[Qemu-devel] [PATCH V2 0/2] block/nfs: add support for libnfs pagecache

[Qemu-devel] [PATCH V2 0/2] block/nfs: add support for libnfs pagecache

[Peter Lieven]

this adds support for the upcoming libnfs cachepage to Qemu.
While at it neglect to use readahead if cache.direct is on.

v1->v2: - move the readahead fix to Patch 1 and CC qemu-stable
        - check for changed cache settings in bdrv_reopen_prepare [Jeff]

Peter Lieven (2):
  block/nfs: refuse readahead if cache.direct is on
  block/nfs: add support for libnfs pagecache

 block/nfs.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 51 insertions(+), 4 deletions(-)

-- 
1.9.1

[Qemu-devel] [PATCH V2 1/2] block/nfs: refuse readahead if cache.direct is on

[Peter Lieven]

if we open a NFS export with disabled cache we should refuse
the readahead feature as it will cache data inside libnfs.

If a export was opened with readahead enabled it should
futher not be allowed to disable the cache while running.

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Lieven <pl@kamp.de>
---
 block/nfs.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/block/nfs.c b/block/nfs.c
index 9f51cc3..60be45e 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
@@ -47,6 +47,7 @@ typedef struct NFSClient {
     bool has_zero_init;
     AioContext *aio_context;
     blkcnt_t st_blocks;
+    bool cache_used;
 } NFSClient;
 
 typedef struct NFSRPC {
@@ -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;
@@ -330,12 +331,18 @@ static int64_t nfs_client_open(NFSClient *client, const char *filename,
             nfs_set_tcp_syncnt(client->context, val);
 #ifdef LIBNFS_FEATURE_READAHEAD
         } else if (!strcmp(qp->p[i].name, "readahead")) {
+            if (open_flags & BDRV_O_NOCACHE) {
+                error_setg(errp, "Cannot enable NFS readahead "
+                                 "if cache.direct = on");
+                goto fail;
+            }
             if (val > QEMU_NFS_MAX_READAHEAD_SIZE) {
                 error_report("NFS Warning: Truncating NFS readahead"
                              " size to %d", QEMU_NFS_MAX_READAHEAD_SIZE);
                 val = QEMU_NFS_MAX_READAHEAD_SIZE;
             }
             nfs_set_readahead(client->context, val);
+            client->cache_used = true;
 #endif
 #ifdef LIBNFS_FEATURE_DEBUG
         } else if (!strcmp(qp->p[i].name, "debug")) {
@@ -418,7 +425,7 @@ 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 +461,7 @@ 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;
     }
@@ -516,6 +523,11 @@ static int nfs_reopen_prepare(BDRVReopenState *state,
         return -EACCES;
     }
 
+    if ((state->flags & BDRV_O_NOCACHE) && client->cache_used) {
+        error_setg(errp, "Cannot disable cache if libnfs readahead is enabled");
+        return -EINVAL;
+    }
+
     /* Update cache for read-only reopens */
     if (!(state->flags & BDRV_O_RDWR)) {
         ret = nfs_fstat(client->context, client->fh, &st);
-- 
1.9.1

[Qemu-devel] [PATCH V2 2/2] block/nfs: add support for libnfs pagecache

[Peter Lieven]

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 | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/block/nfs.c b/block/nfs.c
index 60be45e..15d6832 100644
--- a/block/nfs.c
+++ b/block/nfs.c
@@ -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 {
@@ -342,6 +343,26 @@ 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
+            client->cache_used = true;
+#endif
+#ifdef LIBNFS_FEATURE_PAGECACHE
+            nfs_set_pagecache_ttl(client->context, 0);
+        } 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);
             client->cache_used = true;
 #endif
 #ifdef LIBNFS_FEATURE_DEBUG
@@ -524,7 +545,8 @@ static int nfs_reopen_prepare(BDRVReopenState *state,
     }
 
     if ((state->flags & BDRV_O_NOCACHE) && client->cache_used) {
-        error_setg(errp, "Cannot disable cache if libnfs readahead is enabled");
+        error_setg(errp, "Cannot disable cache if libnfs readahead or"
+                         " pagecache is enabled");
         return -EINVAL;
     }
 
@@ -542,6 +564,15 @@ 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",
@@ -565,6 +596,10 @@ 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

Re: [Qemu-devel] [PATCH V2 0/2] block/nfs: add support for libnfs pagecache

[Jeff Cody]

On Thu, May 19, 2016 at 02:48:01PM +0200, Peter Lieven wrote:
> this adds support for the upcoming libnfs cachepage to Qemu.
> While at it neglect to use readahead if cache.direct is on.
> 
> v1->v2: - move the readahead fix to Patch 1 and CC qemu-stable
>         - check for changed cache settings in bdrv_reopen_prepare [Jeff]
> 
> Peter Lieven (2):
>   block/nfs: refuse readahead if cache.direct is on
>   block/nfs: add support for libnfs pagecache
> 
>  block/nfs.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 51 insertions(+), 4 deletions(-)
> 
> -- 
> 1.9.1
>

Reviewed-by: Jeff Cody <jcody@redhat.com>

Re: [Qemu-devel] [PATCH V2 0/2] block/nfs: add support for libnfs pagecache

[Jeff Cody]

On Thu, May 19, 2016 at 02:48:01PM +0200, Peter Lieven wrote:
> this adds support for the upcoming libnfs cachepage to Qemu.
> While at it neglect to use readahead if cache.direct is on.
> 
> v1->v2: - move the readahead fix to Patch 1 and CC qemu-stable
>         - check for changed cache settings in bdrv_reopen_prepare [Jeff]
> 
> Peter Lieven (2):
>   block/nfs: refuse readahead if cache.direct is on
>   block/nfs: add support for libnfs pagecache
> 
>  block/nfs.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 51 insertions(+), 4 deletions(-)
> 
> -- 
> 1.9.1
> 

Thanks,

Applied to my block branch:

git://github.com/codyprime/qemu-kvm-jtc.git block

-Jeff