[PATCH v2 3/4] conf: add 'multidevs' option

Introduce new 'multidevs' option for filesystem. <filesystem type='mount' accessmode='mapped' multidevs='remap'> <source dir='/path'/> <target dir='mount_tag'> </filesystem> This option prevents misbehaviours on guest if a qemu 9pfs export contains multiple devices, due to the potential file ID collisions this otherwise may cause. Signed-off-by: Christian Schoenebeck <qemu_oss(a)crudebyte.com&gt; --- docs/formatdomain.html.in | 40 ++++++++++++++++++++++++++++++++++- docs/schemas/domaincommon.rng | 10 +++++++++ src/conf/domain_conf.c | 29 +++++++++++++++++++++++++ src/conf/domain_conf.h | 13 ++++++++++++ 4 files changed, 91 insertions(+), 1 deletion(-) diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in index cc2c671c14..13c506988b 100644 --- a/docs/formatdomain.html.in +++ b/docs/formatdomain.html.in @@ -3967,7 +3967,7 @@ &lt;source name='my-vm-template'/&gt; &lt;target dir='/'/&gt; &lt;/filesystem&gt; - &lt;filesystem type='mount' accessmode='passthrough'&gt; + &lt;filesystem type='mount' accessmode='passthrough' multidevs='remap'&gt; &lt;driver type='path' wrpolicy='immediate'/&gt; &lt;source dir='/export/to/guest'/&gt; &lt;target dir='/import/from/host'/&gt; @@ -4092,6 +4092,44 @@ for more details. </p> + <p> + The filesystem element has an optional attribute <code>multidevs</code> + which specifies how to deal with a filesystem export containing more than + one device, in order to avoid file ID collisions on guest when using 9pfs + (<span class="since">since 6.2.0, requires QEMU 4.2</span>). + This attribute is not available for virtiofs. The possible values are: + </p> + + <dl> + <dt><code>default</code></dt> + <dd> + Use QEMU's default setting (which currently is <code>warn</code>). + </dd> + <dt><code>remap</code></dt> + <dd> + This setting allows guest to access multiple devices per export without + encountering misbehaviours. Inode numbers from host are automatically + remapped on guest to actively prevent file ID collisions if guest + accesses one export containing multiple devices. + </dd> + <dt><code>forbid</code></dt> + <dd> + Only allow to access one device per export by guest. Attempts to access + additional devices on the same export will cause the individual + filesystem access by guest to fail with an error and being logged (once) + as error on host side. + </dd> + <dt><code>warn</code></dt> + <dd> + This setting resembles the behaviour of 9pfs prior to QEMU 4.2, that is + no action is performed to prevent any potential file ID collisions if an + export contains multiple devices, with the only exception: a warning is + logged (once) on host side now. This setting may lead to misbehaviours + on guest side if more than one device is exported per export, due to the + potential file ID collisions this may cause on guest side in that case. + </dd> + </dl> + </dd> <p> diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng index 6805420451..9b37740e30 100644 --- a/docs/schemas/domaincommon.rng +++ b/docs/schemas/domaincommon.rng @@ -2676,6 +2676,16 @@ </choice> </attribute> </optional> + <optional> + <attribute name="multidevs"> + <choice> + <value>default</value> + <value>remap</value> + <value>forbid</value> + <value>warn</value> + </choice> + </attribute> + </optional> <optional> <element name='readonly'> <empty/> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index 71535f53f5..6a9a7dd0bb 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -501,6 +501,14 @@ VIR_ENUM_IMPL(virDomainFSModel, "virtio-non-transitional", ); +VIR_ENUM_IMPL(virDomainFSMultidevs, + VIR_DOMAIN_FS_MULTIDEVS_LAST, + "default", + "remap", + "forbid", + "warn", +); + VIR_ENUM_IMPL(virDomainFSCacheMode, VIR_DOMAIN_FS_CACHE_MODE_LAST, "default", @@ -11376,6 +11384,7 @@ virDomainFSDefParseXML(virDomainXMLOptionPtr xmlopt, g_autofree char *usage = NULL; g_autofree char *units = NULL; g_autofree char *model = NULL; + g_autofree char *multidevs = NULL; ctxt->node = node; @@ -11414,6 +11423,17 @@ virDomainFSDefParseXML(virDomainXMLOptionPtr xmlopt, } } + multidevs = virXMLPropString(node, "multidevs"); + if (multidevs) { + if ((def->multidevs = virDomainFSMultidevsTypeFromString(multidevs)) < 0) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, + _("unknown multidevs '%s'"), multidevs); + goto error; + } + } else { + def->multidevs = VIR_DOMAIN_FS_MULTIDEVS_DEFAULT; + } + if (virDomainParseScaledValue("./space_hard_limit[1]", NULL, ctxt, &def->space_hard_limit, 1, ULLONG_MAX, false) < 0) @@ -25397,6 +25417,7 @@ virDomainFSDefFormat(virBufferPtr buf, const char *accessmode = virDomainFSAccessModeTypeToString(def->accessmode); const char *fsdriver = virDomainFSDriverTypeToString(def->fsdriver); const char *wrpolicy = virDomainFSWrpolicyTypeToString(def->wrpolicy); + const char *multidevs = virDomainFSMultidevsTypeToString(def->multidevs); const char *src = def->src->path; g_auto(virBuffer) driverAttrBuf = VIR_BUFFER_INITIALIZER; g_auto(virBuffer) driverBuf = VIR_BUFFER_INIT_CHILD(buf); @@ -25415,6 +25436,12 @@ virDomainFSDefFormat(virBufferPtr buf, return -1; } + if (!multidevs) { + virReportError(VIR_ERR_INTERNAL_ERROR, + _("unexpected multidevs %d"), def->multidevs); + return -1; + } + virBufferAsprintf(buf, "<filesystem type='%s' accessmode='%s'", type, accessmode); @@ -25422,6 +25449,8 @@ virDomainFSDefFormat(virBufferPtr buf, virBufferAsprintf(buf, " model='%s'", virDomainFSModelTypeToString(def->model)); } + if (def->multidevs) + virBufferAsprintf(buf, " multidevs='%s'", multidevs); virBufferAddLit(buf, ">\n"); virBufferAdjustIndent(buf, 2); diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h index 91b776c28a..23b7924781 100644 --- a/src/conf/domain_conf.h +++ b/src/conf/domain_conf.h @@ -796,6 +796,18 @@ typedef enum { VIR_DOMAIN_FS_WRPOLICY_LAST } virDomainFSWrpolicy; +/* How to handle exports containing multiple devices. */ +typedef enum { + VIR_DOMAIN_FS_MULTIDEVS_DEFAULT = 0, /* Use QEMU's default setting */ + VIR_DOMAIN_FS_MULTIDEVS_REMAP, /* Remap inodes from host to guest */ + VIR_DOMAIN_FS_MULTIDEVS_FORBID, /* Prohibit more than one device */ + VIR_DOMAIN_FS_MULTIDEVS_WARN, /* Just log a warning if multiple devices */ + + VIR_DOMAIN_FS_MULTIDEVS_LAST +} virDomainFSMultidevs; + +VIR_ENUM_DECL(virDomainFSMultidevs); + typedef enum { VIR_DOMAIN_FS_MODEL_DEFAULT = 0, VIR_DOMAIN_FS_MODEL_VIRTIO, @@ -820,6 +832,7 @@ struct _virDomainFSDef { int wrpolicy; /* enum virDomainFSWrpolicy */ int format; /* virStorageFileFormat */ int model; /* virDomainFSModel */ + int multidevs; /* virDomainFSMultidevs */ unsigned long long usage; /* in bytes */ virStorageSourcePtr src; char *dst; -- 2.20.1