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>

2 files changed, 7 insertions, 5 deletions

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 478f95d92d73..ed59dee03a71 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -106,6 +106,8 @@ struct backing_dev_info {
 #endif
 };
 
+struct backing_dev_info *inode_to_bdi(struct inode *inode);
+
 int __must_check bdi_init(struct backing_dev_info *bdi);
 void bdi_destroy(struct backing_dev_info *bdi);
 
@@ -303,12 +305,12 @@ static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
 
 static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
 {
-        return bdi_cap_writeback_dirty(mapping->backing_dev_info);
+        return bdi_cap_writeback_dirty(inode_to_bdi(mapping->host));
 }
 
 static inline bool mapping_cap_account_dirty(struct address_space *mapping)
 {
-        return bdi_cap_account_dirty(mapping->backing_dev_info);
+        return bdi_cap_account_dirty(inode_to_bdi(mapping->host));
 }
 
 static inline int bdi_sched_wait(void *word)
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index cee02d65ab3f..74f5207bd090 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -47,7 +47,7 @@ TRACE_EVENT(writeback_dirty_page,
 
         TP_fast_assign(
                 strncpy(__entry->name,
-                        mapping ? dev_name(mapping->backing_dev_info->dev) : "(unknown)", 32);
+                        mapping ? dev_name(inode_to_bdi(mapping->host)->dev) : "(unknown)", 32);
                 __entry->ino = mapping ? mapping->host->i_ino : 0;
                 __entry->index = page->index;
         ),
@@ -72,7 +72,7 @@ DECLARE_EVENT_CLASS(writeback_dirty_inode_template,
         ),
 
         TP_fast_assign(
-                struct backing_dev_info *bdi = inode->i_mapping->backing_dev_info;
+                struct backing_dev_info *bdi = inode_to_bdi(inode);
 
                 /* may be called for files on pseudo FSes w/ unregistered bdi */
                 strncpy(__entry->name,
@@ -116,7 +116,7 @@ DECLARE_EVENT_CLASS(writeback_write_inode_template,
 
         TP_fast_assign(
                 strncpy(__entry->name,
-                        dev_name(inode->i_mapping->backing_dev_info->dev), 32);
+                        dev_name(inode_to_bdi(inode)->dev), 32);
                 __entry->ino            = inode->i_ino;
                 __entry->sync_mode      = wbc->sync_mode;
         ),