Re: [PATCH v10 2/3] fs: introduce super_drop_pagecache()

[Matthew Wilcox <willy@infradead.org>]

On Sat, Feb 18, 2023 at 09:16:43AM +0800, Shiyang Ruan wrote:
> 在 2023/2/18 0:14, Matthew Wilcox 写道:
> > On Fri, Feb 17, 2023 at 02:48:31PM +0000, Shiyang Ruan wrote:
> > > -		invalidate_mapping_pages(inode->i_mapping, 0, -1);
> > > -		iput(toput_inode);
> > > -		toput_inode = inode;
> > > -
> > > -		cond_resched();
> > > -		spin_lock(&sb->s_inode_list_lock);
> > > -	}
> > > -	spin_unlock(&sb->s_inode_list_lock);
> > > -	iput(toput_inode);
> > > +	super_drop_pagecache(sb, invalidate_inode_pages);
> > 
> > I thought I explained last time that you can do this with
> > invalidate_mapping_pages() / invalidate_inode_pages2_range() ?
> > Then you don't need to introduce invalidate_inode_pages().
> > 
> > > +void super_drop_pagecache(struct super_block *sb,
> > > +	int (*invalidator)(struct address_space *))
> > 
> > void super_drop_pagecache(struct super_block *sb,
> > 		int (*invalidate)(struct address_space *, pgoff_t, pgoff_t))
> > 
> > > +		invalidator(inode->i_mapping);
> > 
> > 		invalidate(inode->i_mapping, 0, -1)
> > 
> > ... then all the changes to mm/truncate.c and filemap.h go away.
> 
> Yes, I tried as you suggested, but I found that they don't have same type of
> return value.
> 
> int invalidate_inode_pages2_range(struct address_space *mapping,
> 				  pgoff_t start, pgoff_t end);
> 
> unsigned long invalidate_mapping_pages(struct address_space *mapping,
> 		pgoff_t start, pgoff_t end);

Oh, that's annoying.  Particularly annoying is that the return value
for invalidate_mapping_pages() is used by fs/inode.c to account for
the number of pages invalidate, and the return value for
invalidate_inode_pages2_range() is used by several filesystems
to know whether an error occurred.

Hm.  Shouldn't you be checking for an error from
invalidate_inode_pages2_range()?  Seems like it can return -EBUSY for
DAX entries.

With that in mind, the wrapper you actually want to exist is

static int invalidate_inode_pages_range(struct address_space *mapping,
				pgoff_t start, pgoff_t end)
{
	invalidate_mapping_pages(mapping, start, end);
	return 0;
}

Right?