"This NTFS update fixes the deadlock at mount time reported by several people over the years but it was only recently that someone who reported it actually replied to my response and helped me track it down (I have never been able to reproduce the deadlock)," Anton Altaparmakov explained about a patch against the NTFS filesystem. He summarized the changes:
"The fix was to stop calling ntfs_attr_set() at mount time as that causes balance_dirty_pages_ratelimited() to be called which on systems with little memory actually tries to go and balance the dirty pages which tries to take the s_umount semaphore but because we are still in fill_super() across which the VFS holds s_umount for writing this results in a deadlock.
"We now do the dirty work by hand by submitting individual buffers. This has the annoying 'feature' that mounting can take a few seconds if the journal is large as we have clear it all. One day someone should improve on this by deferring the journal clearing to a helper kernel thread so it can be done in the background but I don't have time for this at the moment and the current solution works fine so I am leaving it like this for now."