diff mbox

btrfs: Ratelimit message printing

Message ID 1468393536-25798-1-git-send-email-kernel@kyup.com (mailing list archive)
State Superseded
Headers show

Commit Message

kernel@kyup.com July 13, 2016, 7:05 a.m. UTC 
Currently most of the messages btrfs produce are not rate limited.
Recently I came accross a case where due to FS corruption an excessive
amount of printk caused the softlockup detector to trigger and reset
the server. This patch does the following changes:

 * The message which was printed is converted to use the ratelimited
 version of btrfs_info function. This will prevent it from exploding
 in the future.

 * In addition to the above change, also add a sort of a "safet net" to
 all non-ratelimited prints by introducing separate ratelimiting for
 every message class when the "naked" btrfs_info is called.

Signed-off-by: Nikolay Borisov <kernel@kyup.com>
---

Hello David, 

How about something like that?

 fs/btrfs/file-item.c |  2 +-
 fs/btrfs/super.c     | 21 +++++++++++++++++++--
 2 files changed, 20 insertions(+), 3 deletions(-)

Comments

David Sterba July 13, 2016, 12:15 p.m. UTC | #1 
On Wed, Jul 13, 2016 at 10:05:36AM +0300, Nikolay Borisov wrote:
> Currently most of the messages btrfs produce are not rate limited.
> Recently I came accross a case where due to FS corruption an excessive
> amount of printk caused the softlockup detector to trigger and reset
> the server. This patch does the following changes:
> 
>  * The message which was printed is converted to use the ratelimited
>  version of btrfs_info function. This will prevent it from exploding
>  in the future.
> 
>  * In addition to the above change, also add a sort of a "safet net" to
>  all non-ratelimited prints by introducing separate ratelimiting for
>  every message class when the "naked" btrfs_info is called.
> 
> Signed-off-by: Nikolay Borisov <kernel@kyup.com>
> ---
> 
> Hello David, 
> 
> How about something like that?

Looks good, but please split the patch so one adds the ratelimiting to
the 'csum not found' message and another that introduces the global rate
limiting and add a comment to the printk_limits table, with the relevant
text from the changelog. Thanks.
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diff mbox

Patch

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 62a81ee13a5f..6b58d0620e2f 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -250,7 +250,7 @@  static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
 						offset + root->sectorsize - 1,
 						EXTENT_NODATASUM);
 				} else {
-					btrfs_info(BTRFS_I(inode)->root->fs_info,
+					btrfs_info_rl(BTRFS_I(inode)->root->fs_info,
 						   "no csum found for inode %llu start %llu",
 					       btrfs_ino(inode), offset);
 				}
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 60e7179ed4b7..01a87dd89732 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -184,6 +184,17 @@  static const char * const logtypes[] = {
 	"debug",
 };
 
+static struct ratelimit_state printk_limits[] = {
+	RATELIMIT_STATE_INIT(printk_limits[0], DEFAULT_RATELIMIT_INTERVAL, 100),
+	RATELIMIT_STATE_INIT(printk_limits[1], DEFAULT_RATELIMIT_INTERVAL, 100),
+	RATELIMIT_STATE_INIT(printk_limits[2], DEFAULT_RATELIMIT_INTERVAL, 100),
+	RATELIMIT_STATE_INIT(printk_limits[3], DEFAULT_RATELIMIT_INTERVAL, 100),
+	RATELIMIT_STATE_INIT(printk_limits[4], DEFAULT_RATELIMIT_INTERVAL, 100),
+	RATELIMIT_STATE_INIT(printk_limits[5], DEFAULT_RATELIMIT_INTERVAL, 100),
+	RATELIMIT_STATE_INIT(printk_limits[6], DEFAULT_RATELIMIT_INTERVAL, 100),
+	RATELIMIT_STATE_INIT(printk_limits[7], DEFAULT_RATELIMIT_INTERVAL, 100),
+};
+
 void btrfs_printk(const struct btrfs_fs_info *fs_info, const char *fmt, ...)
 {
 	struct super_block *sb = fs_info->sb;
@@ -192,6 +203,7 @@  void btrfs_printk(const struct btrfs_fs_info *fs_info, const char *fmt, ...)
 	va_list args;
 	const char *type = logtypes[4];
 	int kern_level;
+	struct ratelimit_state *ratelimit;
 
 	va_start(args, fmt);
 
@@ -202,13 +214,18 @@  void btrfs_printk(const struct btrfs_fs_info *fs_info, const char *fmt, ...)
 		lvl[size] = '\0';
 		fmt += size;
 		type = logtypes[kern_level - '0'];
-	} else
+		ratelimit = &printk_limits[kern_level - '0'];
+	} else {
 		*lvl = '\0';
+		/* Default to debug output */
+		ratelimit = &printk_limits[7];
+	}
 
 	vaf.fmt = fmt;
 	vaf.va = &args;
 
-	printk("%sBTRFS %s (device %s): %pV\n", lvl, type, sb->s_id, &vaf);
+	if (__ratelimit(ratelimit))
+		printk("%sBTRFS %s (device %s): %pV\n", lvl, type, sb->s_id, &vaf);
 
 	va_end(args);
 }