On Tue, 2010-04-27 at 14:35 +1000, Neil Brown wrote: > Hi Trond, > I think the above mentioned commit might have added a new race to replace > the old .... > > I have report of a BUG in nfs_page_async_flush. > > It isn't a vanilla upstream kernel - there are a bunch of SUSE patches > in there - so quoting the line-number won't help you, but it is the > BUG_ON(ret != 0); > after the call to nfs_set_page_writeback. > (https://bugzilla.novell.com/show_bug.cgi?id=599628) > > This implies that nfs_find_and_lock_request got a new lock on the page, > and then we found that it was already flagged for writeback. That's odd. Callers such as write_cache_pages() should normally be doing a wait_on_page_writeback() after taking the page lock but prior to calling the filesystem. > The commit mentioned create just such an opportunity. It reorders things > so that a page is unlocked before writeback is cleared, thus creating a window > for that BUG to fire. > > What is the race that you were trying to fix? I want to ensure that the call to write_inode() immediately after filemap_fdatawait() in the function writeback_single_inode() works correctly. Prior to this fix, there was a race whereby the Pg_writeback flag could be cleared, but the nfs_page structure would still be locked. This again would result in the page being skipped by nfs_scan_list() and so it wouldn't be registered as COMMITed. Cheers Trond -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
