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SubjectRe: [RFC 0/4] Generic file system events interface
  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
>
> ---
>
> 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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--
Jan Kara <jack@suse.cz>
SUSE Labs, CR


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