[PATCH next v3 12/15] printk: introduce a kmsg_dump iterator

[John Ogness <john.ogness@linutronix.de>]

Rather than storing the iterator information in the registered
kmsg_dumper structure, create a separate iterator structure. The
kmsg_dump_iter structure can reside on the stack of the caller, thus
allowing lockless use of the kmsg_dump functions.

This change also means that the kmsg_dumper dump() callback no
longer needs to pass in the kmsg_dumper as an argument. If
kmsg_dumpers want to access the kernel logs, they can use the new
iterator.

Update the kmsg_dumper callback prototype. Update code that accesses
the kernel logs using the kmsg_dumper structure to use the new
kmsg_dump_iter structure. For kmsg_dumpers, this also means adding a
call to kmsg_dump_rewind() to initialize the iterator.

All this is in preparation for removal of @logbuf_lock.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 arch/powerpc/kernel/nvram_64.c             | 14 +++---
 arch/powerpc/platforms/powernv/opal-kmsg.c |  3 +-
 arch/powerpc/xmon/xmon.c                   |  6 +--
 arch/um/kernel/kmsg_dump.c                 |  8 +--
 drivers/hv/vmbus_drv.c                     |  7 +--
 drivers/mtd/mtdoops.c                      |  8 +--
 fs/pstore/platform.c                       |  8 +--
 include/linux/kmsg_dump.h                  | 38 ++++++++-------
 kernel/debug/kdb/kdb_main.c                | 10 ++--
 kernel/printk/printk.c                     | 57 ++++++++++------------
 10 files changed, 81 insertions(+), 78 deletions(-)

diff --git a/arch/powerpc/kernel/nvram_64.c b/arch/powerpc/kernel/nvram_64.c
index 532f22637783..5a64b24a91c2 100644
--- a/arch/powerpc/kernel/nvram_64.c
+++ b/arch/powerpc/kernel/nvram_64.c
@@ -72,8 +72,7 @@ static const char *nvram_os_partitions[] = {
 	NULL
 };
 
-static void oops_to_nvram(struct kmsg_dumper *dumper,
-			  enum kmsg_dump_reason reason);
+static void oops_to_nvram(enum kmsg_dump_reason reason);
 
 static struct kmsg_dumper nvram_kmsg_dumper = {
 	.dump = oops_to_nvram
@@ -642,11 +641,11 @@ void __init nvram_init_oops_partition(int rtas_partition_exists)
  * that we think will compress sufficiently to fit in the lnx,oops-log
  * partition.  If that's too much, go back and capture uncompressed text.
  */
-static void oops_to_nvram(struct kmsg_dumper *dumper,
-			  enum kmsg_dump_reason reason)
+static void oops_to_nvram(enum kmsg_dump_reason reason)
 {
 	struct oops_log_info *oops_hdr = (struct oops_log_info *)oops_buf;
 	static unsigned int oops_count = 0;
+	static struct kmsg_dump_iter iter;
 	static bool panicking = false;
 	static DEFINE_SPINLOCK(lock);
 	unsigned long flags;
@@ -681,13 +680,14 @@ static void oops_to_nvram(struct kmsg_dumper *dumper,
 		return;
 
 	if (big_oops_buf) {
-		kmsg_dump_get_buffer(dumper, false,
+		kmsg_dump_rewind(&iter);
+		kmsg_dump_get_buffer(&iter, false,
 				     big_oops_buf, big_oops_buf_sz, &text_len);
 		rc = zip_oops(text_len);
 	}
 	if (rc != 0) {
-		kmsg_dump_rewind(dumper);
-		kmsg_dump_get_buffer(dumper, false,
+		kmsg_dump_rewind(&iter);
+		kmsg_dump_get_buffer(&iter, false,
 				     oops_data, oops_data_sz, &text_len);
 		err_type = ERR_TYPE_KERNEL_PANIC;
 		oops_hdr->version = cpu_to_be16(OOPS_HDR_VERSION);
diff --git a/arch/powerpc/platforms/powernv/opal-kmsg.c b/arch/powerpc/platforms/powernv/opal-kmsg.c
index 6c3bc4b4da98..a7bd6ac681f4 100644
--- a/arch/powerpc/platforms/powernv/opal-kmsg.c
+++ b/arch/powerpc/platforms/powernv/opal-kmsg.c
@@ -19,8 +19,7 @@
  * may not be completely printed.  This function does not actually dump the
  * message, it just ensures that OPAL completely flushes the console buffer.
  */
-static void kmsg_dump_opal_console_flush(struct kmsg_dumper *dumper,
-				     enum kmsg_dump_reason reason)
+static void kmsg_dump_opal_console_flush(enum kmsg_dump_reason reason)
 {
 	/*
 	 * Outside of a panic context the pollers will continue to run,
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 80ed3e1becf9..5978b90a885f 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -3001,7 +3001,7 @@ print_address(unsigned long addr)
 static void
 dump_log_buf(void)
 {
-	struct kmsg_dumper dumper;
+	struct kmsg_dump_iter iter;
 	unsigned char buf[128];
 	size_t len;
 
@@ -3013,9 +3013,9 @@ dump_log_buf(void)
 	catch_memory_errors = 1;
 	sync();
 
-	kmsg_dump_rewind_nolock(&dumper);
+	kmsg_dump_rewind_nolock(&iter);
 	xmon_start_pagination();
-	while (kmsg_dump_get_line_nolock(&dumper, false, buf, sizeof(buf), &len)) {
+	while (kmsg_dump_get_line_nolock(&iter, false, buf, sizeof(buf), &len)) {
 		buf[len] = '\0';
 		printf("%s", buf);
 	}
diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
index 4869e2cc787c..9fbc5e5b1023 100644
--- a/arch/um/kernel/kmsg_dump.c
+++ b/arch/um/kernel/kmsg_dump.c
@@ -7,9 +7,9 @@
 #include <shared/kern.h>
 #include <os.h>
 
-static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
-				enum kmsg_dump_reason reason)
+static void kmsg_dumper_stdout(enum kmsg_dump_reason reason)
 {
+	static struct kmsg_dump_iter iter;
 	static DEFINE_SPINLOCK(lock);
 	static char line[1024];
 	struct console *con;
@@ -34,8 +34,10 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
 	if (!spin_trylock(&lock))
 		return;
 
+	kmsg_dump_rewind(&iter);
+
 	printf("kmsg_dump:\n");
-	while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) {
+	while (kmsg_dump_get_line(&iter, true, line, sizeof(line), &len)) {
 		line[len] = '\0';
 		printf("%s", line);
 	}
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 10dce9f91216..1b858f280e22 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1388,9 +1388,9 @@ static void vmbus_isr(void)
  * Callback from kmsg_dump. Grab as much as possible from the end of the kmsg
  * buffer and call into Hyper-V to transfer the data.
  */
-static void hv_kmsg_dump(struct kmsg_dumper *dumper,
-			 enum kmsg_dump_reason reason)
+static void hv_kmsg_dump(enum kmsg_dump_reason reason)
 {
+	struct kmsg_dump_iter iter;
 	size_t bytes_written;
 	phys_addr_t panic_pa;
 
@@ -1404,7 +1404,8 @@ static void hv_kmsg_dump(struct kmsg_dumper *dumper,
 	 * Write dump contents to the page. No need to synchronize; panic should
 	 * be single-threaded.
 	 */
-	kmsg_dump_get_buffer(dumper, false, hv_panic_page, HV_HYP_PAGE_SIZE,
+	kmsg_dump_rewind(&iter);
+	kmsg_dump_get_buffer(&iter, false, hv_panic_page, HV_HYP_PAGE_SIZE,
 			     &bytes_written);
 	if (bytes_written)
 		hyperv_report_panic_msg(panic_pa, bytes_written);
diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
index 8bbfba40a554..d179b726a1c9 100644
--- a/drivers/mtd/mtdoops.c
+++ b/drivers/mtd/mtdoops.c
@@ -272,19 +272,21 @@ static void find_next_position(struct mtdoops_context *cxt)
 	mtdoops_inc_counter(cxt);
 }
 
-static void mtdoops_do_dump(struct kmsg_dumper *dumper,
-			    enum kmsg_dump_reason reason)
+static void mtdoops_do_dump(enum kmsg_dump_reason reason)
 {
 	struct mtdoops_context *cxt = container_of(dumper,
 			struct mtdoops_context, dump);
+	struct kmsg_dump_iter iter;
 
 	/* Only dump oopses if dump_oops is set */
 	if (reason == KMSG_DUMP_OOPS && !dump_oops)
 		return;
 
+	kmsg_dump_rewind(&iter);
+
 	if (test_and_set_bit(0, &cxt->oops_buf_busy))
 		return;
-	kmsg_dump_get_buffer(dumper, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE,
+	kmsg_dump_get_buffer(&iter, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE,
 			     record_size - MTDOOPS_HEADER_SIZE, NULL);
 	clear_bit(0, &cxt->oops_buf_busy);
 
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index d963ae7902f9..edfc9504e024 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -382,9 +382,9 @@ void pstore_record_init(struct pstore_record *record,
  * callback from kmsg_dump. Save as much as we can (up to kmsg_bytes) from the
  * end of the buffer.
  */
-static void pstore_dump(struct kmsg_dumper *dumper,
-			enum kmsg_dump_reason reason)
+static void pstore_dump(enum kmsg_dump_reason reason)
 {
+	struct kmsg_dump_iter iter;
 	unsigned long	total = 0;
 	const char	*why;
 	unsigned int	part = 1;
@@ -405,6 +405,8 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		}
 	}
 
+	kmsg_dump_rewind(&iter);
+
 	oopscount++;
 	while (total < kmsg_bytes) {
 		char *dst;
@@ -435,7 +437,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		dst_size -= header_size;
 
 		/* Write dump contents. */
-		if (!kmsg_dump_get_buffer(dumper, true, dst + header_size,
+		if (!kmsg_dump_get_buffer(&iter, true, dst + header_size,
 					  dst_size, &dump_size))
 			break;
 
diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
index 84eaa2090efa..5d3bf20f9f0a 100644
--- a/include/linux/kmsg_dump.h
+++ b/include/linux/kmsg_dump.h
@@ -29,6 +29,16 @@ enum kmsg_dump_reason {
 	KMSG_DUMP_MAX
 };
 
+/**
+ * struct kmsg_dump_iter - iterator for retrieving kernel messages
+ * @cur_seq:	Points to the oldest message to dump
+ * @next_seq:	Points after the newest message to dump
+ */
+struct kmsg_dump_iter {
+	u64	cur_seq;
+	u64	next_seq;
+};
+
 /**
  * struct kmsg_dumper - kernel crash message dumper structure
  * @list:	Entry in the dumper list (private)
@@ -36,35 +46,29 @@ enum kmsg_dump_reason {
  * 		through the record iterator
  * @max_reason:	filter for highest reason number that should be dumped
  * @registered:	Flag that specifies if this is already registered
- * @cur_seq:	Points to the oldest message to dump
- * @next_seq:	Points after the newest message to dump
  */
 struct kmsg_dumper {
 	struct list_head list;
-	void (*dump)(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason);
+	void (*dump)(enum kmsg_dump_reason reason);
 	enum kmsg_dump_reason max_reason;
 	bool registered;
-
-	/* private state of the kmsg iterator */
-	u64 cur_seq;
-	u64 next_seq;
 };
 
 #ifdef CONFIG_PRINTK
 void kmsg_dump(enum kmsg_dump_reason reason);
 
-bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
+bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter, bool syslog,
 			       char *line, size_t size, size_t *len);
 
-bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
+bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
 			char *line, size_t size, size_t *len);
 
-bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
+bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
 			  char *buf, size_t size, size_t *len_out);
 
-void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper);
+void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter);
 
-void kmsg_dump_rewind(struct kmsg_dumper *dumper);
+void kmsg_dump_rewind(struct kmsg_dump_iter *iter);
 
 int kmsg_dump_register(struct kmsg_dumper *dumper);
 
@@ -76,30 +80,30 @@ static inline void kmsg_dump(enum kmsg_dump_reason reason)
 {
 }
 
-static inline bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper,
+static inline bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter,
 					     bool syslog, const char *line,
 					     size_t size, size_t *len)
 {
 	return false;
 }
 
-static inline bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
+static inline bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
 				const char *line, size_t size, size_t *len)
 {
 	return false;
 }
 
-static inline bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
+static inline bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
 					char *buf, size_t size, size_t *len)
 {
 	return false;
 }
 
-static inline void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
+static inline void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter)
 {
 }
 
-static inline void kmsg_dump_rewind(struct kmsg_dumper *dumper)
+static inline void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
 {
 }
 
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 315169d5e119..8544d7a55a57 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2101,7 +2101,7 @@ static int kdb_dmesg(int argc, const char **argv)
 	int adjust = 0;
 	int n = 0;
 	int skip = 0;
-	struct kmsg_dumper dumper;
+	struct kmsg_dump_iter iter;
 	size_t len;
 	char buf[201];
 
@@ -2126,8 +2126,8 @@ static int kdb_dmesg(int argc, const char **argv)
 		kdb_set(2, setargs);
 	}
 
-	kmsg_dump_rewind_nolock(&dumper);
-	while (kmsg_dump_get_line_nolock(&dumper, 1, NULL, 0, NULL))
+	kmsg_dump_rewind_nolock(&iter);
+	while (kmsg_dump_get_line_nolock(&iter, 1, NULL, 0, NULL))
 		n++;
 
 	if (lines < 0) {
@@ -2159,8 +2159,8 @@ static int kdb_dmesg(int argc, const char **argv)
 	if (skip >= n || skip < 0)
 		return 0;
 
-	kmsg_dump_rewind_nolock(&dumper);
-	while (kmsg_dump_get_line_nolock(&dumper, 1, buf, sizeof(buf), &len)) {
+	kmsg_dump_rewind_nolock(&iter);
+	while (kmsg_dump_get_line_nolock(&iter, 1, buf, sizeof(buf), &len)) {
 		if (skip) {
 			skip--;
 			continue;
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 45cb3e9c62c5..e58ccc368348 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3390,7 +3390,6 @@ EXPORT_SYMBOL_GPL(kmsg_dump_reason_str);
 void kmsg_dump(enum kmsg_dump_reason reason)
 {
 	struct kmsg_dumper *dumper;
-	unsigned long flags;
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(dumper, &dump_list, list) {
@@ -3407,21 +3406,15 @@ void kmsg_dump(enum kmsg_dump_reason reason)
 		if (reason > max_reason)
 			continue;
 
-		/* initialize iterator with data about the stored records */
-		logbuf_lock_irqsave(flags);
-		dumper->cur_seq = latched_seq_read_nolock(&clear_seq);
-		dumper->next_seq = prb_next_seq(prb);
-		logbuf_unlock_irqrestore(flags);
-
 		/* invoke dumper which will iterate over records */
-		dumper->dump(dumper, reason);
+		dumper->dump(reason);
 	}
 	rcu_read_unlock();
 }
 
 /**
  * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
- * @dumper: registered kmsg dumper
+ * @iter: kmsg dump iterator
  * @syslog: include the "<4>" prefixes
  * @line: buffer to copy the line to
  * @size: maximum size of the buffer
@@ -3438,7 +3431,7 @@ void kmsg_dump(enum kmsg_dump_reason reason)
  *
  * The function is similar to kmsg_dump_get_line(), but grabs no locks.
  */
-bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
+bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter, bool syslog,
 			       char *line, size_t size, size_t *len)
 {
 	struct printk_info info;
@@ -3451,11 +3444,11 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
 
 	/* Read text or count text lines? */
 	if (line) {
-		if (!prb_read_valid(prb, dumper->cur_seq, &r))
+		if (!prb_read_valid(prb, iter->cur_seq, &r))
 			goto out;
 		l = record_print_text(&r, syslog, printk_time);
 	} else {
-		if (!prb_read_valid_info(prb, dumper->cur_seq,
+		if (!prb_read_valid_info(prb, iter->cur_seq,
 					 &info, &line_count)) {
 			goto out;
 		}
@@ -3464,7 +3457,7 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
 
 	}
 
-	dumper->cur_seq = r.info->seq + 1;
+	iter->cur_seq = r.info->seq + 1;
 	ret = true;
 out:
 	if (len)
@@ -3474,7 +3467,7 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
 
 /**
  * kmsg_dump_get_line - retrieve one kmsg log line
- * @dumper: registered kmsg dumper
+ * @iter: kmsg dump iterator
  * @syslog: include the "<4>" prefixes
  * @line: buffer to copy the line to
  * @size: maximum size of the buffer
@@ -3489,14 +3482,14 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
  * A return value of FALSE indicates that there are no more records to
  * read.
  */
-bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
+bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
 			char *line, size_t size, size_t *len)
 {
 	unsigned long flags;
 	bool ret;
 
 	logbuf_lock_irqsave(flags);
-	ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
+	ret = kmsg_dump_get_line_nolock(iter, syslog, line, size, len);
 	logbuf_unlock_irqrestore(flags);
 
 	return ret;
@@ -3505,7 +3498,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
 
 /**
  * kmsg_dump_get_buffer - copy kmsg log lines
- * @dumper: registered kmsg dumper
+ * @iter: kmsg dump iterator
  * @syslog: include the "<4>" prefixes
  * @buf: buffer to copy the line to
  * @size: maximum size of the buffer
@@ -3522,7 +3515,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
  * A return value of FALSE indicates that there are no more records to
  * read.
  */
-bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
+bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
 			  char *buf, size_t size, size_t *len_out)
 {
 	struct printk_info info;
@@ -3538,15 +3531,15 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
 		goto out;
 
 	logbuf_lock_irqsave(flags);
-	if (prb_read_valid_info(prb, dumper->cur_seq, &info, NULL)) {
-		if (info.seq != dumper->cur_seq) {
+	if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) {
+		if (info.seq != iter->cur_seq) {
 			/* messages are gone, move to first available one */
-			dumper->cur_seq = info.seq;
+			iter->cur_seq = info.seq;
 		}
 	}
 
 	/* last entry */
-	if (dumper->cur_seq >= dumper->next_seq) {
+	if (iter->cur_seq >= iter->next_seq) {
 		logbuf_unlock_irqrestore(flags);
 		goto out;
 	}
@@ -3557,7 +3550,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
 	 * because this function (by way of record_print_text()) will
 	 * not write more than size-1 bytes of text into @buf.
 	 */
-	seq = find_first_fitting_seq(dumper->cur_seq, dumper->next_seq,
+	seq = find_first_fitting_seq(iter->cur_seq, iter->next_seq,
 				     size - 1, syslog, time);
 
 	/*
@@ -3570,7 +3563,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
 
 	len = 0;
 	prb_for_each_record(seq, prb, seq, &r) {
-		if (r.info->seq >= dumper->next_seq)
+		if (r.info->seq >= iter->next_seq)
 			break;
 
 		len += record_print_text(&r, syslog, time);
@@ -3579,7 +3572,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
 		prb_rec_init_rd(&r, &info, buf + len, size - len);
 	}
 
-	dumper->next_seq = next_seq;
+	iter->next_seq = next_seq;
 	ret = true;
 	logbuf_unlock_irqrestore(flags);
 out:
@@ -3591,7 +3584,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
 
 /**
  * kmsg_dump_rewind_nolock - reset the iterator (unlocked version)
- * @dumper: registered kmsg dumper
+ * @iter: kmsg dump iterator
  *
  * Reset the dumper's iterator so that kmsg_dump_get_line() and
  * kmsg_dump_get_buffer() can be called again and used multiple
@@ -3599,26 +3592,26 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
  *
  * The function is similar to kmsg_dump_rewind(), but grabs no locks.
  */
-void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
+void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter)
 {
-	dumper->cur_seq = latched_seq_read_nolock(&clear_seq);
-	dumper->next_seq = prb_next_seq(prb);
+	iter->cur_seq = latched_seq_read_nolock(&clear_seq);
+	iter->next_seq = prb_next_seq(prb);
 }
 
 /**
  * kmsg_dump_rewind - reset the iterator
- * @dumper: registered kmsg dumper
+ * @iter: kmsg dump iterator
  *
  * Reset the dumper's iterator so that kmsg_dump_get_line() and
  * kmsg_dump_get_buffer() can be called again and used multiple
  * times within the same dumper.dump() callback.
  */
-void kmsg_dump_rewind(struct kmsg_dumper *dumper)
+void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
 {
 	unsigned long flags;
 
 	logbuf_lock_irqsave(flags);
-	kmsg_dump_rewind_nolock(dumper);
+	kmsg_dump_rewind_nolock(iter);
 	logbuf_unlock_irqrestore(flags);
 }
 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
-- 
2.20.1