On Wed, 2007-05-30 at 10:21 +1000, David Chinner wrote:
> On Fri, May 25, 2007 at 06:25:31PM +0200, Jean noel Cordenner wrote:
> > Hi,
> >
> > This is an update of the i_version patch.
> > The i_version field is a 64bit counter that is set on every inode
> > creation and that is incremented every time the inode data is modified
> > (similarly to the "ctime" time-stamp).
>
> My understanding (please correct me if I'm wrong) is that the
> requirements are much more rigourous than simply incrementing an in
> memory counter on every change. i.e. the this counter has to
> survive server crashes intact so clients never see the counter go
> backwards. That means version number changes need to be journalled
> along with the operation that caused the change of the version
> number.
>
Yeah, the i_version is the in memeory counter. From the patch it looks
like the counter is being updated inside ext4_mark_iloc_dirty(), so it
is being journalled and being flush to on-disk ext4 inode structure
immediately (On-disk ext4 inode structure is being modified/expanded to
store the counter in the first patch).
>This patch is on top of i_version_update_vfs.
> The i_version field of the inode is set on inode creation and incremented when
> the inode is being modified.
>
> Signed-off-by: Jean Noel Cordenner <jean-noel.cordenner@xxxxxxxx>
>
> Index: linux-2.6.22-rc2-ext4-1/fs/ext4/ialloc.c
> ===================================================================
> --- linux-2.6.22-rc2-ext4-1.orig/fs/ext4/ialloc.c 2007-05-25 18:05:28.000000000 +0200
> +++ linux-2.6.22-rc2-ext4-1/fs/ext4/ialloc.c 2007-05-25 18:05:40.000000000 +0200
> @@ -565,6 +565,7 @@
> inode->i_blocks = 0;
> inode->i_mtime = inode->i_atime = inode->i_ctime = ei->i_crtime =
> ext4_current_time(inode);
> + inode->i_version = 1;
>
> memset(ei->i_data, 0, sizeof(ei->i_data));
> ei->i_dir_start_lookup = 0;
> Index: linux-2.6.22-rc2-ext4-1/fs/ext4/inode.c
> ===================================================================
> --- linux-2.6.22-rc2-ext4-1.orig/fs/ext4/inode.c 2007-05-25 18:05:28.000000000 +0200
> +++ linux-2.6.22-rc2-ext4-1/fs/ext4/inode.c 2007-05-25 18:05:40.000000000 +0200
> @@ -3082,6 +3082,7 @@
> {
> int err = 0;
>
> + inode->i_version++;
> /* the do_update_inode consumes one bh->b_count */
> get_bh(iloc->bh);
>
> Index: linux-2.6.22-rc2-ext4-1/fs/ext4/super.c
> ===================================================================
> --- linux-2.6.22-rc2-ext4-1.orig/fs/ext4/super.c 2007-05-25 18:05:28.000000000 +0200
> +++ linux-2.6.22-rc2-ext4-1/fs/ext4/super.c 2007-05-25 18:05:40.000000000 +0200
> @@ -2839,8 +2839,8 @@
> i_size_write(inode, off+len-towrite);
> EXT4_I(inode)->i_disksize = inode->i_size;
> }
> - inode->i_version++;
> inode->i_mtime = inode->i_ctime = CURRENT_TIME;
> + inode->i_version = 1;
> ext4_mark_inode_dirty(handle, inode);
> mutex_unlock(&inode->i_mutex);
> return len - towrite;
I am not very clear about this part -- what is i_version being used for
with quota? And shall we reset the counter to 1 for ext4_quota_write()?
Mingming
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