Re: [RFC 0/4] Generic file system events interface

[Beata Michalska <b.michalska@samsung.com>]

Hi,

On 04/17/2015 10:17 AM, Jan Kara wrote:
>   Hello,
> 
> On Wed 15-04-15 09:15:43, Beata Michalska wrote:
>> The following patchset is a result of previous discussions regarding
>> file system threshold notifiactions. It introduces support for file
>> system event notifications, sent through generic netlinik interface
>> whenever an fs-related event occurs. Included are also some shmem
>> and ext4 changes showing how the new interface might actually be used.
>>
>> The vary idea of using the generic netlink interface has been previoulsy
>> suggested here:  https://lkml.org/lkml/2011/8/18/169
>>
>> The basic description of the new functionality can be found in
>> the first patch from this set - both in the commit message and
>> in the doc file.
>>
>> Some very basic tests have been performed though still this is
>> a PoC version. Below though is a sample user space application
>> which subscribes to the new multicast group and listens for
>> potential fs-related events. The code has been based on libnl 3.4
>> and its test application for the generic netlink.
>   Thanks for the patches! As a general note for the next posting, please CC
> also linux-fsdevel@vger.kernel.org (since this has implications for other
> filesystems as well, specifically I know about XFS guys thinking about some
> notification system as well) and linux-api@vger.kernel.org (since this is a
> new kernel interface to userspace).
> 
> 								Honza

My bad  - with the CC list. Apologies for that.

BR
Beata

>>
>> ---
>>
>> Beata Michalska (4):
>>   fs: Add generic file system event notifications
>>   ext4: Add helper function to mark group as corrupted
>>   ext4: Add support for generic FS events
>>   shmem: Add support for generic FS events
>>
>>  Documentation/filesystems/events.txt |  254 +++++++++++
>>  fs/Makefile                          |    1 +
>>  fs/events/Makefile                   |    6 +
>>  fs/events/fs_event.c                 |  775 ++++++++++++++++++++++++++++++++++
>>  fs/events/fs_event.h                 |   27 ++
>>  fs/events/fs_event_netlink.c         |   94 +++++
>>  fs/ext4/balloc.c                     |   26 +-
>>  fs/ext4/ext4.h                       |   10 +
>>  fs/ext4/ialloc.c                     |    5 +-
>>  fs/ext4/inode.c                      |    2 +-
>>  fs/ext4/mballoc.c                    |   17 +-
>>  fs/ext4/resize.c                     |    1 +
>>  fs/ext4/super.c                      |   43 ++
>>  fs/namespace.c                       |    1 +
>>  include/linux/fs.h                   |    6 +-
>>  include/linux/fs_event.h             |   69 +++
>>  include/uapi/linux/fs_event.h        |   62 +++
>>  include/uapi/linux/genetlink.h       |    1 +
>>  mm/shmem.c                           |   39 +-
>>  net/netlink/genetlink.c              |    7 +-
>>  20 files changed, 1412 insertions(+), 34 deletions(-)
>>  create mode 100644 Documentation/filesystems/events.txt
>>  create mode 100644 fs/events/Makefile
>>  create mode 100644 fs/events/fs_event.c
>>  create mode 100644 fs/events/fs_event.h
>>  create mode 100644 fs/events/fs_event_netlink.c
>>  create mode 100644 include/linux/fs_event.h
>>  create mode 100644 include/uapi/linux/fs_event.h
>>
>> ---
>> Sample application:
>>
>> #include <netlink/cli/utils.h>
>> #include <fs_event.h>
>>
>> #define ARRAY_SIZE(x) (sizeof(x)/sizeof((x)[0]))
>> #define LOG(args...) fprintf(stderr, args)
>>
>> static int parse_info(struct nl_cache_ops *unused, struct genl_cmd *cmd,
>> 		struct genl_info *info, void *arg)
>> {
>> 	LOG("New trace %d:\n",
>> 		info->attrs[FS_EVENT_ATR_FS_ID]
>> 		?  nla_get_u32(info->attrs[FS_EVENT_ATR_FS_ID])
>> 		: -1);
>> 	LOG("Mout point: %s\n", info->attrs[FS_EVENT_ATR_MOUNT]
>> 		? nla_get_string(info->attrs[FS_EVENT_ATR_MOUNT])
>> 		: "unknown");
>> 	return 0;
>> }
>>
>> static int parse_thres(struct nl_cache_ops *unused, struct genl_cmd *cmd,
>> 		struct genl_info *info, void *arg)
>> {
>>
>> 	LOG("Threshold notification received for trace %d:\n",
>> 		info->attrs[FS_EVENT_ATR_FS_ID]
>> 		?  nla_get_u32(info->attrs[FS_EVENT_ATR_FS_ID])
>> 		: -1);
>>
>> 	if (info->attrs[FS_EVENT_ATR_DEV_MAJOR])
>> 		LOG("Backing dev major: %u\n",
>> 			nla_get_u32(info->attrs[FS_EVENT_ATR_DEV_MAJOR]));
>> 	if (info->attrs[FS_EVENT_ATR_DEV_MINOR])
>> 		LOG("Backing dev minor: %u\n",
>> 			nla_get_u32(info->attrs[FS_EVENT_ATR_DEV_MINOR]));
>> 	LOG("Proc:              %u\n", info->attrs[FS_EVENT_ATR_CAUSED_ID] ?
>> 			nla_get_u32(info->attrs[FS_EVENT_ATR_CAUSED_ID]) : -1);
>> 	LOG("Threshold data:    %llu\n", info->attrs[FS_EVENT_ATR_DATA]
>> 		? nla_get_u64(info->attrs[FS_EVENT_ATR_DATA])
>> 		: 0);
>>
>> 	return 0;
>> }
>>
>> static int parse_warning(struct nl_cache_ops *unused, struct genl_cmd *cmd,
>> 			 struct genl_info *info, void *arg)
>> {
>>
>> 	LOG("Warning recieved for trace %d\n", info->attrs[FS_EVENT_ATR_FS_ID] ?
>> 		nla_get_u32(info->attrs[FS_EVENT_ATR_FS_ID]) : -1);
>> 	if (info->attrs[FS_EVENT_ATR_DEV_MAJOR])
>> 		LOG("Backing dev major: %u\n",
>> 			nla_get_u32(info->attrs[FS_EVENT_ATR_DEV_MAJOR]));
>> 	if (info->attrs[FS_EVENT_ATR_DEV_MINOR])
>> 		LOG("Backing dev minor: %u\n",
>> 			nla_get_u32(info->attrs[FS_EVENT_ATR_DEV_MINOR]));
>> 	LOG("Proc:              %u\n", info->attrs[FS_EVENT_ATR_CAUSED_ID] ?
>> 		nla_get_u32(info->attrs[FS_EVENT_ATR_CAUSED_ID]) : -1);
>> 	LOG("Warning:           %u\n", info->attrs[FS_EVENT_ATR_ID] ?
>> 		nla_get_u32(info->attrs[FS_EVENT_ATR_ID]) : -1);
>>
>> 	return 0;
>> }
>>
>> static struct genl_cmd cmd[] = {
>> 	{
>> 		.c_id = FS_EVENT_TYPE_NEW_TRACE,
>> 		.c_name = "info",
>> 		.c_maxattr = 2,
>> 		.c_msg_parser = parse_info,
>> 	}, {
>> 		.c_id = FS_EVENT_TYPE_THRESH,
>> 		.c_name = "thres",
>> 		.c_maxattr = 6,
>> 		.c_msg_parser = parse_thres,
>> 	}, {
>> 		.c_id = FS_EVENT_TYPE_WARN,
>> 		.c_name = "warn",
>> 		.c_maxattr = 5,
>> 		.c_msg_parser = parse_warning,
>> 	},
>> };
>>
>> static struct genl_ops ops = {
>> 	.o_id = GENL_ID_FS_EVENT,
>> 	.o_name = "FS_EVENT",
>> 	.o_hdrsize = 0,
>> 	.o_cmds = cmd,
>> 	.o_ncmds = ARRAY_SIZE(cmd),
>> };
>>
>>
>> int events_cb(struct nl_msg *msg, void *arg)
>> {
>> 	 return  genl_handle_msg(msg, arg);
>> }
>>
>> int main(int argc, char **argv)
>> {
>> 	struct nl_sock *sock;
>> 	int ret;
>>
>> 	sock = nl_cli_alloc_socket();
>> 	nl_socket_set_local_port(sock, 0);
>> 	nl_socket_disable_seq_check(sock);
>>
>> 	nl_socket_modify_cb(sock, NL_CB_VALID, NL_CB_CUSTOM, events_cb, NULL);
>>
>> 	nl_cli_connect(sock, NETLINK_GENERIC);
>>
>> 	if ((ret = nl_socket_add_membership(sock, GENL_ID_FS_EVENT))) {
>> 		LOG("Failed to add membership\n");
>> 		goto leave;
>> 	}
>>
>> 	if((ret = genl_register_family(&ops))) {
>> 		LOG("Failed to register protocol family\n");
>> 		goto leave;
>> 	}
>>
>> 	if ((ret = genl_ops_resolve(sock, &ops) < 0)) {
>> 		LOG("Unable to resolve the family name\n");
>> 		goto leave;
>> 	}
>>
>> 	if (genl_ctrl_resolve(sock, "FS_EVENT") < 0) {
>> 		LOG("Failed to resolve  the family name\n");
>> 		goto leave;
>> 	}
>>
>> 	while (1) {
>> 		if ((ret = nl_recvmsgs_default(sock)) < 0)
>> 			LOG("Unable to receive message: %s\n", nl_geterror(ret));
>> 	}
>>
>> leave:
>> 	nl_close(sock);
>> 	nl_socket_free(sock);
>> 	return 0;
>> }
>>
>> -- 
>> 1.7.9.5
>>
>> --
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