Hi Jan: On Tue, Jul 12, 2011 at 3:37 PM, Jan Kara <jack@xxxxxxx> wrote: > On Tue 12-07-11 06:41:32, Christoph Hellwig wrote: >> On Tue, Jul 12, 2011 at 12:34:53PM +0200, Jan Kara wrote: >> > > All block device inodes sit on blockdev_superblock, we got rid of inodes >> > > without a superblock long time ago. >> > Sure, we can easily iterate also blockdev_superblock. What I meant is >> > that blockdev_superblock will need a special handling since we otherwise >> > ignore pseudo superblocks... >> >> Pseudo superblocks aren't ignored. They are added to super_blocks like >> all others, and iterate_supers doesn't skip over them. The problem >> is that blockdev_superblock doesn't have a proper s_bdi set, and thus >> gets skipped over by __sync_filesystem. > Yes. But even if it was not skipped writeback_inodes_sb() doesn't have > one flusher thread to kick to actually do the writeout (since each inode on > blockdev_superblock belongs to a different bdi). So it's perfectly fine we > skip blockdev_superblock. > > If we want to fix the problem something like attached patch should do. > Comments? Your patch looks good to me, in that it does hit all the bdevs with both WB_SYNC_NONE and SYNC_ALL. However, I still say that the call to wakeup_flusher_threads() in sys_sync() is superfluous, at least as long as writeback_inodes_sb() waits for completion of the work item that it enqueues. Thanks, Curt > > Honza > > PS: While testing the patch, I've noticed that block device can have any > dirty data only if it is still open (__blkdev_put() writes all dirty pages) > so that somehow limits how much people can be burned by sync not writing > out block devices... > -- > Jan Kara <jack@xxxxxxx> > SUSE Labs, CR > -- 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
