"Verma, Vishal L" <vishal.l.verma@xxxxxxxxx> writes: > On Fri, 2016-04-15 at 12:11 -0400, Jeff Moyer wrote: >> Vishal Verma <vishal.l.verma@xxxxxxxxx> writes: >> > + if (IS_DAX(inode)) { >> > + ret = dax_do_io(iocb, inode, iter, offset, >> > blkdev_get_block, >> > NULL, DIO_SKIP_DIO_COUNT); >> > - return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), >> > iter, offset, >> > + if (ret == -EIO && (iov_iter_rw(iter) == WRITE)) >> > + ret_saved = ret; >> > + else >> > + return ret; >> > + } >> > + >> > + ret = __blockdev_direct_IO(iocb, inode, I_BDEV(inode), >> > iter, offset, >> > blkdev_get_block, NULL, NULL, >> > DIO_SKIP_DIO_COUNT); >> > + if (ret < 0 && ret_saved) >> > + return ret_saved; >> > + >> Hmm, did you just break async DIO? I think you did! :) >> __blockdev_direct_IO can return -EIOCBQUEUED, and you've now turned >> that >> into -EIO. Really, I don't see a reason to save that first >> -EIO. The >> same applies to all instances in this patch. > > The reason I saved it was if __blockdev_direct_IO fails for some > reason, we should return the original cause o the error, which was an > EIO.. i.e. we shouldn't be hiding the EIO if the direct_IO fails with > something else.. OK. > But, how does _EIOCBQUEUED work? Maybe we need an exception for it? For async direct I/O, only the setup phase of the I/O is performed and then we return to the caller. -EIOCBQUEUED signifies this. You're heading towards code that looks like this: if (IS_DAX(inode)) { ret = dax_do_io(iocb, inode, iter, offset, blkdev_get_block, NULL, DIO_SKIP_DIO_COUNT); if (ret == -EIO && (iov_iter_rw(iter) == WRITE)) ret_saved = ret; else return ret; } ret = __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter, offset, blkdev_get_block, NULL, NULL, DIO_SKIP_DIO_COUNT); if (ret < 0 && ret != -EIOCBQUEUED && ret_saved) return ret_saved; There's a lot of special casing here, so you might consider adding comments. Cheers, Jeff -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href