[RFC PATCH 32/79] fs/block: do not rely on page->mapping get it from the context

[jglisse]

From: JÃrÃme Glisse <jglisse@xxxxxxxxxx>

This patch remove most dereference of page->mapping and get the mapping
from the call context (either already available in the function or by
adding it to function arguments).

Signed-off-by: JÃrÃme Glisse <jglisse@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Josef Bacik <jbacik@xxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
---
 fs/block_dev.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 502b6643bc74..dd9da97615e3 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -564,14 +564,14 @@ EXPORT_SYMBOL(thaw_bdev);
 static int blkdev_writepage(struct address_space *mapping, struct page *page,
 			    struct writeback_control *wbc)
 {
-	return block_write_full_page(page->mapping->host, page,
+	return block_write_full_page(mapping->host, page,
 				     blkdev_get_block, wbc);
 }
 
 static int blkdev_readpage(struct file * file, struct address_space *mapping,
 			   struct page * page)
 {
-	return block_read_full_page(page->mapping->host,page,blkdev_get_block);
+	return block_read_full_page(mapping->host,page,blkdev_get_block);
 }
 
 static int blkdev_readpages(struct file *file, struct address_space *mapping,
@@ -1941,7 +1941,7 @@ EXPORT_SYMBOL_GPL(blkdev_read_iter);
 static int blkdev_releasepage(struct address_space *mapping,
 			      struct page *page, gfp_t wait)
 {
-	struct super_block *super = BDEV_I(page->mapping->host)->bdev.bd_super;
+	struct super_block *super = BDEV_I(mapping->host)->bdev.bd_super;
 
 	if (super && super->s_op->bdev_try_to_free_page)
 		return super->s_op->bdev_try_to_free_page(super, page, wait);
-- 
2.14.3