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-rw-r--r--fs/aio.c44
1 files changed, 30 insertions, 14 deletions
diff --git a/fs/aio.c b/fs/aio.c
index a062d75109cb..6bcd3fb5265a 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -68,9 +68,9 @@ struct aio_ring {
#define AIO_RING_PAGES 8
struct kioctx_table {
- struct rcu_head rcu;
- unsigned nr;
- struct kioctx *table[];
+ struct rcu_head rcu;
+ unsigned nr;
+ struct kioctx __rcu *table[];
};
struct kioctx_cpu {
@@ -115,7 +115,8 @@ struct kioctx {
struct page **ring_pages;
long nr_pages;
- struct work_struct free_work;
+ struct rcu_head free_rcu;
+ struct work_struct free_work; /* see free_ioctx() */
/*
* signals when all in-flight requests are done
@@ -329,7 +330,7 @@ static int aio_ring_mremap(struct vm_area_struct *vma)
for (i = 0; i < table->nr; i++) {
struct kioctx *ctx;
- ctx = table->table[i];
+ ctx = rcu_dereference(table->table[i]);
if (ctx && ctx->aio_ring_file == file) {
if (!atomic_read(&ctx->dead)) {
ctx->user_id = ctx->mmap_base = vma->vm_start;
@@ -588,6 +589,12 @@ static int kiocb_cancel(struct aio_kiocb *kiocb)
return cancel(&kiocb->common);
}
+/*
+ * free_ioctx() should be RCU delayed to synchronize against the RCU
+ * protected lookup_ioctx() and also needs process context to call
+ * aio_free_ring(), so the double bouncing through kioctx->free_rcu and
+ * ->free_work.
+ */
static void free_ioctx(struct work_struct *work)
{
struct kioctx *ctx = container_of(work, struct kioctx, free_work);
@@ -601,6 +608,14 @@ static void free_ioctx(struct work_struct *work)
kmem_cache_free(kioctx_cachep, ctx);
}
+static void free_ioctx_rcufn(struct rcu_head *head)
+{
+ struct kioctx *ctx = container_of(head, struct kioctx, free_rcu);
+
+ INIT_WORK(&ctx->free_work, free_ioctx);
+ schedule_work(&ctx->free_work);
+}
+
static void free_ioctx_reqs(struct percpu_ref *ref)
{
struct kioctx *ctx = container_of(ref, struct kioctx, reqs);
@@ -609,8 +624,8 @@ static void free_ioctx_reqs(struct percpu_ref *ref)
if (ctx->rq_wait && atomic_dec_and_test(&ctx->rq_wait->count))
complete(&ctx->rq_wait->comp);
- INIT_WORK(&ctx->free_work, free_ioctx);
- schedule_work(&ctx->free_work);
+ /* Synchronize against RCU protected table->table[] dereferences */
+ call_rcu(&ctx->free_rcu, free_ioctx_rcufn);
}
/*
@@ -651,9 +666,9 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
while (1) {
if (table)
for (i = 0; i < table->nr; i++)
- if (!table->table[i]) {
+ if (!rcu_access_pointer(table->table[i])) {
ctx->id = i;
- table->table[i] = ctx;
+ rcu_assign_pointer(table->table[i], ctx);
spin_unlock(&mm->ioctx_lock);
/* While kioctx setup is in progress,
@@ -834,11 +849,11 @@ static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
}
table = rcu_dereference_raw(mm->ioctx_table);
- WARN_ON(ctx != table->table[ctx->id]);
- table->table[ctx->id] = NULL;
+ WARN_ON(ctx != rcu_access_pointer(table->table[ctx->id]));
+ RCU_INIT_POINTER(table->table[ctx->id], NULL);
spin_unlock(&mm->ioctx_lock);
- /* percpu_ref_kill() will do the necessary call_rcu() */
+ /* free_ioctx_reqs() will do the necessary RCU synchronization */
wake_up_all(&ctx->wait);
/*
@@ -880,7 +895,8 @@ void exit_aio(struct mm_struct *mm)
skipped = 0;
for (i = 0; i < table->nr; ++i) {
- struct kioctx *ctx = table->table[i];
+ struct kioctx *ctx =
+ rcu_dereference_protected(table->table[i], true);
if (!ctx) {
skipped++;
@@ -1069,7 +1085,7 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id)
if (!table || id >= table->nr)
goto out;
- ctx = table->table[id];
+ ctx = rcu_dereference(table->table[id]);
if (ctx && ctx->user_id == ctx_id) {
percpu_ref_get(&ctx->users);
ret = ctx;