fs: export inode_to_bdi and use it in favor of mapping->backing_dev_info

Now that we got rid of the bdi abuse on character devices we can always use
sb->s_bdi to get at the backing_dev_info for a file, except for the block
device special case.  Export inode_to_bdi and replace uses of
mapping->backing_dev_info with it to prepare for the removal of
mapping->backing_dev_info.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/mm/readahead.c b/mm/readahead.c
index 17b9172ec37f..935675844b2e 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -27,7 +27,7 @@
 void
 file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
 {
-        ra->ra_pages = mapping->backing_dev_info->ra_pages;
+        ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages;
         ra->prev_pos = -1;
 }
 EXPORT_SYMBOL_GPL(file_ra_state_init);
@@ -541,7 +541,7 @@ page_cache_async_readahead(struct address_space *mapping,
         /*
          * Defer asynchronous read-ahead on IO congestion.
          */
-        if (bdi_read_congested(mapping->backing_dev_info))
+        if (bdi_read_congested(inode_to_bdi(mapping->host)))
                 return;
 
         /* do read-ahead */