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Date: Tue, 16 Aug 2022 09:43:16 -0400 From: Jeff Layton <jlayton@...nel.org> To: Christian Brauner <brauner@...nel.org> Cc: tytso@....edu, adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, Lukas Czerner <lczerner@...hat.com>, Jan Kara <jack@...e.cz> Subject: Re: [PATCH] ext4: fix i_version handling in ext4 On Tue, 2022-08-16 at 15:33 +0200, Christian Brauner wrote: > On Tue, Aug 16, 2022 at 09:15:22AM -0400, Jeff Layton wrote: > > ext4 currently updates the i_version counter when the atime is updated > > during a read. This is less than ideal as it can cause unnecessary cache > > invalidations with NFSv4. The increment in ext4_mark_iloc_dirty is also > > problematic since it can also corrupt the i_version counter for > > ea_inodes. > > > > We aren't bumping the file times in ext4_mark_iloc_dirty, so changing > > the i_version there seems wrong, and is the cause of both problems. > > Remove that callsite and add increments to the setattr and setxattr > > codepaths (at the same time that we update the ctime). The i_version > > bump that already happens during timestamp updates should take care of > > the rest. > > > > Cc: Lukas Czerner <lczerner@...hat.com> > > Cc: Jan Kara <jack@...e.cz> > > Cc: Christian Brauner <brauner@...nel.org> > > Signed-off-by: Jeff Layton <jlayton@...nel.org> > > --- > > Seems good to me. But it seems that the xfs patch you sent does have > inode_inc_version() right after setattr_copy() as well. So I wonder if > we couldn't just try and move inode_inc_version() into setattr_copy() > itself. > We probably could, but setattr_copy has a lot of callers and most filesystems don't need this. Also, there are some cases where we don't want to update the i_version after a setattr. In particular, if you do a truncate and the size doesn't change, then you really don't want to update the timestamps (and therefore the i_version shouldn't change either). > > fs/ext4/inode.c | 10 +++++----- > > fs/ext4/xattr.c | 2 ++ > > 2 files changed, 7 insertions(+), 5 deletions(-) > > > > I think this patch should probably supersede Lukas' patch entitled: > > > > ext4: don't increase iversion counter for ea_inodes > > > > This will also mean that we'll need to respin the patch to turn on the > > i_version counter unconditionally in ext4 (though that should be > > trivial). > > > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > > index 601214453c3a..a70921df89a5 100644 > > --- a/fs/ext4/inode.c > > +++ b/fs/ext4/inode.c > > @@ -5342,6 +5342,7 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry, > > int error, rc = 0; > > int orphan = 0; > > const unsigned int ia_valid = attr->ia_valid; > > + bool inc_ivers = IS_IVERSION(inode); > > > > if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb)))) > > return -EIO; > > @@ -5425,8 +5426,8 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry, > > return -EINVAL; > > } > > > > - if (IS_I_VERSION(inode) && attr->ia_size != inode->i_size) > > - inode_inc_iversion(inode); > > + if (attr->ia_size == inode->i_size) > > + inc_ivers = false; > > > > if (shrink) { > > if (ext4_should_order_data(inode)) { > > @@ -5528,6 +5529,8 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry, > > } > > > > if (!error) { > > + if (inc_ivers) > > + inode_inc_iversion(inode); > > setattr_copy(mnt_userns, inode, attr); > > mark_inode_dirty(inode); > > } > > @@ -5731,9 +5734,6 @@ int ext4_mark_iloc_dirty(handle_t *handle, > > } > > ext4_fc_track_inode(handle, inode); > > > > - if (IS_I_VERSION(inode)) > > - inode_inc_iversion(inode); > > - > > /* the do_update_inode consumes one bh->b_count */ > > get_bh(iloc->bh); > > > > diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c > > index 533216e80fa2..4d84919d1c9c 100644 > > --- a/fs/ext4/xattr.c > > +++ b/fs/ext4/xattr.c > > @@ -2412,6 +2412,8 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index, > > if (!error) { > > ext4_xattr_update_super_block(handle, inode->i_sb); > > inode->i_ctime = current_time(inode); > > + if (IS_IVERSION(inode)) > > + inode_inc_iversion(inode); > > if (!value) > > no_expand = 0; > > error = ext4_mark_iloc_dirty(handle, inode, &is.iloc); > > -- > > 2.37.2 > > -- Jeff Layton <jlayton@...nel.org>
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