[PATCH 5/6] fsinfo: Export superblock notification counter [ver #5]
From: David Howells
Date: Fri Jun 28 2019 - 11:51:09 EST
Provide an fsinfo attribute to export the superblock notification counter
so that it can be polled in the case of a notification buffer overrun.
This is accessed with:
struct fsinfo_params params = {
.request = FSINFO_ATTR_SB_NOTIFICATIONS,
};
and returns a structure that looks like:
struct fsinfo_sb_notifications {
__u64 watch_id;
__u32 notify_counter;
__u32 __reserved[1];
};
Where watch_id is a number uniquely identifying the superblock in
notification records and notify_counter is incremented for each
superblock notification posted.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
fs/fsinfo.c | 12 ++++++++++++
fs/super.c | 1 +
include/linux/fs.h | 1 +
include/uapi/linux/fsinfo.h | 10 ++++++++++
include/uapi/linux/watch_queue.h | 2 +-
samples/vfs/test-fsinfo.c | 13 +++++++++++++
6 files changed, 38 insertions(+), 1 deletion(-)
diff --git a/fs/fsinfo.c b/fs/fsinfo.c
index 758d1cbf8eba..a328f659ecb3 100644
--- a/fs/fsinfo.c
+++ b/fs/fsinfo.c
@@ -321,6 +321,16 @@ void fsinfo_note_sb_params(struct fsinfo_kparams *params, unsigned int s_flags)
}
EXPORT_SYMBOL(fsinfo_note_sb_params);
+static int fsinfo_generic_sb_notifications(struct path *path,
+ struct fsinfo_sb_notifications *p)
+{
+ struct super_block *sb = path->dentry->d_sb;
+
+ p->watch_id = sb->s_unique_id;
+ p->notify_counter = atomic_read(&sb->s_notify_counter);
+ return sizeof(*p);
+}
+
static int fsinfo_generic_parameters(struct path *path,
struct fsinfo_kparams *params)
{
@@ -357,6 +367,7 @@ int generic_fsinfo(struct path *path, struct fsinfo_kparams *params)
case _genp(MOUNT_DEVNAME, mount_devname);
case _genp(MOUNT_CHILDREN, mount_children);
case _genp(MOUNT_SUBMOUNT, mount_submount);
+ case _gen(SB_NOTIFICATIONS, sb_notifications);
default:
return -EOPNOTSUPP;
}
@@ -645,6 +656,7 @@ static const struct fsinfo_attr_info fsinfo_buffer_info[FSINFO_ATTR__NR] = {
FSINFO_STRING (MOUNT_DEVNAME),
FSINFO_STRUCT_ARRAY (MOUNT_CHILDREN, mount_child),
FSINFO_STRING_N (MOUNT_SUBMOUNT),
+ FSINFO_STRUCT (SB_NOTIFICATIONS, sb_notifications),
};
/**
diff --git a/fs/super.c b/fs/super.c
index 9f631cd4f93b..b338d2c6aca4 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1840,6 +1840,7 @@ EXPORT_SYMBOL(thaw_super);
*/
void post_sb_notification(struct super_block *s, struct superblock_notification *n)
{
+ atomic_inc(&s->s_notify_counter);
post_watch_notification(s->s_watchers, &n->watch, current_cred(),
s->s_unique_id);
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 42adb7a391a9..25586732b127 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1535,6 +1535,7 @@ struct super_block {
#ifdef CONFIG_SB_NOTIFICATIONS
struct watch_list *s_watchers;
#endif
+ atomic_t s_notify_counter;
} __randomize_layout;
/* Helper functions so that in most cases filesystems will
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 401ad9625c11..b9b3026a40a1 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -39,6 +39,7 @@ enum fsinfo_attribute {
FSINFO_ATTR_MOUNT_DEVNAME = 21, /* Mount object device name (string) */
FSINFO_ATTR_MOUNT_CHILDREN = 22, /* Submount list (array) */
FSINFO_ATTR_MOUNT_SUBMOUNT = 23, /* Relative path of Nth submount (string) */
+ FSINFO_ATTR_SB_NOTIFICATIONS = 24, /* sb_notify() information */
FSINFO_ATTR__NR
};
@@ -316,4 +317,13 @@ struct fsinfo_mount_child {
__u32 change_counter; /* Number of changes applied to mount. */
};
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_SB_NOTIFICATIONS).
+ */
+struct fsinfo_sb_notifications {
+ __u64 watch_id; /* Watch ID for superblock. */
+ __u32 notify_counter; /* Number of notifications. */
+ __u32 __reserved[1];
+};
+
#endif /* _UAPI_LINUX_FSINFO_H */
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index c8f0adefd8de..11d1d24b83cb 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -217,7 +217,7 @@ enum superblock_notification_type {
*/
struct superblock_notification {
struct watch_notification watch; /* WATCH_TYPE_SB_NOTIFY */
- __u64 sb_id; /* 64-bit superblock ID [fsinfo_ids::f_sb_id] */
+ __u64 sb_id; /* 64-bit superblock ID [fsinfo_sb_notifications::watch_id] */
};
struct superblock_error_notification {
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index 28c9f3cd2c8c..6cac56bbfe4f 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -90,6 +90,7 @@ static const struct fsinfo_attr_info fsinfo_buffer_info[FSINFO_ATTR__NR] = {
FSINFO_STRING (MOUNT_DEVNAME, mount_devname),
FSINFO_STRUCT_ARRAY (MOUNT_CHILDREN, mount_child),
FSINFO_STRING_N (MOUNT_SUBMOUNT, mount_submount),
+ FSINFO_STRUCT (SB_NOTIFICATIONS, sb_notifications),
};
#define FSINFO_NAME(X,Y) [FSINFO_ATTR_##X] = #Y
@@ -118,6 +119,7 @@ static const char *fsinfo_attr_names[FSINFO_ATTR__NR] = {
FSINFO_NAME (MOUNT_DEVNAME, mount_devname),
FSINFO_NAME (MOUNT_CHILDREN, mount_children),
FSINFO_NAME (MOUNT_SUBMOUNT, mount_submount),
+ FSINFO_NAME (SB_NOTIFICATIONS, sb_notifications),
};
union reply {
@@ -133,6 +135,7 @@ union reply {
struct fsinfo_server_address srv_addr;
struct fsinfo_mount_info mount_info;
struct fsinfo_mount_child mount_children[1];
+ struct fsinfo_sb_notifications sb_notifications;
};
static void dump_hex(unsigned int *data, int from, int to)
@@ -384,6 +387,15 @@ static void dump_attr_MOUNT_CHILDREN(union reply *r, int size)
printf("\t[%u] %8x %8x\n", i++, f->mnt_id, f->change_counter);
}
+static void dump_attr_SB_NOTIFICATIONS(union reply *r, int size)
+{
+ struct fsinfo_sb_notifications *f = &r->sb_notifications;
+
+ printf("\n");
+ printf("\twatch_id: %llx\n", (unsigned long long)f->watch_id);
+ printf("\tnotifs : %llx\n", (unsigned long long)f->notify_counter);
+}
+
/*
*
*/
@@ -402,6 +414,7 @@ static const dumper_t fsinfo_attr_dumper[FSINFO_ATTR__NR] = {
FSINFO_DUMPER(SERVER_ADDRESS),
FSINFO_DUMPER(MOUNT_INFO),
FSINFO_DUMPER(MOUNT_CHILDREN),
+ FSINFO_DUMPER(SB_NOTIFICATIONS),
};
static void dump_fsinfo(enum fsinfo_attribute attr,