[PATCH v2 8/8] Btrfs: extent_write_locked_range() should attach inode->i_wb

[Tejun Heo <tj@kernel.org>]

extent_write_locked_range() is used when we're falling back to buffered
IO from inside of compression.  It allocates its own wbc and should
associate it with the inode's i_wb to make sure the IO goes down from
the correct cgroup.

Also, export the needed symbols from fs-writeback.c.

Signed-off-by: Chris Mason <clm@fb.com>
Build-Breakage-Reported-by: kbuild test robot <lkp@intel.com>
---
v2: Module build fix.

 fs/btrfs/extent_io.c |   10 ++++++----
 fs/fs-writeback.c    |    3 +++
 2 files changed, 9 insertions(+), 4 deletions(-)

--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4178,6 +4178,7 @@ int extent_write_locked_range(struct ino
 		.no_wbc_acct	= 1,
 	};
 
+	wbc_attach_fdatawrite_inode(&wbc_writepages, inode);
 	while (start <= end) {
 		page = find_get_page(mapping, start >> PAGE_SHIFT);
 		if (clear_page_dirty_for_io(page))
@@ -4192,11 +4193,12 @@ int extent_write_locked_range(struct ino
 	}
 
 	ASSERT(ret <= 0);
-	if (ret < 0) {
+	if (ret == 0)
+		ret = flush_write_bio(&epd);
+	else
 		end_write_bio(&epd, ret);
-		return ret;
-	}
-	ret = flush_write_bio(&epd);
+
+	wbc_detach_inode(&wbc_writepages);
 	return ret;
 }
 
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -270,6 +270,7 @@ void __inode_attach_wb(struct inode *ino
 	if (unlikely(cmpxchg(&inode->i_wb, NULL, wb)))
 		wb_put(wb);
 }
+EXPORT_SYMBOL_GPL(__inode_attach_wb);
 
 /**
  * locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it
@@ -582,6 +583,7 @@ void wbc_attach_and_unlock_inode(struct
 	if (unlikely(wb_dying(wbc->wb)))
 		inode_switch_wbs(inode, wbc->wb_id);
 }
+EXPORT_SYMBOL_GPL(wbc_attach_and_unlock_inode);
 
 /**
  * wbc_detach_inode - disassociate wbc from inode and perform foreign detection
@@ -701,6 +703,7 @@ void wbc_detach_inode(struct writeback_c
 	wb_put(wbc->wb);
 	wbc->wb = NULL;
 }
+EXPORT_SYMBOL_GPL(wbc_detach_inode);
 
 /**
  * wbc_account_io - account IO issued during writeback