The patch titled
Subject: zsmalloc: replace get_cpu_var with local_lock
has been added to the -mm tree. Its filename is
zsmalloc-replace-get_cpu_var-with-local_lock.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/zsmalloc-replace-get_cpu_var-with-local_lock.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/zsmalloc-replace-get_cpu_var-with-local_lock.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Mike Galbraith <umgwanakikbuti@xxxxxxxxx>
Subject: zsmalloc: replace get_cpu_var with local_lock
The usage of get_cpu_var() in zs_map_object() is problematic because it
disables preemption and makes it impossible to acquire any sleeping lock
on PREEMPT_RT such as a spinlock_t.
Replace the get_cpu_var() usage with a local_lock_t which is embedded
struct mapping_area. It ensures that the access the struct is
synchronized against all users on the same CPU.
[minchan: remove the bit_spin_lock part and change the title]
Link: https://lkml.kernel.org/r/20211115185909.3949505-10-minchan@xxxxxxxxxx
Signed-off-by: Mike Galbraith <umgwanakikbuti@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zsmalloc.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
--- a/mm/zsmalloc.c~zsmalloc-replace-get_cpu_var-with-local_lock
+++ a/mm/zsmalloc.c
@@ -65,6 +65,7 @@
#include <linux/wait.h>
#include <linux/pagemap.h>
#include <linux/fs.h>
+#include <linux/local_lock.h>
#define ZSPAGE_MAGIC 0x58
@@ -276,6 +277,7 @@ struct zspage {
};
struct mapping_area {
+ local_lock_t lock;
char *vm_buf; /* copy buffer for objects that span pages */
char *vm_addr; /* address of kmap_atomic()'ed pages */
enum zs_mapmode vm_mm; /* mapping mode */
@@ -451,7 +453,9 @@ MODULE_ALIAS("zpool-zsmalloc");
#endif /* CONFIG_ZPOOL */
/* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
-static DEFINE_PER_CPU(struct mapping_area, zs_map_area);
+static DEFINE_PER_CPU(struct mapping_area, zs_map_area) = {
+ .lock = INIT_LOCAL_LOCK(lock),
+};
static __maybe_unused int is_first_page(struct page *page)
{
@@ -1269,7 +1273,8 @@ void *zs_map_object(struct zs_pool *pool
class = zspage_class(pool, zspage);
off = (class->size * obj_idx) & ~PAGE_MASK;
- area = &get_cpu_var(zs_map_area);
+ local_lock(&zs_map_area.lock);
+ area = this_cpu_ptr(&zs_map_area);
area->vm_mm = mm;
if (off + class->size <= PAGE_SIZE) {
/* this object is contained entirely within a page */
@@ -1320,7 +1325,7 @@ void zs_unmap_object(struct zs_pool *poo
__zs_unmap_object(area, pages, off, class->size);
}
- put_cpu_var(zs_map_area);
+ local_unlock(&zs_map_area.lock);
migrate_read_unlock(zspage);
}
_
Patches currently in -mm which might be from umgwanakikbuti@xxxxxxxxx are
zsmalloc-replace-get_cpu_var-with-local_lock.patch
