[PATCH 1/4] introduce __sb_{acquire,release}_write() helpers

[Oleg Nesterov <oleg@redhat.com>]

Preparation to hide the sb->s_writers internals from xfs and btrfs.
Add 2 trivial define's they can use rather than play with ->s_writers
directly. No changes in btrfs/transaction.o and xfs/xfs_aops.o.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 fs/btrfs/transaction.c |    8 ++------
 fs/xfs/xfs_aops.c      |    6 ++----
 include/linux/fs.h     |    5 +++++
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 5628e25..6dca4e9 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1620,9 +1620,7 @@ static void do_async_commit(struct work_struct *work)
 	 * Tell lockdep about it.
 	 */
 	if (ac->newtrans->type & __TRANS_FREEZABLE)
-		rwsem_acquire_read(
-		     &ac->root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
-		     0, 1, _THIS_IP_);
+		__sb_acquire_write(ac->root->fs_info->sb, SB_FREEZE_FS);
 
 	current->journal_info = ac->newtrans;
 
@@ -1661,9 +1659,7 @@ int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
 	 * async commit thread will be the one to unlock it.
 	 */
 	if (ac->newtrans->type & __TRANS_FREEZABLE)
-		rwsem_release(
-			&root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
-			1, _THIS_IP_);
+		__sb_release_write(root->fs_info->sb, SB_FREEZE_FS);
 
 	schedule_work(&ac->work);
 
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index a56960d..8034c78 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -119,8 +119,7 @@ xfs_setfilesize_trans_alloc(
 	 * We may pass freeze protection with a transaction.  So tell lockdep
 	 * we released it.
 	 */
-	rwsem_release(&ioend->io_inode->i_sb->s_writers.lock_map[SB_FREEZE_FS-1],
-		      1, _THIS_IP_);
+	__sb_release_write(ioend->io_inode->i_sb, SB_FREEZE_FS);
 	/*
 	 * We hand off the transaction to the completion thread now, so
 	 * clear the flag here.
@@ -171,8 +170,7 @@ xfs_setfilesize_ioend(
 	 * Similarly for freeze protection.
 	 */
 	current_set_flags_nested(&tp->t_pflags, PF_FSTRANS);
-	rwsem_acquire_read(&VFS_I(ip)->i_sb->s_writers.lock_map[SB_FREEZE_FS-1],
-			   0, 1, _THIS_IP_);
+	__sb_acquire_write(VFS_I(ip)->i_sb, SB_FREEZE_FS);
 
 	return xfs_setfilesize(ip, tp, ioend->io_offset, ioend->io_size);
 }
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 35ec87e..78ac768 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1362,6 +1362,11 @@ extern struct timespec current_fs_time(struct super_block *sb);
 void __sb_end_write(struct super_block *sb, int level);
 int __sb_start_write(struct super_block *sb, int level, bool wait);
 
+#define __sb_acquire_write(sb, lev)	\
+	rwsem_acquire_read(&(sb)->s_writers.lock_map[(lev)-1], 0, 1, _THIS_IP_)
+#define __sb_release_write(sb, lev)	\
+	rwsem_release(&(sb)->s_writers.lock_map[(lev)-1], 1, _THIS_IP_)
+
 /**
  * sb_end_write - drop write access to a superblock
  * @sb: the super we wrote to
-- 
1.5.5.1