The patch titled
Subject: bdi: use refcount_t for reference counting instead atomic_t
has been added to the -mm tree. Its filename is
bdi-use-refcount_t-for-reference-counting-instead-atomic_t.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/bdi-use-refcount_t-for-reference-counting-instead-atomic_t.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/bdi-use-refcount_t-for-reference-counting-instead-atomic_t.patch
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------------------------------------------------------
From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Subject: bdi: use refcount_t for reference counting instead atomic_t
refcount_t type and corresponding API should be used instead of atomic_t
when the variable is used as a reference counter. This permits avoiding
accidental refcounter overflows that might lead to use-after-free
situations.
Link: http://lkml.kernel.org/r/20180703200141.28415-4-bigeasy@xxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/backing-dev-defs.h | 3 ++-
include/linux/backing-dev.h | 4 ++--
mm/backing-dev.c | 12 ++++++------
3 files changed, 10 insertions(+), 9 deletions(-)
diff -puN include/linux/backing-dev-defs.h~bdi-use-refcount_t-for-reference-counting-instead-atomic_t include/linux/backing-dev-defs.h
--- a/include/linux/backing-dev-defs.h~bdi-use-refcount_t-for-reference-counting-instead-atomic_t
+++ a/include/linux/backing-dev-defs.h
@@ -12,6 +12,7 @@
#include <linux/timer.h>
#include <linux/workqueue.h>
#include <linux/kref.h>
+#include <linux/refcount.h>
struct page;
struct device;
@@ -75,7 +76,7 @@ enum wb_reason {
*/
struct bdi_writeback_congested {
unsigned long state; /* WB_[a]sync_congested flags */
- atomic_t refcnt; /* nr of attached wb's and blkg */
+ refcount_t refcnt; /* nr of attached wb's and blkg */
#ifdef CONFIG_CGROUP_WRITEBACK
struct backing_dev_info *__bdi; /* the associated bdi, set to NULL
diff -puN include/linux/backing-dev.h~bdi-use-refcount_t-for-reference-counting-instead-atomic_t include/linux/backing-dev.h
--- a/include/linux/backing-dev.h~bdi-use-refcount_t-for-reference-counting-instead-atomic_t
+++ a/include/linux/backing-dev.h
@@ -404,13 +404,13 @@ static inline bool inode_cgwb_enabled(st
static inline struct bdi_writeback_congested *
wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
{
- atomic_inc(&bdi->wb_congested->refcnt);
+ refcount_inc(&bdi->wb_congested->refcnt);
return bdi->wb_congested;
}
static inline void wb_congested_put(struct bdi_writeback_congested *congested)
{
- if (atomic_dec_and_test(&congested->refcnt))
+ if (refcount_dec_and_test(&congested->refcnt))
kfree(congested);
}
diff -puN mm/backing-dev.c~bdi-use-refcount_t-for-reference-counting-instead-atomic_t mm/backing-dev.c
--- a/mm/backing-dev.c~bdi-use-refcount_t-for-reference-counting-instead-atomic_t
+++ a/mm/backing-dev.c
@@ -473,10 +473,10 @@ retry:
if (new_congested) {
/* !found and storage for new one already allocated, insert */
congested = new_congested;
- new_congested = NULL;
rb_link_node(&congested->rb_node, parent, node);
rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
- goto found;
+ spin_unlock_irqrestore(&cgwb_lock, flags);
+ return congested;
}
spin_unlock_irqrestore(&cgwb_lock, flags);
@@ -486,13 +486,13 @@ retry:
if (!new_congested)
return NULL;
- atomic_set(&new_congested->refcnt, 0);
+ refcount_set(&new_congested->refcnt, 1);
new_congested->__bdi = bdi;
new_congested->blkcg_id = blkcg_id;
goto retry;
found:
- atomic_inc(&congested->refcnt);
+ refcount_inc(&congested->refcnt);
spin_unlock_irqrestore(&cgwb_lock, flags);
kfree(new_congested);
return congested;
@@ -509,7 +509,7 @@ void wb_congested_put(struct bdi_writeba
unsigned long flags;
local_irq_save(flags);
- if (!atomic_dec_and_lock(&congested->refcnt, &cgwb_lock)) {
+ if (!refcount_dec_and_lock(&congested->refcnt, &cgwb_lock)) {
local_irq_restore(flags);
return;
}
@@ -839,7 +839,7 @@ static int cgwb_bdi_init(struct backing_
if (!bdi->wb_congested)
return -ENOMEM;
- atomic_set(&bdi->wb_congested->refcnt, 1);
+ refcount_set(&bdi->wb_congested->refcnt, 1);
err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
if (err) {
_
Patches currently in -mm which might be from bigeasy@xxxxxxxxxxxxx are
ntfs-dont-disable-interrupts-during-kmap_atomic.patch
mm-workingset-remove-local_irq_disable-from-count_shadow_nodes.patch
mm-workingset-make-shadow_lru_isolate-use-locking-suffix.patch
bdi-use-refcount_t-for-reference-counting-instead-atomic_t.patch
userns-use-refcount_t-for-reference-counting-instead-atomic_t.patch
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