On Tue, Jun 23, 2015 at 11:39 AM, Robbie Ko <robbieko@xxxxxxxxxxxx> wrote:
> This reverts commit 5f806c3ae2ff6263a10a6901f97abb74dac03d36.
>
> This is a necessary patch for a subsequent patch in the series (patch 3).
Still confused.
Reverting that commit (5f806c3ae2ff6263a10a6901f97abb74dac03d36) alone
will fix any issue?
Reading the part below gives that understanding, but it's basically a
trimmed down version of the scenario/problem mentioned in patch 3, so
it doesn't seem, nor it's clear, that this revert alone fixes any
problem.
>
> "[PATCH] Btrfs: incremental send, don't delay directory renames
> unnecessarily" changes behavior of wait_for_parent_move function.
> It may cause path loop problem, so fix it in the patch 3.
>
> 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)
>
> This cause will cause path building loop like this : 261 -> 260 -> 259 ->
> 263 -> 262 -> 261
>
> Signed-off-by: Robbie Ko <robbieko@xxxxxxxxxxxx>
> ---
>
> V3: modify comment
>
> fs/btrfs/send.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 59 insertions(+)
>
> diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
> index 1c1f161..257753b 100644
> --- a/fs/btrfs/send.c
> +++ b/fs/btrfs/send.c
> @@ -3080,6 +3080,48 @@ static struct pending_dir_move *get_pending_dir_moves(struct send_ctx *sctx,
> return NULL;
> }
>
> +static int path_loop(struct send_ctx *sctx, struct fs_path *name,
> + u64 ino, u64 gen, u64 *ancestor_ino)
> +{
> + int ret = 0;
> + u64 parent_inode = 0;
> + u64 parent_gen = 0;
> + u64 start_ino = ino;
> +
> + *ancestor_ino = 0;
> + while (ino != BTRFS_FIRST_FREE_OBJECTID) {
> + fs_path_reset(name);
> +
> + if (is_waiting_for_rm(sctx, ino))
> + break;
> + if (is_waiting_for_move(sctx, ino)) {
> + if (*ancestor_ino == 0)
> + *ancestor_ino = ino;
> + 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,
> + &parent_gen, name);
> + if (ret > 0) {
> + ret = 0;
> + break;
> + }
> + }
> + if (ret < 0)
> + break;
> + if (parent_inode == start_ino) {
> + ret = 1;
> + if (*ancestor_ino == 0)
> + *ancestor_ino = ino;
> + break;
> + }
> + ino = parent_inode;
> + gen = parent_gen;
> + }
> + return ret;
> +}
> +
> static int apply_dir_move(struct send_ctx *sctx, struct pending_dir_move *pm)
> {
> struct fs_path *from_path = NULL;
> @@ -3091,6 +3133,7 @@ static int apply_dir_move(struct send_ctx *sctx, struct pending_dir_move *pm)
> struct waiting_dir_move *dm = NULL;
> u64 rmdir_ino = 0;
> int ret;
> + u64 ancestor = 0;
>
> name = fs_path_alloc();
> from_path = fs_path_alloc();
> @@ -3122,6 +3165,22 @@ static int apply_dir_move(struct send_ctx *sctx, struct pending_dir_move *pm)
> goto out;
>
> sctx->send_progress = sctx->cur_ino + 1;
> + ret = path_loop(sctx, name, pm->ino, pm->gen, &ancestor);
> + if (ret) {
> + LIST_HEAD(deleted_refs);
> + ASSERT(ancestor > BTRFS_FIRST_FREE_OBJECTID);
> + ret = add_pending_dir_move(sctx, pm->ino, pm->gen, ancestor,
> + &pm->update_refs, &deleted_refs,
> + pm->is_orphan);
> + if (ret < 0)
> + goto out;
> + if (rmdir_ino) {
> + dm = get_waiting_dir_move(sctx, pm->ino);
> + ASSERT(dm);
> + dm->rmdir_ino = rmdir_ino;
> + }
> + goto out;
> + }
> fs_path_reset(name);
> to_path = name;
> name = NULL;
> --
> 1.9.1
>
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"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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