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aio: fix error handling and rcu usage in "convert the ioctx list to table lookup v3"

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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:
Benjamin LaHaise 2013-08-05 13:21:43 -04:00
parent 6878ea72a5
commit da90382c2e
1 changed files with 9 additions and 8 deletions
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17
fs/aio.c
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@ -475,7 +475,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
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 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
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 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
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 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
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 @@ static void kill_ioctx(struct mm_struct *mm, struct kioctx *ctx)
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;