages == 0)
> + return 0;
> +
> + pagevec_init(, 0);
> + ret = pagevec_lookup(, mapping, index, 1);
> + if (!ret)
> + return 0;
> + ret = (pvec.pages[0]->index <= end);
> + pagevec_release();
> + return ret;
> +}
> +EXPORT_SYMBOL(filemap_range_has_page);
> +

[PATCH 02/10] fs: Introduce filemap_range_has_page()

2017-06-15 Thread Goldwyn Rodrigues 
From: Goldwyn Rodrigues 

filemap_range_has_page() return true if the file's mapping has
a page within the range mentioned. This function will be used
to check if a write() call will cause a writeback of previous
writes.

Reviewed-by: Christoph Hellwig 
Reviewed-by: Jan Kara 
Signed-off-by: Goldwyn Rodrigues 
---
 include/linux/fs.h |  2 ++
 mm/filemap.c   | 33 +
 2 files changed, 35 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index f53867140f43..dc0ab585cd56 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2517,6 +2517,8 @@ extern int filemap_fdatawait(struct address_space *);
 extern void filemap_fdatawait_keep_errors(struct address_space *);
 extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
   loff_t lend);
+extern int filemap_range_has_page(struct address_space *, loff_t lstart,
+ loff_t lend);
 extern int filemap_write_and_wait(struct address_space *mapping);
 extern int filemap_write_and_wait_range(struct address_space *mapping,
loff_t lstart, loff_t lend);
diff --git a/mm/filemap.c b/mm/filemap.c
index 6f1be573a5e6..87aba7698584 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -376,6 +376,39 @@ int filemap_flush(struct address_space *mapping)
 }
 EXPORT_SYMBOL(filemap_flush);
 
+/**
+ * filemap_range_has_page - check if a page exists in range.
+ * @mapping:   address space structure to wait for
+ * @start_byte:offset in bytes where the range starts
+ * @end_byte:  offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback.
+ */
+int filemap_range_has_page(struct address_space *mapping,
+  loff_t start_byte, loff_t end_byte)
+{
+   pgoff_t index = start_byte >> PAGE_SHIFT;
+   pgoff_t end = end_byte >> PAGE_SHIFT;
+   struct pagevec pvec;
+   int ret;
+
+   if (end_byte < start_byte)
+   return 0;
+
+   if (mapping->nrpages == 0)
+   return 0;
+
+   pagevec_init(, 0);
+   ret = pagevec_lookup(, mapping, index, 1);
+   if (!ret)
+   return 0;
+   ret = (pvec.pages[0]->index <= end);
+   pagevec_release();
+   return ret;
+}
+EXPORT_SYMBOL(filemap_range_has_page);
+
 static int __filemap_fdatawait_range(struct address_space *mapping,
 loff_t start_byte, loff_t end_byte)
 {
-- 
2.12.0

[PATCH 02/10] fs: Introduce filemap_range_has_page()

2017-06-06 Thread Goldwyn Rodrigues 
From: Goldwyn Rodrigues 

filemap_range_has_page() return true if the file's mapping has
a page within the range mentioned. This function will be used
to check if a write() call will cause a writeback of previous
writes.

Reviewed-by: Christoph Hellwig 
Reviewed-by: Jan Kara 
Signed-off-by: Goldwyn Rodrigues 
---
 include/linux/fs.h |  2 ++
 mm/filemap.c   | 33 +
 2 files changed, 35 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index f53867140f43..dc0ab585cd56 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2517,6 +2517,8 @@ extern int filemap_fdatawait(struct address_space *);
 extern void filemap_fdatawait_keep_errors(struct address_space *);
 extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
   loff_t lend);
+extern int filemap_range_has_page(struct address_space *, loff_t lstart,
+ loff_t lend);
 extern int filemap_write_and_wait(struct address_space *mapping);
 extern int filemap_write_and_wait_range(struct address_space *mapping,
loff_t lstart, loff_t lend);
diff --git a/mm/filemap.c b/mm/filemap.c
index 6f1be573a5e6..87aba7698584 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -376,6 +376,39 @@ int filemap_flush(struct address_space *mapping)
 }
 EXPORT_SYMBOL(filemap_flush);
 
+/**
+ * filemap_range_has_page - check if a page exists in range.
+ * @mapping:   address space structure to wait for
+ * @start_byte:offset in bytes where the range starts
+ * @end_byte:  offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback.
+ */
+int filemap_range_has_page(struct address_space *mapping,
+  loff_t start_byte, loff_t end_byte)
+{
+   pgoff_t index = start_byte >> PAGE_SHIFT;
+   pgoff_t end = end_byte >> PAGE_SHIFT;
+   struct pagevec pvec;
+   int ret;
+
+   if (end_byte < start_byte)
+   return 0;
+
+   if (mapping->nrpages == 0)
+   return 0;
+
+   pagevec_init(, 0);
+   ret = pagevec_lookup(, mapping, index, 1);
+   if (!ret)
+   return 0;
+   ret = (pvec.pages[0]->index <= end);
+   pagevec_release();
+   return ret;
+}
+EXPORT_SYMBOL(filemap_range_has_page);
+
 static int __filemap_fdatawait_range(struct address_space *mapping,
 loff_t start_byte, loff_t end_byte)
 {
-- 
2.12.0

[PATCH 02/10] fs: Introduce filemap_range_has_page()

2017-06-04 Thread Goldwyn Rodrigues 
From: Goldwyn Rodrigues 

filemap_range_has_page() return true if the file's mapping has
a page within the range mentioned. This function will be used
to check if a write() call will cause a writeback of previous
writes.

Reviewed-by: Christoph Hellwig 
Reviewed-by: Jan Kara 
Signed-off-by: Goldwyn Rodrigues 
---
 include/linux/fs.h |  2 ++
 mm/filemap.c   | 33 +
 2 files changed, 35 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index f53867140f43..dc0ab585cd56 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2517,6 +2517,8 @@ extern int filemap_fdatawait(struct address_space *);
 extern void filemap_fdatawait_keep_errors(struct address_space *);
 extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
   loff_t lend);
+extern int filemap_range_has_page(struct address_space *, loff_t lstart,
+ loff_t lend);
 extern int filemap_write_and_wait(struct address_space *mapping);
 extern int filemap_write_and_wait_range(struct address_space *mapping,
loff_t lstart, loff_t lend);
diff --git a/mm/filemap.c b/mm/filemap.c
index 6f1be573a5e6..87aba7698584 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -376,6 +376,39 @@ int filemap_flush(struct address_space *mapping)
 }
 EXPORT_SYMBOL(filemap_flush);
 
+/**
+ * filemap_range_has_page - check if a page exists in range.
+ * @mapping:   address space structure to wait for
+ * @start_byte:offset in bytes where the range starts
+ * @end_byte:  offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback.
+ */
+int filemap_range_has_page(struct address_space *mapping,
+  loff_t start_byte, loff_t end_byte)
+{
+   pgoff_t index = start_byte >> PAGE_SHIFT;
+   pgoff_t end = end_byte >> PAGE_SHIFT;
+   struct pagevec pvec;
+   int ret;
+
+   if (end_byte < start_byte)
+   return 0;
+
+   if (mapping->nrpages == 0)
+   return 0;
+
+   pagevec_init(, 0);
+   ret = pagevec_lookup(, mapping, index, 1);
+   if (!ret)
+   return 0;
+   ret = (pvec.pages[0]->index <= end);
+   pagevec_release();
+   return ret;
+}
+EXPORT_SYMBOL(filemap_range_has_page);
+
 static int __filemap_fdatawait_range(struct address_space *mapping,
 loff_t start_byte, loff_t end_byte)
 {
-- 
2.12.0

Re: [PATCH 02/10] fs: Introduce filemap_range_has_page()

2017-05-25 Thread Jan Kara 
On Wed 24-05-17 11:41:42, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues 
> 
> filemap_range_has_page() return true if the file's mapping has
> a page within the range mentioned. This function will be used
> to check if a write() call will cause a writeback of previous
> writes.
> 
> Signed-off-by: Goldwyn Rodrigues 
> Reviewed-by: Christoph Hellwig 

Looks good. You can add:

Reviewed-by: Jan Kara 

Honza

> ---
>  include/linux/fs.h |  2 ++
>  mm/filemap.c   | 33 +
>  2 files changed, 35 insertions(+)
> 
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index f53867140f43..dc0ab585cd56 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2517,6 +2517,8 @@ extern int filemap_fdatawait(struct address_space *);
>  extern void filemap_fdatawait_keep_errors(struct address_space *);
>  extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
>  loff_t lend);
> +extern int filemap_range_has_page(struct address_space *, loff_t lstart,
> +   loff_t lend);
>  extern int filemap_write_and_wait(struct address_space *mapping);
>  extern int filemap_write_and_wait_range(struct address_space *mapping,
>   loff_t lstart, loff_t lend);
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 6f1be573a5e6..87aba7698584 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -376,6 +376,39 @@ int filemap_flush(struct address_space *mapping)
>  }
>  EXPORT_SYMBOL(filemap_flush);
>  
> +/**
> + * filemap_range_has_page - check if a page exists in range.
> + * @mapping:   address space structure to wait for
> + * @start_byte:offset in bytes where the range starts
> + * @end_byte:  offset in bytes where the range ends (inclusive)
> + *
> + * Find at least one page in the range supplied, usually used to check if
> + * direct writing in this range will trigger a writeback.
> + */
> +int filemap_range_has_page(struct address_space *mapping,
> +loff_t start_byte, loff_t end_byte)
> +{
> + pgoff_t index = start_byte >> PAGE_SHIFT;
> + pgoff_t end = end_byte >> PAGE_SHIFT;
> + struct pagevec pvec;
> + int ret;
> +
> + if (end_byte < start_byte)
> + return 0;
> +
> + if (mapping->nrpages == 0)
> + return 0;
> +
> + pagevec_init(, 0);
> + ret = pagevec_lookup(, mapping, index, 1);
> + if (!ret)
> + return 0;
> + ret = (pvec.pages[0]->index <= end);
> + pagevec_release();
> + return ret;
> +}
> +EXPORT_SYMBOL(filemap_range_has_page);
> +
>  static int __filemap_fdatawait_range(struct address_space *mapping,
>loff_t start_byte, loff_t end_byte)
>  {
> -- 
> 2.12.0
> 
-- 
Jan Kara 
SUSE Labs, CR

[PATCH 02/10] fs: Introduce filemap_range_has_page()

2017-05-24 Thread Goldwyn Rodrigues 
From: Goldwyn Rodrigues 

filemap_range_has_page() return true if the file's mapping has
a page within the range mentioned. This function will be used
to check if a write() call will cause a writeback of previous
writes.

Signed-off-by: Goldwyn Rodrigues 
Reviewed-by: Christoph Hellwig 
---
 include/linux/fs.h |  2 ++
 mm/filemap.c   | 33 +
 2 files changed, 35 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index f53867140f43..dc0ab585cd56 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2517,6 +2517,8 @@ extern int filemap_fdatawait(struct address_space *);
 extern void filemap_fdatawait_keep_errors(struct address_space *);
 extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
   loff_t lend);
+extern int filemap_range_has_page(struct address_space *, loff_t lstart,
+ loff_t lend);
 extern int filemap_write_and_wait(struct address_space *mapping);
 extern int filemap_write_and_wait_range(struct address_space *mapping,
loff_t lstart, loff_t lend);
diff --git a/mm/filemap.c b/mm/filemap.c
index 6f1be573a5e6..87aba7698584 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -376,6 +376,39 @@ int filemap_flush(struct address_space *mapping)
 }
 EXPORT_SYMBOL(filemap_flush);
 
+/**
+ * filemap_range_has_page - check if a page exists in range.
+ * @mapping:   address space structure to wait for
+ * @start_byte:offset in bytes where the range starts
+ * @end_byte:  offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback.
+ */
+int filemap_range_has_page(struct address_space *mapping,
+  loff_t start_byte, loff_t end_byte)
+{
+   pgoff_t index = start_byte >> PAGE_SHIFT;
+   pgoff_t end = end_byte >> PAGE_SHIFT;
+   struct pagevec pvec;
+   int ret;
+
+   if (end_byte < start_byte)
+   return 0;
+
+   if (mapping->nrpages == 0)
+   return 0;
+
+   pagevec_init(, 0);
+   ret = pagevec_lookup(, mapping, index, 1);
+   if (!ret)
+   return 0;
+   ret = (pvec.pages[0]->index <= end);
+   pagevec_release();
+   return ret;
+}
+EXPORT_SYMBOL(filemap_range_has_page);
+
 static int __filemap_fdatawait_range(struct address_space *mapping,
 loff_t start_byte, loff_t end_byte)
 {
-- 
2.12.0

[PATCH 02/10] fs: Introduce filemap_range_has_page()

2017-05-11 Thread Goldwyn Rodrigues 
From: Goldwyn Rodrigues 

filemap_range_has_page() return true if the file's mapping has
a page within the range mentioned. This function will be used
to check if a write() call will cause a writeback of previous
writes.

Signed-off-by: Goldwyn Rodrigues 
Reviewed-by: Christoph Hellwig 
---
 include/linux/fs.h |  2 ++
 mm/filemap.c   | 33 +
 2 files changed, 35 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 869c9a6fe58d..2e6fc6a23f91 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2513,6 +2513,8 @@ extern int filemap_fdatawait(struct address_space *);
 extern void filemap_fdatawait_keep_errors(struct address_space *);
 extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
   loff_t lend);
+extern int filemap_range_has_page(struct address_space *, loff_t lstart,
+ loff_t lend);
 extern int filemap_write_and_wait(struct address_space *mapping);
 extern int filemap_write_and_wait_range(struct address_space *mapping,
loff_t lstart, loff_t lend);
diff --git a/mm/filemap.c b/mm/filemap.c
index 1694623a6289..fae5a361befb 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -376,6 +376,39 @@ int filemap_flush(struct address_space *mapping)
 }
 EXPORT_SYMBOL(filemap_flush);
 
+/**
+ * filemap_range_has_page - check if a page exists in range.
+ * @mapping:   address space structure to wait for
+ * @start_byte:offset in bytes where the range starts
+ * @end_byte:  offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback.
+ */
+int filemap_range_has_page(struct address_space *mapping,
+  loff_t start_byte, loff_t end_byte)
+{
+   pgoff_t index = start_byte >> PAGE_SHIFT;
+   pgoff_t end = end_byte >> PAGE_SHIFT;
+   struct pagevec pvec;
+   int ret;
+
+   if (end_byte < start_byte)
+   return 0;
+
+   if (mapping->nrpages == 0)
+   return 0;
+
+   pagevec_init(, 0);
+   ret = pagevec_lookup(, mapping, index, 1);
+   if (!ret)
+   return 0;
+   ret = (pvec.pages[0]->index <= end);
+   pagevec_release();
+   return ret;
+}
+EXPORT_SYMBOL(filemap_range_has_page);
+
 static int __filemap_fdatawait_range(struct address_space *mapping,
 loff_t start_byte, loff_t end_byte)
 {
-- 
2.12.0