nfsd41: replace page based DRC with buffer based DRC

Use NFSD_SLOT_CACHE_SIZE size buffers for sessions DRC instead of holding nfsd
pages in cache.

Connectathon testing has shown that 1024 bytes for encoded compound operation
responses past the sequence operation is sufficient, 512 bytes is a little too
small. Set NFSD_SLOT_CACHE_SIZE to 1024.

Allocate memory for the session DRC in the CREATE_SESSION operation
to guarantee that the memory resource is available for caching responses.
Allocate each slot individually in preparation for slot table size negotiation.

Remove struct nfsd4_cache_entry and helper functions for the old page-based
DRC.

The iov_len calculation in nfs4svc_encode_compoundres is now always
correct.  Replay is now done in nfsd4_sequence under the state lock, so
the session ref count is only bumped on non-replay. Clean up the
nfs4svc_encode_compoundres session logic.

The nfsd4_compound_state statp pointer is also not used.
Remove nfsd4_set_statp().

Move useful nfsd4_cache_entry fields into nfsd4_slot.

Signed-off-by: Andy Adamson <andros@netapp.com
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 10 insertions, 17 deletions

diff --git a/include/linux/nfsd/state.h b/include/linux/nfsd/state.h
index ff0b771efde6..70ef5f4abbbc 100644
--- a/include/linux/nfsd/state.h
+++ b/include/linux/nfsd/state.h
@@ -94,30 +94,23 @@ struct nfs4_cb_conn {
 
 /* Maximum number of slots per session. 160 is useful for long haul TCP */
 #define NFSD_MAX_SLOTS_PER_SESSION     160
-/* Maximum number of pages per slot cache entry */
-#define NFSD_PAGES_PER_SLOT     1
-#define NFSD_SLOT_CACHE_SIZE            PAGE_SIZE
 /* Maximum number of operations per session compound */
 #define NFSD_MAX_OPS_PER_COMPOUND       16
+/* Maximum  session per slot cache size */
+#define NFSD_SLOT_CACHE_SIZE            1024
 /* Maximum number of NFSD_SLOT_CACHE_SIZE slots per session */
 #define NFSD_CACHE_SIZE_SLOTS_PER_SESSION       32
 #define NFSD_MAX_MEM_PER_SESSION  \
                 (NFSD_CACHE_SIZE_SLOTS_PER_SESSION * NFSD_SLOT_CACHE_SIZE)
 
-struct nfsd4_cache_entry {
-        __be32          ce_status;
-        struct kvec     ce_datav; /* encoded NFSv4.1 data in rq_res.head[0] */
-        struct page     *ce_respages[NFSD_PAGES_PER_SLOT + 1];
-        int             ce_cachethis;
-        short           ce_resused;
-        int             ce_opcnt;
-        int             ce_rpchdrlen;
-};
-
 struct nfsd4_slot {
-        bool                            sl_inuse;
-        u32                             sl_seqid;
-        struct nfsd4_cache_entry        sl_cache_entry;
+        bool    sl_inuse;
+        bool    sl_cachethis;
+        u16     sl_opcnt;
+        u32     sl_seqid;
+        __be32  sl_status;
+        u32     sl_datalen;
+        char    sl_data[];
 };
 
 struct nfsd4_channel_attrs {
@@ -159,7 +152,7 @@ struct nfsd4_session {
         struct nfs4_sessionid   se_sessionid;
         struct nfsd4_channel_attrs se_fchannel;
         struct nfsd4_channel_attrs se_bchannel;
-        struct nfsd4_slot       se_slots[];     /* forward channel slots */
+        struct nfsd4_slot       *se_slots[];    /* forward channel slots */
 };
 
 static inline void