linux-ext4 - Re: [PATCH 04/13] mm: Add functions to lock invalidate

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Date:   Wed, 26 May 2021 15:45:18 +0200
From:   Jan Kara <jack@...e.cz>
To:     Damien Le Moal <Damien.LeMoal@....com>
Cc:     Jan Kara <jack@...e.cz>, "Darrick J. Wong" <djwong@...nel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "hch@...radead.org" <hch@...radead.org>,
        Dave Chinner <david@...morbit.com>,
        "ceph-devel@...r.kernel.org" <ceph-devel@...r.kernel.org>,
        Chao Yu <yuchao0@...wei.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Jeff Layton <jlayton@...nel.org>,
        Johannes Thumshirn <jth@...nel.org>,
        "linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>,
        "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        "linux-f2fs-devel@...ts.sourceforge.net" 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        Steve French <sfrench@...ba.org>, Ted Tso <tytso@....edu>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH 04/13] mm: Add functions to lock invalidate_lock for two
 mappings

On Wed 26-05-21 12:11:43, Damien Le Moal wrote:
> On 2021/05/26 19:07, Jan Kara wrote:
> > On Tue 25-05-21 13:48:05, Darrick J. Wong wrote:
> >> On Tue, May 25, 2021 at 03:50:41PM +0200, Jan Kara wrote:
> >>> Some operations such as reflinking blocks among files will need to lock
> >>> invalidate_lock for two mappings. Add helper functions to do that.
> >>>
> >>> Signed-off-by: Jan Kara <jack@...e.cz>
> >>> ---
> >>>  include/linux/fs.h |  6 ++++++
> >>>  mm/filemap.c       | 38 ++++++++++++++++++++++++++++++++++++++
> >>>  2 files changed, 44 insertions(+)
> >>>
> >>> diff --git a/include/linux/fs.h b/include/linux/fs.h
> >>> index 897238d9f1e0..e6f7447505f5 100644
> >>> --- a/include/linux/fs.h
> >>> +++ b/include/linux/fs.h
> >>> @@ -822,6 +822,12 @@ static inline void inode_lock_shared_nested(struct inode *inode, unsigned subcla
> >>>  void lock_two_nondirectories(struct inode *, struct inode*);
> >>>  void unlock_two_nondirectories(struct inode *, struct inode*);
> >>>  
> >>> +void filemap_invalidate_down_write_two(struct address_space *mapping1,
> >>> +				       struct address_space *mapping2);
> >>> +void filemap_invalidate_up_write_two(struct address_space *mapping1,
> >>
> >> TBH I find myself wishing that the invalidate_lock used the same
> >> lock/unlock style wrappers that we use for i_rwsem.
> >>
> >> filemap_invalidate_lock(inode1->mapping);
> >> filemap_invalidate_lock_two(inode1->i_mapping, inode2->i_mapping);
> > 
> > OK, and filemap_invalidate_lock_shared() for down_read()? I guess that
> > works for me.
> 
> What about filemap_invalidate_lock_read() and filemap_invalidate_lock_write() ?
> That reminds the down_read()/down_write() without the slightly confusing down/up.

Well, if we go for lock wrappers as Darrick suggested, I'd mirror naming
used for inode_lock(). That is IMO the least confusing option... And that
naming has _lock and _lock_shared suffixes.

								Honza

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