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From: Chengguang Xu <cgxu519@mykernel.net>
To: "Jan Kara" <jack@suse.cz>
Cc: "miklos" <miklos@szeredi.hu>, "amir73il" <amir73il@gmail.com>,
	"linux-unionfs" <linux-unionfs@vger.kernel.org>,
	"linux-fsdevel" <linux-fsdevel@vger.kernel.org>
Subject: Re: [RFC PATCH v3 07/10] ovl: implement overlayfs' ->write_inode operation
Date: Tue, 10 Nov 2020 23:12:14 +0800
Message-ID: <175b2b6ef3d.11f9425843834.4407023737229017217@mykernel.net> (raw)
In-Reply-To: <20201110134551.GA28132@quack2.suse.cz>

 ---- 在 星期二, 2020-11-10 21:45:51 Jan Kara <jack@suse.cz> 撰写 ----
 > On Sun 08-11-20 22:03:04, Chengguang Xu wrote:
 > > +static int ovl_write_inode(struct inode *inode,
 > > +               struct writeback_control *wbc)
 > > +{
 > > +    struct ovl_fs *ofs = inode->i_sb->s_fs_info;
 > > +    struct inode *upper = ovl_inode_upper(inode);
 > > +    unsigned long iflag = 0;
 > > +    int ret = 0;
 > > +
 > > +    if (!upper)
 > > +        return 0;
 > > +
 > > +    if (!ovl_should_sync(ofs))
 > > +        return 0;
 > > +
 > > +    if (upper->i_sb->s_op->write_inode)
 > > +        ret = upper->i_sb->s_op->write_inode(inode, wbc);
 > > +
 > > +    iflag |= upper->i_state & I_DIRTY_ALL;
 > > +
 > > +    if (mapping_writably_mapped(upper->i_mapping) ||
 > > +        mapping_tagged(upper->i_mapping, PAGECACHE_TAG_WRITEBACK))
 > > +        iflag |= I_DIRTY_PAGES;
 > > +
 > > +    if (iflag)
 > > +        ovl_mark_inode_dirty(inode);
 > 
 > I think you didn't incorporate feedback we were speaking about in the last
 > version of the series. May comment in [1] still applies - you can miss
 > inodes dirtied through mmap when you decide to clean the inode here. So
 > IMHO you need something like:
 > 
 >     if (inode_is_open_for_write(inode))
 >         ovl_mark_inode_dirty(inode);
 > 
 > here to keep inode dirty while it is open for write (and not based on upper
 > inode state which is unreliable).

Hi Jan,

I not only checked upper inode state but also checked upper inode mmap(shared) state
using  mapping_writably_mapped(upper->i_mapping). Maybe it's better to move i_state check
after mmap check but isn't above checks enough for mmapped file? 

Below code is the definition of mmapping_writably_mapped(), I think it will check shared mmap
regardless write or read permission though the function name is quite confusable.

static inline int mapping_writably_mapped(struct address_space *mapping)
{
	return atomic_read(&mapping->i_mmap_writable) > 0;
}



Thanks,
Chengguang


 > 
 >                                 Honza
 > 
 > [1] https://lore.kernel.org/linux-fsdevel/20201105140332.GG32718@quack2.suse.cz/
 > 
 > > +
 > > +    return ret;
 > > +}
 > > +
 > >  static void ovl_evict_inode(struct inode *inode)
 > >  {
 > >      struct ovl_fs *ofs = inode->i_sb->s_fs_info;
 > > @@ -411,6 +440,7 @@ static const struct super_operations ovl_super_operations = {
 > >      .destroy_inode    = ovl_destroy_inode,
 > >      .drop_inode    = generic_delete_inode,
 > >      .evict_inode    = ovl_evict_inode,
 > > +    .write_inode    = ovl_write_inode,
 > >      .put_super    = ovl_put_super,
 > >      .sync_fs    = ovl_sync_fs,
 > >      .statfs        = ovl_statfs,
 > > -- 
 > > 2.26.2
 > > 
 > > 
 > -- 
 > Jan Kara <jack@suse.com>
 > SUSE Labs, CR
 > 

  reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-08 14:02 [RFC PATCH v3 00/10] implement containerized syncfs for overlayfs Chengguang Xu
2020-11-08 14:02 ` [RFC PATCH v3 01/10] ovl: setup overlayfs' private bdi Chengguang Xu
2020-11-08 14:02 ` [RFC PATCH v3 02/10] ovl: introduce waiting list for syncfs Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 03/10] ovl: implement ->writepages operation Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 04/10] ovl: implement overlayfs' ->evict_inode operation Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 05/10] ovl: mark overlayfs' inode dirty on modification Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 06/10] ovl: mark overlayfs' inode dirty on shared mmap Chengguang Xu
2020-11-11 13:05   ` 回复:[RFC " Chengguang Xu
2020-11-11 15:20     ` [RFC " Amir Goldstein
2020-11-11 16:09       ` Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 07/10] ovl: implement overlayfs' ->write_inode operation Chengguang Xu
2020-11-10 13:45   ` Jan Kara
2020-11-10 15:12     ` Chengguang Xu [this message]
2020-11-11 10:54       ` Jan Kara
2020-11-10 16:18     ` Amir Goldstein
2020-11-08 14:03 ` [RFC PATCH v3 08/10] ovl: cache dirty overlayfs' inode Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 09/10] ovl: introduce helper of syncfs writeback inode waiting Chengguang Xu
2020-11-09  3:33   ` 回复:[RFC " Chengguang Xu
2020-11-09  7:07     ` [RFC " Amir Goldstein
2020-11-09  8:34       ` Chengguang Xu
2020-11-09 10:07         ` Amir Goldstein
2020-11-09 12:06           ` Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 10/10] ovl: implement containerized syncfs for overlayfs Chengguang Xu

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