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Re: [Qemu-devel] [PATCH v2 1/2] block/nfs: Introduce runtime_opts in NFS


From: Peter Lieven
Subject: Re: [Qemu-devel] [PATCH v2 1/2] block/nfs: Introduce runtime_opts in NFS
Date: Tue, 25 Oct 2016 16:25:17 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0

Am 25.10.2016 um 16:02 schrieb Kevin Wolf:
Peter, there is a question for you hidden somewhere below.

Am 24.10.2016 um 21:27 hat Ashijeet Acharya geschrieben:
Make NFS block driver use various fine grained runtime_opts.
Set .bdrv_parse_filename() to nfs_parse_filename() and introduce two
new functions nfs_parse_filename() and nfs_parse_uri() to help parsing
the URI.

Signed-off-by: Ashijeet Acharya <address@hidden>
---
  block/nfs.c | 348 +++++++++++++++++++++++++++++++++++++++++++-----------------
  1 file changed, 253 insertions(+), 95 deletions(-)

diff --git a/block/nfs.c b/block/nfs.c
index 8602a44..666ccf2 100644
--- a/block/nfs.c
+++ b/block/nfs.c
@@ -35,8 +35,12 @@
  #include "qemu/uri.h"
  #include "qemu/cutils.h"
  #include "sysemu/sysemu.h"
+#include "qapi/qmp/qdict.h"
+#include "qapi/qmp/qint.h"
+#include "qapi/qmp/qstring.h"
  #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
@@ -61,6 +65,118 @@ typedef struct NFSRPC {
      NFSClient *client;
  } NFSRPC;
+static int nfs_parse_uri(const char *filename, QDict *options, Error **errp)
+{
+    URI *uri = NULL;
+    QueryParams *qp = NULL;
+    int ret = 0, i;
+
+    uri = uri_parse(filename);
+    if (!uri) {
+        error_setg(errp, "Invalid URI specified");
+        ret = -EINVAL;
+        goto out;
+    }
+    if (strcmp(uri->scheme, "nfs") != 0) {
+        error_setg(errp, "URI scheme must be 'nfs'");
+        ret = -EINVAL;
+        goto out;
+    }
+
+    if (!uri->server) {
+        error_setg(errp, "missing hostname in URI");
+        ret = -EINVAL;
+        goto out;
+    }
+
+    if (!uri->path) {
+        error_setg(errp, "missing file path in URI");
+        ret = -EINVAL;
+        goto out;
+    }
+
+    qp = query_params_parse(uri->query);
+    if (!qp) {
+        error_setg(errp, "could not parse query parameters");
+        ret = -EINVAL;
+        goto out;
+    }
+
+    qdict_put(options, "host", qstring_from_str(uri->server));
+
+    qdict_put(options, "path", qstring_from_str(uri->path));
Just style, but why the empty line between both qdict_put() calls?

+
+    for (i = 0; i < qp->n; i++) {
+        if (!qp->p[i].value) {
+            error_setg(errp, "Value for NFS parameter expected: %s",
+                       qp->p[i].name);
+            goto out;
You need to set ret = -EINVAL here.

+        }
+        if (parse_uint_full(qp->p[i].value, NULL, 0)) {
+            error_setg(errp, "Illegal value for NFS parameter: %s",
+                       qp->p[i].name);
+            goto out;
And here.

+        }
+        if (!strcmp(qp->p[i].name, "uid")) {
+            qdict_put(options, "uid",
+                      qstring_from_str(qp->p[i].value));
+        } else if (!strcmp(qp->p[i].name, "gid")) {
+            qdict_put(options, "gid",
+                      qstring_from_str(qp->p[i].value));
+        } else if (!strcmp(qp->p[i].name, "tcp-syncnt")) {
+            qdict_put(options, "tcp-syncnt",
+                      qstring_from_str(qp->p[i].value));
+        } else if (!strcmp(qp->p[i].name, "readahead")) {
+            qdict_put(options, "readahead",
+                      qstring_from_str(qp->p[i].value));
+        } else if (!strcmp(qp->p[i].name, "pagecache")) {
+            qdict_put(options, "pagecache",
+                      qstring_from_str(qp->p[i].value));
+        } else if (!strcmp(qp->p[i].name, "debug")) {
+            qdict_put(options, "debug",
+                      qstring_from_str(qp->p[i].value));
+        } else {
+            error_setg(errp, "Unknown NFS parameter name: %s",
+                       qp->p[i].name);
+            goto out;
And here.

If you prefer, you can set ret = -EINVAL at the top of the function and
do a ret = 0 only right before out:

+        }
+    }
+out:
+    if (qp) {
+        query_params_free(qp);
+    }
+    if (uri) {
+        uri_free(uri);
+    }
+    return ret;
+}
+
+static void nfs_parse_filename(const char *filename, QDict *options,
+                               Error **errp)
+{
+    int ret = 0;
+
+    if (qdict_haskey(options, "host") ||
+        qdict_haskey(options, "path") ||
+        qdict_haskey(options, "uid") ||
+        qdict_haskey(options, "gid") ||
+        qdict_haskey(options, "tcp-syncnt") ||
+        qdict_haskey(options, "readahead") ||
+        qdict_haskey(options, "pagecache") ||
+        qdict_haskey(options, "debug")) {
+        error_setg(errp, "host/path/uid/gid/tcp-syncnt/readahead/pagecache"
+                         "/debug and a filename may not be used at the same"
+                         " time");
+        return;
+    }
+
+    ret = nfs_parse_uri(filename, options, errp);
+    if (ret < 0) {
+        error_setg(errp, "No valid URL specified");
errp has already been set by nfs_parse_uri(), you must not set it a
second time. Otherwise, this is what you get:

$ x86_64-softmmu/qemu-system-x86_64 -drive file=nfs://foo
qemu-system-x86_64: util/error.c:57: error_setv: Assertion `*errp == ((void 
*)0)' failed.
Aborted

+    }
+    return;
+}
+
  static void nfs_process_read(void *arg);
  static void nfs_process_write(void *arg);
@@ -228,15 +344,49 @@ static int coroutine_fn nfs_co_flush(BlockDriverState *bs)
      return task.ret;
  }
-/* TODO Convert to fine grained options */
  static QemuOptsList runtime_opts = {
      .name = "nfs",
      .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
      .desc = {
          {
-            .name = "filename",
+            .name = "host",
+            .type = QEMU_OPT_STRING,
+            .help = "Host to connect to",
+        },
+        {
+            .name = "path",
              .type = QEMU_OPT_STRING,
-            .help = "URL to the NFS file",
+            .help = "Path of the image on the host",
+        },
+        {
+            .name = "uid",
+            .type = QEMU_OPT_NUMBER,
+            .help = "UID value to use when talking to the server",
+        },
+        {
+            .name = "gid",
+            .type = QEMU_OPT_NUMBER,
+            .help = "GID value to use when talking to the server",
+        },
+        {
+            .name = "tcp-syncnt",
+            .type = QEMU_OPT_NUMBER,
+            .help = "Number of SYNs to send during the session establish",
+        },
+        {
+            .name = "readahead",
+            .type = QEMU_OPT_NUMBER,
+            .help = "Set the readahead size in bytes",
+        },
+        {
+            .name = "pagecache",
+            .type = QEMU_OPT_NUMBER,
+            .help = "Set the pagecache size in bytes",
+        },
+        {
+            .name = "debug",
+            .type = QEMU_OPT_NUMBER,
+            .help = "Set the NFS debug level (max 2)",
          },
          { /* end of list */ }
      },
@@ -279,25 +429,40 @@ static void nfs_file_close(BlockDriverState *bs)
      nfs_client_close(client);
  }
-static int64_t nfs_client_open(NFSClient *client, const char *filename,
+static int64_t nfs_client_open(NFSClient *client, QDict *options,
                                 int flags, Error **errp, int open_flags)
  {
-    int ret = -EINVAL, i;
+    int ret = -EINVAL;
+    QemuOpts *opts = NULL;
+    Error *local_err = NULL;
      struct stat st;
-    URI *uri;
-    QueryParams *qp = NULL;
      char *file = NULL, *strp = NULL;
+    const char *host, *path;
+    unsigned long long val;
- uri = uri_parse(filename);
-    if (!uri) {
-        error_setg(errp, "Invalid URL specified");
-        goto fail;
+    opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto out;
      }
-    if (!uri->server) {
-        error_setg(errp, "Invalid URL specified");
-        goto fail;
+
+    host = qemu_opt_get(opts, "host");
+    if (!host) {
+        ret = -EINVAL;
+        error_setg(errp, "No hostname was specified");
+        goto out;
      }
-    strp = strrchr(uri->path, '/');
+
+    path = qemu_opt_get(opts, "path");
+    if (!path) {
+        ret = -EINVAL;
+        error_setg(errp, "No path was specified");
+        goto out;
+    }
+
+    strp = strrchr(path, '/');
      if (strp == NULL) {
          error_setg(errp, "Invalid URL specified");
          goto fail;
This is inconsistent. Either all error paths before initialising the
context should 'goto fail' anyway (and I'd prefer this), or they should
all 'goto out'. I don't like mixing both.

@@ -311,79 +476,77 @@ static int64_t nfs_client_open(NFSClient *client, const 
char *filename,
          goto fail;
      }
- qp = query_params_parse(uri->query);
-    for (i = 0; i < qp->n; i++) {
-        unsigned long long val;
-        if (!qp->p[i].value) {
-            error_setg(errp, "Value for NFS parameter expected: %s",
-                       qp->p[i].name);
+    if (qemu_opt_get(opts, "uid")) {
+        nfs_set_uid(client->context,
+                    qemu_opt_get_number(opts, "uid", getuid()));
Isn't the getuid() useless here? We already check that an "uid" option
is passed (and I think doing that is correct), so the default is never
used. We could just as well pass 0 as the default.

+    }
+
+    if (qemu_opt_get(opts, "gid")) {
+        nfs_set_gid(client->context,
+                    qemu_opt_get_number(opts, "gid", getgid()));
Here, too.

+    }
+
+    if (qemu_opt_get(opts, "tcp-syncnt")) {
+        nfs_set_tcp_syncnt(client->context,
+                           qemu_opt_get_number(opts, "tcp-syncnt", 0));
+    }
+
+#ifdef LIBNFS_FEATURE_READAHEAD
+    if (qemu_opt_get(opts, "readahead")) {
+        if (open_flags & BDRV_O_NOCACHE) {
+            error_setg(errp, "Cannot enable NFS readahead "
+                             "if cache.direct = on");
              goto fail;
          }
-        if (parse_uint_full(qp->p[i].value, &val, 0)) {
-            error_setg(errp, "Illegal value for NFS parameter: %s",
-                       qp->p[i].name);
-            goto fail;
+        val = qemu_opt_get_number(opts, "readahead", 0);
+        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;
          }
-        if (!strcmp(qp->p[i].name, "uid")) {
-            nfs_set_uid(client->context, val);
-        } else if (!strcmp(qp->p[i].name, "gid")) {
-            nfs_set_gid(client->context, val);
-        } else if (!strcmp(qp->p[i].name, "tcp-syncnt")) {
-            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);
+        nfs_set_readahead(client->context, val);
  #ifdef LIBNFS_FEATURE_PAGECACHE
-            nfs_set_pagecache_ttl(client->context, 0);
+        nfs_set_pagecache_ttl(client->context, 0);
  #endif
-            client->cache_used = true;
+        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;
+    nfs_set_pagecache_ttl(client->context, 0);
We have a functional change here. I'm not completely sure yet whether
you're fixing a bug here or you're just turning one bug into a different
bug, but the old code doesn't look right anyway.

If LIBNFS_FEATURE_READAHEAD was defined, but LIBNFS_FEATURE_PAGECACHE
wasn't, the nfs_set_pagecache_ttl() would end up in the "tcp-syncnt"
option handling, which is probably completely wrong.

I suspect that commit d99b26c4 added the second call accidentally
(intended just a copy and paste of the #ifdef line?) and this line
should simply be dropped.

That line is accidently duplicated, but it has no negative impact since
if LIBNFS_FEATURE_PAGECACHE is defined, LIBNFS_FEATURE_READAHEAD
must be as well.

Peter




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