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authorWang Shilong <wangsl.fnst@cn.fujitsu.com>2014-01-07 17:25:19 +0800
committerChris Mason <clm@fb.com>2014-01-28 13:20:21 -0800
commit18f687d538449373c37cbe52b03f5f3d42b7c7ed (patch)
treeda340e3522b0e22516af99a7f3cb44d96cfdd6cf /fs
parent896c14f97f700aec6565154f2451605d7c5ce3ed (diff)
Btrfs: fix protection between send and root deletion
We should gurantee that parent and clone roots can not be destroyed during send, for this we have two ideas. 1.by holding @subvol_sem, this might be a nightmare, because it will block all subvolumes deletion for a long time. 2.Miao pointed out we can reuse @send_in_progress, that mean we will skip snapshot deletion if root sending is in progress. Here we adopt the second approach since it won't block other subvolumes deletion for a long time. Besides in btrfs_clean_one_deleted_snapshot(), we only check first root , if this root is involved in send, we return directly rather than continue to check.There are several reasons about it: 1.this case happen seldomly. 2.after sending,cleaner thread can continue to drop that root. 3.make code simple Cc: David Sterba <dsterba@suse.cz> Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com> Reviewed-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Chris Mason <clm@fb.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/send.c16
-rw-r--r--fs/btrfs/transaction.c13
2 files changed, 29 insertions, 0 deletions
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 5b697851646..4e2461b857f 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -4753,6 +4753,7 @@ long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
u64 *clone_sources_tmp = NULL;
int clone_sources_to_rollback = 0;
int sort_clone_roots = 0;
+ int index;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
@@ -4893,8 +4894,12 @@ long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
key.objectid = clone_sources_tmp[i];
key.type = BTRFS_ROOT_ITEM_KEY;
key.offset = (u64)-1;
+
+ index = srcu_read_lock(&fs_info->subvol_srcu);
+
clone_root = btrfs_read_fs_root_no_name(fs_info, &key);
if (IS_ERR(clone_root)) {
+ srcu_read_unlock(&fs_info->subvol_srcu, index);
ret = PTR_ERR(clone_root);
goto out;
}
@@ -4903,10 +4908,13 @@ long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
clone_root->send_in_progress++;
if (!btrfs_root_readonly(clone_root)) {
spin_unlock(&clone_root->root_item_lock);
+ srcu_read_unlock(&fs_info->subvol_srcu, index);
ret = -EPERM;
goto out;
}
spin_unlock(&clone_root->root_item_lock);
+ srcu_read_unlock(&fs_info->subvol_srcu, index);
+
sctx->clone_roots[i].root = clone_root;
}
vfree(clone_sources_tmp);
@@ -4917,19 +4925,27 @@ long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
key.objectid = arg->parent_root;
key.type = BTRFS_ROOT_ITEM_KEY;
key.offset = (u64)-1;
+
+ index = srcu_read_lock(&fs_info->subvol_srcu);
+
sctx->parent_root = btrfs_read_fs_root_no_name(fs_info, &key);
if (IS_ERR(sctx->parent_root)) {
+ srcu_read_unlock(&fs_info->subvol_srcu, index);
ret = PTR_ERR(sctx->parent_root);
goto out;
}
+
spin_lock(&sctx->parent_root->root_item_lock);
sctx->parent_root->send_in_progress++;
if (!btrfs_root_readonly(sctx->parent_root)) {
spin_unlock(&sctx->parent_root->root_item_lock);
+ srcu_read_unlock(&fs_info->subvol_srcu, index);
ret = -EPERM;
goto out;
}
spin_unlock(&sctx->parent_root->root_item_lock);
+
+ srcu_read_unlock(&fs_info->subvol_srcu, index);
}
/*
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index e5fe801659b..da2ac4c6d78 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1972,6 +1972,19 @@ int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
}
root = list_first_entry(&fs_info->dead_roots,
struct btrfs_root, root_list);
+ /*
+ * Make sure root is not involved in send,
+ * if we fail with first root, we return
+ * directly rather than continue.
+ */
+ spin_lock(&root->root_item_lock);
+ if (root->send_in_progress) {
+ spin_unlock(&fs_info->trans_lock);
+ spin_unlock(&root->root_item_lock);
+ return 0;
+ }
+ spin_unlock(&root->root_item_lock);
+
list_del_init(&root->root_list);
spin_unlock(&fs_info->trans_lock);