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Message-ID: <4ae4e646-7e28-e389-50d1-681723d022e1@amd.com>
Date: Sat, 17 Apr 2021 17:03:30 +0200
From: Christian König <christian.koenig@....com>
To: Muchun Song <songmuchun@...edance.com>,
Peter Enderborg <Peter.Enderborg@...y.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Sumit Semwal <sumit.semwal@...aro.org>,
Alexey Dobriyan <adobriyan@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Roman Gushchin <guro@...com>,
Shakeel Butt <shakeelb@...gle.com>,
Michal Hocko <mhocko@...e.com>, Neil Brown <neilb@...e.de>,
Sami Tolvanen <samitolvanen@...gle.com>,
Mike Rapoport <rppt@...nel.org>, linux-media@...r.kernel.org,
dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
Matthew Wilcox <willy@...radead.org>
Subject: Re: [External] [PATCH v4] dma-buf: Add DmaBufTotal counter in meminfo
Am 17.04.21 um 16:21 schrieb Muchun Song:
> On Sat, Apr 17, 2021 at 9:44 PM <Peter.Enderborg@...y.com> wrote:
>> On 4/17/21 3:07 PM, Muchun Song wrote:
>>> On Sat, Apr 17, 2021 at 6:41 PM Peter Enderborg
>>> <peter.enderborg@...y.com> wrote:
>>>> This adds a total used dma-buf memory. Details
>>>> can be found in debugfs, however it is not for everyone
>>>> and not always available. dma-buf are indirect allocated by
>>>> userspace. So with this value we can monitor and detect
>>>> userspace applications that have problems.
>>>>
>>>> Signed-off-by: Peter Enderborg <peter.enderborg@...y.com>
>>>> ---
>>>> drivers/dma-buf/dma-buf.c | 13 +++++++++++++
>>>> fs/proc/meminfo.c | 5 ++++-
>>>> include/linux/dma-buf.h | 1 +
>>>> 3 files changed, 18 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
>>>> index f264b70c383e..197e5c45dd26 100644
>>>> --- a/drivers/dma-buf/dma-buf.c
>>>> +++ b/drivers/dma-buf/dma-buf.c
>>>> @@ -37,6 +37,7 @@ struct dma_buf_list {
>>>> };
>>>>
>>>> static struct dma_buf_list db_list;
>>>> +static atomic_long_t dma_buf_global_allocated;
>>>>
>>>> static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
>>>> {
>>>> @@ -79,6 +80,7 @@ static void dma_buf_release(struct dentry *dentry)
>>>> if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
>>>> dma_resv_fini(dmabuf->resv);
>>>>
>>>> + atomic_long_sub(dmabuf->size, &dma_buf_global_allocated);
>>>> module_put(dmabuf->owner);
>>>> kfree(dmabuf->name);
>>>> kfree(dmabuf);
>>>> @@ -586,6 +588,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
>>>> mutex_lock(&db_list.lock);
>>>> list_add(&dmabuf->list_node, &db_list.head);
>>>> mutex_unlock(&db_list.lock);
>>>> + atomic_long_add(dmabuf->size, &dma_buf_global_allocated);
>>>>
>>>> return dmabuf;
>>>>
>>>> @@ -1346,6 +1349,16 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
>>>> }
>>>> EXPORT_SYMBOL_GPL(dma_buf_vunmap);
>>>>
>>>> +/**
>>>> + * dma_buf_allocated_pages - Return the used nr of pages
>>>> + * allocated for dma-buf
>>>> + */
>>>> +long dma_buf_allocated_pages(void)
>>>> +{
>>>> + return atomic_long_read(&dma_buf_global_allocated) >> PAGE_SHIFT;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(dma_buf_allocated_pages);
>>> dma_buf_allocated_pages is only called from fs/proc/meminfo.c.
>>> I am confused why it should be exported. If it won't be called
>>> from the driver module, we should not export it.
>> Ah. I thought you did not want the GPL restriction. I don't have real
>> opinion about it. It's written to be following the rest of the module.
>> It is not needed for the usage of dma-buf in kernel module. But I
>> don't see any reason for hiding it either.
> The modules do not need dma_buf_allocated_pages, hiding it
> can prevent the module from calling it. So I think that
> EXPORT_SYMBOL_GPL is unnecessary. If one day someone
> want to call it from the module, maybe it’s not too late to export
> it at that time.
Yeah, that is a rather good point. Only symbols which should be used by
modules/drivers should be exported.
Christian.
>
>>
>>> Thanks.
>>>
>>>> +
>>>> #ifdef CONFIG_DEBUG_FS
>>>> static int dma_buf_debug_show(struct seq_file *s, void *unused)
>>>> {
>>>> diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
>>>> index 6fa761c9cc78..ccc7c40c8db7 100644
>>>> --- a/fs/proc/meminfo.c
>>>> +++ b/fs/proc/meminfo.c
>>>> @@ -16,6 +16,7 @@
>>>> #ifdef CONFIG_CMA
>>>> #include <linux/cma.h>
>>>> #endif
>>>> +#include <linux/dma-buf.h>
>>>> #include <asm/page.h>
>>>> #include "internal.h"
>>>>
>>>> @@ -145,7 +146,9 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>>>> show_val_kb(m, "CmaFree: ",
>>>> global_zone_page_state(NR_FREE_CMA_PAGES));
>>>> #endif
>>>> -
>>>> +#ifdef CONFIG_DMA_SHARED_BUFFER
>>>> + show_val_kb(m, "DmaBufTotal: ", dma_buf_allocated_pages());
>>>> +#endif
>>>> hugetlb_report_meminfo(m);
>>>>
>>>> arch_report_meminfo(m);
>>>> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
>>>> index efdc56b9d95f..5b05816bd2cd 100644
>>>> --- a/include/linux/dma-buf.h
>>>> +++ b/include/linux/dma-buf.h
>>>> @@ -507,4 +507,5 @@ int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
>>>> unsigned long);
>>>> int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
>>>> void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
>>>> +long dma_buf_allocated_pages(void);
>>>> #endif /* __DMA_BUF_H__ */
>>>> --
>>>> 2.17.1
>>>>
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