[3/3] iscsi: add iscsi=<iscsi-id> option

Commit Message

Stefan Hajnoczi Sept. 7, 2016, 9:23 p.m. UTC

An iSCSI block driver instance is implicitly matched with an -iscsi
object that has id=<target-iqn>.  If no -iscsi object with that id
exists then the first -iscsi object is used.

This patch adds a -drive ...,iscsi=<iscsi-id> option so the relationship
between the block driver instance and an -iscsi object can be specified
explicitly.  When the iscsi=<iscsi-id> parameter is used there is no
fallback to the first -iscsi option (which is weird legacy behavior).

This makes it possible to connect to multiple LUNs on the same target
with different credentials whereas previously the same -iscsi object
would be associated with all block driver instances for that iSCSI
target.

Example:

  $ qemu-system-x86_64 -iscsi id=test,user=foo,password=x,\
          initiator-name=iqn.2001-04.com.example:my-initiator \
          -drive driver=iscsi,filename=iscsi://127.0.0.1/iqn.2003-01.org.linux-iscsi.test.x8664:sn.d964cc832811/0,iscsi=test

Signed-off-by: Stefan Hajnoczi <[e-mail]>
---
 block/iscsi.c   | 21 ++++++++++++++-------
 qemu-options.hx |  8 ++++++--
 2 files changed, 20 insertions(+), 9 deletions(-)

Patch

diff --git a/block/iscsi.c b/block/iscsi.c
index 4eb9a36..b5a813f 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -1199,7 +1199,7 @@  retry:
 }
 
 /* Look up the -iscsi command-line option */
-static QemuOpts *find_iscsi_opts(const char *id)
+static QemuOpts *find_iscsi_opts(const char *id, bool default_to_first)
 {
     QemuOptsList *list;
     QemuOpts *opts;
@@ -1210,13 +1210,9 @@  static QemuOpts *find_iscsi_opts(const char *id)
     }
 
     opts = qemu_opts_find(list, id);
-    if (opts == NULL) {
+    if (opts == NULL && default_to_first) {
         opts = QTAILQ_FIRST(&list->head);
-        if (!opts) {
-            return NULL;
-        }
     }
-
     return opts;
 }
 
@@ -1411,6 +1407,11 @@  static QemuOptsList runtime_opts = {
             .type = QEMU_OPT_STRING,
             .help = "URL to the iscsi image",
         },
+        {
+            .name = "iscsi",
+            .type = QEMU_OPT_STRING,
+            .help = "id of iscsi object",
+        },
         { /* end of list */ }
     },
 };
@@ -1550,6 +1551,7 @@  static int iscsi_open(BlockDriverState *bs, QDict *options, int flags,
     QemuOpts *iscsi_opts;
     Error *local_err = NULL;
     const char *filename;
+    const char *iscsi_opts_id;
     int i, ret = 0, timeout = 0;
 
     opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
@@ -1571,7 +1573,12 @@  static int iscsi_open(BlockDriverState *bs, QDict *options, int flags,
 
     memset(iscsilun, 0, sizeof(IscsiLun));
 
-    iscsi_opts = find_iscsi_opts(iscsi_url->target);
+    iscsi_opts_id = qemu_opt_get(opts, "iscsi");
+    if (iscsi_opts_id) {
+        iscsi_opts = find_iscsi_opts(iscsi_opts_id, false);
+    } else {
+        iscsi_opts = find_iscsi_opts(iscsi_url->target, true);
+    }
 
     initiator_name = parse_initiator_name(iscsi_opts);
 
diff --git a/qemu-options.hx b/qemu-options.hx
index a71aaf8..89da93d 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2515,14 +2515,18 @@  LIBISCSI_CHAP_PASSWORD="password" \
 qemu-system-i386 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
 @end example
 
+An iSCSI drive is associated with an -iscsi option as follows.  If -drive
+...,iscsi=<iscsi-id> is present then the -iscsi option with that id is used.
+Otherwise an -iscsi option whose id matches the drive's target IQN is searched
+and if the search fails the first -iscsi option is used.
+
 iSCSI support is an optional feature of QEMU and only available when
 compiled and linked against libiscsi.
 ETEXI
 DEF("iscsi", HAS_ARG, QEMU_OPTION_iscsi,
     "-iscsi [user=user][,password=password]\n"
     "       [,header-digest=CRC32C|CR32C-NONE|NONE-CRC32C|NONE\n"
-    "       [,initiator-name=initiator-iqn][,id=target-iqn]\n"
-    "       [,timeout=timeout]\n"
+    "       [,initiator-name=initiator-iqn][,id=id][,timeout=timeout]\n"
     "                iSCSI session parameters\n", QEMU_ARCH_ALL)
 STEXI