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Message-ID: <08e2ca4c8f6344bdcd76d75b821116c6147fd57a.camel@kernel.org> Date: Tue, 26 Jul 2022 07:15:32 -0400 From: Jeff Layton <jlayton@...nel.org> To: Lukas Czerner <lczerner@...hat.com> Cc: tytso@....edu, adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org, Dave Chinner <david@...morbit.com>, Benjamin Coddington <bcodding@...hat.com>, Christoph Hellwig <hch@...radead.org>, kzak@...hat.com Subject: Re: [PATCH] ext4: unconditionally enable the i_version counter On Tue, 2022-07-26 at 09:10 +0200, Lukas Czerner wrote: > On Mon, Jul 25, 2022 at 03:29:46PM -0400, Jeff Layton wrote: > > The original i_version implementation was pretty expensive, requiring a > > log flush on every change. Because of this, it was gated behind a mount > > option (implemented via the MS_I_VERSION mountoption flag). > > > > Commit ae5e165d855d (fs: new API for handling inode->i_version) made the > > i_version flag much less expensive, so there is no longer a performance > > penalty from enabling it. > > > > Have ext4 ignore the SB_I_VERSION flag, and just enable it > > unconditionally. > > Hi Jeff, > > the ext4 specific i_version option is deprecated and it's perfect time > to remove it as well. > > As for enabling iversion by default, as I said before I am fine with > that. With this patch we're left with no means of disabling it, which > might be ok, I don't have a strong opinion. > > However I don't like the fact that the noiversion mount option is going > to be just silently ignored and only on some file systems. The > inconsistency bugs me and will create confusion when things go wrong. > > Shouldn't we introduce something like SB_NOIVERSION to give fs a clean > way to inform user we're ignoring it, or even change the default? Or > perhaps 'noinversion' should be removed? > Ordinarily, I'd agree here. I like leaving some mechanism to revert an unconditional change like this. Unfortunately, the problem here is that the original mount option was implemented via a mountflag and was parsed by the userland helper. Trying to rework how "-o {no}iversion" options work is going to be messy. We can't rely on /bin/mount and the kernel being in sync. If we did want to add something like this, then we might need to add a new mount option that doesn't match the old one (e.g. -o no_i_version). Alternately, could that be made settable via mkfs/tune2fs? > > > > > Cc: Dave Chinner <david@...morbit.com> > > Cc: Lukas Czerner <lczerner@...hat.com> > > Cc: Benjamin Coddington <bcodding@...hat.com> > > Cc: Christoph Hellwig <hch@...radead.org> > > Signed-off-by: Jeff Layton <jlayton@...nel.org> > > --- > > fs/ext4/inode.c | 5 ++--- > > fs/ext4/super.c | 8 ++++---- > > 2 files changed, 6 insertions(+), 7 deletions(-) > > > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > > index 84c0eb55071d..c785c0b72116 100644 > > --- a/fs/ext4/inode.c > > +++ b/fs/ext4/inode.c > > @@ -5411,7 +5411,7 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry, > > return -EINVAL; > > } > > > > - if (IS_I_VERSION(inode) && attr->ia_size != inode->i_size) > > + if (attr->ia_size != inode->i_size) > > inode_inc_iversion(inode); > > > > if (shrink) { > > @@ -5717,8 +5717,7 @@ int ext4_mark_iloc_dirty(handle_t *handle, > > } > > ext4_fc_track_inode(handle, inode); > > > > - if (IS_I_VERSION(inode)) > > - inode_inc_iversion(inode); > > + inode_inc_iversion(inode); > > > > /* the do_update_inode consumes one bh->b_count */ > > get_bh(iloc->bh); > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > > index 845f2f8aee5f..30645d4343b6 100644 > > --- a/fs/ext4/super.c > > +++ b/fs/ext4/super.c > > @@ -2142,8 +2142,7 @@ static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param) > > return 0; > > case Opt_i_version: > > ext4_msg(NULL, KERN_WARNING, deprecated_msg, param->key, "5.20"); > > - ext4_msg(NULL, KERN_WARNING, "Use iversion instead\n"); > > - ctx_set_flags(ctx, SB_I_VERSION); > > + ext4_msg(NULL, KERN_WARNING, "i_version counter is always enabled.\n"); > > return 0; > > case Opt_inlinecrypt: > > #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT > > @@ -2970,8 +2969,6 @@ static int _ext4_show_options(struct seq_file *seq, struct super_block *sb, > > SEQ_OPTS_PRINT("min_batch_time=%u", sbi->s_min_batch_time); > > if (nodefs || sbi->s_max_batch_time != EXT4_DEF_MAX_BATCH_TIME) > > SEQ_OPTS_PRINT("max_batch_time=%u", sbi->s_max_batch_time); > > - if (sb->s_flags & SB_I_VERSION) > > - SEQ_OPTS_PUTS("i_version"); > > if (nodefs || sbi->s_stripe) > > SEQ_OPTS_PRINT("stripe=%lu", sbi->s_stripe); > > if (nodefs || EXT4_MOUNT_DATA_FLAGS & > > @@ -4630,6 +4627,9 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb) > > sb->s_flags = (sb->s_flags & ~SB_POSIXACL) | > > (test_opt(sb, POSIX_ACL) ? SB_POSIXACL : 0); > > > > + /* i_version is always enabled now */ > > + sb->s_flags |= SB_I_VERSION; > > + > > if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV && > > (ext4_has_compat_features(sb) || > > ext4_has_ro_compat_features(sb) || > > -- > > 2.37.1 > > > -- Jeff Layton <jlayton@...nel.org>
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