From: Andreas Dilger Subject: Re: [PATCH] mke2fs: further updates for mke2fs(8) man page Date: Tue, 17 Dec 2013 15:22:15 -0700 Message-ID: <83B3938A-DEF8-4C05-9511-BA830DCCD692@dilger.ca> References: <1387268271-8285-1-git-send-email-adilger@dilger.ca> <52B06996.5090005@redhat.com> Mime-Version: 1.0 (Mac OS X Mail 7.0 \(1822\)) Content-Type: multipart/signed; boundary="Apple-Mail=_D978D374-905C-4D55-A0DE-48F73E21DBD1"; protocol="application/pgp-signature"; micalg=pgp-sha1 Cc: Theodore Ts'o , Ext4 Developers List To: Eric Sandeen Return-path: Received: from mail-pa0-f53.google.com ([209.85.220.53]:47365 "EHLO mail-pa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752072Ab3LQWWV (ORCPT ); Tue, 17 Dec 2013 17:22:21 -0500 Received: by mail-pa0-f53.google.com with SMTP id hz1so5030669pad.26 for ; Tue, 17 Dec 2013 14:22:21 -0800 (PST) In-Reply-To: <52B06996.5090005@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: --Apple-Mail=_D978D374-905C-4D55-A0DE-48F73E21DBD1 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 On Dec 17, 2013, at 8:11 AM, Eric Sandeen wrote: > On 12/17/13, 2:17 AM, Andreas Dilger wrote: >> The mke2fs(8) man page was updated in 4727c67dc2, but needs some >> more clear descriptions for extra_isize and metadta_csum features. >> The uninit_bg feature is supported by all ext4-capable kernels, >> and does have a slow e2fsck pass for newly-formatted filesystems, >> so remove the caveat. >=20 > Looks ok to me, but I think there's still one thing missing; > it mentions metadata checksums but nothing in the manpage says > how to turn those on, AFAICT: Actually, the comments about metadata checksums is commented out in the man page. That isn't obvious at first glance. I had just seen it in the previous page, and the old description "a superset of the uninit_bg feature" wasn't very useful. As with anything, no complaints about the previous patch - it definitely improved the old content, and there is much more that needs to be done to document the metadata checksum feature (tune2fs, e2fsck, etc). Every bit helps. Cheers, Andreas > $ grep -i2 "checksum\|csum\|crc" misc/mke2fs.8 > .B uninit_bg > Create a filesystem without initializing all of the block groups. = This > feature also enables checksums and highest-inode-used statistics in = each > blockgroup. This feature can > speed up filesystem creation time noticeably (if lazy_itable_init is >=20 >=20 > (maybe I'm dense & missing it?) >=20 > -Eric >=20 >> Signed-off-by: Andreas Dilger >> --- >> misc/mke2fs.8.in | 36 ++++++++++++++++++++++-------------- >> 1 files changed, 22 insertions(+), 14 deletions(-) >>=20 >> diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in >> index df244de..4486014 100644 >> --- a/misc/mke2fs.8.in >> +++ b/misc/mke2fs.8.in >> @@ -210,8 +210,8 @@ in earlier versions of >> .BR mke2fs . >> The >> .B \-R >> -option is still accepted for backwards compatibility. The >> -following extended options are supported: >> +option is still accepted for backwards compatibility, but is = deprecated. >> +The following extended options are supported: >> .RS 1.2i >> .TP >> .BI mmp_update_interval=3D interval >> @@ -548,7 +548,7 @@ of e2fsprogs will not support file systems with = this feature enabled. >> .TP >> .B bigalloc >> .br >> -This feature enables clustered allocation, so that the unit of >> +This feature enables clustered block allocation, so that the unit of >> allocation is a power of two number of blocks. That is, each bit in = the >> what had traditionally been known as the block allocation bitmap now >> indicates whether a cluster is in use or not, where a cluster is by >> @@ -570,7 +570,7 @@ features be enabled. >> .TP >> .B dir_index >> .br >> -Use hashed b-trees to speed up lookups in large directories. >> +Use hashed b-trees to speed up name lookups in large directories. >> .TP >> .B dir_nlink >> .br >> @@ -590,8 +590,15 @@ historical/backwards compatibility reasons.) >> .TP >> .B extra_isize >> .br >> -This feature enables storage of nanosecond timestamps and creation >> -time, if the inode size is larger than 256 bytes or larger. >> +This feature reserves a specific amount of space in each inode for >> +extended metadata such as nanosecond timestamps and file creation = time, >> +even if the current kernel does not current need to reserve this = much >> +space. Without this feature, the kernel will reserve the amount of >> +space for features currently it currently needs, and the rest may be >> +consumed by extended attributes. >> + >> +For this feature to be useful the inode size must be 256 bytes in = size >> +or larger. >> .TP >> .B ext_attr >> .br >> @@ -649,10 +656,16 @@ set this feature automatically when a file > = 2GiB is created.) >> .\" .TP >> .\" .B metadata_csum >> .\" .br >> -.\" Filesystem supports metadata checksumming. This feature enables = a >> -.\" superset of the functionality of the >> +.\" Filesystem supports metadata checksumming. This feature stores >> +.\" checksums for all of the filesystem metadata (superblock, group >> +.\" descriptor blocks, inode and block bitmaps, directories, and >> +.\" extent tree blocks). The checksum algorithm used for the = metadata >> +.\" blocks is different than the one used for group descriptors with = the >> .\" .B uninit_bg >> -.\" feature. >> +.\" feature, these two features are incompatible and >> +.\" .B metadata_csum >> +.\" will be used preferentially instead of >> +.\" .BR uninit_bg . >> .\" .br >> .\" .B Future feature, available in e2fsprogs 1.43-WIP >> .TP >> @@ -719,11 +732,6 @@ and keep a high watermark for the unused inodes = in a filesystem, to reduce >> .BR e2fsck (8) >> time. The result is that it can speed up filesystem creation time = noticeably >> (if lazy_itable_init is enabled). >> -.IP >> -This first e2fsck run after enabling this feature will take the >> -full time, but subsequent e2fsck runs will take only a fraction of = the >> -original time, depending on how full the file system is. >> -It is only supported by the ext4 filesystem in recent Linux kernels. >> .RE >> .TP >> .B \-q >>=20 >=20 Cheers, Andreas --Apple-Mail=_D978D374-905C-4D55-A0DE-48F73E21DBD1 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - http://gpgtools.org iQIVAwUBUrDOmHKl2rkXzB/gAQILIw//a8ASTETO+++Mfk5+RWBRX2nTlg5dxoJd qmLT2rSQjDJxgtS0VkJnGqeXj1Pp7kKJaTMsESq4giu2G9cyB/PrsNZYWRoDf/H/ x2j6yczJz302F2VjQRMQA9NMr74qjIak7Vezq5zI7tXr9doTkfrMRXAjHeN5mvh2 hzLUseH21Vs9tHhuTbZvYcNVfGpUgdgTHDtVvZ0fYZWLLnJ/Lf5Wu7NYQfmJSClC isPQmnT+7UOThGoNgVXWvvJWKo8Lp8jPO5p0DSBTM7k+UceIYct0vc0VkW2WxzNJ 7PdnmKNAnnQ6GpuhetPZr4u/l593Rw7S5wdnX6XfokiJ9Z9dnmBeSrsOVIgS2jjW 6v630po9kR2gepkfeh9zC7Tib34SNAPiuua/vXtex8udM9L+znzptJoA3SGrNdi8 E7TLaxeJglTiEzYB690gGJP/UO/tdMIVPtpUghrgvznkGnUH0CKsn4v+VXA6znVL 4fazbSvO+O+CFopftBoJFH3lla3xm5vfSGzyEE/xap1Nwv2kZmYpZQ4OWkoDuTls InIgwgyYKalJpHNAvzK7AR7szVPyA+pS3adFyHdUybGAGCPS20BAJZAdUkeTFvix P8k+bEvlQoj4jzT0WEzckJYKrw3/s0T9pC2ZwsgPCKTtpmY90UUjXsWp5F2UDYDY QG0hYE728n4= =tvtt -----END PGP SIGNATURE----- --Apple-Mail=_D978D374-905C-4D55-A0DE-48F73E21DBD1--