Hi, I encounter a problem when running xfstests on NOVA. I appreciate your help very much. Some background: NOVA adopts a per-inode logging design. Metadata changes are appended to the log and persisted before returning to the user space. For example, a write() in NOVA works like this: Allocate new pmem blocks and fill with user data Append the metadata that describes this write to the end of the inode log Update the log tail pointer atomically to commit the write Update in-DRAM radix tree to point to the metadata (for fast lookup) The log appending and radix tree update are protected by inode_lock(). For mmap, nova_dax_get_blocks (similar to ext2_get_blocks) needs to persist the metadata for new allocations. So it has to append the new allocation metadata to the log, and hence needs to lock the inode. This causes deadlock in xfstests 344 with concurrent pwrite and mmap write: Thread 1: pwrite -> nova_dax_file_write() ---> inode_lock() -----> invalidate_inode_pages2_range() -------> schedule() Thread 2: dax_fault -> nova_dax_get_blocks() ---> inode_lock() // deadlock If I remove invalidate_inode_pages2_range() in write path, xfstests 344 passed, but 428 will fail. It appears to me that ext2/ext4 does not have this issue because they don't persist metadata immediately and hence do not take inode lock. But nova_dax_get_blocks() has to persist the metadata and needs to lock the inode to access the log. Is there a way to workaround this? Thank you very much. Thanks, Andiry
