On Mon, Mar 10, 2008 at 03:24:26PM +0100, Jan Kara wrote: > > This one came up again when i was doing the mmap ENOSPC patch. Now the > > current code with migrate is taking i_mutex to protech against all > > writes. But it seems a write to a mmap area mapping a hole can still go > > through fine. And that path cannot take i_mutex. > > > > So i guess the migrate locking need to be fixed. Any suggestion ? > Hmm, thinking about it a bit more. One possibility is that we could just > use i_mutex to protect against ordinary writes, and before swapping blocks > for extents we'd check whether some holes were not filled in the mean time. > If yes, we can retry the migrate, or fail it and retry later. > Another possibility would be to make ext4 use page_mkwrite to fill in > holes. There we could safely acquire i_mutex and be done. > page_mkwrite is called with mmap_sem help and we can't take inode->i_mutex in page_mkwrite. The DIO write have inode->i_mutex -> mmap_sem locking order. I "fixed" it by introducing i_migrate_sem http://article.gmane.org/gmane.comp.file-systems.ext4/5402 -aneesh -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
