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 <robbieko@xxxxxxxxxxxx>
---
V3: add error handling and modify comment and coding style
fs/btrfs/send.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 48 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 95dc1d4..ca8cb87 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -3089,13 +3089,18 @@ 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;
+ if (wdm->orphanized)
+ break;
ret = get_first_ref(sctx->parent_root, ino,
&parent_inode, &parent_gen, name);
} else {
@@ -3748,6 +3753,48 @@ verbose_printk("btrfs: process_recorded_refs %llu\n", sctx->cur_ino);
}
/*
+ * need to check whether rename/move causes path loop.
+ * If it does, need to delay the rename of the current
+ * inode (sctx->cur_ino), then perform after the rename of
+ * its ancestor.
+ */
+ if (S_ISDIR(sctx->cur_inode_mode) &&
+ sctx->parent_root && can_rename) {
+ struct fs_path *name = NULL;
+ u64 ancestor;
+ u64 old_send_progress = sctx->send_progress;
+
+ name = fs_path_alloc();
+ 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);
+ 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);
+ if (ret < 0)
+ goto out;
+ }
+
+ /*
* 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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