On Tue, Jul 8, 2025 at 10:37 AM Vlastimil Babka <vba...@suse.cz> wrote:
>
> On 7/4/25 08:07, Suren Baghdasaryan wrote:
> > Back in 2.6 era, last_addr used to be stored in seq_file->version
> > variable, which was unsigned long. As a result, sentinels to represent
> > gate vma and end of all vmas used unsigned values. In more recent
> > kernels we don't used seq_file->version anymore and therefore conversion
> > from loff_t into unsigned type is not needed. Similarly, sentinel values
> > don't need to be unsigned. Remove type conversion for set_file position
> > and change sentinel values to signed.
> >
> > Signed-off-by: Suren Baghdasaryan <sur...@google.com>
>
> Reviewed-by: Vlastimil Babka <vba...@suse.cz>
>
> Some stuff in the code gave me a pause but it's out of scope here so just in
> case someone wants to do some extra churn...
>
> > ---
> > fs/proc/task_mmu.c | 14 +++++++-------
> > 1 file changed, 7 insertions(+), 7 deletions(-)
> >
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index 751479eb128f..b8bc06d05a72 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -135,7 +135,7 @@ static struct vm_area_struct *proc_get_vma(struct
> > proc_maps_private *priv,
> > if (vma) {
> > *ppos = vma->vm_start;
> > } else {
> > - *ppos = -2UL;
> > + *ppos = -2;
> > vma = get_gate_vma(priv->mm);
> > }
> >
> > @@ -145,11 +145,11 @@ static struct vm_area_struct *proc_get_vma(struct
> > proc_maps_private *priv,
> > static void *m_start(struct seq_file *m, loff_t *ppos)
> > {
> > struct proc_maps_private *priv = m->private;
> > - unsigned long last_addr = *ppos;
> > + loff_t last_addr = *ppos;
> > struct mm_struct *mm;
> >
> > /* See m_next(). Zero at the start or after lseek. */
> > - if (last_addr == -1UL)
> > + if (last_addr == -1)
> > return NULL;
> >
> > priv->task = get_proc_task(priv->inode);
> > @@ -170,9 +170,9 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
> > return ERR_PTR(-EINTR);
> > }
> >
> > - vma_iter_init(&priv->iter, mm, last_addr);
> > + vma_iter_init(&priv->iter, mm, (unsigned long)last_addr);
>
> I wonder if this should rather be done only after dealing with the -2 case
> below. It seems wrong to init the iterator with a bogus address. What if it
> acquires some sanity checks?
>
> > hold_task_mempolicy(priv);
>
> It seems suboptimal to do that mempolicy refcount dance for numa_maps sake
> even if we're reading a different /proc file... maybe priv could have a flag
> to determine?
>
> > - if (last_addr == -2UL)
> > + if (last_addr == -2)
> > return get_gate_vma(mm);
>
> I think only after the above it makes sense to init the iterator?
Yes makes sense but let me do that outside of this patchset as it's
rather unrelated.
>
> > return proc_get_vma(priv, ppos);
> > @@ -180,8 +180,8 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
> >
> > static void *m_next(struct seq_file *m, void *v, loff_t *ppos)
> > {
> > - if (*ppos == -2UL) {
> > - *ppos = -1UL;
> > + if (*ppos == -2) {
> > + *ppos = -1;
> > return NULL;
> > }
> > return proc_get_vma(m->private, ppos);
>
