btrfs: only set the device specific options after devices are opened

btrfs: only set the device specific options after devices are opened

[BUG]
With v6.17-rc kernels, btrfs will always set 'ssd' mount option even if
the block device is not a rotating one:

  # cat /sys/block/sdd/queue/rotational
  1
  # cat /etc/fstab:
  LABEL=DATA2     /data2  btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/,nofail,nosuid,nodev      0 0

  # mount
  [...]
  /dev/sdd on /data2 type btrfs (rw,nosuid,nodev,relatime,ssd,space_cache=v2,subvolid=5,subvol=/)

[CAUSE]
The 'ssd' mount option is set by set_device_specific_options(), and it
expects that if there is any rotating device in the btrfs, it will set
fs_devices::rotating.

However after commit bddf57a70781 ("btrfs: delay btrfs_open_devices()
until super block is created"), the device opening is delayed until the
super block is created.

But the timing of set_device_specific_options() is still left as is,
this makes the function be called without any device opened.

Since no device is opened, thus fs_devices::rotating will never be set,
making btrfs incorrectly set 'ssd' mount option.

[FIX]
Only call set_device_specific_options() after btrfs_open_devices().

Also only call set_device_specific_options() after a new mount, if we're
mounting a mounted btrfs, there is no need to set the device specific
mount options again.

Reported-by: HAN Yuwei <hrx@bupt.moe>
Link: https://lore.kernel.org/linux-btrfs/C8FF75669DFFC3C5+5f93bf8a-80a0-48a6-81bf-4ec890abc99a@bupt.moe/
Fixes: bddf57a70781 ("btrfs: delay btrfs_open_devices() until super block is created")
CC: stable@vger.kernel.org # 6.17
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>