linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: support zero sized file truncate for device aliasing files

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Message-ID: <CACOAw_yhfZtmVkmuN0jNVxiEkcEdpmQrSZPiK2CTY6mjjcrUKw@mail.gmail.com>
Date: Fri, 21 Mar 2025 14:16:21 -0700
From: Daeho Jeong <daeho43@...il.com>
To: Chao Yu <chao@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net, 
	kernel-team@...roid.com, Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: support zero sized file truncate for
 device aliasing files

On Mon, Mar 17, 2025 at 8:45 PM Chao Yu <chao@...nel.org> wrote:
>
> On 3/18/25 03:08, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@...gle.com>
> >
> > support a file truncation to zero size for device aliasing files.
> >
> > Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> > ---
> >  fs/f2fs/file.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index f92a9fba9991..7ae5a5af5ed9 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -1036,7 +1036,7 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> >
> >       if ((attr->ia_valid & ATTR_SIZE)) {
> >               if (!f2fs_is_compress_backend_ready(inode) ||
> > -                             IS_DEVICE_ALIASING(inode))
> > +                             (IS_DEVICE_ALIASING(inode) && attr->ia_size))
> >                       return -EOPNOTSUPP;
> >               if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED) &&
> >                       !IS_ALIGNED(attr->ia_size,
> > @@ -1117,6 +1117,9 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> >               if (err)
> >                       return err;
>
> Daeho,
>
> If truncate(, 0) failed due to some reasons, maybe, the file was partially
> truncated, should we tag it as inconsistent status to avoid its later access?
> thoughts?

Hmm, looks like I did it wrong.
Instead of invoking f2fs_destroy_extent_tree(), I need to make the
length of the extent to zero when truncating the file.
Is it okay with you?

>
> Thanks,
>
> >
> > +             if (IS_DEVICE_ALIASING(inode))
> > +                     f2fs_destroy_extent_tree(inode);
> > +
> >               spin_lock(&fi->i_size_lock);
> >               inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
> >               fi->last_disk_size = i_size_read(inode);
>