pnfs/blocklayout: use scoped_with_init_fs() for SCSI device lookup

bl_open_path() resolves pNFS block device paths under /dev/disk/by-id/
via bdev_file_open_by_path() -> lookup_bdev() -> kern_path(). This
path resolution uses current->fs->root.

With kthreads now starting in nullfs, this fails when the call
originates from writeback kworker context because current->fs->root
points at the empty nullfs. The full callchain from kworker is:

  wb_workfn                              [kworker writeback callback]
    ...
      nfs_writepages                     [address_space_operations.writepages]
        nfs_do_writepage
          nfs_pageio_add_request
            ...
              bl_pg_init_write           [nfs_pageio_ops.pg_init]
                pnfs_generic_pg_init_write
                  pnfs_update_layout
                    nfs4_proc_layoutget  [synchronous RPC]
                      pnfs_layout_process
                        bl_alloc_lseg
                          bl_alloc_extent
                            bl_find_get_deviceid
                              bl_alloc_deviceid_node
                                bl_parse_deviceid
                                  bl_parse_scsi
                                    bl_open_path
                                      bdev_file_open_by_path
                                        lookup_bdev
                                          kern_path  <- current->fs->root

bl_open_path() can also be reached from userspace process context (e.g.
open, read, write syscalls via pnfs_update_layout). In that case
current->fs must not be overridden as the path should resolve against
the calling process's filesystem root.

Add a tsk_is_kthread() conditional in bl_open_path() to only apply
scoped_with_init_fs() in kthread context.

Link: https://patch.msgid.link/20260601-work-kthread-nullfs-v4-16-77ee053060e0@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

0 files changed, 0 insertions, 0 deletions