Re: [PATCH v5 18/19] btrfs: only dirty the inode in btrfs_update_time if something was changed

Liu Bo
2018-01-11T19:37:10Z

Hi Jeff,

On Tue, Jan 09, 2018 at 09:10:58AM -0500, Jeff Layton wrote:
> From: Jeff Layton <jlayton@redhat.com>
>
> At this point, we know that "now" and the file times may differ, and we
> suspect that the i_version has been flagged to be bumped. Attempt to
> bump the i_version, and only mark the inode dirty if that actually
> occurred or if one of the times was updated.
>
> Signed-off-by: Jeff Layton <jlayton@redhat.com>
> Acked-by: David Sterba <dsterba@suse.com>
> ---
> fs/btrfs/inode.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index ac8692849a81..76245323a7c8 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -6107,19 +6107,20 @@ static int btrfs_update_time(struct inode *inode, struct timespec *now,
> int flags)
> {
> struct btrfs_root *root = BTRFS_I(inode)->root;
> + bool dirty = flags & ~S_VERSION;
>
> if (btrfs_root_readonly(root))
> return -EROFS;
>
> if (flags & S_VERSION)
> - inode_inc_iversion(inode);
> + dirty |= inode_maybe_inc_iversion(inode, dirty);
> if (flags & S_CTIME)
> inode->i_ctime = *now;
> if (flags & S_MTIME)
> inode->i_mtime = *now;
> if (flags & S_ATIME)
> inode->i_atime = *now;
> - return btrfs_dirty_inode(inode);
> + return dirty ? btrfs_dirty_inode(inode) : 0;
> }
>

In order to have a easier error handling for ENOSPC, btrfs has split
file_update_time() into 2-step work,
- step 1 is to update time/iversion of in-memory inode in
update_time_for_write(),
- step 2 is to update the time/iversion of on-disk inode in
btrfs_update_inode()->fill_inode_item().

I think update_time_for_write() also needs to be updated to use the
new iversion API.

With that,

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>

Thanks,

-liubo
> /*
> --
> 2.14.3
>