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

Eric Biggers
2020-05-05T16:58:56Z

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().

- Eric