Date:   Tue,  6 Oct 2020 21:05:58 -0400
From:   jglisse@...hat.com
To:     linux-kernel@...r.kernel.org
Cc:     Jérôme Glisse <jglisse@...hat.com>,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Tejun Heo <tj@...nel.org>, Jan Kara <jack@...e.cz>,
        Josef Bacik <jbacik@...com>
Subject: [PATCH 09/14] mm: add struct address_space to freepage() callback

From: Jérôme Glisse <jglisse@...hat.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 freepage() 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 freepage.

// 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 = {..., .freepage = 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

// Add address_space argument to the function (freepage callback one)
@p2r1 depends on part2@
identifier virtual.fn;
identifier I1;
type T1;
@@
void fn(
+struct address_space *__mapping,
T1 I1) { ... }

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

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

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

// 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;
identifier FN;
position P;
@@
FN@P(...) {...
(
E1.a_ops->freepage(E2)
|
E1->a_ops->freepage(E2)
)
...}

@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 (*freepage)(
+struct address_space *,
struct page *, ...); ... };

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

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

Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
Cc: linux-mm@...ck.org
Cc: linux-fsdevel@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: linux-fsdevel@...r.kernel.org
Cc: Tejun Heo <tj@...nel.org>
Cc: Jan Kara <jack@...e.cz>
Cc: Josef Bacik <jbacik@...com>
---
 fs/nfs/dir.c        | 9 +++++----
 fs/orangefs/inode.c | 3 ++-
 include/linux/fs.h  | 2 +-
 mm/filemap.c        | 4 ++--
 mm/truncate.c       | 2 +-
 mm/vmscan.c         | 2 +-
 6 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 5a5c021967d3f..d8e66c98db3ea 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -53,7 +53,7 @@ static int nfs_closedir(struct inode *, struct file *);
 static int nfs_readdir(struct file *, struct dir_context *);
 static int nfs_fsync_dir(struct file *, loff_t, loff_t, int);
 static loff_t nfs_llseek_dir(struct file *, loff_t, int);
-static void nfs_readdir_clear_array(struct page*);
+static void nfs_readdir_clear_array(struct address_space *, struct page*);
 
 const struct file_operations nfs_dir_operations = {
 	.llseek		= nfs_llseek_dir,
@@ -177,7 +177,8 @@ void nfs_readdir_init_array(struct page *page)
  * we are freeing strings created by nfs_add_to_readdir_array()
  */
 static
-void nfs_readdir_clear_array(struct page *page)
+void nfs_readdir_clear_array(struct address_space *__mapping,
+			     struct page *page)
 {
 	struct nfs_cache_array *array;
 	int i;
@@ -725,7 +726,7 @@ int nfs_readdir_filler(void *data, struct address_space *__mapping,
 	unlock_page(page);
 	return 0;
  error:
-	nfs_readdir_clear_array(page);
+	nfs_readdir_clear_array(MAPPING_NULL, page);
 	unlock_page(page);
 	return ret;
 }
@@ -875,7 +876,7 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc)
 	status = nfs_do_filldir(desc);
 
  out_release:
-	nfs_readdir_clear_array(desc->page);
+	nfs_readdir_clear_array(MAPPING_NULL, desc->page);
 	cache_page_release(desc);
  out:
 	dfprintk(DIRCACHE, "NFS: %s: returns %d\n",
diff --git a/fs/orangefs/inode.c b/fs/orangefs/inode.c
index 1534dc2df6e5c..8b47bcbf0ca4d 100644
--- a/fs/orangefs/inode.c
+++ b/fs/orangefs/inode.c
@@ -526,7 +526,8 @@ static int orangefs_releasepage(struct address_space *__mapping,
 	return !PagePrivate(page);
 }
 
-static void orangefs_freepage(struct page *page)
+static void orangefs_freepage(struct address_space *__mapping,
+			      struct page *page)
 {
 	kfree(detach_page_private(page));
 }
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 989e505de9182..a952aa9d93e7f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -400,7 +400,7 @@ struct address_space_operations {
 	void (*invalidatepage) (struct address_space *, struct page *,
 				unsigned int, unsigned int);
 	int (*releasepage) (struct address_space *, struct page *, gfp_t);
-	void (*freepage)(struct page *);
+	void (*freepage)(struct address_space *, struct page *);
 	ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
 	/*
 	 * migrate the contents of a page to the specified target. If
diff --git a/mm/filemap.c b/mm/filemap.c
index eccd5d0554851..faa190598cba8 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -243,7 +243,7 @@ static void page_cache_free_page(struct address_space *mapping,
 				struct page *page)
 {
 	if (mapping->a_ops->freepage)
-		mapping->a_ops->freepage(page);
+		mapping->a_ops->freepage(MAPPING_NULL, page);
 
 	if (PageTransHuge(page) && !PageHuge(page)) {
 		page_ref_sub(page, HPAGE_PMD_NR);
@@ -816,7 +816,7 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 		__inc_lruvec_page_state(new, NR_SHMEM);
 	xas_unlock_irqrestore(&xas, flags);
 	if (mapping->a_ops->freepage)
-		mapping->a_ops->freepage(old);
+		mapping->a_ops->freepage(MAPPING_NULL, old);
 	put_page(old);
 
 	return 0;
diff --git a/mm/truncate.c b/mm/truncate.c
index e26b232b66c01..e24688115c903 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -653,7 +653,7 @@ invalidate_complete_page2(struct address_space *mapping, struct page *page)
 	xa_unlock_irqrestore(&mapping->i_pages, flags);
 
 	if (mapping->a_ops->freepage)
-		mapping->a_ops->freepage(page);
+		mapping->a_ops->freepage(MAPPING_NULL, page);
 
 	put_page(page);	/* pagecache ref */
 	return 1;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4322bc5ee2d84..bae7fb9c3512a 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -926,7 +926,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
 		xa_unlock_irqrestore(&mapping->i_pages, flags);
 
 		if (mapping->a_ops->freepage != NULL)
-			mapping->a_ops->freepage(page);
+			mapping->a_ops->freepage(MAPPING_NULL, page);
 	}
 
 	return 1;
-- 
2.26.2

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