xfs: add configuration of error failure speed

On reception of an error, we can fail immediately, perform some
bound amount of retries or retry indefinitely. The current behaviour
we have is to retry forever.

However, we'd like the ability to choose how long the filesystem
should try after an error, it can either fail immediately, retry a
few times, or retry forever. This is implemented by using
max_retries sysfs attribute, to hold the amount of times we allow
the filesystem to retry after an error. Being -1 a special case
where the filesystem will retry indefinitely.

Add both a maximum retry count and a retry timeout so that we can
bound by time and/or physical IO attempts.

Finally, plumb these into xfs_buf_iodone error processing so that
the error behaviour follows the selected configuration.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_buf.h

@@ -183,7 +183,26 @@ typedef struct xfs_buf {
 	unsigned int		b_page_count;	/* size of page array */
 	unsigned int		b_offset;	/* page offset in first page */
 	int			b_error;	/* error code on I/O */
-	int			b_last_error;	/* previous async I/O error */
+
+	/*
+	 * async write failure retry count. Initialised to zero on the first
+	 * failure, then when it exceeds the maximum configured without a
+	 * success the write is considered to be failed permanently and the
+	 * iodone handler will take appropriate action.
+	 *
+	 * For retry timeouts, we record the jiffie of the first failure. This
+	 * means that we can change the retry timeout for buffers already under
+	 * I/O and thus avoid getting stuck in a retry loop with a long timeout.
+	 *
+	 * last_error is used to ensure that we are getting repeated errors, not
+	 * different errors. e.g. a block device might change ENOSPC to EIO when
+	 * a failure timeout occurs, so we want to re-initialise the error
+	 * retry behaviour appropriately when that happens.
+	 */
+	int			b_retries;
+	unsigned long		b_first_retry_time; /* in jiffies */
+	int			b_last_error;
+
 	const struct xfs_buf_ops	*b_ops;
 
 #ifdef XFS_BUF_LOCK_TRACKING

fs/xfs/xfs_buf_item.c

@@ -1085,6 +1085,9 @@ xfs_buf_iodone_callback_error(
 		bp->b_flags |= (XBF_WRITE | XBF_ASYNC |
 			        XBF_DONE | XBF_WRITE_FAIL);
 		bp->b_last_error = bp->b_error;
+		bp->b_retries = 0;
+		bp->b_first_retry_time = jiffies;
+
 		xfs_buf_ioerror(bp, 0);
 		xfs_buf_submit(bp);
 		return true;
@@ -1095,8 +1098,13 @@ xfs_buf_iodone_callback_error(
 	 * error configuration we have been set up to use.
 	 */
 	cfg = xfs_error_get_cfg(mp, XFS_ERR_METADATA, bp->b_error);
-	if (!cfg->max_retries)
-		goto permanent_error;
+
+	if (cfg->max_retries != XFS_ERR_RETRY_FOREVER &&
+	    ++bp->b_retries > cfg->max_retries)
+			goto permanent_error;
+	if (cfg->retry_timeout &&
+	    time_after(jiffies, cfg->retry_timeout + bp->b_first_retry_time))
+			goto permanent_error;
 
 	/* still a transient error, higher layers will retry */
 	xfs_buf_ioerror(bp, 0);
@@ -1139,6 +1147,7 @@ xfs_buf_iodone_callbacks(
 	 * retry state here in preparation for the next error that may occur.
 	 */
 	bp->b_last_error = 0;
+	bp->b_retries = 0;
 
 	xfs_buf_do_callbacks(bp);
 	bp->b_fspriv = NULL;

fs/xfs/xfs_mount.h

@@ -52,9 +52,12 @@ enum {
 	XFS_ERR_ERRNO_MAX,
 };
 
+#define XFS_ERR_RETRY_FOREVER	-1
+
 struct xfs_error_cfg {
 	struct xfs_kobj	kobj;
 	int		max_retries;
+	unsigned long	retry_timeout;	/* in jiffies, 0 = no timeout */
 };
 
 typedef struct xfs_mount {

fs/xfs/xfs_sysfs.c

@@ -374,17 +374,86 @@ struct kobj_type xfs_log_ktype = {
  * and any other future type of IO (e.g. special inode or directory error
  * handling) we care to support.
  */
-static struct attribute *xfs_error_attrs[] = {
-	NULL,
-};
-
 static inline struct xfs_error_cfg *
 to_error_cfg(struct kobject *kobject)
 {
 	struct xfs_kobj *kobj = to_kobj(kobject);
 	return container_of(kobj, struct xfs_error_cfg, kobj);
 }
 
+static ssize_t
+max_retries_show(
+	struct kobject	*kobject,
+	char		*buf)
+{
+	struct xfs_error_cfg *cfg = to_error_cfg(kobject);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", cfg->max_retries);
+}
+
+static ssize_t
+max_retries_store(
+	struct kobject	*kobject,
+	const char	*buf,
+	size_t		count)
+{
+	struct xfs_error_cfg *cfg = to_error_cfg(kobject);
+	int		ret;
+	int		val;
+
+	ret = kstrtoint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	if (val < -1)
+		return -EINVAL;
+
+	cfg->max_retries = val;
+	return count;
+}
+XFS_SYSFS_ATTR_RW(max_retries);
+
+static ssize_t
+retry_timeout_seconds_show(
+	struct kobject	*kobject,
+	char		*buf)
+{
+	struct xfs_error_cfg *cfg = to_error_cfg(kobject);
+
+	return snprintf(buf, PAGE_SIZE, "%ld\n",
+			jiffies_to_msecs(cfg->retry_timeout) / MSEC_PER_SEC);
+}
+
+static ssize_t
+retry_timeout_seconds_store(
+	struct kobject	*kobject,
+	const char	*buf,
+	size_t		count)
+{
+	struct xfs_error_cfg *cfg = to_error_cfg(kobject);
+	int		ret;
+	int		val;
+
+	ret = kstrtoint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	/* 1 day timeout maximum */
+	if (val < 0 || val > 86400)
+		return -EINVAL;
+
+	cfg->retry_timeout = msecs_to_jiffies(val * MSEC_PER_SEC);
+	return count;
+}
+XFS_SYSFS_ATTR_RW(retry_timeout_seconds);
+
+static struct attribute *xfs_error_attrs[] = {
+	ATTR_LIST(max_retries),
+	ATTR_LIST(retry_timeout_seconds),
+	NULL,
+};
+
+
 struct kobj_type xfs_error_cfg_ktype = {
 	.release = xfs_sysfs_release,
 	.sysfs_ops = &xfs_sysfs_ops,
@@ -404,11 +473,13 @@ struct kobj_type xfs_error_ktype = {
 struct xfs_error_init {
 	char		*name;
 	int		max_retries;
+	int		retry_timeout;	/* in seconds */
 };
 
 static const struct xfs_error_init xfs_error_meta_init[XFS_ERR_ERRNO_MAX] = {
 	{ .name = "default",
 	  .max_retries = -1,
+	  .retry_timeout = 0,
 	},
 };
 
@@ -439,6 +510,8 @@ xfs_error_sysfs_init_class(
 			goto out_error;
 
 		cfg->max_retries = init[i].max_retries;
+		cfg->retry_timeout = msecs_to_jiffies(
+					init[i].retry_timeout * MSEC_PER_SEC);
 	}
 	return 0;