ping... On 02/28/2014 06:27 PM, Gu Zheng wrote:
> Using rcu_dereference_protected() rather than the "rcu_read_lock--> > rcu_dereference-->rcu_read_unlock" group to simplify fetching the > ioctx_table pointer in ioctx_add_table and kill_ioctx, because it > is protected by the ioctx_lock. > And in the exit_aio(), there are no other users manipulating ioctx_table > at this stage, so we can use rcu_access_pointer directly. > > Signed-off-by: Gu Zheng <[email protected]> > --- > fs/aio.c | 42 ++++++++++++++++-------------------------- > 1 files changed, 16 insertions(+), 26 deletions(-) > > diff --git a/fs/aio.c b/fs/aio.c > index 062a5f6..7eaa631 100644 > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -544,8 +544,8 @@ 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_protected(mm->ioctx_table, > + lockdep_is_held(&mm->ioctx_lock)); > > while (1) { > if (table) > @@ -553,7 +553,6 @@ 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); > > ring = kmap_atomic(ctx->ring_pages[0]); > @@ -564,7 +563,6 @@ 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 *) * > @@ -575,8 +573,8 @@ 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_protected(mm->ioctx_table, > + lockdep_is_held(&mm->ioctx_lock)); > > if (!old) { > rcu_assign_pointer(mm->ioctx_table, table); > @@ -711,12 +709,11 @@ static void kill_ioctx(struct mm_struct *mm, struct > kioctx *ctx) > struct kioctx_table *table; > > spin_lock(&mm->ioctx_lock); > - rcu_read_lock(); > - table = rcu_dereference(mm->ioctx_table); > + table = rcu_dereference_protected(mm->ioctx_table, > + lockdep_is_held(&mm->ioctx_lock)); > > 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() */ > @@ -765,27 +762,17 @@ EXPORT_SYMBOL(wait_on_sync_kiocb); > void exit_aio(struct mm_struct *mm) > { > struct kioctx_table *table; > - struct kioctx *ctx; > unsigned i = 0; > > - while (1) { > - rcu_read_lock(); > - table = rcu_dereference(mm->ioctx_table); > - > - do { > - if (!table || i >= table->nr) { > - rcu_read_unlock(); > - rcu_assign_pointer(mm->ioctx_table, NULL); > - if (table) > - kfree(table); > - return; > - } > - > - ctx = table->table[i++]; > - } while (!ctx); > + table = rcu_access_pointer(mm->ioctx_table); > + if (!table) > + return; > > - rcu_read_unlock(); > + while (i < table->nr) { > + struct kioctx *ctx = table->table[i++]; > > + if (!ctx) > + continue; > /* > * We don't need to bother with munmap() here - > * exit_mmap(mm) is coming and it'll unmap everything. > @@ -798,6 +785,9 @@ void exit_aio(struct mm_struct *mm) > > kill_ioctx(mm, ctx); > } > + > + rcu_assign_pointer(mm->ioctx_table, NULL); > + kfree(table); > } > > static void put_reqs_available(struct kioctx *ctx, unsigned nr) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
