The new address_space_ops is_partially_uptodate was added at 2.6.27-rc1.
On ext3, this aops checks whether buffer_heads that are attached to a page are
uptodate or not when a page is not uptodate. When all buffers which correspond
to a portion we want to read are uptodate even if a page is not uptodate,
we can avoid actual read IO.
I wrote is_partially_uptodate aops for nfs named nfs_is_partially_uptodate.This aops
checks whether read IO to a page is between wb_pgbase and wb_pgbase + wb_bytes of
nfs_page that is attached to this page. If this aops succeed, we do not have to do actual read.
I think random read/write mixed workloads or random read after random write
workloads can be optimized with this patch.
Signed-off-by: Hisashi Hifumi <firstname.lastname@example.org>
diff -Nrup linux-2.6.27-rc5.org/fs/nfs/file.c linux-2.6.27-rc5.nfs/fs/nfs/file.c
--- linux-2.6.27-rc5.org/fs/nfs/file.c 2008-09-03 14:56:16.000000000 +0900
+++ linux-2.6.27-rc5.nfs/fs/nfs/file.c 2008-09-08 10:53:00.000000000 +0900
@@ -446,6 +446,7 @@ const struct address_space_operations nf
.releasepage = nfs_release_page,
.direct_IO = nfs_direct_IO,
.launder_page = nfs_launder_page,
+ .is_partially_uptodate = nfs_is_partially_uptodate,
static int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct page *page)
diff -Nrup linux-2.6.27-rc5.org/fs/nfs/read.c linux-2.6.27-rc5.nfs/fs/nfs/read.c
--- linux-2.6.27-rc5.org/fs/nfs/read.c 2008-07-14 06:51:29.000000000 +0900
+++ linux-2.6.27-rc5.nfs/fs/nfs/read.c 2008-09-08 11:02:59.000000000 +0900
@@ -605,6 +605,33 @@ out:
+int nfs_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
+ unsigned long from)
+ struct inode *inode = page->mapping->host;
+ unsigned to;
+ struct nfs_page *req = ...