Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262809AbVDBBMK (ORCPT ); Fri, 1 Apr 2005 20:12:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262947AbVDBBMK (ORCPT ); Fri, 1 Apr 2005 20:12:10 -0500 Received: from fire.osdl.org ([65.172.181.4]:5310 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S262809AbVDBBLk (ORCPT ); Fri, 1 Apr 2005 20:11:40 -0500 Subject: [PATCH] Direct IO async short read bug followup From: Daniel McNeil To: Badari Pulavarty , Andrew Morton Cc: =?ISO-8859-1?Q?S=E9bastien_Dugu=E9?= , jean-pierre.dion@bull.net, gh@us.ibm.com, janetmor@us.ibm.com, Linux Kernel Mailing List , "linux-aio@kvack.org" In-Reply-To: <42442743.40600@us.ibm.com> References: <1111743607.1299.85.camel@frecb000686> <20050325014307.4395012e.akpm@osdl.org> <1111745400.1299.89.camel@frecb000686> <20050325022416.01c2535b.akpm@osdl.org> <42442743.40600@us.ibm.com> Content-Type: text/plain Message-Id: <1112404259.29841.19.camel@ibm-c.pdx.osdl.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Fri, 01 Apr 2005 17:11:00 -0800 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2930 Lines: 87 On Fri, 2005-03-25 at 06:59, Badari Pulavarty wrote: > Andrew, > > When I debugged the problem, the issue seems to be only for the last > block of the file. Filesize is not multiple of 4K blocks. (say 17K). > So, on the disk we have a 4K block for the last block. The test is > trying to read 20K. Since we have a block on the disk, get_block() > won't complain and we do the IO. Once the IO is done, we can truncate > the result to match the filesize. > > I tried fixing the problem by limiting the IO submits to the size of > the file - which became really ugly (since I have to adjust the > iovec[]). > > Daniel McNeil wanted to take a stab at it. Dan what happend to the fix ? > > Thanks, > Badari I updated the patch to add an i_size element to the dio structure and sample i_size during i/o submission. When i/o completes the result can be truncated to match the file size without using i_size_read(), thus the aio result now matches the number of bytes read to the end of file. Here's the patch. It applies to 2.6.11 and the latest bk. Daniel --- linux-2.6.11.orig/fs/direct-io.c 2005-04-01 15:33:11.000000000 -0800 +++ linux-2.6.11/fs/direct-io.c 2005-03-31 16:59:15.000000000 -0800 @@ -66,6 +66,7 @@ struct dio { struct bio *bio; /* bio under assembly */ struct inode *inode; int rw; + ssize_t i_size; /* i_size when submitted */ int lock_type; /* doesn't change */ unsigned blkbits; /* doesn't change */ unsigned blkfactor; /* When we're using an alignment which @@ -230,17 +231,29 @@ static void finished_one_bio(struct dio spin_lock_irqsave(&dio->bio_lock, flags); if (dio->bio_count == 1) { if (dio->is_async) { + ssize_t transferred; + loff_t offset; + /* * Last reference to the dio is going away. * Drop spinlock and complete the DIO. */ spin_unlock_irqrestore(&dio->bio_lock, flags); - dio_complete(dio, dio->block_in_file << dio->blkbits, - dio->result); + + /* Check for short read case */ + transferred = dio->result; + offset = dio->iocb->ki_pos; + + if ((dio->rw == READ) && + ((offset + transferred) > dio->i_size)) + transferred = dio->i_size - offset; + + dio_complete(dio, offset, transferred); + /* Complete AIO later if falling back to buffered i/o */ if (dio->result == dio->size || ((dio->rw == READ) && dio->result)) { - aio_complete(dio->iocb, dio->result, 0); + aio_complete(dio->iocb, transferred, 0); kfree(dio); return; } else { @@ -951,6 +964,7 @@ direct_io_worker(int rw, struct kiocb *i dio->page_errors = 0; dio->result = 0; dio->iocb = iocb; + dio->i_size = i_size_read(inode); /* * BIO completion state. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/