[Qemu-devel] [PATCH 1/2] block/nfs: add support for libnfs pagecache

[Peter Lieven <pl@kamp.de>]

upcoming libnfs will have support for a read cache that can
significantly help to speed up requests since libnfs by design
circumvents the kernel cache.

Example:
 qemu -cdrom nfs://127.0.0.1/iso/my.iso?pagecache=1024

The pagecache parameters takes the maximum amount of pages to
cache.  A page in libnfs is always the NFS_BLKSIZE which is
4KB.

Signed-off-by: Peter Lieven <pl@kamp.de>
---
 block/nfs.c | 40 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 36 insertions(+), 4 deletions(-)

diff --git a/block/nfs.c b/block/nfs.c
index 9f51cc3..975510f 100644
--- a/block/nfs.c
+++ b/block/nfs.c
@@ -1,7 +1,7 @@
 /*
  * QEMU Block driver for native access to files on NFS shares
  *
- * Copyright (c) 2014 Peter Lieven <pl@kamp.de>
+ * Copyright (c) 2014-2016 Peter Lieven <pl@kamp.de>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -38,6 +38,7 @@
 #include <nfsc/libnfs.h>
 
 #define QEMU_NFS_MAX_READAHEAD_SIZE 1048576
+#define QEMU_NFS_MAX_PAGECACHE_SIZE (8388608 / NFS_BLKSIZE)
 #define QEMU_NFS_MAX_DEBUG_LEVEL 2
 
 typedef struct NFSClient {
@@ -278,7 +279,7 @@ static void nfs_file_close(BlockDriverState *bs)
 }
 
 static int64_t nfs_client_open(NFSClient *client, const char *filename,
-                               int flags, Error **errp)
+                               int flags, Error **errp, int open_flags)
 {
     int ret = -EINVAL, i;
     struct stat st;
@@ -336,6 +337,9 @@ static int64_t nfs_client_open(NFSClient *client, const char *filename,
                 val = QEMU_NFS_MAX_READAHEAD_SIZE;
             }
             nfs_set_readahead(client->context, val);
+#ifdef LIBNFS_FEATURE_PAGECACHE
+            nfs_set_pagecache_ttl(client->context, 0);
+#endif
 #endif
 #ifdef LIBNFS_FEATURE_DEBUG
         } else if (!strcmp(qp->p[i].name, "debug")) {
@@ -348,6 +352,21 @@ static int64_t nfs_client_open(NFSClient *client, const char *filename,
             }
             nfs_set_debug(client->context, val);
 #endif
+#ifdef LIBNFS_FEATURE_PAGECACHE
+        } else if (!strcmp(qp->p[i].name, "pagecache")) {
+            if (open_flags & BDRV_O_NOCACHE) {
+                error_setg(errp, "Cannot enable NFS pagecache "
+                                 "if cache.direct = on");
+                goto fail;
+            }
+            if (val > QEMU_NFS_MAX_PAGECACHE_SIZE) {
+                error_report("NFS Warning: Truncating NFS pagecache"
+                             " size to %d pages", QEMU_NFS_MAX_PAGECACHE_SIZE);
+                val = QEMU_NFS_MAX_PAGECACHE_SIZE;
+            }
+            nfs_set_pagecache(client->context, val);
+            nfs_set_pagecache_ttl(client->context, 0);
+#endif
         } else {
             error_setg(errp, "Unknown NFS parameter name: %s",
                        qp->p[i].name);
@@ -418,7 +437,7 @@ static int nfs_file_open(BlockDriverState *bs, QDict *options, int flags,
     }
     ret = nfs_client_open(client, qemu_opt_get(opts, "filename"),
                           (flags & BDRV_O_RDWR) ? O_RDWR : O_RDONLY,
-                          errp);
+                          errp, bs->open_flags);
     if (ret < 0) {
         goto out;
     }
@@ -454,7 +473,7 @@ static int nfs_file_create(const char *url, QemuOpts *opts, Error **errp)
     total_size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
                           BDRV_SECTOR_SIZE);
 
-    ret = nfs_client_open(client, url, O_CREAT, errp);
+    ret = nfs_client_open(client, url, O_CREAT, errp, 0);
     if (ret < 0) {
         goto out;
     }
@@ -530,6 +549,15 @@ static int nfs_reopen_prepare(BDRVReopenState *state,
     return 0;
 }
 
+#ifdef LIBNFS_FEATURE_PAGECACHE
+static void nfs_invalidate_cache(BlockDriverState *bs,
+                                 Error **errp)
+{
+    NFSClient *client = bs->opaque;
+    nfs_pagecache_invalidate(client->context, client->fh);
+}
+#endif
+
 static BlockDriver bdrv_nfs = {
     .format_name                    = "nfs",
     .protocol_name                  = "nfs",
@@ -553,6 +581,10 @@ static BlockDriver bdrv_nfs = {
 
     .bdrv_detach_aio_context        = nfs_detach_aio_context,
     .bdrv_attach_aio_context        = nfs_attach_aio_context,
+
+#ifdef LIBNFS_FEATURE_PAGECACHE
+    .bdrv_invalidate_cache          = nfs_invalidate_cache,
+#endif
 };
 
 static void nfs_block_init(void)
-- 
1.9.1