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Message-ID: <ZRQvEFUepsUH/BUi@MiWiFi-R3L-srv>
Date: Wed, 27 Sep 2023 21:33:04 +0800
From: "bhe@...hat.com" <bhe@...hat.com>
To: Uladzislau Rezki <urezki@...il.com>
Cc: Jaeseon Sim <jason.sim@...sung.com>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"hch@...radead.org" <hch@...radead.org>,
"lstoakes@...il.com" <lstoakes@...il.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Jaewon Kim <jaewon31.kim@...sung.com>
Subject: Re: [PATCH] mm/vmalloc: Remove WARN_ON_ONCE related to
adjust_va_to_fit_type
On 09/27/23 at 01:49pm, Uladzislau Rezki wrote:
> > > Yes, but GFP_NOWAIT-alloc-error can easily occur for low-memory device.
> > >
> > Agree. You are really in a low memory condition. We end up here only if
> > pre-loading also has not succeeded, i.e. GFP_KERNEL also fails.
> >
> > But i agree with you, we should "improve the warning" because we drain
> > and repeat.
> >
> > > How about changing fix as below?:
> > >
> > > <snip>
> > > --- a/mm/vmalloc.c
> > > +++ b/mm/vmalloc.c
> > > @@ -1468,6 +1468,7 @@ adjust_va_to_fit_type(struct rb_root *root, struct list_head *head,
> > > */
> > > va->va_start = nva_start_addr + size;
> > > } else {
> > > + WARN_ON_ONCE(1);
> > > return -1;
> > > }
> > >
> > > @@ -1522,7 +1523,7 @@ __alloc_vmap_area(struct rb_root *root, struct list_head *head,
> > >
> > > /* Update the free vmap_area. */
> > > ret = adjust_va_to_fit_type(root, head, va, nva_start_addr, size);
> > > - if (WARN_ON_ONCE(ret))
> > > + if (ret)
> > > return vend;
> > >
> > > #if DEBUG_AUGMENT_LOWEST_MATCH_CHECK
> > > @@ -4143,7 +4144,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
> > > ret = adjust_va_to_fit_type(&free_vmap_area_root,
> > > &free_vmap_area_list,
> > > va, start, size);
> > > - if (WARN_ON_ONCE(unlikely(ret)))
> > > + if (unlikely(ret))
> > > /* It is a BUG(), but trigger recovery instead. */
> > > goto recovery;
> > >
> > > <snip>
> > > It will WARN_ONCE_ONCE() only if classify_va_fit_type() is "(type == NOTHING_FIT)".
> > >
> > This is good but i think it should be improved further. We need to
> > understand from the warning when no memory and when there is no a
> > vmap space, so:
> >
> > - if NOTHING_FIT, we should WARN() for sure;
> > - Second place in the pcpu_get_vm_area(), we do not use NE_FIT. Only in
> > the begging after boot, but potentially we can trigger -ENOMEM and we
> > should warn in this case. Otherwise you just hide it;
> > - And last one if after repeating we still do not manage to allocate.
> >
>
> We should understand a reason of failing. I think error handling should
> be improved. Something like:
This looks good to me, while the parameter 'error' looks a little ugly.
How about this?
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index ef8599d394fd..32805c82373b 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1454,7 +1454,7 @@ adjust_va_to_fit_type(struct rb_root *root, struct list_head *head,
*/
lva = kmem_cache_alloc(vmap_area_cachep, GFP_NOWAIT);
if (!lva)
- return -1;
+ return -ENOMEM;
}
/*
@@ -1468,7 +1468,7 @@ adjust_va_to_fit_type(struct rb_root *root, struct list_head *head,
*/
va->va_start = nva_start_addr + size;
} else {
- return -1;
+ return -EINVAL;
}
if (type != FL_FIT_TYPE) {
@@ -1509,7 +1509,7 @@ __alloc_vmap_area(struct rb_root *root, struct list_head *head,
va = find_vmap_lowest_match(root, size, align, vstart, adjust_search_size);
if (unlikely(!va))
- return vend;
+ return -ENOENT;
if (va->va_start > vstart)
nva_start_addr = ALIGN(va->va_start, align);
@@ -1518,12 +1518,12 @@ __alloc_vmap_area(struct rb_root *root, struct list_head *head,
/* Check the "vend" restriction. */
if (nva_start_addr + size > vend)
- return vend;
+ return -ERANGE;
/* Update the free vmap_area. */
ret = adjust_va_to_fit_type(root, head, va, nva_start_addr, size);
- if (WARN_ON_ONCE(ret))
- return vend;
+ if (ret)
+ return ret;
#if DEBUG_AUGMENT_LOWEST_MATCH_CHECK
find_vmap_lowest_match_check(root, head, size, align);
@@ -1616,13 +1616,13 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
size, align, vstart, vend);
spin_unlock(&free_vmap_area_lock);
- trace_alloc_vmap_area(addr, size, align, vstart, vend, addr == vend);
+ trace_alloc_vmap_area(addr, size, align, vstart, vend, IS_ERR(addr));
/*
- * If an allocation fails, the "vend" address is
+ * If an allocation fails, the error value is
* returned. Therefore trigger the overflow path.
*/
- if (unlikely(addr == vend))
+ if (unlikely(IS_ERR(addr)))
goto overflow;
va->va_start = addr;
@@ -1662,8 +1662,9 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
}
if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit())
- pr_warn("vmap allocation for size %lu failed: use vmalloc=<size> to increase size\n",
- size);
+ pr_warn("vmap allocation for size %lu failed: "
+ "use vmalloc=<size> to increase size, errno: (%d)\n",
+ size, addr);
kmem_cache_free(vmap_area_cachep, va);
return ERR_PTR(-EBUSY);
@@ -4143,8 +4144,8 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
ret = adjust_va_to_fit_type(&free_vmap_area_root,
&free_vmap_area_list,
va, start, size);
- if (WARN_ON_ONCE(unlikely(ret)))
- /* It is a BUG(), but trigger recovery instead. */
+ if ((unlikely(ret)))
+ WARN_ONCE(1, "%s error: errno (%d)\n", __func__, ret);
goto recovery;
/* Allocated area. */
>
> <snip>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index ef8599d394fd..03a36921a3fc 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1454,7 +1454,7 @@ adjust_va_to_fit_type(struct rb_root *root, struct list_head *head,
> */
> lva = kmem_cache_alloc(vmap_area_cachep, GFP_NOWAIT);
> if (!lva)
> - return -1;
> + return -ENOMEM;
> }
>
> /*
> @@ -1468,7 +1468,7 @@ adjust_va_to_fit_type(struct rb_root *root, struct list_head *head,
> */
> va->va_start = nva_start_addr + size;
> } else {
> - return -1;
> + return -EINVAL;
> }
>
> if (type != FL_FIT_TYPE) {
> @@ -1488,7 +1488,8 @@ adjust_va_to_fit_type(struct rb_root *root, struct list_head *head,
> static __always_inline unsigned long
> __alloc_vmap_area(struct rb_root *root, struct list_head *head,
> unsigned long size, unsigned long align,
> - unsigned long vstart, unsigned long vend)
> + unsigned long vstart, unsigned long vend,
> + int *error)
> {
> bool adjust_search_size = true;
> unsigned long nva_start_addr;
> @@ -1508,8 +1509,10 @@ __alloc_vmap_area(struct rb_root *root, struct list_head *head,
> adjust_search_size = false;
>
> va = find_vmap_lowest_match(root, size, align, vstart, adjust_search_size);
> - if (unlikely(!va))
> + if (unlikely(!va)) {
> + *error = -ENOENT;
> return vend;
> + }
>
> if (va->va_start > vstart)
> nva_start_addr = ALIGN(va->va_start, align);
> @@ -1517,13 +1520,17 @@ __alloc_vmap_area(struct rb_root *root, struct list_head *head,
> nva_start_addr = ALIGN(vstart, align);
>
> /* Check the "vend" restriction. */
> - if (nva_start_addr + size > vend)
> + if (nva_start_addr + size > vend) {
> + *error = -ERANGE;
> return vend;
> + }
>
> /* Update the free vmap_area. */
> ret = adjust_va_to_fit_type(root, head, va, nva_start_addr, size);
> - if (WARN_ON_ONCE(ret))
> + if (ret) {
> + *error = ret;
> return vend;
> + }
>
> #if DEBUG_AUGMENT_LOWEST_MATCH_CHECK
> find_vmap_lowest_match_check(root, head, size, align);
> @@ -1589,7 +1596,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> unsigned long freed;
> unsigned long addr;
> int purged = 0;
> - int ret;
> + int ret, error;
>
> if (unlikely(!size || offset_in_page(size) || !is_power_of_2(align)))
> return ERR_PTR(-EINVAL);
> @@ -1613,7 +1620,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> retry:
> preload_this_cpu_lock(&free_vmap_area_lock, gfp_mask, node);
> addr = __alloc_vmap_area(&free_vmap_area_root, &free_vmap_area_list,
> - size, align, vstart, vend);
> + size, align, vstart, vend, &error);
> spin_unlock(&free_vmap_area_lock);
>
> trace_alloc_vmap_area(addr, size, align, vstart, vend, addr == vend);
> @@ -1662,8 +1669,9 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> }
>
> if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit())
> - pr_warn("vmap allocation for size %lu failed: use vmalloc=<size> to increase size\n",
> - size);
> + pr_warn("vmap allocation for size %lu failed: "
> + "use vmalloc=<size> to increase size, errno: (%d)\n",
> + size, error);
>
> kmem_cache_free(vmap_area_cachep, va);
> return ERR_PTR(-EBUSY);
> @@ -4143,9 +4151,10 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
> ret = adjust_va_to_fit_type(&free_vmap_area_root,
> &free_vmap_area_list,
> va, start, size);
> - if (WARN_ON_ONCE(unlikely(ret)))
> - /* It is a BUG(), but trigger recovery instead. */
> + if (unlikely(ret)) {
> + WARN_ONCE(1, "%s error: errno (%d)\n", __func__, ret);
> goto recovery;
> + }
>
> /* Allocated area. */
> va = vas[area];
> <snip>
>
> Any thoughts?
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