On Mon, Mar 8, 2021 at 1:25 PM Chengguang Xu <cgxu519@xxxxxxxxxxxx> wrote:
>
> Currently copy-up will copy whole lower file to upper
> regardless of the data range which is needed for further
> operation. This patch avoids unnecessary copy when truncate
> size is smaller than the file size.
>
> Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
Nice!
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
This reminds me. I think this comment in ovl_nlink_start() can be removed:
* TODO: implement metadata only index copy up when called with
* ovl_copy_up_flags(dentry, O_PATH).
It was added in 2017 and not removed when metacopy was implemented.
Technically, I think that truncate() could also be a metacopy, but it seems
like a corner case that is not worth the trouble...
Thanks,
Amir.
> ---
> fs/overlayfs/copy_up.c | 16 +++++++++-------
> fs/overlayfs/inode.c | 4 +++-
> fs/overlayfs/overlayfs.h | 2 +-
> 3 files changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index 0b2891c6c71e..b426a3f59636 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -866,7 +866,7 @@ static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
> }
>
> static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
> - int flags)
> + int flags, loff_t size)
> {
> int err;
> DEFINE_DELAYED_CALL(done);
> @@ -903,6 +903,8 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
> /* maybe truncate regular file. this has no effect on dirs */
> if (flags & O_TRUNC)
> ctx.stat.size = 0;
> + if (size)
> + ctx.stat.size = size;
>
> if (S_ISLNK(ctx.stat.mode)) {
> ctx.link = vfs_get_link(ctx.lowerpath.dentry, &done);
> @@ -929,7 +931,7 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
> return err;
> }
>
> -static int ovl_copy_up_flags(struct dentry *dentry, int flags)
> +static int ovl_copy_up_flags(struct dentry *dentry, int flags, loff_t size)
> {
> int err = 0;
> const struct cred *old_cred = ovl_override_creds(dentry->d_sb);
> @@ -962,7 +964,7 @@ static int ovl_copy_up_flags(struct dentry *dentry, int flags)
> next = parent;
> }
>
> - err = ovl_copy_up_one(parent, next, flags);
> + err = ovl_copy_up_one(parent, next, flags, size);
>
> dput(parent);
> dput(next);
> @@ -994,7 +996,7 @@ int ovl_maybe_copy_up(struct dentry *dentry, int flags)
> if (ovl_open_need_copy_up(dentry, flags)) {
> err = ovl_want_write(dentry);
> if (!err) {
> - err = ovl_copy_up_flags(dentry, flags);
> + err = ovl_copy_up_flags(dentry, flags, 0);
> ovl_drop_write(dentry);
> }
> }
> @@ -1002,12 +1004,12 @@ int ovl_maybe_copy_up(struct dentry *dentry, int flags)
> return err;
> }
>
> -int ovl_copy_up_with_data(struct dentry *dentry)
> +int ovl_copy_up_with_data(struct dentry *dentry, loff_t size)
> {
> - return ovl_copy_up_flags(dentry, O_WRONLY);
> + return ovl_copy_up_flags(dentry, O_WRONLY, size);
> }
>
> int ovl_copy_up(struct dentry *dentry)
> {
> - return ovl_copy_up_flags(dentry, 0);
> + return ovl_copy_up_flags(dentry, 0, 0);
> }
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index 003cf83bf78a..5eb99e4c3c73 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -44,7 +44,9 @@ int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
> if (!full_copy_up)
> err = ovl_copy_up(dentry);
> else
> - err = ovl_copy_up_with_data(dentry);
> + err = ovl_copy_up_with_data(dentry,
> + attr->ia_size < i_size_read(d_inode(dentry)) ?
> + attr->ia_size : 0);
> if (!err) {
> struct inode *winode = NULL;
>
> diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
> index 95cff83786a5..1bc17ca87158 100644
> --- a/fs/overlayfs/overlayfs.h
> +++ b/fs/overlayfs/overlayfs.h
> @@ -524,7 +524,7 @@ long ovl_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
>
> /* copy_up.c */
> int ovl_copy_up(struct dentry *dentry);
> -int ovl_copy_up_with_data(struct dentry *dentry);
> +int ovl_copy_up_with_data(struct dentry *dentry, loff_t size);
> int ovl_maybe_copy_up(struct dentry *dentry, int flags);
> int ovl_copy_xattr(struct super_block *sb, struct dentry *old,
> struct dentry *new);
> --
> 2.27.0
>
>
