NFS: create common nfs_pgio_header for both read and write

In order to avoid duplicating all the data in nfs_read_data whenever we
split it up into multiple RPC calls (either due to a short read result
or due to rsize < PAGE_SIZE), we split out the bits that are the same
per RPC call into a separate "header" structure.

The goal this patch moves towards is to have a single header
refcounted by several rpc_data structures.  Thus, want to always refer
from rpc_data to the header, and not the other way.  This patch comes
close to that ideal, but the directio code currently needs some
special casing, isolated in the nfs_direct_[read_write]hdr_release()
functions.  This will be dealt with in a future patch.

Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 27 insertions, 21 deletions

diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index 8fb036a0d489..fee324175391 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -1168,52 +1168,58 @@ struct nfs_page;
 #define NFS_PAGEVEC_SIZE        (8U)
 
 struct nfs_read_data {
+        struct nfs_pgio_header  *header;
+        struct list_head        list;
         struct rpc_task         task;
-        struct inode            *inode;
-        struct rpc_cred         *cred;
         struct nfs_fattr        fattr;  /* fattr storage */
-        struct list_head        pages;  /* Coalesced read requests */
-        struct list_head        list;   /* lists of struct nfs_read_data */
-        struct nfs_page         *req;   /* multi ops per nfs_page */
         struct page             **pagevec;
         unsigned int            npages; /* Max length of pagevec */
         struct nfs_readargs args;
         struct nfs_readres  res;
         unsigned long           timestamp;      /* For lease renewal */
-        struct pnfs_layout_segment *lseg;
-        struct nfs_client       *ds_clp;        /* pNFS data server */
-        const struct rpc_call_ops *mds_ops;
         int (*read_done_cb) (struct rpc_task *task, struct nfs_read_data *data);
         __u64                   mds_offset;
-        int                     pnfs_error;
         struct page             *page_array[NFS_PAGEVEC_SIZE];
+        struct nfs_client       *ds_clp;        /* pNFS data server */
+};
+
+struct nfs_pgio_header {
+        struct inode            *inode;
+        struct rpc_cred         *cred;
+        struct list_head        pages;
+        struct nfs_page         *req;
+        struct pnfs_layout_segment *lseg;
+        const struct rpc_call_ops *mds_ops;
+        int                     pnfs_error;
+};
+
+struct nfs_read_header {
+        struct nfs_pgio_header  header;
+        struct nfs_read_data    rpc_data;
 };
 
 struct nfs_direct_req;
 
 struct nfs_write_data {
+        struct nfs_pgio_header  *header;
+        struct list_head        list;
         struct rpc_task         task;
-        struct inode            *inode;
-        struct rpc_cred         *cred;
         struct nfs_fattr        fattr;
         struct nfs_writeverf    verf;
-        struct list_head        pages;          /* Coalesced requests we wish to flush */
-        struct list_head        list;           /* lists of struct nfs_write_data */
-        struct nfs_page         *req;           /* multi ops per nfs_page */
         struct page             **pagevec;
         unsigned int            npages;         /* Max length of pagevec */
         struct nfs_writeargs    args;           /* argument struct */
         struct nfs_writeres     res;            /* result struct */
-        struct pnfs_layout_segment *lseg;
-        struct nfs_client       *ds_clp;        /* pNFS data server */
-        const struct rpc_call_ops *mds_ops;
-        int (*write_done_cb) (struct rpc_task *task, struct nfs_write_data *data);
-#ifdef CONFIG_NFS_V4
         unsigned long           timestamp;      /* For lease renewal */
-#endif
+        int (*write_done_cb) (struct rpc_task *task, struct nfs_write_data *data);
         __u64                   mds_offset;     /* Filelayout dense stripe */
-        int                     pnfs_error;
         struct page             *page_array[NFS_PAGEVEC_SIZE];
+        struct nfs_client       *ds_clp;        /* pNFS data server */
+};
+
+struct nfs_write_header {
+        struct nfs_pgio_header  header;
+        struct nfs_write_data   rpc_data;
 };
 
 struct nfs_commit_data {