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>

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 8e1709a679b724aaaf323671308e1cd32399cf4d..b2c52b3a1484f1c57c4b098bf9706fe21c186ac0 100644 (file)
--- 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,
 };