Commit 2f1f465a authored Mar 02, 2015 by Filipe Manana Committed by Chris Mason Mar 26, 2015

Btrfs: send, don't leave without decrementing clone root's send_progress



If the clone root was not readonly or the dead flag was set on it, we were
leaving without decrementing the root's send_progress counter (and before
we just incremented it). If a concurrent snapshot deletion was in progress
and ended up being aborted, it would be impossible to later attempt to
delete again the snapshot, since the root's send_in_progress counter could
never go back to 0.

We were also setting clone_sources_to_rollback to i + 1 too early - if we
bailed out because the clone root we got is not readonly or flagged as dead
we ended up later derreferencing a null pointer because we didn't assign
the clone root to sctx->clone_roots[i].root:

		for (i = 0; sctx && i < clone_sources_to_rollback; i++)
			btrfs_root_dec_send_in_progress(
					sctx->clone_roots[i].root);

So just don't increment the send_in_progress counter if the root is readonly
or flagged as dead.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

parent 5cc2b17e

fs/btrfs/send.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -5852,9 +5852,7 @@ long btrfs_ioctl_send(struct file mnt_file, void __user arg_)
		ret = PTR_ERR(clone_root);
		goto out;
		}
		clone_sources_to_rollback = i + 1;
		spin_lock(&clone_root->root_item_lock);
		clone_root->send_in_progress++;
		if (!btrfs_root_readonly(clone_root) \|\|
		btrfs_root_dead(clone_root)) {
		spin_unlock(&clone_root->root_item_lock);
		@@ -5862,10 +5860,12 @@ long btrfs_ioctl_send(struct file mnt_file, void __user arg_)
		ret = -EPERM;
		goto out;
		}
		clone_root->send_in_progress++;
		spin_unlock(&clone_root->root_item_lock);
		srcu_read_unlock(&fs_info->subvol_srcu, index);

		sctx->clone_roots[i].root = clone_root;
		clone_sources_to_rollback = i + 1;
		}
		vfree(clone_sources_tmp);
		clone_sources_tmp = NULL;

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