On Wed, May 04, 2011 at 08:51:39AM -0600, Andreas Dilger wrote: > I was aware of REQ_META, but I didn't know there was any benefit to > using it. I think it would be easy to set REQ_META on all ext4 metadata > if there was a reason to do so. The CFQ ioscheduler pays attention to it (prioritising metadata accesses over data accesses), and blocktrace will print an 'M' for metadata requests if it's set, so I think that's two excellent reasons to set REQ_META today. However, ext3, ext4, and XFS already use it: fs/ext3/inode.c:1105: ll_rw_block(READ_META, 1, &bh); fs/ext3/inode.c:2754: submit_bh(READ_META, bh); fs/ext3/namei.c:924: ll_rw_block(READ_META, 1, &bh); fs/ext4/inode.c:1500: ll_rw_block(READ_META, 1, &bh); fs/ext4/inode.c:4775: submit_bh(READ_META, bh); fs/ext4/namei.c:924: ll_rw_block(READ_META, 1, &bh); fs/gfs2/log.c:597: submit_bh(WRITE_SYNC | REQ_META, bh); fs/gfs2/log.c:599: submit_bh(WRITE_FLUSH_FUA | REQ_META, bh); fs/gfs2/meta_io.c:39: int write_op = REQ_META | fs/gfs2/meta_io.c:228: submit_bh(READ_SYNC | REQ_META, bh); fs/gfs2/meta_io.c:435: ll_rw_block(READ_SYNC | REQ_META, 1, &first_bh); fs/gfs2/ops_fstype.c:221: submit_bio(READ_SYNC | REQ_META, bio); fs/gfs2/quota.c:710: ll_rw_block(READ_META, 1, &bh); fs/xfs/linux-2.6/xfs_buf.c:1321: rw = (bp->b_flags & XBF_WRITE) ? WRITE_META : READ_META; include/linux/fs.h:164:#define READ_META (READ | REQ_META) include/linux/fs.h:168:#define WRITE_META (WRITE | REQ_META) btrfs seems to not use REQ_META yet. *poke* *poke* :-) -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- 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
