On Wed, Apr 02, 2014 at 10:07:57AM -0400, Matthew Wilcox wrote: > Looking forther down the call stack, this call to ext4_commit_super() > comes via __ext4_abort's call to save_error_info() which calls > ext4_commit_super(). I've had a good look around, and I can't see any > locking that prevents ext4_commit_super() from being called in parallel > with ... well, anything else. Ext4_commit_super() only gets called: * When mounting and unmounting the file system (where the code path has exclusive access to the superblock) * When remounting the file system read-only * When reporting an error So what you're probably seeing is a case where we have multiple cpu's calling some form of ext4_error* in parallel, and indeed there is nothing prevent us from trying to update the superblock and calling ext4_commit_super() in parallel. We'll need to be careful because at the moment we don't make any assumptions about any mutexes being locked --- or not locked --- when we call into ext4_error(). Since this is happening on the error paths, and these are just warnings, it's not a disaster. But we really should do something to clean up the warning, and the fact that we aren't being careful about what happens if two CPU's are trying to update the s_last_error_* information might mean that the information that we get back is misleading, so this is something we should fix. Thanks for pointing this out! - Ted -- 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
