On Thu, Jan 4, 2018 at 7:20 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> Lookup overlay inode in cache by origin inode, so we can decode a file
> handle of an open file even if the index has a whiteout index entry to
> mark this overlay inode was unlinked.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/overlayfs/export.c | 22 ++++++++++++++++++++--
> fs/overlayfs/inode.c | 16 ++++++++++++++++
> fs/overlayfs/overlayfs.h | 1 +
> 3 files changed, 37 insertions(+), 2 deletions(-)
>
> diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
> index 602bada474ba..6ecb54d4b52c 100644
> --- a/fs/overlayfs/export.c
> +++ b/fs/overlayfs/export.c
> @@ -385,13 +385,21 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
> struct ovl_path *stack = &origin;
> struct dentry *dentry = NULL;
> struct dentry *index = NULL;
> + struct inode *inode = NULL;
> + bool is_deleted = false;
> int err;
>
> /* First lookup indexed upper by fh */
> index = ovl_get_index_fh(ofs, fh);
> err = PTR_ERR(index);
> - if (IS_ERR(index))
> - return ERR_PTR(err);
> + if (IS_ERR(index)) {
> + if (err != -ESTALE)
> + return ERR_PTR(err);
> +
> + /* Found a whiteout index - treat as deleted inode */
> + is_deleted = true;
> + index = NULL;
Ouch! it seems I was misleading you.
If we find a whiteout index for dir, we *do* decode+reconnect origin,
because we want to find out if this is an unlinked but open non-dir.
I guess there are 2 ways to avoid this unneeded decode:
1. mark a "directory index whiteout" differently than "non-dir index whiteout"
2. lookup icache by file handle
> + }
>
> /* Then lookup origin by fh */
> err = ovl_check_origin_fh(fh, NULL, ofs->lower_layers, ofs->numlower,
> @@ -404,6 +412,15 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
> err = ovl_verify_origin(index, origin.dentry, false, false);
> if (err)
> goto out_err;
> + } else if (is_deleted && origin.dentry && !d_is_dir(origin.dentry)) {
> + /* Lookup deleted overlay inode by origin inode */
> + inode = ovl_lookup_inode(sb, origin.dentry);
> + err = -ESTALE;
> + if (!inode || atomic_read(&inode->i_count) == 1)
> + goto out_err;
> +
> + /* Deleted but still open? */
> + index = dget(ovl_i_dentry_upper(inode));
> }
And to top that up, we even try to lookup the origin dir path in overlay
instead of returning ESTALE right away.
Sheesh! that's embarrassing.
Thanks,
Amir.
