On 3.07.2018 08:12, Anand Jain wrote:
> When a device is deleted, the btrfs_super_block::number_devices is
> reduced by 1, but we do that after the commit transaction, so this
> change did not made it to the disk and waits for the next commit
> transaction whenever it happens.
>
> This can be easily demonstrated using the following test case where I
> use the btrfs device ready cli to read the disk and report.
>
> mkfs.btrfs -fq -dsingle -msingle $dev1 $dev2
> mount $dev1 /btrfs
> btrfs dev del $dev2 /btrfs
> btrfs dev ready $dev1; echo RESULT=$? <-- 1
> Without this patch RESULT returns 1, indicating not ready!
>
> Testing with a seed device:
>
> mkfs.btrfs -fq $dev1
> btrfstune -S1 $dev1
> mount $dev1 /btrfs
> btrfs dev add -f $dev2 /btrfs
> umount /btrfs
> mount $dev2 /btrfs
> btrfs dev del $dev1 /btrfs
> btrfs dev ready $dev2; echo RESULT=$? <-- 1
Turn those into fully fledged xfstests
>
> Fix this by bringing in the num_devices update with in the
> current commit transaction.
>
> Signed-off-by: Anand Jain <anand.j...@oracle.com>
> ---
> fs/btrfs/volumes.c | 38 ++++++++++++++++++--------------------
> 1 file changed, 18 insertions(+), 20 deletions(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 6b807b166ca3..18cd73703951 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1823,46 +1823,32 @@ static void update_dev_time(const char *path_name)
> }
>
> static int btrfs_rm_dev_item(struct btrfs_fs_info *fs_info,
> - struct btrfs_device *device)
> + struct btrfs_device *device,
> + struct btrfs_trans_handle *trans)
> {
While doing this, refactor the function to take transaction as the first
argument and remove the fs_info arg. fs_info in turn can be referenced
from the transaction handle
> struct btrfs_root *root = fs_info->chunk_root;
> int ret;
> struct btrfs_path *path;
> struct btrfs_key key;
> - struct btrfs_trans_handle *trans;
>
> path = btrfs_alloc_path();
> if (!path)
> return -ENOMEM;
>
> - trans = btrfs_start_transaction(root, 0);
> - if (IS_ERR(trans)) {
> - btrfs_free_path(path);
> - return PTR_ERR(trans);
> - }
> key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
> key.type = BTRFS_DEV_ITEM_KEY;
> key.offset = device->devid;
>
> ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
> - if (ret) {
> - if (ret > 0)
> - ret = -ENOENT;
> - btrfs_abort_transaction(trans, ret);
> - btrfs_end_transaction(trans);
> + if (ret > 0) {
> + ret = -ENOENT;
> goto out;
> }
>
> ret = btrfs_del_item(trans, root, path);
> - if (ret) {
> - btrfs_abort_transaction(trans, ret);
> - btrfs_end_transaction(trans);
> - }
>
> out:
> btrfs_free_path(path);
> - if (!ret)
> - ret = btrfs_commit_transaction(trans);
> return ret;
> }
>
> @@ -1946,7 +1932,9 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info,
> const char *device_path,
> u64 devid)
> {
> struct btrfs_device *device;
> + struct btrfs_trans_handle *trans;
> struct btrfs_fs_devices *cur_devices;
> + struct btrfs_root *root = fs_info->dev_root;
> struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
> u64 num_devices;
> int ret = 0;
> @@ -1994,14 +1982,23 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info,
> const char *device_path,
> if (ret)
> goto error_undo;
>
> + trans = btrfs_start_transaction(root, 0);
> + if (IS_ERR(trans)) {
> + ret = PTR_ERR(trans);
> + goto error_undo;
> + }
> +
> /*
> * TODO: the superblock still includes this device in its num_devices
> * counter although write_all_supers() is not locked out. This
> * could give a filesystem state which requires a degraded mount.
> */
Isn't introducing the transaction fixing this TODO item so it can be
removed?
> - ret = btrfs_rm_dev_item(fs_info, device);
> - if (ret)
> + ret = btrfs_rm_dev_item(fs_info, device, trans);
> + if (ret) {
> + btrfs_abort_transaction(trans, ret);
> + btrfs_end_transaction(trans);
> goto error_undo;
> + }
>
> clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
> btrfs_scrub_cancel_dev(fs_info, device);
> @@ -2070,6 +2067,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info,
> const char *device_path,
> free_fs_devices(cur_devices);
> }
>
> + ret = btrfs_commit_transaction(trans);
> out:
> mutex_unlock(&uuid_mutex);
> return ret;
>
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