On Tue, Nov 06, 2012 at 05:38:25PM +0100, Stefan Behrens wrote:
> The new function btrfs_find_device_missing_or_by_path() will be
> used for the device replace procedure. This function itself calls
> the second new function btrfs_find_device_by_path().
> Unfortunately, it is not possible to currently make the rest of the
> code use these functions as well, since all functions that look
> similar at first view are all a little bit different in what they
> are doing. But in the future, new code could benefit from these
> two new functions, and currently, device replace uses them.
>
> Signed-off-by: Stefan Behrens <sbehr...@giantdisaster.de>
> ---
> fs/btrfs/volumes.c | 74
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> fs/btrfs/volumes.h | 5 ++++
> 2 files changed, 79 insertions(+)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index eeed97d..bcd3097 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1512,6 +1512,80 @@ error_undo:
> goto error_brelse;
> }
>
> +int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,
> + struct btrfs_device **device)
> +{
> + int ret = 0;
> + struct btrfs_super_block *disk_super;
> + u64 devid;
> + u8 *dev_uuid;
> + struct block_device *bdev;
> + struct buffer_head *bh = NULL;
> +
> + *device = NULL;
> + mutex_lock(&uuid_mutex);
Since the caller have held volume_mutex, we can get rid of the
mutex_lock here, can't we?
> + bdev = blkdev_get_by_path(device_path, FMODE_READ,
> + root->fs_info->bdev_holder);
> + if (IS_ERR(bdev)) {
> + ret = PTR_ERR(bdev);
> + bdev = NULL;
> + goto out;
> + }
> +
> + set_blocksize(bdev, 4096);
> + invalidate_bdev(bdev);
> + bh = btrfs_read_dev_super(bdev);
> + if (!bh) {
> + ret = -EINVAL;
> + goto out;
> + }
I made a scan for this 'get bdev & bh' in the code, I think
maybe we can make a function,
func_get(device_path, flags, mode, &bdev, &bh, flush)
where we need to take care of setting bdev = NULL, bh = NULL, and
'flush' is for filemap_bdev(). Besides, we also need to make
some proper error handling.
thanks,
liubo
> + disk_super = (struct btrfs_super_block *)bh->b_data;
> + devid = btrfs_stack_device_id(&disk_super->dev_item);
> + dev_uuid = disk_super->dev_item.uuid;
> + *device = btrfs_find_device(root, devid, dev_uuid,
> + disk_super->fsid);
> + brelse(bh);
> + if (!*device)
> + ret = -ENOENT;
> +out:
> + mutex_unlock(&uuid_mutex);
> + if (bdev)
> + blkdev_put(bdev, FMODE_READ);
> + return ret;
> +}
> +
> +int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
> + char *device_path,
> + struct btrfs_device **device)
> +{
> + *device = NULL;
> + if (strcmp(device_path, "missing") == 0) {
> + struct list_head *devices;
> + struct btrfs_device *tmp;
> +
> + devices = &root->fs_info->fs_devices->devices;
> + /*
> + * It is safe to read the devices since the volume_mutex
> + * is held by the caller.
> + */
> + list_for_each_entry(tmp, devices, dev_list) {
> + if (tmp->in_fs_metadata && !tmp->bdev) {
> + *device = tmp;
> + break;
> + }
> + }
> +
> + if (!*device) {
> + pr_err("btrfs: no missing device found\n");
> + return -ENOENT;
> + }
> +
> + return 0;
> + } else {
> + return btrfs_find_device_by_path(root, device_path, device);
> + }
> +}
> +
> /*
> * does all the dirty work required for changing file system's UUID.
> */
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 1789cda..657bb12 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -268,6 +268,11 @@ int btrfs_scan_one_device(const char *path, fmode_t
> flags, void *holder,
> struct btrfs_fs_devices **fs_devices_ret);
> int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
> void btrfs_close_extra_devices(struct btrfs_fs_devices *fs_devices);
> +int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
> + char *device_path,
> + struct btrfs_device **device);
> +int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,
> + struct btrfs_device **device);
> int btrfs_add_device(struct btrfs_trans_handle *trans,
> struct btrfs_root *root,
> struct btrfs_device *device);
> --
> 1.8.0
>
> --
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