GFS2: Use ->writepages for ordered writes

Instead of using a list of buffers to write ahead of the journal
flush, this now uses a list of inodes and calls ->writepages
via filemap_fdatawrite() in order to achieve the same thing. For
most use cases this results in a shorter ordered write list,
as well as much larger i/os being issued.

The ordered write list is sorted by inode number before writing
in order to retain the disk block ordering between inodes as
per the previous code.

The previous ordered write code used to conflict in its assumptions
about how to write out the disk blocks with mpage_writepages()
so that with this updated version we can also use mpage_writepages()
for GFS2's ordered write, writepages implementation. So we will
also send larger i/os from writeback too.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 19750bcb1ce..1533cf8b426 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -340,6 +340,7 @@ enum {
 	GIF_QD_LOCKED		= 1,
 	GIF_ALLOC_FAILED	= 2,
 	GIF_SW_PAGED		= 3,
+	GIF_ORDERED		= 4,
 };
 
 struct gfs2_inode {
@@ -356,6 +357,7 @@ struct gfs2_inode {
 	struct gfs2_rgrpd *i_rgd;
 	u64 i_goal;	/* goal block for allocations */
 	struct rw_semaphore i_rw_mutex;
+	struct list_head i_ordered;
 	struct list_head i_trunc_list;
 	__be64 *i_hash_cache;
 	u32 i_entries;
@@ -722,6 +724,7 @@ struct gfs2_sbd {
 	struct list_head sd_log_le_revoke;
 	struct list_head sd_log_le_databuf;
 	struct list_head sd_log_le_ordered;
+	spinlock_t sd_ordered_lock;
 
 	atomic_t sd_log_thresh1;
 	atomic_t sd_log_thresh2;