On Tue, Nov 05, 2019 at 11:28:55AM -0500, Theodore Y. Ts'o wrote: > On Tue, Nov 05, 2019 at 11:02:39PM +1100, Matthew Bobrowski wrote: > > + ret = iomap_dio_rw(iocb, from, &ext4_iomap_ops, &ext4_dio_write_ops, > > + is_sync_kiocb(iocb) || unaligned_aio || extend); > > + > > + if (extend) > > + ret = ext4_handle_inode_extension(inode, offset, ret, count); > > + > > Can we do a slight optimization here like this? > > ret = iomap_dio_rw(iocb, from, &ext4_iomap_ops, &ext4_dio_write_ops, > is_sync_kiocb(iocb) || unaligned_aio || extend); > > if (extend && ret != -EBIOCQUEUED) > ret = ext4_handle_inode_extension(inode, offset, ret, count); > > > If iomap_dio_rw() returns -EBIOCQUEUED, there's no need to do any of > the ext4_handle_inode_extension --- in particular, there's no need to > call ext4_truncate_failed_write(), which has a bunch of extra > overhead, including taking and releasing i_data_sem. Hm, but for extension, unaligned asynchronous IO, or synchronous IO cases, 'wait_for_completion' within iomap_dio_rw() is set to true and as a result we'd never expect to receive -EIOCBQUEUED from iomap_dio_rw()? So, with that said, would the above change be necessary seeing as though we'd never expect ret == -EIOCBQUEUED when extend == true? Maybe I'm missing something? /M
