From: Goswin von Brederlow Subject: Re: [PATCH 15/15][e2fsprogs] 64-bit mke2fs cleanup Date: Wed, 16 Jul 2008 17:21:58 +0200 Message-ID: <87bq0x97mx.fsf@frosties.localdomain> References: <20080715164332.28567.27913.stgit@ichigo> <20080715165129.28567.7837.stgit@ichigo> <87tzeq0z95.fsf@frosties.localdomain> <20080716090931.6c8ca875@ichigo> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Goswin von Brederlow , "Theodore Ts'o" , linux-ext4@vger.kernel.org To: "Jose R. Santos" Return-path: Received: from fmmailgate03.web.de ([217.72.192.234]:41750 "EHLO fmmailgate03.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761195AbYGPPWA (ORCPT ); Wed, 16 Jul 2008 11:22:00 -0400 In-Reply-To: <20080716090931.6c8ca875@ichigo> (Jose R. Santos's message of "Wed, 16 Jul 2008 09:09:31 -0500") Sender: linux-ext4-owner@vger.kernel.org List-ID: "Jose R. Santos" writes: > On Wed, 16 Jul 2008 14:50:14 +0200 > Goswin von Brederlow wrote: > >> "Jose R. Santos" writes: >> >> > diff --git a/misc/mke2fs.c b/misc/mke2fs.c >> > index 7171990..817be56 100644 >> > --- a/misc/mke2fs.c >> > +++ b/misc/mke2fs.c >> > @@ -1402,12 +1402,12 @@ static void PRS(int argc, char *argv[]) >> > >> > fs_param.s_log_frag_size = fs_param.s_log_block_size; >> > >> > - if (noaction && fs_param.s_blocks_count) { >> > - dev_size = fs_param.s_blocks_count; >> > + if (noaction && ext2fs_blocks_count(&fs_param)) { >> > + dev_size = ext2fs_blocks_count(&fs_param); >> > retval = 0; >> > } else { >> > retry: >> > - retval = ext2fs_get_device_size(device_name, >> > + retval = ext2fs_get_device_size2(device_name, >> > EXT2_BLOCK_SIZE(&fs_param), >> > &dev_size); >> > if ((retval == EFBIG) && >> >> You should not assume that ext2fs_get_device_size2() will return EFBIG >> if the size exceed 2^32 blocks. The point of ext2fs_get_device_size2() >> was to be able to support more than 2^32 blocks and the library >> function will certainly change to return larger numbers in the future. >> >> So you need something like >> >> if ((retval == EFBIG || dev_size >= (1ULL << 32)) && > > No, ext2fs_get_device_size2() should return EFBIG size if the device is > larger than 48-bit. I need to fix that on ext2fs_get_device_size2() but > this check here is ok. > >> MfG >> Goswin > > -JRS Why? The decision what device size if too big depends on the features for this filesystem. By default 32bit is the limit, with EXT4_FEATURE_INCOMPAT_64BIT it is 48bit. (shouldn't that be named EXT4_FEATURE_INCOMPAT_48BIT?). Maybe later there will be a true 64bit feature. If you make ext2fs_get_device_size2() return EFBIG for >48bit then you have to check for EFBIG and conditionally for 2^32 which makes the code more complex. Better to just check the actual size the device has in mke2fs.c. Also the user might give a size that is actually small enough while the device would be too big. Say, with current mke2fs, you have a disk that is 16.000001TiB large. You could tell mke2fs to only use 2^32-1 blocks. The EFBIG check prevents that. See the patch I just send. MfG Goswin