aio: fix error handling and rcu usage in "convert the ioctx list to table lookup v3"
In the patch "aio: convert the ioctx list to table lookup v3", incorrect handling in the ioctx_alloc() error path was introduced that lead to an ioctx being added via ioctx_add_table() while freed when the ioctx_alloc() call returned -EAGAIN due to hitting the aio_max_nr limit. Fix this by only calling ioctx_add_table() as the last step in ioctx_alloc(). Also, several unnecessary rcu_dereference() calls were added that lead to RCU warnings where the system was already protected by a spin lock for accessing mm->ioctx_table. Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
This commit is contained in:
Родитель
6878ea72a5
Коммит
da90382c2e
17
fs/aio.c
17
fs/aio.c
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@ -475,7 +475,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
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struct aio_ring *ring;
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spin_lock(&mm->ioctx_lock);
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table = rcu_dereference(mm->ioctx_table);
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table = mm->ioctx_table;
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while (1) {
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if (table)
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@ -503,7 +503,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
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table->nr = new_nr;
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spin_lock(&mm->ioctx_lock);
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old = rcu_dereference(mm->ioctx_table);
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old = mm->ioctx_table;
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if (!old) {
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rcu_assign_pointer(mm->ioctx_table, table);
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@ -579,10 +579,6 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
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if (ctx->req_batch < 1)
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ctx->req_batch = 1;
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err = ioctx_add_table(ctx, mm);
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if (err)
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goto out_cleanup_noerr;
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/* limit the number of system wide aios */
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spin_lock(&aio_nr_lock);
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if (aio_nr + nr_events > (aio_max_nr * 2UL) ||
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@ -595,13 +591,18 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
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percpu_ref_get(&ctx->users); /* io_setup() will drop this ref */
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err = ioctx_add_table(ctx, mm);
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if (err)
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goto out_cleanup_put;
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pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
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ctx, ctx->user_id, mm, ctx->nr_events);
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return ctx;
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out_cleanup_put:
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percpu_ref_put(&ctx->users);
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out_cleanup:
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err = -EAGAIN;
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out_cleanup_noerr:
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aio_free_ring(ctx);
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out_freepcpu:
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free_percpu(ctx->cpu);
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@ -626,7 +627,7 @@ static void kill_ioctx(struct mm_struct *mm, struct kioctx *ctx)
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struct kioctx_table *table;
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spin_lock(&mm->ioctx_lock);
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table = rcu_dereference(mm->ioctx_table);
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table = mm->ioctx_table;
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WARN_ON(ctx != table->table[ctx->id]);
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table->table[ctx->id] = NULL;
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