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108 lines
3.2 KiB
Diff
108 lines
3.2 KiB
Diff
From 6710e594f71ccaad8101bc64321152af7cd9ea28 Mon Sep 17 00:00:00 2001
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From: Tejun Heo <tj@kernel.org>
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Date: Wed, 25 May 2016 11:48:25 -0400
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Subject: percpu: fix synchronization between synchronous map extension and
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chunk destruction
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For non-atomic allocations, pcpu_alloc() can try to extend the area
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map synchronously after dropping pcpu_lock; however, the extension
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wasn't synchronized against chunk destruction and the chunk might get
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freed while extension is in progress.
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This patch fixes the bug by putting most of non-atomic allocations
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under pcpu_alloc_mutex to synchronize against pcpu_balance_work which
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is responsible for async chunk management including destruction.
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Signed-off-by: Tejun Heo <tj@kernel.org>
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Reported-and-tested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
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Reported-by: Vlastimil Babka <vbabka@suse.cz>
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Reported-by: Sasha Levin <sasha.levin@oracle.com>
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Cc: stable@vger.kernel.org # v3.18+
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Fixes: 1a4d76076cda ("percpu: implement asynchronous chunk population")
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---
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mm/percpu.c | 16 ++++++++--------
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1 file changed, 8 insertions(+), 8 deletions(-)
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diff --git a/mm/percpu.c b/mm/percpu.c
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index b1d2a38..9903830 100644
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--- a/mm/percpu.c
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+++ b/mm/percpu.c
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@@ -162,7 +162,7 @@ static struct pcpu_chunk *pcpu_reserved_chunk;
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static int pcpu_reserved_chunk_limit;
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static DEFINE_SPINLOCK(pcpu_lock); /* all internal data structures */
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-static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop */
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+static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop, map ext */
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static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
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@@ -444,6 +444,8 @@ static int pcpu_extend_area_map(struct pcpu_chunk *chunk, int new_alloc)
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size_t old_size = 0, new_size = new_alloc * sizeof(new[0]);
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unsigned long flags;
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+ lockdep_assert_held(&pcpu_alloc_mutex);
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+
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new = pcpu_mem_zalloc(new_size);
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if (!new)
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return -ENOMEM;
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@@ -890,6 +892,9 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
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return NULL;
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}
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+ if (!is_atomic)
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+ mutex_lock(&pcpu_alloc_mutex);
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+
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spin_lock_irqsave(&pcpu_lock, flags);
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/* serve reserved allocations from the reserved chunk if available */
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@@ -962,12 +967,9 @@ restart:
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if (is_atomic)
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goto fail;
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- mutex_lock(&pcpu_alloc_mutex);
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-
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if (list_empty(&pcpu_slot[pcpu_nr_slots - 1])) {
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chunk = pcpu_create_chunk();
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if (!chunk) {
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- mutex_unlock(&pcpu_alloc_mutex);
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err = "failed to allocate new chunk";
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goto fail;
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}
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@@ -978,7 +980,6 @@ restart:
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spin_lock_irqsave(&pcpu_lock, flags);
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}
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- mutex_unlock(&pcpu_alloc_mutex);
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goto restart;
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area_found:
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@@ -988,8 +989,6 @@ area_found:
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if (!is_atomic) {
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int page_start, page_end, rs, re;
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- mutex_lock(&pcpu_alloc_mutex);
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-
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page_start = PFN_DOWN(off);
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page_end = PFN_UP(off + size);
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@@ -1000,7 +999,6 @@ area_found:
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spin_lock_irqsave(&pcpu_lock, flags);
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if (ret) {
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- mutex_unlock(&pcpu_alloc_mutex);
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pcpu_free_area(chunk, off, &occ_pages);
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err = "failed to populate";
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goto fail_unlock;
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@@ -1040,6 +1038,8 @@ fail:
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/* see the flag handling in pcpu_blance_workfn() */
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pcpu_atomic_alloc_failed = true;
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pcpu_schedule_balance_work();
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+ } else {
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+ mutex_unlock(&pcpu_alloc_mutex);
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}
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return NULL;
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}
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--
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cgit v1.1
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