104 lines
3.4 KiB
Diff
104 lines
3.4 KiB
Diff
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Mon, 7 May 2018 16:51:09 +0200
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Subject: [PATCH] bdi: use refcount_t for reference counting instead atomic_t
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.18/older/patches-4.18.5-rt3.tar.xz
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refcount_t type and corresponding API should be used instead of atomic_t when
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the variable is used as a reference counter. This allows to avoid accidental
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refcounter overflows that might lead to use-after-free situations.
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Suggested-by: Peter Zijlstra <peterz@infradead.org>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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include/linux/backing-dev-defs.h | 3 ++-
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include/linux/backing-dev.h | 4 ++--
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mm/backing-dev.c | 12 ++++++------
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3 files changed, 10 insertions(+), 9 deletions(-)
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--- a/include/linux/backing-dev-defs.h
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+++ b/include/linux/backing-dev-defs.h
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@@ -12,6 +12,7 @@
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#include <linux/timer.h>
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#include <linux/workqueue.h>
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#include <linux/kref.h>
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+#include <linux/refcount.h>
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struct page;
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struct device;
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@@ -75,7 +76,7 @@ enum wb_reason {
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*/
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struct bdi_writeback_congested {
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unsigned long state; /* WB_[a]sync_congested flags */
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- atomic_t refcnt; /* nr of attached wb's and blkg */
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+ refcount_t refcnt; /* nr of attached wb's and blkg */
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#ifdef CONFIG_CGROUP_WRITEBACK
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struct backing_dev_info *__bdi; /* the associated bdi, set to NULL
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--- a/include/linux/backing-dev.h
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+++ b/include/linux/backing-dev.h
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@@ -404,13 +404,13 @@ static inline bool inode_cgwb_enabled(st
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static inline struct bdi_writeback_congested *
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wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
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{
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- atomic_inc(&bdi->wb_congested->refcnt);
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+ refcount_inc(&bdi->wb_congested->refcnt);
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return bdi->wb_congested;
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}
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static inline void wb_congested_put(struct bdi_writeback_congested *congested)
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{
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- if (atomic_dec_and_test(&congested->refcnt))
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+ if (refcount_dec_and_test(&congested->refcnt))
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kfree(congested);
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}
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--- a/mm/backing-dev.c
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+++ b/mm/backing-dev.c
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@@ -438,10 +438,10 @@ wb_congested_get_create(struct backing_d
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if (new_congested) {
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/* !found and storage for new one already allocated, insert */
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congested = new_congested;
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- new_congested = NULL;
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rb_link_node(&congested->rb_node, parent, node);
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rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
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- goto found;
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+ spin_unlock_irqrestore(&cgwb_lock, flags);
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+ return congested;
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}
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spin_unlock_irqrestore(&cgwb_lock, flags);
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@@ -451,13 +451,13 @@ wb_congested_get_create(struct backing_d
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if (!new_congested)
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return NULL;
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- atomic_set(&new_congested->refcnt, 0);
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+ refcount_set(&new_congested->refcnt, 1);
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new_congested->__bdi = bdi;
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new_congested->blkcg_id = blkcg_id;
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goto retry;
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found:
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- atomic_inc(&congested->refcnt);
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+ refcount_inc(&congested->refcnt);
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spin_unlock_irqrestore(&cgwb_lock, flags);
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kfree(new_congested);
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return congested;
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@@ -474,7 +474,7 @@ void wb_congested_put(struct bdi_writeba
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unsigned long flags;
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local_irq_save(flags);
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- if (!atomic_dec_and_lock(&congested->refcnt, &cgwb_lock)) {
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+ if (!refcount_dec_and_lock(&congested->refcnt, &cgwb_lock)) {
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local_irq_restore(flags);
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return;
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}
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@@ -804,7 +804,7 @@ static int cgwb_bdi_init(struct backing_
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if (!bdi->wb_congested)
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return -ENOMEM;
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- atomic_set(&bdi->wb_congested->refcnt, 1);
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+ refcount_set(&bdi->wb_congested->refcnt, 1);
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err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
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if (err) {
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