[PATCH v7 16/31] netfs: Add a tracepoint to log failures that would be otherwise unseen

David Howells
2021-04-23T13:32:31Z

Add a tracepoint to log internal failures (such as cache errors) that we
don't otherwise want to pass back to the netfs.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Dave Wysochanski <dwysocha@redhat.com>
Tested-By: Marc Dionne <marc.dionne@auristor.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/161781048813.463527.1557000804674707986.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/161789082749.6155.15498680577213140870.stgit@warthog.procyon.org.uk/ # v6
---

fs/netfs/read_helper.c | 14 +++++++++-
include/trace/events/netfs.h | 58 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index cd3b61d5e192..1d3b50c5db6d 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -271,6 +271,8 @@ static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error,

if (IS_ERR_VALUE(transferred_or_error)) {
netfs_stat(&netfs_n_rh_write_failed);
+ trace_netfs_failure(rreq, subreq, transferred_or_error,
+ netfs_fail_copy_to_cache);
} else {
netfs_stat(&netfs_n_rh_write_done);
}
@@ -323,6 +325,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
ret = cres->ops->prepare_write(cres, &subreq->start, &subreq->len,
rreq->i_size);
if (ret < 0) {
+ trace_netfs_failure(rreq, subreq, ret, netfs_fail_prepare_write);
trace_netfs_sreq(subreq, netfs_sreq_trace_write_skip);
continue;
}
@@ -627,6 +630,8 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,

if (IS_ERR_VALUE(transferred_or_error)) {
subreq->error = transferred_or_error;
+ trace_netfs_failure(rreq, subreq, transferred_or_error,
+ netfs_fail_read);
goto failed;
}

@@ -996,8 +1001,10 @@ int netfs_readpage(struct file *file,
} while (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags));

ret = rreq->error;
- if (ret == 0 && rreq->submitted < rreq->len)
+ if (ret == 0 && rreq->submitted < rreq->len) {
+ trace_netfs_failure(rreq, NULL, ret, netfs_fail_short_readpage);
ret = -EIO;
+ }
out:
netfs_put_read_request(rreq, false);
return ret;
@@ -1069,6 +1076,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
/* Allow the netfs (eg. ceph) to flush conflicts. */
ret = ops->check_write_begin(file, pos, len, page, _fsdata);
if (ret < 0) {
+ trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin);
if (ret == -EAGAIN)
goto retry;
goto error;
@@ -1145,8 +1153,10 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
}

ret = rreq->error;
- if (ret == 0 && rreq->submitted < rreq->len)
+ if (ret == 0 && rreq->submitted < rreq->len) {
+ trace_netfs_failure(rreq, NULL, ret, netfs_fail_short_write_begin);
ret = -EIO;
+ }
netfs_put_read_request(rreq, false);
if (ret < 0)
goto error;
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index e3ebeabd3852..de1c64635e42 100644
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -47,6 +47,15 @@ enum netfs_sreq_trace {
netfs_sreq_trace_write_term,
};

+enum netfs_failure {
+ netfs_fail_check_write_begin,
+ netfs_fail_copy_to_cache,
+ netfs_fail_read,
+ netfs_fail_short_readpage,
+ netfs_fail_short_write_begin,
+ netfs_fail_prepare_write,
+};
+
#endif

#define netfs_read_traces \
@@ -81,6 +90,14 @@ enum netfs_sreq_trace {
EM(netfs_sreq_trace_write_skip, "SKIP ") \
E_(netfs_sreq_trace_write_term, "WTERM")

+#define netfs_failures \
+ EM(netfs_fail_check_write_begin, "check-write-begin") \
+ EM(netfs_fail_copy_to_cache, "copy-to-cache") \
+ EM(netfs_fail_read, "read") \
+ EM(netfs_fail_short_readpage, "short-readpage") \
+ EM(netfs_fail_short_write_begin, "short-write-begin") \
+ E_(netfs_fail_prepare_write, "prep-write")
+

/*
* Export enum symbols via userspace.
@@ -94,6 +111,7 @@ netfs_read_traces;
netfs_rreq_traces;
netfs_sreq_sources;
netfs_sreq_traces;
+netfs_failures;

/*
* Now redefine the EM() and E_() macros to map the enums to the strings that
@@ -197,6 +215,46 @@ TRACE_EVENT(netfs_sreq,
__entry->error)
);

+TRACE_EVENT(netfs_failure,
+ TP_PROTO(struct netfs_read_request *rreq,
+ struct netfs_read_subrequest *sreq,
+ int error, enum netfs_failure what),
+
+ TP_ARGS(rreq, sreq, error, what),
+
+ TP_STRUCT__entry(
+ __field(unsigned int, rreq )
+ __field(unsigned short, index )
+ __field(short, error )
+ __field(unsigned short, flags )
+ __field(enum netfs_read_source, source )
+ __field(enum netfs_failure, what )
+ __field(size_t, len )
+ __field(size_t, transferred )
+ __field(loff_t, start )
+ ),
+
+ TP_fast_assign(
+ __entry->rreq = rreq->debug_id;
+ __entry->index = sreq ? sreq->debug_index : 0;
+ __entry->error = error;
+ __entry->flags = sreq ? sreq->flags : 0;
+ __entry->source = sreq ? sreq->source : NETFS_INVALID_READ;
+ __entry->what = what;
+ __entry->len = sreq ? sreq->len : 0;
+ __entry->transferred = sreq ? sreq->transferred : 0;
+ __entry->start = sreq ? sreq->start : 0;
+ ),
+
+ TP_printk("R=%08x[%u] %s f=%02x s=%llx %zx/%zx %s e=%d",
+ __entry->rreq, __entry->index,
+ __print_symbolic(__entry->source, netfs_sreq_sources),
+ __entry->flags,
+ __entry->start, __entry->transferred, __entry->len,
+ __print_symbolic(__entry->what, netfs_failures),
+ __entry->error)
+ );
+
#endif /* _TRACE_NETFS_H */

/* This part must be outside protection */