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| author | Oleg Nesterov <oleg@redhat.com> | 2014-04-30 16:16:36 +0200 |
|---|---|---|
| committer | Benjamin LaHaise <bcrl@kvack.org> | 2014-06-24 18:10:25 -0400 |
| commit | 855ef0dec7271ff7be7381feaaf3f4aed80bd503 (patch) | |
| tree | 1291243a3364240702b03ef74bac539c674583ab /fs/aio.c | |
| parent | 4b70ac5fd9b58bfaa5f25b4ea48f528aefbf3308 (diff) | |
| download | lwn-855ef0dec7271ff7be7381feaaf3f4aed80bd503.tar.gz lwn-855ef0dec7271ff7be7381feaaf3f4aed80bd503.zip | |
aio: kill the misleading rcu read locks in ioctx_add_table() and kill_ioctx()
ioctx_add_table() is the writer, it does not need rcu_read_lock() to
protect ->ioctx_table. It relies on mm->ioctx_lock and rcu locks just
add the confusion.
And it doesn't need rcu_dereference() by the same reason, it must see
any updates previously done under the same ->ioctx_lock. We could use
rcu_dereference_protected() but the patch uses rcu_dereference_raw(),
the function is simple enough.
The same for kill_ioctx(), although it does not update the pointer.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Diffstat (limited to 'fs/aio.c')
| -rw-r--r-- | fs/aio.c | 14 |
1 files changed, 3 insertions, 11 deletions
@@ -554,8 +554,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm) struct aio_ring *ring; spin_lock(&mm->ioctx_lock); - rcu_read_lock(); - table = rcu_dereference(mm->ioctx_table); + table = rcu_dereference_raw(mm->ioctx_table); while (1) { if (table) @@ -563,7 +562,6 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm) if (!table->table[i]) { ctx->id = i; table->table[i] = ctx; - rcu_read_unlock(); spin_unlock(&mm->ioctx_lock); /* While kioctx setup is in progress, @@ -577,8 +575,6 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm) } new_nr = (table ? table->nr : 1) * 4; - - rcu_read_unlock(); spin_unlock(&mm->ioctx_lock); table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) * @@ -589,8 +585,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm) table->nr = new_nr; spin_lock(&mm->ioctx_lock); - rcu_read_lock(); - old = rcu_dereference(mm->ioctx_table); + old = rcu_dereference_raw(mm->ioctx_table); if (!old) { rcu_assign_pointer(mm->ioctx_table, table); @@ -737,12 +732,9 @@ static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx, spin_lock(&mm->ioctx_lock); - rcu_read_lock(); - table = rcu_dereference(mm->ioctx_table); - + table = rcu_dereference_raw(mm->ioctx_table); WARN_ON(ctx != table->table[ctx->id]); table->table[ctx->id] = NULL; - rcu_read_unlock(); spin_unlock(&mm->ioctx_lock); /* percpu_ref_kill() will do the necessary call_rcu() */ |