Re: [External] [PATCH v4] dma-buf: Add DmaBufTotal counter in meminfo

[Peter.Enderborg]

On 4/17/21 3:07 PM, Muchun Song wrote:
> On Sat, Apr 17, 2021 at 6:41 PM Peter Enderborg
> <peter.enderborg@xxxxxxxx> 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@xxxxxxxx>
>> ---
>>  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.


> 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
>>