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

[Christian König]

Am 17.04.21 um 16:21 schrieb Muchun Song:
> On Sat, Apr 17, 2021 at 9:44 PM <Peter.Enderborg@xxxxxxxx> wrote:
> > 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.
> 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