[PATCH 14/14] mm: add struct address_space to is_dirty_writeback() callback

[jglisse@redhat.com]

From: Jérôme Glisse <jglisse@redhat.com>

This is part of patchset to remove dependency on struct page.mapping
field so that we can temporarily update it to point to a special
structure tracking temporary page state (note that original mapping
pointer is preserved and can still be accessed but at a cost).

Add struct address_space to is_dirty_writeback() callback arguments.

Note that this patch does not make use of the new argument, nor does
it use a valid one at call site (by default this patch just use NULL
for new argument value).

Use following script (from root of linux kernel tree):

./that-script.sh that-semantic-patch.spatch

%<--------------------------------------------------------------------
#!/bin/sh
spatch_file=$1

echo PART1 ===========================================================

# P1 find callback functions name
spatch  --dir . --no-includes -D part1 --sp-file $spatch_file

echo PART2 ===========================================================

# P2 change callback function prototype
cat /tmp/unicorn-functions | sort | uniq | while read func ; do
    for file in $( git grep -l $func -- '*.[ch]' ) ; do
        echo $file
        spatch --no-includes --in-place -D part2 \
               -D fn=$func --sp-file $spatch_file $file
    done
done

echo PART 3 ==========================================================

# P3 find all function which call the callback
spatch --dir . --include-headers -D part3 --sp-file $spatch_file

echo PART 4===========================================================

# P4 change all funcitons which call the callback
cat /tmp/unicorn-files | sort | uniq | while read file ; do
    echo $file
    spatch --no-includes --in-place -D part4 \
           --sp-file $spatch_file $file
done
-------------------------------------------------------------------->%

With the following semantic patch:

%<--------------------------------------------------------------------
virtual part1, part2, part3, part4

// ----------------------------------------------------------------------------
// Part 1 is grepping all function that are use as callback for is_dirty_writeback.

// initialize file where we collect all function name (erase it)
@initialize:python depends on part1@
@@
file=open('/tmp/unicorn-functions', 'w')
file.close()

// match function name use as a callback
@p1r2 depends on part1@
identifier I1, FN;
@@
struct address_space_operations I1 = {..., .is_dirty_writeback = FN, ...};

@script:python p1r3 depends on p1r2@
funcname << p1r2.FN;
@@
if funcname != "NULL":
  file=open('/tmp/unicorn-functions', 'a')
  file.write(funcname + '\n')
  file.close()

// -------------------------------------------------------------------
// Part 2 modify callback

@p2r1 depends on part2@
identifier virtual.fn;
identifier I1, I2, I3;
type T1, T2, T3;
@@
void fn(
+struct address_space *__mapping,
T1 I1, T2 I2, T3 I3) { ... }

@p2r2 depends on part2@
identifier virtual.fn;
identifier I1, I2, I3;
type T1, T2, T3;
@@
void fn(
+struct address_space *__mapping,
T1 I1, T2 I2, T3 I3);

@p2r3 depends on part2@
identifier virtual.fn;
expression E1, E2, E3;
@@
fn(
+MAPPING_NULL,
E1, E2, E3)

// ----------------------------------------------------------------------------
// Part 3 is grepping all function that are use the callback for is_dirty_writeback.

// initialize file where we collect all function name (erase it)
@initialize:python depends on part3@
@@
file=open('/tmp/unicorn-files', 'w')
file.write("./include/linux/pagemap.h\n")
file.write("./include/linux/mm.h\n")
file.write("./include/linux/fs.h\n")
file.write("./mm/readahead.c\n")
file.write("./mm/filemap.c\n")
file.close()

@p3r1 depends on part3 exists@
expression E1, E2, E3, E4;
identifier FN;
position P;
@@
FN@P(...) {...
(
E1.a_ops->is_dirty_writeback(E2, E3, E4)
|
E1->a_ops->is_dirty_writeback(E2, E3, E4)
)
...}

@script:python p3r2 depends on p3r1@
P << p3r1.P;
@@
file=open('/tmp/unicorn-files', 'a')
file.write(P[0].file + '\n')
file.close()

// -------------------------------------------------------------------
// Part 4 generic modification
@p4r1 depends on part4@
@@
struct address_space_operations { ... void (*is_dirty_writeback)(
+struct address_space *,
struct page *, ...); ... };

@p4r2 depends on part4@
expression E1, E2, E3, E4;
@@
E1.a_ops->is_dirty_writeback(
+MAPPING_NULL,
E2, E3, E4)

@p4r3 depends on part4@
expression E1, E2, E3, E4;
@@
E1->a_ops->is_dirty_writeback(
+MAPPING_NULL,
E2, E3, E4)
-------------------------------------------------------------------->%

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: linux-mm@kvack.org
Cc: linux-fsdevel@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Tejun Heo <tj@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Josef Bacik <jbacik@fb.com>
---
 fs/buffer.c                 | 3 ++-
 fs/nfs/file.c               | 5 +++--
 include/linux/buffer_head.h | 3 ++-
 include/linux/fs.h          | 3 ++-
 mm/vmscan.c                 | 3 ++-
 5 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 7adf0af7530ba..d050ef5bf9d7b 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -83,7 +83,8 @@ EXPORT_SYMBOL(unlock_buffer);
  * are unlocked and clean then the PageDirty information is stale. If
  * any of the pages are locked, it is assumed they are locked for IO.
  */
-void buffer_check_dirty_writeback(struct page *page,
+void buffer_check_dirty_writeback(struct address_space *__mapping,
+				     struct page *page,
 				     bool *dirty, bool *writeback)
 {
 	struct buffer_head *head, *bh;
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index b1ba143de48d9..d99b2db7ba3a3 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -437,8 +437,9 @@ static int nfs_release_page(struct address_space *__mapping,
 	return nfs_fscache_release_page(page, gfp);
 }
 
-static void nfs_check_dirty_writeback(struct page *page,
-				bool *dirty, bool *writeback)
+static void nfs_check_dirty_writeback(struct address_space *__mapping,
+				      struct page *page,
+				      bool *dirty, bool *writeback)
 {
 	struct nfs_inode *nfsi;
 	struct address_space *mapping = page_file_mapping(page);
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 89a3758531889..b19998fa8e4d4 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -145,7 +145,8 @@ BUFFER_FNS(Defer_Completion, defer_completion)
 	})
 #define page_has_buffers(page)	PagePrivate(page)
 
-void buffer_check_dirty_writeback(struct page *page,
+void buffer_check_dirty_writeback(struct address_space *__mapping,
+				     struct page *page,
 				     bool *dirty, bool *writeback);
 
 /*
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6798a13e3c980..ebdb961016925 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -415,7 +415,8 @@ struct address_space_operations {
 	int (*is_partially_uptodate) (struct address_space *, struct page *,
 					unsigned long,
 					unsigned long);
-	void (*is_dirty_writeback) (struct page *, bool *, bool *);
+	void (*is_dirty_writeback) (struct address_space *, struct page *,
+				    bool *, bool *);
 	int (*error_remove_page)(struct address_space *, struct page *);
 
 	/* swapfile support */
diff --git a/mm/vmscan.c b/mm/vmscan.c
index bae7fb9c3512a..d402f94e14f2f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1058,7 +1058,8 @@ static void page_check_dirty_writeback(struct page *page,
 
 	mapping = page_mapping(page);
 	if (mapping && mapping->a_ops->is_dirty_writeback)
-		mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
+		mapping->a_ops->is_dirty_writeback(MAPPING_NULL, page, dirty,
+						   writeback);
 }
 
 /*
-- 
2.26.2