Re: [libvirt] [PATCH v4 3/4] nwfilter: Convert _virNWFilterObjList to use virObjectRWLockable

Wednesday, 31 January 2018

On 12/08/2017 09:01 AM, John Ferlan wrote:
...
 Implement the self locking object list for nwfilter object lists
 that uses two hash tables to store the nwfilter object by UUID or
 by Name.

 As part of this alter the uuid argument to virNWFilterObjLookupByUUID
 to expect an already formatted uuidstr.

 Alter the existing list traversal code to implement the hash table
 find/lookup/search functionality.

 Signed-off-by: John Ferlan <jferlan(a)redhat.com&gt;
 ---
   src/conf/virnwfilterobj.c      | 402 ++++++++++++++++++++++++++++-------------
   src/conf/virnwfilterobj.h      |   2 +-
   src/nwfilter/nwfilter_driver.c |   5 +-
   3 files changed, 282 insertions(+), 127 deletions(-)

 diff --git a/src/conf/virnwfilterobj.c b/src/conf/virnwfilterobj.c
 index 6b4758656..a4e6a03d2 100644
 --- a/src/conf/virnwfilterobj.c
 +++ b/src/conf/virnwfilterobj.c
 @@ -43,12 +43,21 @@ struct _virNWFilterObj {
   };

   struct _virNWFilterObjList {
 -    size_t count;
 -    virNWFilterObjPtr *objs;
 +    virObjectRWLockable parent;
 +
 +    /* uuid string -> virNWFilterObj  mapping
 +     * for O(1), lockless lookup-by-uuid */
 +    virHashTable *objs;
 +
 +    /* name -> virNWFilterObj mapping for O(1),
 +     * lockless lookup-by-name */
 +    virHashTable *objsName;
   };

   static virClassPtr virNWFilterObjClass;
 +static virClassPtr virNWFilterObjListClass;
   static void virNWFilterObjDispose(void *opaque);
 +static void virNWFilterObjListDispose(void *opaque);

   static int
 @@ -60,6 +69,12 @@ virNWFilterObjOnceInit(void)
                                               virNWFilterObjDispose)))
           return -1;

 +    if (!(virNWFilterObjListClass = virClassNew(virClassForObjectRWLockable(),
 +                                                "virNWFilterObjList",
 +                                                sizeof(virNWFilterObjList),
 +                                                virNWFilterObjListDispose)))
 +        return -1;
 +
       return 0;
   }

 @@ -144,14 +159,20 @@ virNWFilterObjDispose(void *opaque)
   }

 +static void
 +virNWFilterObjListDispose(void *opaque)
 +{
 +    virNWFilterObjListPtr nwfilters = opaque;
 +
 +    virHashFree(nwfilters->objs);
 +    virHashFree(nwfilters->objsName);
 +}
 +
 +
   void
   virNWFilterObjListFree(virNWFilterObjListPtr nwfilters)
   {
 -    size_t i;
 -    for (i = 0; i < nwfilters->count; i++)
 -        virObjectUnref(nwfilters->objs[i]);
 -    VIR_FREE(nwfilters->objs);
 -    VIR_FREE(nwfilters);
 +    virObjectUnref(nwfilters);
   }

 @@ -160,8 +181,23 @@ virNWFilterObjListNew(void)
   {
       virNWFilterObjListPtr nwfilters;

 -    if (VIR_ALLOC(nwfilters) < 0)
 +    if (virNWFilterObjInitialize() < 0)
 +        return NULL;
 +
 +    if (!(nwfilters = virObjectRWLockableNew(virNWFilterObjListClass)))
 +        return NULL;
 +
 +    if (!(nwfilters->objs = virHashCreate(10, virObjectFreeHashData))) {
 +        virObjectUnref(nwfilters);
 +        return NULL;
 +    }
 +
 +    if (!(nwfilters->objsName = virHashCreate(10, virObjectFreeHashData))) {
 +        virHashFree(nwfilters->objs);
 +        virObjectUnref(nwfilters);
           return NULL;
 +    }
 +
       return nwfilters;
   }

 @@ -170,83 +206,105 @@ void
   virNWFilterObjListRemove(virNWFilterObjListPtr nwfilters,
                            virNWFilterObjPtr obj)
   {
 -    size_t i;
 -
 -    virObjectRWUnlock(obj);
 +    char uuidstr[VIR_UUID_STRING_BUFLEN];
 +    virNWFilterDefPtr def;

 -    for (i = 0; i < nwfilters->count; i++) {
 -        virObjectRWLockWrite(nwfilters->objs[i]);
 -        if (nwfilters->objs[i] == obj) {
 -            virObjectRWUnlock(nwfilters->objs[i]);
 -            virObjectUnref(nwfilters->objs[i]);
 +    if (!obj)
 +        return;
 +    def = obj->def;

 -            VIR_DELETE_ELEMENT(nwfilters->objs, i, nwfilters->count);
 -            break;
 -        }
 -        virObjectRWUnlock(nwfilters->objs[i]);
 -    }
 +    virUUIDFormat(def->uuid, uuidstr);
 +    virObjectRef(obj);
 +    virObjectRWUnlock(obj);
 +    virObjectRWLockWrite(nwfilters);
 +    virObjectRWLockWrite(obj);
 +    virHashRemoveEntry(nwfilters->objs, uuidstr); Unref here after successful
removal from hash bucket?
...
 +    virHashRemoveEntry(nwfilters->objsName, def->name);
Again unref here after successful removal ?
...
 +    virObjectRWUnlock(obj);
 +    virObjectUnref(obj);
 +    virObjectRWUnlock(nwfilters);
   }

   /**
 - * virNWFilterObjListFindByUUID
 + * virNWFilterObjListFindByUUID[Locked]
    * @nwfilters: Pointer to filter list
 - * @uuid: UUID to use to lookup the object
 + * @uuidstr: UUID to use to lookup the object
 + *
 + * The static [Locked] version would only be used when the Object List is
 + * already locked, such as is the case during virNWFilterObjListAssignDef.
 + * The caller is thus responsible for locking the object.
    *
    * Search for the object by uuidstr in the hash table and return a read
    * locked copy of the object.
    *
 + * Returns: A reffed object or NULL on error
 + */
 +static virNWFilterObjPtr
 +virNWFilterObjListFindByUUIDLocked(virNWFilterObjListPtr nwfilters,
 +                                   const char *uuidstr)
 +{
 +    return virObjectRef(virHashLookup(nwfilters->objs, uuidstr));
 +}
 +
 +
 +/*
    * Returns: A reffed and read locked object or NULL on error
    */
   virNWFilterObjPtr
   virNWFilterObjListFindByUUID(virNWFilterObjListPtr nwfilters,
 -                             const unsigned char *uuid)
 +                             const char *uuidstr)
   {
 -    size_t i;
       virNWFilterObjPtr obj;
 -    virNWFilterDefPtr def;

 -    for (i = 0; i < nwfilters->count; i++) {
 -        obj = nwfilters->objs[i];
 +    virObjectRWLockRead(nwfilters);
 +    obj = virNWFilterObjListFindByUUIDLocked(nwfilters, uuidstr);
 +    virObjectRWUnlock(nwfilters);
 +    if (obj)
           virObjectRWLockRead(obj);
 -        def = obj->def;
 -        if (!memcmp(def->uuid, uuid, VIR_UUID_BUFLEN))
 -            return virObjectRef(obj);
 -        virObjectRWUnlock(obj);
 -    }

 -    return NULL;
 +    return obj;
   }

   /**
 - * virNWFilterObjListFindByName
 + * virNWFilterObjListFindByName[Locked]
    * @nwfilters: Pointer to filter list
    * @name: filter name to use to lookup the object
    *
 + * The static [Locked] version would only be used when the Object List is
 + * already locked, such as is the case during virNWFilterObjListAssignDef.
 + * The caller is thus responsible for locking the object.
 + *
    * Search for the object by name in the hash table and return a read
    * locked copy of the object.
    *
 + * Returns: A reffed object or NULL on error
 + */
 +static virNWFilterObjPtr
 +virNWFilterObjListFindByNameLocked(virNWFilterObjListPtr nwfilters,
 +                                   const char *name)
 +{
 +    return virObjectRef(virHashLookup(nwfilters->objsName, name));
 +}
 +
 +
 +/*
    * Returns: A reffed and read locked object or NULL on error
    */
   virNWFilterObjPtr
   virNWFilterObjListFindByName(virNWFilterObjListPtr nwfilters,
                                const char *name)
   {
 -    size_t i;
       virNWFilterObjPtr obj;
 -    virNWFilterDefPtr def;

 -    for (i = 0; i < nwfilters->count; i++) {
 -        obj = nwfilters->objs[i];
 +    virObjectRWLockRead(nwfilters);
 +    obj = virNWFilterObjListFindByNameLocked(nwfilters, name);
 +    virObjectRWUnlock(nwfilters);
 +    if (obj)
           virObjectRWLockRead(obj);
 -        def = obj->def;
 -        if (STREQ_NULLABLE(def->name, name))
 -            return virObjectRef(obj);
 -        virObjectRWUnlock(obj);
 -    }

 -    return NULL;
 +    return obj;
   }

 @@ -391,8 +449,11 @@ virNWFilterObjListAssignDef(virNWFilterObjListPtr nwfilters,
   {
       virNWFilterObjPtr obj;
       virNWFilterDefPtr objdef;
 +    char uuidstr[VIR_UUID_STRING_BUFLEN];

 -    if ((obj = virNWFilterObjListFindByUUID(nwfilters, def->uuid))) {
 +    virUUIDFormat(def->uuid, uuidstr);
 +
 +    if ((obj = virNWFilterObjListFindByUUID(nwfilters, uuidstr))) {
           objdef = obj->def;

           if (STRNEQ(def->name, objdef->name)) {
 @@ -406,10 +467,7 @@ virNWFilterObjListAssignDef(virNWFilterObjListPtr nwfilters,
           virNWFilterObjEndAPI(&obj);
       } else {
           if ((obj = virNWFilterObjListFindByName(nwfilters, def->name))) {
 -            char uuidstr[VIR_UUID_STRING_BUFLEN];
 -
               objdef = obj->def;
 -            virUUIDFormat(objdef->uuid, uuidstr);
               virReportError(VIR_ERR_OPERATION_FAILED,
                              _("filter '%s' already exists with uuid
%s"),
                              def->name, uuidstr);
 @@ -424,11 +482,13 @@ virNWFilterObjListAssignDef(virNWFilterObjListPtr nwfilters,
           return NULL;
       }

 -
 -    /* Get a READ lock and immediately promote to WRITE while we adjust
 -     * data within. */
 -    if ((obj = virNWFilterObjListFindByName(nwfilters, def->name))) {
 -        virNWFilterObjPromoteToWrite(obj);
 +    /* We're about to make some changes to objects on the list - so get
 +     * the list READ lock in order to Find the object and WRITE lock it
 +     * while we adjust data within. */
 +    virObjectRWLockRead(nwfilters);
 +    if ((obj = virNWFilterObjListFindByNameLocked(nwfilters, def->name))) {
 +        virObjectRWUnlock(nwfilters);
 +        virObjectRWLockWrite(obj);

           objdef = obj->def;
           if (virNWFilterDefEqual(def, objdef)) { 
I think you should have left the above PromoteToWrite(obj) rather than 
doing a virObjectRWLockWrite(obj) now and would then adapt the code here 
as mentioned in review of 2/4.

...
 @@ -458,37 +518,112 @@
virNWFilterObjListAssignDef(virNWFilterObjListPtr nwfilters,
           return obj;
       }

 +    /* Promote the nwfilters to add a new object */
 +    virObjectRWUnlock(nwfilters);
 +    virObjectRWLockWrite(nwfilters);
       if (!(obj = virNWFilterObjNew()))
 -        return NULL;
 +        goto cleanup;

 -    if (VIR_APPEND_ELEMENT_COPY(nwfilters->objs,
 -                                nwfilters->count, obj) < 0) {
 -        virNWFilterObjEndAPI(&obj);
 -        return NULL;
 +    if (virHashAddEntry(nwfilters->objs, uuidstr, obj) < 0)
 +        goto error;
 +    virObjectRef(obj); 
good, here you take a reference because obj ended in the hash bucket. 
Therefore, further above, you have to unref when taking it out of the 
hash bucket.

...
 +
 +    if (virHashAddEntry(nwfilters->objsName, def->name, obj) < 0) {
 +        virHashRemoveEntry(nwfilters->objs, uuidstr);
 +        goto error;
       }
 +    virObjectRef(obj);
 + Same comment here. Looks also better to me since taking the reference is 
done 'closer' to virHashAddEntry() call.

...
       obj->def = def;

 -    return virObjectRef(obj);
 + cleanup:
 +    virObjectRWUnlock(nwfilters);
 +    return obj;
 +
 + error:
 +    virObjectRWUnlock(obj);
 +    virObjectUnref(obj);
 +    virObjectRWUnlock(nwfilters);
 +    return NULL;
   }

 +struct virNWFilterCountData {
 +    virConnectPtr conn;
 +    virNWFilterObjListFilter filter;
 +    int nelems;
 +};
 +
 +static int
 +virNWFilterObjListNumOfNWFiltersCallback(void *payload,
 +                                         const void *name ATTRIBUTE_UNUSED,
 +                                         void *opaque)
 +{
 +    virNWFilterObjPtr obj = payload;
 +    struct virNWFilterCountData *data = opaque;
 +
 +    virObjectRWLockRead(obj);
 +    if (!data->filter || data->filter(data->conn, obj->def))
 +        data->nelems++;
 +    virObjectRWUnlock(obj);
 +    return 0;
 +}
 +
   int
   virNWFilterObjListNumOfNWFilters(virNWFilterObjListPtr nwfilters,
                                    virConnectPtr conn,
                                    virNWFilterObjListFilter filter)
   {
 -    size_t i;
 -    int nfilters = 0;
 +    struct virNWFilterCountData data = { .conn = conn,
 +        .filter = filter, .nelems = 0 }; 
style: one of these per line ?

...

 -    for (i = 0; i < nwfilters->count; i++) {
 -        virNWFilterObjPtr obj = nwfilters->objs[i];
 -        virObjectRWLockRead(obj);
 -        if (!filter || filter(conn, obj->def))
 -            nfilters++;
 -        virObjectRWUnlock(obj);
 +    virObjectRWLockRead(nwfilters);
 +    virHashForEach(nwfilters->objs, virNWFilterObjListNumOfNWFiltersCallback,
 +                   &data);
 +    virObjectRWUnlock(nwfilters);
 +
 +    return data.nelems;
 +}
 +
 +
 +struct virNWFilterListData {
 +    virConnectPtr conn;
 +    virNWFilterObjListFilter filter;
 +    int nelems;
 +    char **elems;
 +    int maxelems;
 +    bool error;
 +};
 +
 +static int
 +virNWFilterObjListGetNamesCallback(void *payload,
 +                                   const void *name ATTRIBUTE_UNUSED,
 +                                   void *opaque)
 +{
 +    virNWFilterObjPtr obj = payload;
 +    virNWFilterDefPtr def;
 +    struct virNWFilterListData *data = opaque;
 +
 +    if (data->error)
 +        return 0;
 +
 +    if (data->maxelems >= 0 && data->nelems == data->maxelems)
 +        return 0;
 +
 +    virObjectRWLockRead(obj);
 +    def = obj->def;
 +
 +    if (!data->filter || data->filter(data->conn, def)) {
 +        if (VIR_STRDUP(data->elems[data->nelems], def->name) < 0) {
 +            data->error = true;
 +            goto cleanup;
 +        }
 +        data->nelems++;
       }

 -    return nfilters;
 + cleanup:
 +    virObjectRWUnlock(obj);
 +    return 0;
   }

 @@ -499,82 +634,103 @@ virNWFilterObjListGetNames(virNWFilterObjListPtr nwfilters,
                              char **const names,
                              int maxnames)
   {
 -    int nnames = 0;
 -    size_t i;
 -    virNWFilterDefPtr def;
 +    struct virNWFilterListData data = { .conn = conn, .filter = filter,
 +        .nelems = 0, .elems = names, .maxelems = maxnames, .error = false };

 -    for (i = 0; i < nwfilters->count && nnames < maxnames; i++) {
 -        virNWFilterObjPtr obj = nwfilters->objs[i];
 -        virObjectRWLockRead(obj);
 -        def = obj->def;
 -        if (!filter || filter(conn, def)) {
 -            if (VIR_STRDUP(names[nnames], def->name) < 0) {
 -                virObjectRWUnlock(obj);
 -                goto failure;
 -            }
 -            nnames++;
 -        }
 -        virObjectRWUnlock(obj);
 -    }
 +    virObjectRWLockRead(nwfilters);
 +    virHashForEach(nwfilters->objs, virNWFilterObjListGetNamesCallback, &data);
 +    virObjectRWUnlock(nwfilters);

 -    return nnames;
 +    if (data.error)
 +        goto error;

 - failure:
 -    while (--nnames >= 0)
 -        VIR_FREE(names[nnames]);
 +    return data.nelems;

 + error:
 +    while (--data.nelems >= 0)
 +        VIR_FREE(data.elems[data.nelems]);
       return -1;
   }

 +struct virNWFilterExportData {
 +    virConnectPtr conn;
 +    virNWFilterObjListFilter filter;
 +    virNWFilterPtr *filters;
 +    int nfilters;
 +    bool error;
 +};
 +
 +static int
 +virNWFilterObjListExportCallback(void *payload,
 +                                 const void *name ATTRIBUTE_UNUSED,
 +                                 void *opaque)
 +{
 +    virNWFilterObjPtr obj = payload;
 +     virNWFilterDefPtr def;
 + nit: indentation error

...
 +    struct virNWFilterExportData *data = opaque;
 +    virNWFilterPtr nwfilter;
 +
 +    if (data->error)
 +        return 0;
 +
 +    virObjectRWLockRead(obj);
 +    def = obj->def;
 +
 +    if (data->filter && !data->filter(data->conn, def))
 +        goto cleanup;
 +
 +    if (!data->filters) {
 +        data->nfilters++;
 +        goto cleanup;
 +    }
 +
 +    if (!(nwfilter = virGetNWFilter(data->conn, def->name, def->uuid))) {
 +        data->error = true;
 +        goto cleanup;
 +    }
 +    data->filters[data->nfilters++] = nwfilter;
 +
 + cleanup:
 +    virObjectRWUnlock(obj);
 +    return 0;
 +}
 +
 +
   int
   virNWFilterObjListExport(virConnectPtr conn,
                            virNWFilterObjListPtr nwfilters,
                            virNWFilterPtr **filters,
                            virNWFilterObjListFilter filter)
   {
 -    virNWFilterPtr *tmp_filters = NULL;
 -    int nfilters = 0;
 -    virNWFilterPtr nwfilter = NULL;
 -    virNWFilterObjPtr obj = NULL;
 -    virNWFilterDefPtr def;
 -    size_t i;
 -    int ret = -1;
 +    struct virNWFilterExportData data = { .conn = conn, .filter = filter,
 +        .filters = NULL, .nfilters = 0, .error = false };

 -    if (!filters) {
 -        ret = nwfilters->count;
 -        goto cleanup;
 +    virObjectRWLockRead(nwfilters);
 +    if (filters &&
 +        VIR_ALLOC_N(data.filters, virHashSize(nwfilters->objs) + 1) < 0) {
 +        virObjectRWUnlock(nwfilters);
 +        return -1;
       }

 -    if (VIR_ALLOC_N(tmp_filters, nwfilters->count + 1) < 0)
 -        goto cleanup;
 +    virHashForEach(nwfilters->objs, virNWFilterObjListExportCallback, &data);
 +    virObjectRWUnlock(nwfilters);

 -    for (i = 0; i < nwfilters->count; i++) {
 -        obj = nwfilters->objs[i];
 -        virObjectRWLockRead(obj);
 -        def = obj->def;
 -        if (!filter || filter(conn, def)) {
 -            if (!(nwfilter = virGetNWFilter(conn, def->name, def->uuid))) {
 -                virObjectRWUnlock(obj);
 -                goto cleanup;
 -            }
 -            tmp_filters[nfilters++] = nwfilter;
 -        }
 -        virObjectRWUnlock(obj);
 +    if (data.error)
 +         goto cleanup;
 +
 +    if (data.filters) {
 +        /* trim the array to the final size */
 +        ignore_value(VIR_REALLOC_N(data.filters, data.nfilters + 1)); 
can we ignore errors here and not return -1 in case an error occurs ?

...
 +        *filters = data.filters;
       }

 -    *filters = tmp_filters;
 -    tmp_filters = NULL;
 -    ret = nfilters;
 +    return data.nfilters;

    cleanup:
 -    if (tmp_filters) {
 -        for (i = 0; i < nfilters; i ++)
 -            virObjectUnref(tmp_filters[i]);
 -    }
 -    VIR_FREE(tmp_filters);
 -
 -    return ret;
 +    virObjectListFree(data.filters);
 +    return -1;
   }

 diff --git a/src/conf/virnwfilterobj.h b/src/conf/virnwfilterobj.h
 index 0281bc5f5..cabb42a71 100644
 --- a/src/conf/virnwfilterobj.h
 +++ b/src/conf/virnwfilterobj.h
 @@ -65,7 +65,7 @@ virNWFilterObjListRemove(virNWFilterObjListPtr nwfilters,

   virNWFilterObjPtr
   virNWFilterObjListFindByUUID(virNWFilterObjListPtr nwfilters,
 -                             const unsigned char *uuid);
 +                             const char *uuidstr);

   virNWFilterObjPtr
   virNWFilterObjListFindByName(virNWFilterObjListPtr nwfilters,
 diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c
 index b38740b15..b24f59379 100644
 --- a/src/nwfilter/nwfilter_driver.c
 +++ b/src/nwfilter/nwfilter_driver.c
 @@ -369,11 +369,10 @@ nwfilterObjFromNWFilter(const unsigned char *uuid)
       virNWFilterObjPtr obj;
       char uuidstr[VIR_UUID_STRING_BUFLEN];

 -    if (!(obj = virNWFilterObjListFindByUUID(driver->nwfilters, uuid))) {
 -        virUUIDFormat(uuid, uuidstr);
 +    virUUIDFormat(uuid, uuidstr);
 +    if (!(obj = virNWFilterObjListFindByUUID(driver->nwfilters, uuidstr)))
           virReportError(VIR_ERR_NO_NWFILTER,
                          _("no nwfilter with matching uuid '%s'"),
uuidstr);
 -    }
       return obj;
   }

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Re: [libvirt] [PATCH v4 3/4] nwfilter: Convert _virNWFilterObjList to use virObjectRWLockable