linux-kernel - Re: [RFC PATCH V6 3/7] ovl: implement overlayfs' own ->write

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Date:   Fri, 26 Nov 2021 21:09:36 +0800
From:   Chengguang Xu <cgxu519@...ernel.net>
To:     "Jan Kara" <jack@...e.cz>
Cc:     "miklos" <miklos@...redi.hu>, "amir73il" <amir73il@...il.com>,
        "linux-unionfs" <linux-unionfs@...r.kernel.org>,
        "linux-fsdevel" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel" <linux-kernel@...r.kernel.org>,
        "Chengguang Xu" <charliecgxu@...cent.com>,
        "ronyjin" <ronyjin@...cent.com>
Subject: Re: [RFC PATCH V6 3/7] ovl: implement overlayfs' own ->write_inode
 operation

 ---- 在 星期五, 2021-11-26 17:14:30 Jan Kara <jack@...e.cz> 撰写 ----
 > On Mon 22-11-21 11:00:34, Chengguang Xu wrote:
 > > From: Chengguang Xu <charliecgxu@...cent.com>
 > > 
 > > Sync dirty data and meta of upper inode in overlayfs' ->write_inode()
 > > and redirty overlayfs' inode.
 > > 
 > > Signed-off-by: Chengguang Xu <charliecgxu@...cent.com>
 > 
 > Looks good. I'm still not 100% convinced keeping inodes dirty all the time
 > will not fire back in excessive writeback activity (e.g. flush worker will
 > traverse the list of all dirty inodes every 30 seconds and try to write
 > them) but I guess we can start with this and if people complain, dirtiness
 > handling can be improved. 

Hi Jan,

Thanks for the review and suggestion.


Thanks,
Chengguang



 > So feel free to add:
 > 
 > Reviewed-by: Jan Kara <jack@...e.cz>
 > 
 >                                 Honza
 > 
 > > ---
 > >  fs/overlayfs/super.c | 21 +++++++++++++++++++++
 > >  1 file changed, 21 insertions(+)
 > > 
 > > diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
 > > index 18a12088a37b..12acf0ec7395 100644
 > > --- a/fs/overlayfs/super.c
 > > +++ b/fs/overlayfs/super.c
 > > @@ -15,6 +15,7 @@
 > >  #include <linux/seq_file.h>
 > >  #include <linux/posix_acl_xattr.h>
 > >  #include <linux/exportfs.h>
 > > +#include <linux/writeback.h>
 > >  #include "overlayfs.h"
 > >  
 > >  MODULE_AUTHOR("Miklos Szeredi <miklos@...redi.hu>");
 > > @@ -406,12 +407,32 @@ static int ovl_remount(struct super_block *sb, int *flags, char *data)
 > >      return ret;
 > >  }
 > >  
 > > +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_inode = ovl_inode_upper(inode);
 > > +    int ret = 0;
 > > +
 > > +    if (!upper_inode)
 > > +        return 0;
 > > +
 > > +    if (!ovl_should_sync(ofs))
 > > +        return 0;
 > > +
 > > +    ret = write_inode_now(upper_inode, wbc->sync_mode == WB_SYNC_ALL);
 > > +    mark_inode_dirty(inode);
 > > +
 > > +    return ret;
 > > +}
 > > +
 > >  static const struct super_operations ovl_super_operations = {
 > >      .alloc_inode    = ovl_alloc_inode,
 > >      .free_inode    = ovl_free_inode,
 > >      .destroy_inode    = ovl_destroy_inode,
 > >      .drop_inode    = generic_delete_inode,
 > >      .put_super    = ovl_put_super,
 > > +    .write_inode    = ovl_write_inode,
 > >      .sync_fs    = ovl_sync_fs,
 > >      .statfs        = ovl_statfs,
 > >      .show_options    = ovl_show_options,
 > > -- 
 > > 2.27.0
 > > 
 > > 
 > -- 
 > Jan Kara <jack@...e.com>
 > SUSE Labs, CR
 >