On Tue, Dec 06, 2011 at 06:23:23AM -0500, Christoph Hellwig wrote: > On Tue, Dec 06, 2011 at 07:06:40PM +0800, Miao Xie wrote: > > > I can't see why you need the writeout when the trylocks fails. Umount > > > needs to take care of writing out all pending file data anyway, so doing > > > it from the cleaner thread in addition doesn't sound like it would help. > > > > umount invokes sync_fs() and write out all the dirty file data. For the > > other file systems, its OK because the file system does not introduce dirty pages > > by itself. But btrfs is different. Its automatic defragment will make lots of dirty > > pages after sync_fs() and reserve lots of meta-data space for those pages. > > And then the cleaner thread may find there is no enough space to reserve, it must > > sync the dirty file data and release the reserved space which is for the dirty > > file data. > > I think the safest way to fix is is to write out all dirty data again > once the cleaner thread has been safely stopped. > Said another way we want to stop the autodefrag code before the unmount is ready to continue. We also want to stop balancing, scrub etc. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
