On Mon, Jun 22, 2015 at 10:08 AM, Robbie Ko <robbi...@synology.com> wrote:
> There's one more case where we can't issue a rename operation for a directory
> as soon as we process it. We move a directory from ancestor to descendant.
>
> |---- a
> |---- b
> |---- c
> |---- d
> "Move a directory from ancestor to descendant" means moving dir. a into dir. c
>
> This case will happen after applying "[PATCH] Btrfs: incremental send,
> don't delay directory renames unnecessarily".
> Because, that patch changes behavior of wait_for_parent_move function.
>
> Example:
> Parent snapshot:
> |---- @tmp/ (ino 257)
> |---- pre/ (ino 260)
> |---- wait_dir (ino 261)
> |---- ance/ (ino 263)
> |---- wait_at_below_ance/ (ino 259)
> |---- desc/ (ino 262)
> |---- other_dir/ (ino 264)
>
> Send snapshot:
> |---- @tmp/ (ino 257)
> |---- other_dir/ (ino 264)
> |---- wait_at_below_ance/ (ino 259)
> |---- pre/ (ino 260)
> |---- wait_dir/ (ino 261)
> |---- desc/ (ino 262)
> |---- ance/ (ino 263)
>
> 1. 259 must move to @tmp/other_dir, so it is waiting on other_dir(264).
>
> 2. 260 is able to rename as ance/wait_at_below_ance/pre since
> wait_at_below_ance(259) is waiting and 260 is not the ancestor of
> wait_at_below_ance(259).
>
> 3. 261 must move to @tmp/other_dir, so it is waiting on other_dir(264).
>
> 4. 262 is able to rename as ance/wait_at_below_ance/pre/wait_dir/desc since
> wait_dir(261) is waiting and 262 is not the ancestor of wait_dir(261).
>
> 5. 263 is rename as ance/wait_at_below_ance/pre/wait_dir/desc/ance since
> wait_dir(261) is waiting and 263 is not the ancestor of wait_dir(261).
> At the same time, receiving side will encounter error.
> If anyone calls get_cur_path() to any element in
> ance/wait_at_below_ance/pre/wait_dir/desc/ance like wait_dir(260),
> there will cause path building loop like this : 261 -> 260 -> 259 ->
> 263 -> 262 -> 261
>
> So fix the problem by check path_loop for this case.
>
> Signed-off-by: Robbie Ko <robbi...@synology.com>
> ---
>
> V2: Always check path_loop, and check Allocation ret value.
>
> fs/btrfs/send.c | 46 +++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 43 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
> index 44ad144..b946067 100644
> --- a/fs/btrfs/send.c
> +++ b/fs/btrfs/send.c
> @@ -3088,15 +3088,23 @@ static int path_loop(struct send_ctx *sctx, struct
> fs_path *name,
>
> *ancestor_ino = 0;
> while (ino != BTRFS_FIRST_FREE_OBJECTID) {
> + struct waiting_dir_move *wdm;
> fs_path_reset(name);
>
> if (is_waiting_for_rm(sctx, ino))
> break;
> - if (is_waiting_for_move(sctx, ino)) {
> +
> + wdm = get_waiting_dir_move(sctx, ino);
> + if (wdm) {
> if (*ancestor_ino == 0)
> *ancestor_ino = ino;
> - ret = get_first_ref(sctx->parent_root, ino,
> - &parent_inode, &parent_gen, name);
> + if (wdm->orphanized) {
> + ret = gen_unique_name(sctx, ino, gen, name);
> + break;
> + } else {
> + ret = get_first_ref(sctx->parent_root, ino,
> +
> &parent_inode, &parent_gen, name);
> + }
> } else {
> ret = __get_cur_name_and_parent(sctx, ino, gen,
> &parent_inode,
> @@ -3743,6 +3751,38 @@ verbose_printk("btrfs: process_recorded_refs %llu\n",
> sctx->cur_ino);
> }
>
> /*
> + * if cur_ino is cur ancestor, can't move now,
> + * find descendant who is waiting, waiting it.
> + */
If cur_ino is current ancestor of whom?
"find descendant" -> but below we're looking for an ancestor and
delaying the rename of the current inode (sctx->cur_ino) to happen
after the rename of that ancestor.
> + if(can_rename) {
Again, please run checkpath.pl against the files.
Kernel coding style, add a space between if and the opening
parenthesis: if (...) {
> + struct fs_path *name = NULL;
> + u64 ancestor;
> + u64 old_send_progress = sctx->send_progress;
> +
> + name = fs_path_alloc();
> + if (!valid_path) {
Wrong variable. Must be:
if (!name) {
(...)
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + sctx->send_progress = sctx->cur_ino + 1;
> + ret = path_loop(sctx, name, sctx->cur_ino,
> sctx->cur_inode_gen, &ancestor);
Need to check if ret < 0 and "goto out" if so.
> + if (ret) {
> + ret = add_pending_dir_move(sctx,
> sctx->cur_ino, sctx->cur_inode_gen,
> + ancestor,
> &sctx->new_refs, &sctx->deleted_refs, is_orphan);
> + if (ret < 0) {
> + sctx->send_progress =
> old_send_progress;
> + fs_path_free(name);
> + goto out;
> + }
> + can_rename = false;
> + *pending_move = 1;
> + }
> + sctx->send_progress = old_send_progress;
> + fs_path_free(name);
> + }
> +
> + /*
> * link/move the ref to the new place. If we have an orphan
> * inode, move it and update valid_path. If not, link or move
> * it depending on the inode mode.
> --
> 1.9.1
>
> --
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--
Filipe David Manana,
"Reasonable men adapt themselves to the world.
Unreasonable men adapt the world to themselves.
That's why all progress depends on unreasonable men."
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