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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 6/8] fsinfo: Export superblock notification counter [ver #2] From: David Howells To: viro@zeniv.linux.org.uk Cc: dhowells@redhat.com, raven@themaw.net, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-block@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 04 Jun 2019 17:36:00 +0100 Message-ID: <155966616030.17449.8157292331675001618.stgit@warthog.procyon.org.uk> In-Reply-To: <155966609977.17449.5624614375035334363.stgit@warthog.procyon.org.uk> References: <155966609977.17449.5624614375035334363.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Tue, 04 Jun 2019 16:36:03 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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 --- 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 3ec64d3cba08..1456e26d2f7c 100644 --- a/fs/fsinfo.c +++ b/fs/fsinfo.c @@ -284,6 +284,16 @@ static int fsinfo_generic_param_enum(struct file_system_type *f, return sizeof(*p); } +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 void fsinfo_insert_sb_flag_parameters(struct path *path, struct fsinfo_kparams *params) { @@ -331,6 +341,7 @@ 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; } @@ -606,6 +617,7 @@ static const struct fsinfo_attr_info fsinfo_buffer_info[FSINFO_ATTR__NR] = { FSINFO_STRING_N (SERVER_NAME, server_name), FSINFO_STRUCT_NM (SERVER_ADDRESS, server_address), FSINFO_STRING (CELL_NAME, cell_name), + FSINFO_STRUCT (SB_NOTIFICATIONS, sb_notifications), }; /** diff --git a/fs/super.c b/fs/super.c index ae44745e6e2c..832d1a1865c9 100644 --- a/fs/super.c +++ b/fs/super.c @@ -1823,6 +1823,7 @@ 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 02ba4bfb9cc3..06e272a25ed7 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1536,6 +1536,7 @@ 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 7247088332c2..b4c9446305bb 100644 --- a/include/uapi/linux/fsinfo.h +++ b/include/uapi/linux/fsinfo.h @@ -39,6 +39,7 @@ enum fsinfo_attribute { FSINFO_ATTR_SERVER_NAME = 21, /* Name of the Nth server (string) */ FSINFO_ATTR_SERVER_ADDRESS = 22, /* Mth address of the Nth server */ FSINFO_ATTR_CELL_NAME = 23, /* Cell name (string) */ + FSINFO_ATTR_SB_NOTIFICATIONS = 24, /* sb_notify() information */ FSINFO_ATTR__NR }; @@ -308,4 +309,13 @@ struct fsinfo_server_address { struct __kernel_sockaddr_storage address; }; +/* + * 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 1f09247e49f3..02c330462af8 100644 --- a/include/uapi/linux/watch_queue.h +++ b/include/uapi/linux/watch_queue.h @@ -145,7 +145,7 @@ 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 af29da74559e..0f8f9ded0925 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_N (SERVER_NAME, server_name), FSINFO_STRUCT_NM (SERVER_ADDRESS, server_address), FSINFO_STRING (CELL_NAME, cell_name), + 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 (SERVER_NAME, server_name), FSINFO_NAME (SERVER_ADDRESS, server_address), FSINFO_NAME (CELL_NAME, cell_name), + FSINFO_NAME (SB_NOTIFICATIONS, sb_notifications), }; union reply { @@ -133,6 +135,7 @@ union reply { struct fsinfo_mount_info mount_info; struct fsinfo_mount_child mount_children[1]; struct fsinfo_server_address srv_addr; + struct fsinfo_sb_notifications sb_notifications; }; static void dump_hex(unsigned int *data, int from, int to) @@ -377,6 +380,15 @@ static void dump_attr_MOUNT_CHILDREN(union reply *r, int size) printf("\t[%u] %8x %8x\n", i++, f->mnt_id, f->notify_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); +} + /* * */ @@ -395,6 +407,7 @@ static const dumper_t fsinfo_attr_dumper[FSINFO_ATTR__NR] = { FSINFO_DUMPER(MOUNT_INFO), FSINFO_DUMPER(MOUNT_CHILDREN), FSINFO_DUMPER(SERVER_ADDRESS), + FSINFO_DUMPER(SB_NOTIFICATIONS), }; static void dump_fsinfo(enum fsinfo_attribute attr,