Re: [f2fs-dev] [PATCH] f2fs: get parent inode when recovering pino

Eric Biggers
2020-05-05T17:59:12Z

On Tue, May 05, 2020 at 09:58:47AM -0700, Eric Biggers wrote:
> On Tue, May 05, 2020 at 08:31:39AM -0700, Jaegeuk Kim wrote:
> > We had to grab the inode before retrieving i_ino.
> >
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> > fs/f2fs/file.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index a0a4413d6083b..9d4c3e3503567 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -168,6 +168,7 @@ static const struct vm_operations_struct f2fs_file_vm_ops = {
> > static int get_parent_ino(struct inode *inode, nid_t *pino)
> > {
> > struct dentry *dentry;
> > + struct inode *parent;
> >
> > inode = igrab(inode);
> > dentry = d_find_any_alias(inode);
> > @@ -175,8 +176,13 @@ static int get_parent_ino(struct inode *inode, nid_t *pino)
> > if (!dentry)
> > return 0;
> >
> > - *pino = parent_ino(dentry);
> > + parent = igrab(d_inode(dentry->d_parent));
> > dput(dentry);
> > + if (!parent)
> > + return 0;
> > +
> > + *pino = parent->i_ino;
> > + iput(parent);
> > return 1;
>
> This doesn't appear to be necessary. parent_ino() is:
>
> spin_lock(&dentry->d_lock);
> res = dentry->d_parent->d_inode->i_ino;
> spin_unlock(&dentry->d_lock);
>
> Since dentry is locked and referenced, ->d_parent is stable and positive.
>
> In the encrypt+casefold patch I was reviewing, it's indeed necessary, but only
> because there was a check of inode->i_flags added outside the locked region.
> The following would be simpler:
>
> spin_lock(&dentry->d_lock);
> dir = dentry->d_parent->d_inode;
> *pino = dir->i_ino;
> needs_recovery = IS_ENCRYPTED(dir) && IS_CASEFOLDED(dir);
> spin_unlock(&dentry->d_lock);
>
> BTW, d_find_any_alias() is unnecessary too. This code should just be using
> file_dentry(file) from f2fs_do_sync_file().
>

Also, what is this code trying to accomplish? If it's trying to find the parent
directory of an inode with i_nlink == 1, this isn't the correct way to do it.
The fsync could be done via a deleted file, which would make the wrong p_ino be
set. I think the correct approach would be to iterate through all the dentry's
aliases, and choose the parent directory that's !IS_DEADDIR().

- Eric