Re: INFO: task hung in generic_file_write_iter

[Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>]

On 2018/07/18 19:28, Tetsuo Handa wrote:
> There are many reports which are stalling inside __getblk_gfp().

Currently 18 reports out of 65 "INFO: task hung in " reports.

  INFO: task hung in aead_recvmsg
  INFO: task hung in inode_sleep_on_writeback
  INFO: task hung in __writeback_inodes_sb_nr
  INFO: task hung in __blkdev_get (2)
  INFO: task hung in lookup_slow
  INFO: task hung in iterate_supers
  INFO: task hung in flush_work
  INFO: task hung in vfs_setxattr
  INFO: task hung in lock_mount
  INFO: task hung in __get_super
  INFO: task hung in do_unlinkat
  INFO: task hung in fat_fallocate
  INFO: task hung in generic_file_write_iter
  INFO: task hung in d_alloc_parallel
  INFO: task hung in __fdget_pos (2)
  INFO: task hung in path_openat
  INFO: task hung in do_truncate
  INFO: task hung in filename_create

> And there is horrible comment for __getblk_gfp():
> 
>   /*
>    * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
>    * which corresponds to the passed block_device, block and size. The
>    * returned buffer has its reference count incremented.
>    *
>    * __getblk_gfp() will lock up the machine if grow_dev_page's
>    * try_to_free_buffers() attempt is failing.  FIXME, perhaps?
>    */
> 
> This report is stalling after mount() completed and process used remap_file_pages().
> I think that we might need to use debug printk(). But I don't know what to examine.
> 

Andrew, can you pick up this debug printk() patch?
I guess we can get the result within one week.