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, 6 insertions, 7 deletions

diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index 92340dd23bba..24f414f0ce61 100644
--- a/fs/gfs2/aops.c
+++ b/fs/gfs2/aops.c
@@ -230,16 +230,14 @@ out_ignore:
 }
 
 /**
- * gfs2_writeback_writepages - Write a bunch of dirty pages back to disk
+ * gfs2_writepages - Write a bunch of dirty pages back to disk
  * @mapping: The mapping to write
  * @wbc: Write-back control
  *
- * For the data=writeback case we can already ignore buffer heads
- * and write whole extents at once. This is a big reduction in the
- * number of I/O requests we send and the bmap calls we make in this case.
+ * Used for both ordered and writeback modes.
  */
-static int gfs2_writeback_writepages(struct address_space *mapping,
-                                     struct writeback_control *wbc)
+static int gfs2_writepages(struct address_space *mapping,
+                           struct writeback_control *wbc)
 {
         return mpage_writepages(mapping, wbc, gfs2_get_block_noalloc);
 }
@@ -1102,7 +1100,7 @@ cannot_release:
 
 static const struct address_space_operations gfs2_writeback_aops = {
         .writepage = gfs2_writeback_writepage,
-        .writepages = gfs2_writeback_writepages,
+        .writepages = gfs2_writepages,
         .readpage = gfs2_readpage,
         .readpages = gfs2_readpages,
         .write_begin = gfs2_write_begin,
@@ -1118,6 +1116,7 @@ static const struct address_space_operations gfs2_writeback_aops = {
 
 static const struct address_space_operations gfs2_ordered_aops = {
         .writepage = gfs2_ordered_writepage,
+        .writepages = gfs2_writepages,
         .readpage = gfs2_readpage,
         .readpages = gfs2_readpages,
         .write_begin = gfs2_write_begin,