* Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx> [230518 02:10]:
>
>
> 在 2023/5/18 02:17, Liam R. Howlett 写道:
> > * Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx> [230517 04:58]:
> > > Use mas_empty_area{_rev}() to refactor mtree_alloc_{range,rrange}()
> > >
> > > Signed-off-by: Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx>
> > > ---
> > > lib/maple_tree.c | 63 ++++++++++++++++++++++++------------------------
> > > 1 file changed, 32 insertions(+), 31 deletions(-)
> > >
> > > diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> > > index 4eb220008f72..e1820e90f167 100644
> > > --- a/lib/maple_tree.c
> > > +++ b/lib/maple_tree.c
> > > @@ -6493,32 +6493,31 @@ int mtree_alloc_range(struct maple_tree *mt, unsigned long *startp,
> > > {
> > > int ret = 0;
> > > - MA_STATE(mas, mt, min, min);
> > > + MA_STATE(mas, mt, 0, 0);
> > > if (!mt_is_alloc(mt))
> > > return -EINVAL;
> > > if (WARN_ON_ONCE(mt_is_reserved(entry)))
> > > return -EINVAL;
> > > - if (min > max)
> > > - return -EINVAL;
> > > -
> > > - if (max < size)
> > > - return -EINVAL;
> > > -
> > > - if (!size)
> > > - return -EINVAL;
> > > -
> > > mtree_lock(mt);
> > > retry:
> > > - mas.offset = 0;
> > > - mas.index = min;
> > > - mas.last = max - size + 1;
> > > - ret = mas_alloc(&mas, entry, size, startp);
> > > - if (mas_nomem(&mas, gfp))
> > > - goto retry;
> > > -
> > > + ret = mas_empty_area(&mas, min, max, size);
> > > + if (!ret) {
> > > + mas_insert(&mas, entry);
> > > + /*
> > > + * mas_nomem() may release the lock, causing the allocated area
> > > + * to be unavailable, so try to allocate a free area again.
> > > + */
> > > + if (mas_nomem(&mas, gfp))
> > > + goto retry;
> > > + }
> > > mtree_unlock(mt);
> > > + if (!ret) {
> >
> > Checking for a mas_is_err() should probably be outside if (!ret)
> > statement. If mas_insert() returns something besides ENOMEM, we will
> > not detect the error. I'm not sure if this is possible today since this
> > should never return an -EEXISTS, but having it this way doesn't add much
> > to the overhead.
> I don't think there will be error that can't be detected here.
> In fact, there are two sources of errors:
>
> 1. mas_empty_area(), the error number is in the variable ret,
> and may also be in mas->node, but ret must contain all errors.
>
> 2. mas_insert(), the error number is in mas->node
>
> When we check errors, we should first check errors from
> mas_empty_area(). If there is no error in mas_empty_area(), we
> will check errors from mas_insert().
> So, mas_is_err() is inside the if (!ret) statement, no problem here.
>
> Of course, even if mas_insert() returns -EEXISTS, it can be detected
> under the current encoding, because "if (!ret)" is true in this case.
> But I don't think this can happen, if it happens, it's a bug of maple
> tree.
Right, thanks.
>
> I don't think it's good to put mas_is_err() outside, because the error
> number stored in mas->node may come from mas_empty_area(). We should use
> the ret variable to detect the error from mas_empty_area() first.
Yeah, I would structure it as a 'goto' to undo the locking to avoid the
if (!ret) nesting, and move the unlock to just before the return:
if (ret)
goto unlock;
...
*startp = mas.index;
unlock:
mtree_unlock(mt);
return ret;
mas_empty_area() is an external interface and so already decodes the
error in the node using mas_is_err(), so this can be dropped completely.
I don't think holding the lock for the one extra assignment will make a
difference.
> >
> > > + if (mas_is_err(&mas))
> > > + return xa_err(mas.node);
> > > + *startp = mas.index;
> > > + }
> > > return ret;
> > > }
> > > EXPORT_SYMBOL(mtree_alloc_range);
> > > @@ -6529,29 +6528,31 @@ int mtree_alloc_rrange(struct maple_tree *mt, unsigned long *startp,
> > > {
> > > int ret = 0;
> > > - MA_STATE(mas, mt, min, max - size + 1);
> > > + MA_STATE(mas, mt, 0, 0);
> > > if (!mt_is_alloc(mt))
> > > return -EINVAL;
> > > if (WARN_ON_ONCE(mt_is_reserved(entry)))
> > > return -EINVAL;
> > > - if (min > max)
> > > - return -EINVAL;
> > > -
> > > - if (max < size - 1)
> > > - return -EINVAL;
> > > -
> > > - if (!size)
> > > - return -EINVAL;
> > > -
> > > mtree_lock(mt);
> > > retry:
> > > - ret = mas_rev_alloc(&mas, min, max, entry, size, startp);
> > > - if (mas_nomem(&mas, gfp))
> > > - goto retry;
> > > -
> > > + ret = mas_empty_area_rev(&mas, min, max, size);
> > > + if (!ret) {
> > > + mas_insert(&mas, entry);
> > > + /*
> > > + * mas_nomem() may release the lock, causing the allocated area
> > > + * to be unavailable, so try to allocate a free area again.
> > > + */
> > > + if (mas_nomem(&mas, gfp))
> > > + goto retry;
> > > + }
> > > mtree_unlock(mt);
> > > + if (!ret) {
> >
> > Same here.
> >
> > > + if (mas_is_err(&mas))
> > > + return xa_err(mas.node);
> > > + *startp = mas.index;
> > > + }
> > > return ret;
> > > }
> > > EXPORT_SYMBOL(mtree_alloc_rrange);
> > > --
> > > 2.20.1
> > >
