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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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    > the body of a message to majordomo@vger.kernel.org
    > More majordomo info at http://vger.kernel.org/majordomo-info.html
    --
    Jan Kara <jack@suse.cz>
    SUSE Labs, CR


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