Btrfs: send, fix more issues related to directory renames

This is a continuation of the previous changes titled:

   Btrfs: fix incremental send's decision to delay a dir move/rename
   Btrfs: part 2, fix incremental send's decision to delay a dir move/rename

There's a few more cases where a directory rename/move must be delayed which was
previously overlooked. If our immediate ancestor has a lower inode number than
ours and it doesn't have a delayed rename/move operation associated to it, it
doesn't mean there isn't any non-direct ancestor of our current inode that needs
to be renamed/moved before our current inode (i.e. with a higher inode number
than ours).

So we can't stop the search if our immediate ancestor has a lower inode number than
ours, we need to navigate the directory hierarchy upwards until we hit the root or:

1) find an ancestor with an higher inode number that was renamed/moved in the send
   root too (or already has a pending rename/move registered);
2) find an ancestor that is a new directory (higher inode number than ours and
   exists only in the send root).

Reproducer for case 1)

    $ mkfs.btrfs -f /dev/sdd
    $ mount /dev/sdd /mnt

    $ mkdir -p /mnt/a/b
    $ mkdir -p /mnt/a/c/d
    $ mkdir /mnt/a/b/e
    $ mkdir /mnt/a/c/d/f
    $ mv /mnt/a/b /mnt/a/c/d/2b
    $ mkdir /mnt/a/x
    $ mkdir /mnt/a/y

    $ btrfs subvolume snapshot -r /mnt /mnt/snap1
    $ btrfs send /mnt/snap1 -f /tmp/base.send

    $ mv /mnt/a/x /mnt/a/y
    $ mv /mnt/a/c/d/2b/e /mnt/a/c/d/2b/2e
    $ mv /mnt/a/c/d /mnt/a/h/2d
    $ mv /mnt/a/c /mnt/a/h/2d/2b/2c

    $ btrfs subvolume snapshot -r /mnt /mnt/snap2
    $ btrfs send -p /mnt/snap1 /mnt/snap2 -f /tmp/incremental.send

Simple reproducer for case 2)

    $ mkfs.btrfs -f /dev/sdd
    $ mount /dev/sdd /mnt

    $ mkdir -p /mnt/a/b
    $ mkdir /mnt/a/c
    $ mv /mnt/a/b /mnt/a/c/b2
    $ mkdir /mnt/a/e

    $ btrfs subvolume snapshot -r /mnt /mnt/snap1
    $ btrfs send /mnt/snap1 -f /tmp/base.send

    $ mv /mnt/a/c/b2 /mnt/a/e/b3
    $ mkdir /mnt/a/e/b3/f
    $ mkdir /mnt/a/h
    $ mv /mnt/a/c /mnt/a/e/b3/f/c2
    $ mv /mnt/a/e /mnt/a/h/e2

    $ btrfs subvolume snapshot -r /mnt /mnt/snap2
    $ btrfs send -p /mnt/snap1 /mnt/snap2 -f /tmp/incremental.send

Another simple reproducer for case 2)

    $ mkfs.btrfs -f /dev/sdd
    $ mount /dev/sdd /mnt

    $ mkdir -p /mnt/a/b
    $ mkdir /mnt/a/c
    $ mkdir /mnt/a/b/d
    $ mkdir /mnt/a/c/e

    $ btrfs subvolume snapshot -r /mnt /mnt/snap1
    $ btrfs send /mnt/snap1 -f /tmp/base.send

    $ mkdir /mnt/a/b/d/f
    $ mkdir /mnt/a/b/g
    $ mv /mnt/a/c/e /mnt/a/b/g/e2
    $ mv /mnt/a/c /mnt/a/b/d/f/c2
    $ mv /mnt/a/b/d/f /mnt/a/b/g/e2/f2

    $ btrfs subvolume snapshot -r /mnt /mnt/snap2
    $ btrfs send -p /mnt/snap1 /mnt/snap2 -f /tmp/incremental.send

More complex reproducer for case 2)

    $ mkfs.btrfs -f /dev/sdd
    $ mount /dev/sdd /mnt

    $ mkdir -p /mnt/a/b
    $ mkdir -p /mnt/a/c/d
    $ mkdir /mnt/a/b/e
    $ mkdir /mnt/a/c/d/f
    $ mv /mnt/a/b /mnt/a/c/d/2b
    $ mkdir /mnt/a/x
    $ mkdir /mnt/a/y

    $ btrfs subvolume snapshot -r /mnt /mnt/snap1
    $ btrfs send /mnt/snap1 -f /tmp/base.send

    $ mv /mnt/a/x /mnt/a/y
    $ mv /mnt/a/c/d/2b/e /mnt/a/c/d/2b/2e
    $ mv /mnt/a/c/d /mnt/a/h/2d
    $ mv /mnt/a/c /mnt/a/h/2d/2b/2c

    $ btrfs subvolume snapshot -r /mnt /mnt/snap2
    $ btrfs send -p /mnt/snap1 /mnt/snap2 -f /tmp/incremental.send

For both cases the incremental send would enter an infinite loop when building
path strings.

While solving these cases, this change also re-implements the code to detect
when directory moves/renames should be delayed. Instead of dealing with several
specific cases separately, it's now more generic handling all cases with a simple
detection algorithm and if when applying a delayed move/rename there's a path loop
detected, it further delays the move/rename registering a new ancestor inode as
the dependency inode (so our rename happens after that ancestor is renamed).

Tests for these cases is being added to xfstests too.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index fb6aeed9c223527617f1e9dc764eaecb673122c3..3f14b31c0c961ca5751faf4238918f6d720dcdb7 100644 (file)
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -2940,7 +2940,9 @@ static void free_waiting_dir_move(struct send_ctx *sctx,
 static int add_pending_dir_move(struct send_ctx *sctx,
                                u64 ino,
                                u64 ino_gen,
-                               u64 parent_ino)
+                               u64 parent_ino,
+                               struct list_head *new_refs,
+                               struct list_head *deleted_refs)
 {
        struct rb_node **p = &sctx->pending_dir_moves.rb_node;
        struct rb_node *parent = NULL;
@@ -2972,12 +2974,12 @@ static int add_pending_dir_move(struct send_ctx *sctx,
                }
        }
 
-       list_for_each_entry(cur, &sctx->deleted_refs, list) {
+       list_for_each_entry(cur, deleted_refs, list) {
                ret = dup_ref(cur, &pm->update_refs);
                if (ret < 0)
                        goto out;
        }
-       list_for_each_entry(cur, &sctx->new_refs, list) {
+       list_for_each_entry(cur, new_refs, list) {
                ret = dup_ref(cur, &pm->update_refs);
                if (ret < 0)
                        goto out;
@@ -3020,6 +3022,48 @@ 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;
@@ -3031,6 +3075,7 @@ 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();
@@ -3057,11 +3102,25 @@ static int apply_dir_move(struct send_ctx *sctx, struct pending_dir_move *pm)
        if (ret < 0)
                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);
+               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;
-
-       sctx->send_progress = sctx->cur_ino + 1;
        ret = get_cur_path(sctx, pm->ino, pm->gen, to_path);
        if (ret < 0)
                goto out;
@@ -3185,127 +3244,74 @@ out:
 static int wait_for_parent_move(struct send_ctx *sctx,
                                struct recorded_ref *parent_ref)
 {
-       int ret;
+       int ret = 0;
        u64 ino = parent_ref->dir;
        u64 parent_ino_before, parent_ino_after;
-       u64 old_gen;
        struct fs_path *path_before = NULL;
        struct fs_path *path_after = NULL;
        int len1, len2;
-       int register_upper_dirs;
-       u64 gen;
-
-       if (is_waiting_for_move(sctx, ino))
-               return 1;
-
-       if (parent_ref->dir <= sctx->cur_ino)
-               return 0;
-
-       ret = get_inode_info(sctx->parent_root, ino, NULL, &old_gen,
-                            NULL, NULL, NULL, NULL);
-       if (ret == -ENOENT)
-               return 0;
-       else if (ret < 0)
-               return ret;
-
-       if (parent_ref->dir_gen != old_gen)
-               return 0;
-
-       path_before = fs_path_alloc();
-       if (!path_before)
-               return -ENOMEM;
-
-       ret = get_first_ref(sctx->parent_root, ino, &parent_ino_before,
-                           NULL, path_before);
-       if (ret == -ENOENT) {
-               ret = 0;
-               goto out;
-       } else if (ret < 0) {
-               goto out;
-       }
 
        path_after = fs_path_alloc();
-       if (!path_after) {
+       path_before = fs_path_alloc();
+       if (!path_after || !path_before) {
                ret = -ENOMEM;
                goto out;
        }
 
-       ret = get_first_ref(sctx->send_root, ino, &parent_ino_after,
-                           &gen, path_after);
-       if (ret == -ENOENT) {
-               ret = 0;
-               goto out;
-       } else if (ret < 0) {
-               goto out;
-       }
-
-       len1 = fs_path_len(path_before);
-       len2 = fs_path_len(path_after);
-       if (parent_ino_before != parent_ino_after || len1 != len2 ||
-            memcmp(path_before->start, path_after->start, len1)) {
-               ret = 1;
-               goto out;
-       }
-       ret = 0;
-
        /*
-        * Ok, our new most direct ancestor has a higher inode number but
-        * wasn't moved/renamed. So maybe some of the new ancestors higher in
-        * the hierarchy have an higher inode number too *and* were renamed
-        * or moved - in this case we need to wait for the ancestor's rename
-        * or move operation before we can do the move/rename for the current
-        * inode.
+        * Our current directory inode may not yet be renamed/moved because some
+        * ancestor (immediate or not) has to be renamed/moved first. So find if
+        * such ancestor exists and make sure our own rename/move happens after
+        * that ancestor is processed.
         */
-       register_upper_dirs = 0;
-       ino = parent_ino_after;
-again:
-       while ((ret == 0 || register_upper_dirs) && ino > sctx->cur_ino) {
-               u64 parent_gen;
+       while (ino > BTRFS_FIRST_FREE_OBJECTID) {
+               if (is_waiting_for_move(sctx, ino)) {
+                       ret = 1;
+                       break;
+               }
 
                fs_path_reset(path_before);
                fs_path_reset(path_after);
 
                ret = get_first_ref(sctx->send_root, ino, &parent_ino_after,
-                                   &parent_gen, path_after);
+                                   NULL, path_after);
                if (ret < 0)
                        goto out;
                ret = get_first_ref(sctx->parent_root, ino, &parent_ino_before,
                                    NULL, path_before);
-               if (ret == -ENOENT) {
-                       ret = 0;
-                       break;
-               } else if (ret < 0) {
+               if (ret < 0 && ret != -ENOENT) {
                        goto out;
+               } else if (ret == -ENOENT) {
+                       ret = 1;
+                       break;
                }
 
                len1 = fs_path_len(path_before);
                len2 = fs_path_len(path_after);
-               if (parent_ino_before != parent_ino_after || len1 != len2 ||
-                   memcmp(path_before->start, path_after->start, len1)) {
+               if (ino > sctx->cur_ino &&
+                   (parent_ino_before != parent_ino_after || len1 != len2 ||
+                    memcmp(path_before->start, path_after->start, len1))) {
                        ret = 1;
-                       if (register_upper_dirs) {
-                               break;
-                       } else {
-                               register_upper_dirs = 1;
-                               ino = parent_ref->dir;
-                               gen = parent_ref->dir_gen;
-                               goto again;
-                       }
-               } else if (register_upper_dirs) {
-                       ret = add_pending_dir_move(sctx, ino, gen,
-                                                  parent_ino_after);
-                       if (ret < 0 && ret != -EEXIST)
-                               goto out;
+                       break;
                }
-
                ino = parent_ino_after;
-               gen = parent_gen;
        }
 
 out:
        fs_path_free(path_before);
        fs_path_free(path_after);
 
+       if (ret == 1) {
+               ret = add_pending_dir_move(sctx,
+                                          sctx->cur_ino,
+                                          sctx->cur_inode_gen,
+                                          ino,
+                                          &sctx->new_refs,
+                                          &sctx->deleted_refs);
+               if (!ret)
+                       ret = 1;
+       }
+
        return ret;
 }
 
@@ -3466,10 +3472,6 @@ verbose_printk("btrfs: process_recorded_refs %llu\n", sctx->cur_ino);
                                if (ret < 0)
                                        goto out;
                                if (ret) {
-                                       ret = add_pending_dir_move(sctx,
-                                                          sctx->cur_ino,
-                                                          sctx->cur_inode_gen,
-                                                          cur->dir);
                                        *pending_move = 1;
                                } else {
                                        ret = send_rename(sctx, valid_path,