nfs: add support for multiple nfs reqs per page
Add "page groups" - a circular list of nfs requests (struct nfs_page)
that all reference the same page. This gives nfs read and write paths
the ability to account for sub-page regions independently. This
somewhat follows the design of struct buffer_head's sub-page
accounting.
Only "head" requests are ever added/removed from the inode list in
the buffered write path. "head" and "sub" requests are treated the
same through the read path and the rest of the write/commit path.
Requests are given an extra reference across the life of the list.
Page groups are never rejoined after being split. If the read/write
request fails and the client falls back to another path (ie revert
to MDS in PNFS case), the already split requests are pushed through
the recoalescing code again, which may split them further and then
coalesce them into properly sized requests on the wire. Fragmentation
shouldn't be a problem with the current design, because we flush all
requests in page group when a non-contiguous request is added, so
the only time resplitting should occur is on a resend of a read or
write.
This patch lays the groundwork for sub-page splitting, but does not
actually do any splitting. For now all page groups have one request
as pg_test functions don't yet split pages. There are several related
patches that are needed support multiple requests per page group.
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index 13d59af..986c0c2 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -26,6 +26,9 @@
PG_MAPPED, /* page private set for buffered io */
PG_CLEAN, /* write succeeded */
PG_COMMIT_TO_DS, /* used by pnfs layouts */
+ PG_INODE_REF, /* extra ref held by inode (head req only) */
+ PG_HEADLOCK, /* page group lock of wb_head */
+ PG_TEARDOWN, /* page group sync for destroy */
};
struct nfs_inode;
@@ -41,6 +44,8 @@
struct kref wb_kref; /* reference count */
unsigned long wb_flags;
struct nfs_write_verifier wb_verf; /* Commit cookie */
+ struct nfs_page *wb_this_page; /* list of reqs for this page */
+ struct nfs_page *wb_head; /* head pointer for req list */
};
struct nfs_pageio_descriptor;
@@ -87,9 +92,10 @@
extern struct nfs_page *nfs_create_request(struct nfs_open_context *ctx,
struct page *page,
+ struct nfs_page *last,
unsigned int offset,
unsigned int count);
-extern void nfs_release_request(struct nfs_page *req);
+extern void nfs_release_request(struct nfs_page *);
extern void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
@@ -108,7 +114,10 @@
struct nfs_page *req);
extern int nfs_wait_on_request(struct nfs_page *);
extern void nfs_unlock_request(struct nfs_page *req);
-extern void nfs_unlock_and_release_request(struct nfs_page *req);
+extern void nfs_unlock_and_release_request(struct nfs_page *);
+extern void nfs_page_group_lock(struct nfs_page *);
+extern void nfs_page_group_unlock(struct nfs_page *);
+extern bool nfs_page_group_sync_on_bit(struct nfs_page *, unsigned int);
/*
* Lock the page of an asynchronous request