[PATCH 3/7] xfs: add configurable error support to metadata buffers

Carlos Maiolino
2016-05-04T15:43:32Z

With the error configuration handle for async metadata write errors
in place, we can now add initial support to the IO error processing
in xfs_buf_iodone_error().

Add an infrastructure function to look up the configuration handle,
and rearrange the error handling to prepare the way for different
error handling conigurations to be used.

Changelog:

V3:
- in xfs_buf_iodone_callbacks, use cfg->max_retries to
determine if the filesystem should fail or not, a zero value
means it should never retry.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
---
fs/xfs/xfs_buf.h | 1 +
fs/xfs/xfs_buf_item.c | 112 ++++++++++++++++++++++++++++++--------------------
fs/xfs/xfs_mount.h | 3 ++
fs/xfs/xfs_sysfs.c | 17 ++++++++
4 files changed, 88 insertions(+), 45 deletions(-)

diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 4eb89bd..adef116 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -183,6 +183,7 @@ 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 */
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 99e91a0..3a30a88 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -1042,35 +1042,22 @@ xfs_buf_do_callbacks(
}
}

-/*
- * This is the iodone() function for buffers which have had callbacks
- * attached to them by xfs_buf_attach_iodone(). It should remove each
- * log item from the buffer's list and call the callback of each in turn.
- * When done, the buffer's fsprivate field is set to NULL and the buffer
- * is unlocked with a call to iodone().
- */
-void
-xfs_buf_iodone_callbacks(
+static bool
+xfs_buf_iodone_callback_error(
struct xfs_buf *bp)
{
struct xfs_log_item *lip = bp->b_fspriv;
struct xfs_mount *mp = lip->li_mountp;
static ulong lasttime;
static xfs_buftarg_t *lasttarg;
-
- if (likely(!bp->b_error))
- goto do_callbacks;
+ struct xfs_error_cfg *cfg;

/*
* If we've already decided to shutdown the filesystem because of
* I/O errors, there's no point in giving this a retry.
*/
- if (XFS_FORCED_SHUTDOWN(mp)) {
- xfs_buf_stale(bp);
- bp->b_flags |= XBF_DONE;
- trace_xfs_buf_item_iodone(bp, _RET_IP_);
- goto do_callbacks;
- }
+ if (XFS_FORCED_SHUTDOWN(mp))
+ goto out_stale;

if (bp->b_target != lasttarg ||
time_after(jiffies, (lasttime + 5*HZ))) {
@@ -1079,45 +1066,80 @@ xfs_buf_iodone_callbacks(
}
lasttarg = bp->b_target;

+ /* synchronous writes will have callers process the error */
+ if (!(bp->b_flags & XBF_ASYNC))
+ goto out_stale;
+
+ trace_xfs_buf_item_iodone_async(bp, _RET_IP_);
+ ASSERT(bp->b_iodone != NULL);
+
/*
* If the write was asynchronous then no one will be looking for the
- * error. Clear the error state and write the buffer out again.
- *
- * XXX: This helps against transient write errors, but we need to find
- * a way to shut the filesystem down if the writes keep failing.
- *
- * In practice we'll shut the filesystem down soon as non-transient
- * errors tend to affect the whole device and a failing log write
- * will make us give up. But we really ought to do better here.
+ * error. If this is the first failure of this type, clear the error
+ * state and write the buffer out again. This means we always retry an
+ * async write failure at least once, but we also need to set the buffer
+ * up to behave correctly now for repeated failures.
*/
- if (bp->b_flags & XBF_ASYNC) {
- ASSERT(bp->b_iodone != NULL);
-
- trace_xfs_buf_item_iodone_async(bp, _RET_IP_);
+ cfg = xfs_error_get_cfg(mp, XFS_ERR_METADATA, bp->b_error);
+ if (!(bp->b_flags & (XBF_STALE|XBF_WRITE_FAIL)) ||
+ bp->b_last_error != bp->b_error) {
+ bp->b_flags |= (XBF_WRITE | XBF_ASYNC |
+ XBF_DONE | XBF_WRITE_FAIL);
+ bp->b_last_error = bp->b_error;
+ xfs_buf_ioerror(bp, 0);
+ xfs_buf_submit(bp);
+ return true;
+ }

- xfs_buf_ioerror(bp, 0); /* errno of 0 unsets the flag */
+ /*
+ * 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 (!(bp->b_flags & (XBF_STALE|XBF_WRITE_FAIL))) {
- bp->b_flags |= XBF_WRITE | XBF_ASYNC |
- XBF_DONE | XBF_WRITE_FAIL;
- xfs_buf_submit(bp);
- } else {
- xfs_buf_relse(bp);
- }
-
- return;
- }
+ /* still a transient error, higher layers will retry */
+ xfs_buf_ioerror(bp, 0);
+ xfs_buf_relse(bp);
+ return true;

/*
- * If the write of the buffer was synchronous, we want to make
- * sure to return the error to the caller of xfs_bwrite().
+ * Permanent error - we need to trigger a shutdown if we haven't already
+ * to indicate that inconsistency will result from this action.
*/
+permanent_error:
+ xfs_force_shutdown(mp, SHUTDOWN_META_IO_ERROR);
+out_stale:
xfs_buf_stale(bp);
bp->b_flags |= XBF_DONE;
-
trace_xfs_buf_error_relse(bp, _RET_IP_);
+ return false;
+}
+
+/*
+ * This is the iodone() function for buffers which have had callbacks attached
+ * to them by xfs_buf_attach_iodone(). We need to iterate the items on the
+ * callback list, mark the buffer as having no more callbacks and then push the
+ * buffer through IO completion processing.
+ */
+void
+xfs_buf_iodone_callbacks(
+ struct xfs_buf *bp)
+{
+ /*
+ * If there is an error, process it. Some errors require us
+ * to run callbacks after failure processing is done so we
+ * detect that and take appropriate action.
+ */
+ if (bp->b_error && xfs_buf_iodone_callback_error(bp))
+ return;
+
+ /*
+ * Successful IO or permanent error. Either way, we can clear the
+ * retry state here in preparation for the next error that may occur.
+ */
+ bp->b_last_error = 0;

-do_callbacks:
xfs_buf_do_callbacks(bp);
bp->b_fspriv = NULL;
bp->b_iodone = NULL;
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 352a5c8..0c5a976 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -387,4 +387,7 @@ extern void xfs_set_low_space_thresholds(struct xfs_mount *);
int xfs_zero_extent(struct xfs_inode *ip, xfs_fsblock_t start_fsb,
xfs_off_t count_fsb);

+struct xfs_error_cfg * xfs_error_get_cfg(struct xfs_mount *mp,
+ int error_class, int error);
+
#endif /* __XFS_MOUNT_H__ */
diff --git a/fs/xfs/xfs_sysfs.c b/fs/xfs/xfs_sysfs.c
index 7180cff..0a9adcd 100644
--- a/fs/xfs/xfs_sysfs.c
+++ b/fs/xfs/xfs_sysfs.c
@@ -447,3 +447,20 @@ xfs_error_sysfs_del(
xfs_sysfs_del(&mp->m_error_meta_kobj);
xfs_sysfs_del(&mp->m_error_kobj);
}
+
+struct xfs_error_cfg *
+xfs_error_get_cfg(
+ struct xfs_mount *mp,
+ int error_class,
+ int error)
+{
+ struct xfs_error_cfg *cfg;
+
+ switch (error) {
+ default:
+ cfg = &mp->m_error_cfg[error_class][XFS_ERR_DEFAULT];
+ break;
+ }
+
+ return cfg;
+}
--
2.4.11