[libvirt] [PATCH v8 2/7] qapi: Introduce add-fd, remove-fd, query-fdsets
Corey Bryant
coreyb at linux.vnet.ibm.com
Fri Aug 10 16:41:03 UTC 2012
On 08/10/2012 12:08 PM, Kevin Wolf wrote:
> Am 10.08.2012 04:10, schrieb Corey Bryant:
>> This patch adds support that enables passing of file descriptors
>> to the QEMU monitor where they will be stored in specified file
>> descriptor sets.
>>
>> A file descriptor set can be used by a client like libvirt to
>> store file descriptors for the same file. This allows the
>> client to open a file with different access modes (O_RDWR,
>> O_WRONLY, O_RDONLY) and add/remove the passed fds to/from an fd
>> set as needed. This will allow QEMU to (in a later patch in this
>> series) "open" and "reopen" the same file by dup()ing the fd in
>> the fd set that corresponds to the file, where the fd has the
>> matching access mode flag that QEMU requests.
>>
>> The new QMP commands are:
>> add-fd: Add a file descriptor to an fd set
>> remove-fd: Remove a file descriptor from an fd set
>> query-fdsets: Return information describing all fd sets
>>
>> Note: These commands are not compatible with the existing getfd
>> and closefd QMP commands.
>>
>> Signed-off-by: Corey Bryant <coreyb at linux.vnet.ibm.com>
>> ---
>> v5:
>> -This patch is new in v5 and replaces the pass-fd QMP command
>> from v4.
>> -By grouping fds in fd sets, we ease managability with an fd
>> set per file, addressing concerns raised in v4 about handling
>> "reopens" and preventing fd leakage. (eblake at redhat.com,
>> kwolf at redhat.com, dberrange at redhat.com)
>>
>> v6
>> -Make @fd optional for remove-fd (eblake at redhat.com)
>> -Make @fdset-id optional for add-fd (eblake at redhat.com)
>>
>> v7:
>> -Share fd sets among all monitor connections (kwolf at redhat.com)
>> -Added mon_refcount to keep track of monitor connection count.
>>
>> v8:
>> -Add opaque string to add-fd/query-fdsets.
>> (stefanha at linux.vnet.ibm.com)
>> -Use camel case for structures. (stefanha at linux.vnet.ibm.com)
>> -Don't return in-use and refcount from query-fdsets.
>> (stefanha at linux.vnet.ibm.com)
>> -Don't return removed fd's from query-fdsets.
>> (stefanha at linux.vnet.ibm.com)
>> -Use fdset-id rather than fdset_id. (eblake at redhat.com)
>> -Fix fd leak in qmp_add_fd(). (stefanha at linux.vnet.ibm.com)
>> -Update QMP errors. (stefanha at linux.vnet.ibm.com, eblake at redhat.com)
>>
>> monitor.c | 188 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> qapi-schema.json | 98 ++++++++++++++++++++++++++++
>> qmp-commands.hx | 117 +++++++++++++++++++++++++++++++++
>> 3 files changed, 403 insertions(+)
>>
>> diff --git a/monitor.c b/monitor.c
>> index 49dccfe..f9a0577 100644
>> --- a/monitor.c
>> +++ b/monitor.c
>> @@ -140,6 +140,24 @@ struct mon_fd_t {
>> QLIST_ENTRY(mon_fd_t) next;
>> };
>>
>> +/* file descriptor associated with a file descriptor set */
>> +typedef struct MonFdsetFd MonFdsetFd;
>> +struct MonFdsetFd {
>> + int fd;
>> + bool removed;
>> + char *opaque;
>> + QLIST_ENTRY(MonFdsetFd) next;
>> +};
>> +
>> +/* file descriptor set containing fds passed via SCM_RIGHTS */
>> +typedef struct MonFdset MonFdset;
>> +struct MonFdset {
>> + int64_t id;
>> + int refcount;
>> + QLIST_HEAD(, MonFdsetFd) fds;
>> + QLIST_ENTRY(MonFdset) next;
>> +};
>> +
>> typedef struct MonitorControl {
>> QObject *id;
>> JSONMessageParser parser;
>> @@ -211,6 +229,8 @@ static inline int mon_print_count_get(const Monitor *mon) { return 0; }
>> #define QMP_ACCEPT_UNKNOWNS 1
>>
>> static QLIST_HEAD(mon_list, Monitor) mon_list;
>> +static QLIST_HEAD(mon_fdsets, MonFdset) mon_fdsets;
>> +static int mon_refcount;
>
> You introduce mon_refcount in this patch and check it against 0 in one
> place, but it never gets changed until patch 3 is applied. Would it make
> sense to do both in the same patch?
Yes, I'll go ahead and move the mon_refcount code from this patch to
patch 3.
--
Regards,
Corey
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