From: Eric Sandeen Subject: Re: [PATCH] ext4: Support "check=none" "nocheck" mount options Date: Wed, 11 Jan 2012 09:13:40 -0600 Message-ID: <4F0DA724.2040506@redhat.com> References: <20120110174118.GB3015@zod.bos.redhat.com> <4F0C78CD.6070809@redhat.com> <7A0721E1-689F-4B9B-BD8C-86A03DDF20CE@dilger.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Josh Boyer , "Theodore Ts'o" , linux-ext4@vger.kernel.org, kernel-team@fedoraproject.org To: Andreas Dilger Return-path: Received: from mx1.redhat.com ([209.132.183.28]:7438 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757096Ab2AKPNp (ORCPT ); Wed, 11 Jan 2012 10:13:45 -0500 In-Reply-To: <7A0721E1-689F-4B9B-BD8C-86A03DDF20CE@dilger.ca> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 1/11/12 4:07 AM, Andreas Dilger wrote: > On 2012-01-10, at 10:43 AM, Eric Sandeen wrote: >> On 1/10/12 11:41 AM, Josh Boyer wrote: >>> The ext2/ext3 filesystems supported "check=none" and "nocheck" as mount options >>> even though that was already the default behavior and it essentially did >>> nothing. When using ext4 to mount ext2/ext3 filesystems, that mount option >>> causes the mount to fail. That isn't as backward compatible as it could be, >>> so add support to ext4 to accept the option. >> >> The only thing ext2 does with those options today is to clear the flag, >> and I can't find anything in userspace or kernelspace which would have set >> it in any case. It seem dead, but we do need the compatibility in ext4 >> if it's to handle ext2&3 seamlessly, I guess. > > At a minimum the use of obsolete options like this should print a warning > at mount time so that there is some chance the user will notice and remove > the old option from their config. Otherwise it is impossible to even get > rid of old useless cruft like this if we need to maintain functionally-useless > compatibility forever. > > Dredging through my memories, I recall that this option used to disable > the checks done at mount(?) time that compared the bits set in the block > and inode bitmaps against the summary values in the group descriptors > (AFAIR). Or maybe it was comparing the group descriptor summary values > against the superblock values? > > In any case, I can't imagine why a user would have this set for a kernel > option that might have last been valid 10 years ago, and why the 5 users > in the world that might have this set cannot simply remove it from their > fstab, since it does absolutely nothing? Well, I agree that it should be deprecated, but that's a separate issue from making ext4 handle all current ext2/3 mount options. Let's just push this one in, and can do another patch to add the dire deprecation warnings to all filesystems, ok? Then in 5 more years we can remember to remove it ;) -Eric >>> --- >>> fs/ext4/super.c | 7 ++++++- >>> 1 files changed, 6 insertions(+), 1 deletions(-) >>> >>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c >>> index 3e1329e..5ff09e7 100644 >>> --- a/fs/ext4/super.c >>> +++ b/fs/ext4/super.c >>> @@ -1333,7 +1333,7 @@ enum { >>> Opt_nomblk_io_submit, Opt_block_validity, Opt_noblock_validity, >>> Opt_inode_readahead_blks, Opt_journal_ioprio, >>> Opt_dioread_nolock, Opt_dioread_lock, >>> - Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable, >>> + Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable, Opt_nocheck, >>> }; >>> >>> static const match_table_t tokens = { >>> @@ -1409,6 +1409,8 @@ static const match_table_t tokens = { >>> {Opt_init_itable, "init_itable=%u"}, >>> {Opt_init_itable, "init_itable"}, >>> {Opt_noinit_itable, "noinit_itable"}, >>> + {Opt_nocheck, "check=none"}, >>> + {Opt_nocheck, "nocheck"}, >>> {Opt_err, NULL}, >>> }; >>> >>> @@ -1905,6 +1907,9 @@ set_qf_format: >>> case Opt_noinit_itable: >>> clear_opt(sb, INIT_INODE_TABLE); >>> break; >>> + case Opt_nocheck: >>> + /* ext2/ext3 used to "support" this option. Silently eat it */ >>> + break; >>> default: >>> ext4_msg(sb, KERN_ERR, >>> "Unrecognized mount option \"%s\" " >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > Cheers, Andreas > > > > >