[PATCH 5/7] xfs: add configuration of error failure speed

Carlos Maiolino
2016-05-03T17:55:51Z

From: Dave Chinner <dchinner@redhat.com>

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 what behaviour we have, and
that requires the ability to configure the behaviour through the new
sysfs interfaces.

max_retries is used to set the number of retries to do until permanently fail,
the only special case is when it is set to -1, which, will cause the system to
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>
---
fs/xfs/xfs_buf.h | 23 ++++++++++++++-
fs/xfs/xfs_buf_item.c | 13 +++++++--
fs/xfs/xfs_mount.h | 3 +-
fs/xfs/xfs_sysfs.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++---
4 files changed, 112 insertions(+), 8 deletions(-)

diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index adef116..bd978f0 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -183,7 +183,28 @@ 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 and it on the next error
+ * it will be checked against the newly configured timeout. This
+ * prevents buffers getting stuck in retry loops with a really 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
diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index 3a30a88..68ed2a0 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -1086,6 +1086,9 @@ 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(
* Repeated failure on an async write. Take action according to the
* error configuration we have been set up to use.
*/
- if (!cfg->max_retries)
- goto permanent_error;
+ if (cfg->max_retries >= 0)
+ if (++bp->b_retries > cfg->max_retries)
+ goto permanent_error;
+ if (cfg->retry_timeout)
+ if (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;
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 0c5a976..0382140 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -54,7 +54,8 @@ enum {

struct xfs_error_cfg {
struct xfs_kobj kobj;
- int max_retries;
+ int max_retries; /* -1 = retry forever */
+ unsigned long retry_timeout; /* in jiffies, 0 = no timeout */
};

typedef struct xfs_mount {
diff --git a/fs/xfs/xfs_sysfs.c b/fs/xfs/xfs_sysfs.c
index e49a6de..fa291c4 100644
--- a/fs/xfs/xfs_sysfs.c
+++ b/fs/xfs/xfs_sysfs.c
@@ -374,10 +374,6 @@ 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)
{
@@ -385,6 +381,79 @@ to_error_cfg(struct kobject *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 || val > INT_MAX)
+ 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;