Hi Roger,
I think this patch isn't need at all. You can directly read
total_swap_pages variable in TTM. See the comment:
/* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
long total_swap_pages;
there are many places using it directly, you just couldn't change its
value. Reading it doesn't need lock.
Regards,
David Zhou
On 2018年01月29日 16:29, Roger He wrote:
ttm module needs it to determine its internal parameter setting.
Signed-off-by: Roger He <Hongbo.He@xxxxxxx>
---
include/linux/swap.h | 6 ++++++
mm/swapfile.c | 15 +++++++++++++++
2 files changed, 21 insertions(+)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index c2b8128..708d66f 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -484,6 +484,7 @@ extern int try_to_free_swap(struct page *);
struct backing_dev_info;
extern int init_swap_address_space(unsigned int type, unsigned long nr_pages);
extern void exit_swap_address_space(unsigned int type);
+extern long get_total_swap_pages(void);
#else /* CONFIG_SWAP */
@@ -516,6 +517,11 @@ static inline void show_swap_cache_info(void)
{
}
+long get_total_swap_pages(void)
+{
+ return 0;
+}
+
#define free_swap_and_cache(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
#define swapcache_prepare(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 3074b02..a0062eb 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -98,6 +98,21 @@ static atomic_t proc_poll_event = ATOMIC_INIT(0);
atomic_t nr_rotate_swap = ATOMIC_INIT(0);
+/*
+ * expose this value for others use
+ */
+long get_total_swap_pages(void)
+{
+ long ret;
+
+ spin_lock(&swap_lock);
+ ret = total_swap_pages;
+ spin_unlock(&swap_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(get_total_swap_pages);
+
static inline unsigned char swap_count(unsigned char ent)
{
return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
--
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