Re: [f2fs-dev] [PATCH] f2fs: synchronize atomic write aborts

[Chao Yu]

On 2023/2/14 4:14, Daeho Jeong wrote:
> > > diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> > > index 28c9c72dda2a..7bf660d4cad9 100644
> > > --- a/fs/f2fs/inode.c
> > > +++ b/fs/f2fs/inode.c
> > > @@ -777,11 +777,18 @@ int f2fs_write_inode(struct inode *inode, struct writeback_control *wbc)
> > >    void f2fs_evict_inode(struct inode *inode)
> > >    {
> > >        struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> > > -     nid_t xnid = F2FS_I(inode)->i_xattr_nid;
> > > +     struct f2fs_inode_info *fi = F2FS_I(inode);
> > > +     nid_t xnid = fi->i_xattr_nid;
> > >        int err = 0;
> > >
> > >        f2fs_abort_atomic_write(inode, true);
> > >
> > > +     if (fi->cow_inode) {
> > > +             clear_inode_flag(fi->cow_inode, FI_COW_FILE);
> > > +             iput(fi->cow_inode);
> > > +             fi->cow_inode = NULL;
> > > +     }
> >
> > It looks "fi->cow_inode = NULL" here may race w/ cow_inode allocation in
> > f2fs_ioc_start_atomic_write due to f2fs_write_inode() has not been covered
> > by inode_lock()? IIUC.
>
> Sorry, I couldn't understand it, since I couldn't find any relation
> between f2fs_ioc_start_atomic_write and f2fs_write_inode. Could you
> elaborate more on this? I thought the code might be safe, since it
> happens in the inode eviction phase.

int f2fs_write_inode(struct inode *inode, struct writeback_control *wbc)
void f2fs_evict_inode(struct inode *inode)

Oops, it looks I was misled by f2fs_write_inode() above f2fs_evict_inode(),
please ignore my comments, sorry. :(

Thanks,