Re: [PATCH 1/1] f2fs: fix args passed to trace_f2fs_lookup_end

[Chao Yu]

On 2023/5/27 1:21, Jaegeuk Kim wrote:
> On 05/24, Wu Bo wrote:
> > The NULL return of 'd_splice_alias' dosen't mean error.
> >
> > Signed-off-by: Wu Bo <bo.wu@xxxxxxxx>
> > ---
> >   fs/f2fs/namei.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
> > index 77a71276ecb1..e5a3e39ce90c 100644
> > --- a/fs/f2fs/namei.c
> > +++ b/fs/f2fs/namei.c
> > @@ -577,7 +577,7 @@ static struct dentry *f2fs_lookup(struct inode *dir, struct dentry *dentry,
> >   #endif
> >   	new = c(inode, dentry);
> >   	err = PTR_ERR_OR_ZERO(new);
> > -	trace_f2fs_lookup_end(dir, dentry, ino, !new ? -ENOENT : err);
> > +	trace_f2fs_lookup_end(dir, new ? new : dentry, ino, err);
>
> Shouldn't give an error pointer to the dentry field.
>
> How about just giving the err?
>
> -       err = PTR_ERR_OR_ZERO(new);
> -       trace_f2fs_lookup_end(dir, dentry, ino, !new ? -ENOENT : err);
> +       trace_f2fs_lookup_end(dir, dentry, ino, PTR_ERR_OR_ZERO(new));

static inline int __must_check PTR_ERR_OR_ZERO(__force const void *ptr)
{
	if (IS_ERR(ptr))
		return PTR_ERR(ptr);
	else
		return 0;
}

For below two cases, PTR_ERR_OR_ZERO(new) will return zero:
a) f2fs_lookup found existed dentry
b) f2fs_lookup didn't find existed dentry (-ENOENT case)

So in below commit, I passed -ENOENT to tracepoint for case b), so we can
distinguish result of f2fs_lookup in tracepoint, actually, -ENOENT is expected
value when we create a new file/directory.

Commit 84597b1f9b05 ("f2fs: fix wrong value of tracepoint parameter")

> >   	return new;
> >   out_iput:
> >   	iput(inode);
> > --
> > 2.35.3