linux-kernel - Re: [PATCH v2 1/8] introduce __sb_{acquire,release}

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Date:	Thu, 13 Aug 2015 11:56:17 +0200
From:	Jan Kara <jack@...e.cz>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Dave Chinner <david@...morbit.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Jan Kara <jack@...e.cz>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/8] introduce __sb_{acquire,release}_write() helpers

On Thu 13-08-15 11:45:52, Jan Kara wrote:
> On Tue 11-08-15 19:03:58, Oleg Nesterov wrote:
> > 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@...hat.com>
> 
> Looks good. You can add:
> 
> Reviewed-by: Jan Kara <jack@...e.com>

One comment when looking at other patches - I'd prefer somewhat better name
than __sb_acquire_write(). It doesn't tell that it's only a trylock
acquisition. Maybe something like

__sb_writers_acquire_nowait()

and then

__sb_writers_release()?

								Honza
> > ---
> >  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
> > 
> -- 
> Jan Kara <jack@...e.com>
> SUSE Labs, CR
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR
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