zdb/ztest: send dbgmsg output to stderr

And, make the output fd an arg to zfs_dbgmsg_print(). This is a change
in behaviour, but keeps it consistent with where crash traces go, and
it's easy to argue this is what we want anyway; this is information
about the task, not the actual output of the task.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Rob Norris <[email protected]>
Closes #16181

1 files changed, 9 insertions, 10 deletions

diff --git a/module/os/linux/zfs/zfs_debug.c b/module/os/linux/zfs/zfs_debug.c
index bc5c028dc..9ee40771f 100644
--- a/module/os/linux/zfs/zfs_debug.c
+++ b/module/os/linux/zfs/zfs_debug.c
@@ -221,7 +221,7 @@ __dprintf(boolean_t dprint, const char *file, const char *func,
 #else
 
 void
-zfs_dbgmsg_print(const char *tag)
+zfs_dbgmsg_print(int fd, const char *tag)
 {
 	ssize_t ret __attribute__((unused));
 
@@ -231,20 +231,19 @@ zfs_dbgmsg_print(const char *tag)
 	 * We use write() in this function instead of printf()
 	 * so it is safe to call from a signal handler.
 	 */
-	ret = write(STDOUT_FILENO, "ZFS_DBGMSG(", 11);
-	ret = write(STDOUT_FILENO, tag, strlen(tag));
-	ret = write(STDOUT_FILENO, ") START:\n", 9);
+	ret = write(fd, "ZFS_DBGMSG(", 11);
+	ret = write(fd, tag, strlen(tag));
+	ret = write(fd, ") START:\n", 9);
 
 	for (zfs_dbgmsg_t *zdm = list_head(&zfs_dbgmsgs.pl_list); zdm != NULL;
 	    zdm = list_next(&zfs_dbgmsgs.pl_list, zdm)) {
-		ret = write(STDOUT_FILENO, zdm->zdm_msg,
-		    strlen(zdm->zdm_msg));
-		ret = write(STDOUT_FILENO, "\n", 1);
+		ret = write(fd, zdm->zdm_msg, strlen(zdm->zdm_msg));
+		ret = write(fd, "\n", 1);
 	}
 
-	ret = write(STDOUT_FILENO, "ZFS_DBGMSG(", 11);
-	ret = write(STDOUT_FILENO, tag, strlen(tag));
-	ret = write(STDOUT_FILENO, ") END\n", 6);
+	ret = write(fd, "ZFS_DBGMSG(", 11);
+	ret = write(fd, tag, strlen(tag));
+	ret = write(fd, ") END\n", 6);
 
 	mutex_exit(&zfs_dbgmsgs.pl_lock);
 }