linux-ext4 - [PATCH RFC 5/7] vfs: Include origin of the SB error notification

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Date:   Tue, 20 Oct 2020 15:15:41 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     dhowells@...hat.com
Cc:     viro@...iv.linux.org.uk, tytso@....edu, khazhy@...gle.com,
        adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel@...labora.com
Subject: [PATCH RFC 5/7] vfs: Include origin of the SB error notification

When reporting a filesystem error, we really need to know where the
error came from, therefore, include "function:line" information in the
notification sent to userspace.  There is no current users of notify_sb
in the kernel, so there are no callers to update.

Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
---
 include/linux/fs.h               | 10 ++++++++--
 include/uapi/linux/watch_queue.h |  3 +++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index d24905e10623..be9f7b480f50 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3516,12 +3516,14 @@ static inline void notify_sb(struct super_block *s,
 /**
  * notify_sb_error: Post superblock error notification.
  * @s: The superblock the notification is about.
+ * @function: function name reported as source of the warning.
+ * @line: source code line reported as source of the warning.
  * @error: The error number to be recorded.
  * @fmt: Formating string for extra information appended to the notification
  * @args: arguments for extra information string appended to the notification
  */
-static inline int notify_sb_error(struct super_block *s, int error,
-				  const char *fmt, va_list *args)
+static inline int notify_sb_error(struct super_block *s, const char *function,
+				  int line, int error, const char *fmt, va_list *args)
 {
 #ifdef CONFIG_SB_NOTIFICATIONS
 	if (unlikely(s->s_watchers)) {
@@ -3532,8 +3534,12 @@ static inline int notify_sb_error(struct super_block *s, int error,
 			.s.sb_id	= s->s_unique_id,
 			.error_number	= error,
 			.error_cookie	= 0,
+			.line		= line,
 		};
 
+		memcpy(&n.function, function, SB_NOTIFICATION_FNAME_LEN);
+		n.function[SB_NOTIFICATION_FNAME_LEN-1] = '\0';
+
 		post_sb_notification(s, &n.s, fmt, args);
 	}
 #endif
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index 5899936534f4..d0a45a4ded7d 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -114,6 +114,7 @@ enum superblock_notification_type {
 
 #define NOTIFY_SUPERBLOCK_IS_NOW_RO	WATCH_INFO_FLAG_0 /* Superblock changed to R/O */
 
+#define SB_NOTIFICATION_FNAME_LEN 30
 /*
  * Superblock notification record.
  * - watch.type = WATCH_TYPE_MOUNT_NOTIFY
@@ -128,6 +129,8 @@ struct superblock_error_notification {
 	struct superblock_notification s; /* subtype = notify_superblock_error */
 	__u32	error_number;
 	__u32	error_cookie;
+	char	function[SB_NOTIFICATION_FNAME_LEN];
+	__u16	line;
 	char	desc[0];
 };
 
-- 
2.28.0