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>
diff --git a/fs/aio.c b/fs/aio.c
index 588aff9..3bc068c 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -475,7 +475,7 @@
struct aio_ring *ring;
spin_lock(&mm->ioctx_lock);
- table = rcu_dereference(mm->ioctx_table);
+ table = mm->ioctx_table;
while (1) {
if (table)
@@ -503,7 +503,7 @@
table->nr = new_nr;
spin_lock(&mm->ioctx_lock);
- old = rcu_dereference(mm->ioctx_table);
+ old = mm->ioctx_table;
if (!old) {
rcu_assign_pointer(mm->ioctx_table, table);
@@ -579,10 +579,6 @@
if (ctx->req_batch < 1)
ctx->req_batch = 1;
- err = ioctx_add_table(ctx, mm);
- if (err)
- goto out_cleanup_noerr;
-
/* limit the number of system wide aios */
spin_lock(&aio_nr_lock);
if (aio_nr + nr_events > (aio_max_nr * 2UL) ||
@@ -595,13 +591,18 @@
percpu_ref_get(&ctx->users); /* io_setup() will drop this ref */
+ err = ioctx_add_table(ctx, mm);
+ if (err)
+ goto out_cleanup_put;
+
pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
ctx, ctx->user_id, mm, ctx->nr_events);
return ctx;
+out_cleanup_put:
+ percpu_ref_put(&ctx->users);
out_cleanup:
err = -EAGAIN;
-out_cleanup_noerr:
aio_free_ring(ctx);
out_freepcpu:
free_percpu(ctx->cpu);
@@ -626,7 +627,7 @@
struct kioctx_table *table;
spin_lock(&mm->ioctx_lock);
- table = rcu_dereference(mm->ioctx_table);
+ table = mm->ioctx_table;
WARN_ON(ctx != table->table[ctx->id]);
table->table[ctx->id] = NULL;