linux-kernel - [PATCH 2/2] fs: clarify rate limit suppressed buffer I/O errors

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Date:	Wed, 27 Aug 2014 10:52:05 -0500
From:	Robert Elliott <elliott@...com>
To:	axboe@...nel.dk, webbnh@...com, linux-kernel@...r.kernel.org,
	relliott@...rdog.cce.hp.com, linux-fsdevel@...r.kernel.org,
	viro@...iv.linux.org.uk, elliott@...com,
	scameron@...rdog.cce.hp.com
Subject: [PATCH 2/2] fs: clarify rate limit suppressed buffer I/O errors

When quiet_error applies rate limiting to buffer_io_error calls, what the
they apply to is unclear because the name is so generic, particularly
if the messages are interleaved with others:

[ 1936.063572] quiet_error: 664293 callbacks suppressed
[ 1936.065297] Buffer I/O error on dev sdr, logical block 257429952, lost async page write
[ 1936.067814] Buffer I/O error on dev sdr, logical block 257429953, lost async page write

Also, the function uses printk_ratelimit(), although printk.h includes a
comment advising "Please don't use... Instead use printk_ratelimited()."

Change buffer_io_error to check the BH_Quiet bit itself, drop the
printk_ratelimit call, and print using printk_ratelimited.

This makes the messages look like:

[  387.208839] buffer_io_error: 676394 callbacks suppressed
[  387.210693] Buffer I/O error on dev sdr, logical block 211291776, lost async page write
[  387.213432] Buffer I/O error on dev sdr, logical block 211291777, lost async page write

Signed-off-by: Robert Elliott <elliott@...com>
Reviewed-by: Webb Scales <webbnh@...com>
---
 fs/buffer.c |   23 +++++++----------------
 1 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index c6cb0ee..3710a68 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -128,19 +128,13 @@ __clear_page_buffers(struct page *page)
 	page_cache_release(page);
 }
 
-
-static int quiet_error(struct buffer_head *bh)
-{
-	if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
-		return 0;
-	return 1;
-}
-
-
 static void buffer_io_error(struct buffer_head *bh, char *msg)
 {
 	char b[BDEVNAME_SIZE];
-	printk(KERN_ERR "Buffer I/O error on dev %s, logical block %llu%s\n",
+
+	if (!test_bit(BH_Quiet, &bh->b_state))
+		printk_ratelimited(KERN_ERR
+			"Buffer I/O error on dev %s, logical block %llu%s\n",
 			bdevname(bh->b_bdev, b),
 			(unsigned long long)bh->b_blocknr, msg);
 }
@@ -180,8 +174,7 @@ void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
 	if (uptodate) {
 		set_buffer_uptodate(bh);
 	} else {
-		if (!quiet_error(bh))
-			buffer_io_error(bh, ", lost sync page write");
+		buffer_io_error(bh, ", lost sync page write");
 		set_buffer_write_io_error(bh);
 		clear_buffer_uptodate(bh);
 	}
@@ -298,8 +291,7 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
 		set_buffer_uptodate(bh);
 	} else {
 		clear_buffer_uptodate(bh);
-		if (!quiet_error(bh))
-			buffer_io_error(bh, ", async page read");
+		buffer_io_error(bh, ", async page read");
 		SetPageError(page);
 	}
 
@@ -358,8 +350,7 @@ void end_buffer_async_write(struct buffer_head *bh, int uptodate)
 	if (uptodate) {
 		set_buffer_uptodate(bh);
 	} else {
-		if (!quiet_error(bh))
-			buffer_io_error(bh, ", lost async page write");
+		buffer_io_error(bh, ", lost async page write");
 		set_bit(AS_EIO, &page->mapping->flags);
 		set_buffer_write_io_error(bh);
 		clear_buffer_uptodate(bh);

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