ocfs2: Pagecache usage optimization on ocfs2

A page can have multiple buffers and even if a page is not uptodate, some buffers
can be uptodate on pagesize != blocksize environment.
This aops checks that all buffers which correspond to a part of a file
that we want to read are uptodate. If so, we do not have to issue actual
read IO to HDD even if a page is not uptodate because the portion we
want to read are uptodate.
"block_is_partially_uptodate" function is already used by ext2/3/4.
With the following patch random read/write mixed workloads or random read after
random write workloads can be optimized and we can get performance improvement.

Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

1 files changed, 12 insertions, 11 deletions

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 8e1709a679b..b2c52b3a148 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1956,15 +1956,16 @@ static int ocfs2_write_end(struct file *file, struct address_space *mapping,
 }
 
 const struct address_space_operations ocfs2_aops = {
-        .readpage       = ocfs2_readpage,
-        .readpages      = ocfs2_readpages,
-        .writepage      = ocfs2_writepage,
-        .write_begin    = ocfs2_write_begin,
-        .write_end      = ocfs2_write_end,
-        .bmap           = ocfs2_bmap,
-        .sync_page      = block_sync_page,
-        .direct_IO      = ocfs2_direct_IO,
-        .invalidatepage = ocfs2_invalidatepage,
-        .releasepage    = ocfs2_releasepage,
-        .migratepage    = buffer_migrate_page,
+        .readpage               = ocfs2_readpage,
+        .readpages              = ocfs2_readpages,
+        .writepage              = ocfs2_writepage,
+        .write_begin            = ocfs2_write_begin,
+        .write_end              = ocfs2_write_end,
+        .bmap                   = ocfs2_bmap,
+        .sync_page              = block_sync_page,
+        .direct_IO              = ocfs2_direct_IO,
+        .invalidatepage         = ocfs2_invalidatepage,
+        .releasepage            = ocfs2_releasepage,
+        .migratepage            = buffer_migrate_page,
+        .is_partially_uptodate  = block_is_partially_uptodate,
 };