On 6/16/2015 9:09 PM, Beata Michalska wrote: > Introduce configurable generic interface for file > system-wide event notifications, to provide file > systems with a common way of reporting any potential > issues as they emerge. ... snip ... > + > +Sample request could look like the following: > + > + echo /sample/mount/point G T 710000 500000 > /sys/fs/events/config > + > +Multiple request might be specified provided they are separated with > semicolon. > + > +The configuration itself might be modified at any time. One can add/remove > +particular event types for given fielsystem, modify the threshold levels, > +and remove single or all entries from the 'config' file. > + > + - Adding new event type: > + > + $ echo MOUNT EVENT_TYPE > /sys/fs/events/config > + > +(Note that is is enough to provide the event type to be enabled without
Should be "Note that it is ... " here ? > +the already set ones.) > + > + - Removing event type: > + > + $ echo '!MOUNT EVENT_TYPE' > /sys/fs/events/config > + > + - Updating threshold limits: > + > + $ echo MOUNT T L1 L2 > /sys/fs/events/config > + > + - Removing single entry: > + > + $ echo '!MOUNT' > /sys/fs/events/config > + > + - Removing all entries: > + > + $ echo > /sys/fs/events/config > + > +Reading the file will list all registered entries with their current set-up > +along with some additional info like the filesystem type and the backing > device > +name if available. > + > +Final, though a very important note on the configuration: when and if the > +actual events are being triggered falls way beyond the scope of the generic > +filesystem events interface. It is up to a particular filesystem > +implementation which events are to be supported - if any at all. So if > +given filesystem does not support the event notifications, an attempt to > +enable those through 'config' file will fail. > + > + > +3. The generic netlink interface support: > +========================================= > + > +Whenever an event notification is triggered (by given filesystem) the current > +configuration is being validated to decide whether a userpsace notification > +should be launched. If there has been no request (in a mean of 'config' file > +entry) for given event, one will be silently disregarded. If, on the other > +hand, someone is 'watching' given filesystem for specific events, a generic > +netlink message will be sent. A dedicated multicast group has been provided > +solely for this purpose so in order to receive such notifications, one should > +subscribe to this new multicast group. As for now only the init network > +namespace is being supported. > + > +3.1 Message format > + > +The FS_NL_C_EVENT shall be stored within the generic netlink message header > +as the command field. The message payload will provide more detailed info: > +the backing device major and minor numbers, the event code and the id of > +the process which action led to the event occurrence. In case of threshold > +notifications, the current number of available blocks will be included > +in the payload as well. > + > + > + 0 1 2 3 > + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 > + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > + | NETLINK MESSAGE HEADER | > + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > + | GENERIC NETLINK MESSAGE HEADER | > + | (with FS_NL_C_EVENT as genlmsghdr cdm field) | cmd, not cdm. > + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > + | Optional user specific message header | > + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > + | GENERIC MESSAGE PAYLOAD: | > + +---------------------------------------------------------------+ > + | FS_NL_A_EVENT_ID (NLA_U32) | > + +---------------------------------------------------------------+ > + | FS_NL_A_DEV_MAJOR (NLA_U32) | > + +---------------------------------------------------------------+ > + | FS_NL_A_DEV_MINOR (NLA_U32) | > + +---------------------------------------------------------------+ > + | FS_NL_A_CAUSED_ID (NLA_U32) | Should be NLA_U64 ? The following uses as, + if (nla_put_u64(skb, FS_NL_A_CAUSED_ID, pid_vnr(task_pid(current)))) + return -EINVAL; Also, I'd like FS_NL_A_CAUSED_PID than FS_NL_A_CAUSED_ID. > + +---------------------------------------------------------------+ > + | FS_NL_A_DATA (NLA_U64) | > + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > + > + > +The above figure is based on: > + > http://www.linuxfoundation.org/collaborate/workgroups/networking/generic_netlink_howto#Message_Format > + > + ... snip... > + seq_putc(m, ' '); > + if (sb->s_op->show_devname) { > + sb->s_op->show_devname(m, en->mnt_path.mnt->mnt_root); > + } else { > + seq_escape(m, r_mnt->mnt_devname ? r_mnt->mnt_devname : "none", > + " \t\n\\"); > + } > + seq_puts(m, " ("); > + > + nmask = en->notify; > + for (match = fs_etypes; match->pattern; ++match) { > + if (match->token & nmask) { > + seq_puts(m, match->pattern); Print here is better. if (match->pattern & FS_EVENT_THRESH) seq_printf(m, " %llu %llu", en->th.lrange, en->th.urange); > + nmask &= ~match->token; > + if (nmask) > + seq_putc(m, ','); > + } > + } > + seq_printf(m, " %llu %llu", en->th.lrange, en->th.urange); Don't print the lrange/urange (always be zero) when without FS_EVENT_THRESH. > + seq_puts(m, ")\n"); > + return 0; > +} > + > +static const struct seq_operations fs_trace_seq_ops = { > + .start = fs_trace_seq_start, > + .next = fs_trace_seq_next, > + .stop = fs_trace_seq_stop, > + .show = fs_trace_seq_show, > +}; > + > +static int fs_trace_open(struct inode *inode, struct file *file) > +{ > + return seq_open(file, &fs_trace_seq_ops); > +} > + > +static const struct file_operations fs_trace_fops = { > + .owner = THIS_MODULE, > + .open = fs_trace_open, > + .write = fs_trace_write, > + .read = seq_read, > + .llseek = seq_lseek, > + .release = seq_release, > +}; > + > +static int fs_trace_init(void) > +{ > + fs_trace_cachep = KMEM_CACHE(fs_trace_entry, 0); > + if (!fs_trace_cachep) > + return -EINVAL; > + init_waitqueue_head(&trace_wq); > + return 0; > +} > + > +/* VFS support */ > +static int fs_trace_fill_super(struct super_block *sb, void *data, int silen) > +{ > + int ret; > + static struct tree_descr desc[] = { > + [2] = { > + .name = "config", > + .ops = &fs_trace_fops, > + .mode = S_IWUSR | S_IRUGO, > + }, > + {""}, > + }; > + > + ret = simple_fill_super(sb, 0x7246332, desc); > + return !ret ? fs_trace_init() : ret; > +} > + > +static struct dentry *fs_trace_do_mount(struct file_system_type *fs_type, > + int ntype, const char *dev_name, void *data) > +{ > + return mount_single(fs_type, ntype, data, fs_trace_fill_super); > +} > + > +static void fs_trace_kill_super(struct super_block *sb) > +{ > + /* > + * The rcu_barrier here will/should make sure all call_rcu > + * callbacks are completed - still there might be some active > + * trace objects in use which can make calling the > + * kmem_cache_destroy unsafe. So we wait until all traces > + * are finally released. > + */ > + fs_remove_all_traces(); > + rcu_barrier(); > + wait_event(trace_wq, !atomic_read(&stray_traces)); > + > + kmem_cache_destroy(fs_trace_cachep); > + kill_litter_super(sb); > +} > + > +static struct kset *fs_trace_kset; > + > +static struct file_system_type fs_trace_fstype = { > + .name = "fstrace", > + .mount = fs_trace_do_mount, > + .kill_sb = fs_trace_kill_super, > +}; > + > +static void __init fs_trace_vfs_init(void) > +{ > + fs_trace_kset = kset_create_and_add("events", NULL, fs_kobj); > + > + if (!fs_trace_kset) > + return; > + > + if (!register_filesystem(&fs_trace_fstype)) { > + if (!fs_event_netlink_register()) > + return; > + unregister_filesystem(&fs_trace_fstype); > + } > + kset_unregister(fs_trace_kset); > +} > + > +static int __init fs_trace_evens_init(void) > +{ > + fs_trace_vfs_init(); > + return 0; > +}; > +module_init(fs_trace_evens_init); > + > diff --git a/fs/events/fs_event.h b/fs/events/fs_event.h > new file mode 100644 > index 0000000..23f24c8 > --- /dev/null > +++ b/fs/events/fs_event.h > @@ -0,0 +1,22 @@ > +/* > + * Copyright(c) 2015 Samsung Electronics. All rights reserved. > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms of the GNU General Public License version 2. > + * > + * The full GNU General Public License is included in this distribution in > the > + * file called COPYING. > + * > + * This program is distributed in the hope that it will be useful, but > WITHOUT > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for > + * more details. > + */ > + > +#ifndef __GENERIC_FS_EVENTS_H > +#define __GENERIC_FS_EVENTS_H > + > +int fs_event_netlink_register(void); > +void fs_event_netlink_unregister(void); > + > +#endif /* __GENERIC_FS_EVENTS_H */ > diff --git a/fs/events/fs_event_netlink.c b/fs/events/fs_event_netlink.c > new file mode 100644 > index 0000000..0c97eb7 > --- /dev/null > +++ b/fs/events/fs_event_netlink.c > @@ -0,0 +1,104 @@ > +/* > + * Copyright(c) 2015 Samsung Electronics. All rights reserved. > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms of the GNU General Public License version 2. > + * > + * The full GNU General Public License is included in this distribution in > the > + * file called COPYING. > + * > + * This program is distributed in the hope that it will be useful, but > WITHOUT > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for > + * more details. > + */ > +#include <linux/fs.h> > +#include <linux/init.h> > +#include <linux/kernel.h> > +#include <linux/sched.h> > +#include <linux/slab.h> > +#include <net/netlink.h> > +#include <net/genetlink.h> > +#include "fs_event.h" > + > +static const struct genl_multicast_group fs_event_mcgroups[] = { > + { .name = FS_EVENTS_MCAST_GRP_NAME, }, > +}; > + > +static struct genl_family fs_event_family = { > + .id = GENL_ID_GENERATE, > + .name = FS_EVENTS_FAMILY_NAME, > + .version = 1, > + .maxattr = FS_NL_A_MAX, > + .mcgrps = fs_event_mcgroups, > + .n_mcgrps = ARRAY_SIZE(fs_event_mcgroups), > +}; > + > +int fs_netlink_send_event(size_t size, unsigned int event_id, > + int (*compose_msg)(struct sk_buff *skb, void *data), > + void *cbdata) > +{ > + static atomic_t seq; > + struct sk_buff *skb; > + void *msg_head; > + int ret = 0; > + > + if (!size || !compose_msg) > + return -EINVAL; > + > + /* Skip if there are no listeners */ > + if (!genl_has_listeners(&fs_event_family, &init_net, 0)) > + return 0; > + > + if (event_id != FS_EVENT_NONE) > + size += nla_total_size(sizeof(u32)); > + size += nla_total_size(sizeof(u64)); What is this for ? thanks Kinglong Mee -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
