Variable Order Page Cache: Add order field in mapping
Add an "order" field in the address space structure that
specifies the page order of pages in an address space.
Set the field to zero by default so that filesystems not prepared to
deal with higher pages can be left as is.
Putting page order in the address space structure means that the order of the
pages in the page cache can be varied per file that a filesystem creates.
This means we can keep small 4k pages for small files. Larger files can
be configured by the file system to use a higher order.
Signed-off-by: Christoph Lameter <[EMAIL PROTECTED]>
---
fs/inode.c | 1 +
include/linux/fs.h | 1 +
2 files changed, 2 insertions(+)
Index: linux-2.6.21-rc7/fs/inode.c
===================================================================
--- linux-2.6.21-rc7.orig/fs/inode.c 2007-04-18 21:21:56.000000000 -0700
+++ linux-2.6.21-rc7/fs/inode.c 2007-04-18 21:26:31.000000000 -0700
@@ -145,6 +145,7 @@ static struct inode *alloc_inode(struct
mapping->a_ops = &empty_aops;
mapping->host = inode;
mapping->flags = 0;
+ mapping->order = 0;
mapping_set_gfp_mask(mapping, GFP_HIGHUSER);
mapping->assoc_mapping = NULL;
mapping->backing_dev_info = &default_backing_dev_info;
Index: linux-2.6.21-rc7/include/linux/fs.h
===================================================================
--- linux-2.6.21-rc7.orig/include/linux/fs.h 2007-04-18 21:21:56.000000000
-0700
+++ linux-2.6.21-rc7/include/linux/fs.h 2007-04-18 21:26:31.000000000 -0700
@@ -435,6 +435,7 @@ struct address_space {
struct inode *host; /* owner: inode, block_device */
struct radix_tree_root page_tree; /* radix tree of all pages */
rwlock_t tree_lock; /* and rwlock protecting it */
+ unsigned int order; /* Page order in this space */
unsigned int i_mmap_writable;/* count VM_SHARED mappings */
struct prio_tree_root i_mmap; /* tree of private and shared
mappings */
struct list_head i_mmap_nonlinear;/*list VM_NONLINEAR mappings */
-
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