[PATCH v1 14/15] NFS: Trace short NFS READs

Chuck Lever
2020-05-12T21:14:08Z

A short read can generate an -EIO error without there being an error
on the wire. This tracepoint acts as an eyecatcher when there is no
obvious I/O error.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
fs/nfs/nfstrace.h | 47 +++++++++++++++++++++++++++++++++++++++++++++++
fs/nfs/read.c | 2 ++
2 files changed, 49 insertions(+)

diff --git a/fs/nfs/nfstrace.h b/fs/nfs/nfstrace.h
index e90651431804..b35998c5c9ca 100644
--- a/fs/nfs/nfstrace.h
+++ b/fs/nfs/nfstrace.h
@@ -961,6 +961,53 @@
)
);

+TRACE_EVENT(nfs_readpage_short,
+ TP_PROTO(
+ const struct rpc_task *task,
+ const struct nfs_pgio_header *hdr
+ ),
+
+ TP_ARGS(task, hdr),
+
+ TP_STRUCT__entry(
+ __field(dev_t, dev)
+ __field(u32, fhandle)
+ __field(u64, fileid)
+ __field(loff_t, offset)
+ __field(u32, arg_count)
+ __field(u32, res_count)
+ __field(bool, eof)
+ __field(int, status)
+ ),
+
+ TP_fast_assign(
+ const struct inode *inode = hdr->inode;
+ const struct nfs_inode *nfsi = NFS_I(inode);
+ const struct nfs_fh *fh = hdr->args.fh ?
+ hdr->args.fh : &nfsi->fh;
+
+ __entry->status = task->tk_status;
+ __entry->offset = hdr->args.offset;
+ __entry->arg_count = hdr->args.count;
+ __entry->res_count = hdr->res.count;
+ __entry->eof = hdr->res.eof;
+ __entry->dev = inode->i_sb->s_dev;
+ __entry->fileid = nfsi->fileid;
+ __entry->fhandle = nfs_fhandle_hash(fh);
+ ),
+
+ TP_printk(
+ "fileid=%02x:%02x:%llu fhandle=0x%08x "
+ "offset=%lld count=%u res=%u status=%d%s",
+ MAJOR(__entry->dev), MINOR(__entry->dev),
+ (unsigned long long)__entry->fileid,
+ __entry->fhandle,
+ (long long)__entry->offset, __entry->arg_count,
+ __entry->res_count, __entry->status,
+ __entry->eof ? " eof" : ""
+ )
+);
+
TRACE_DEFINE_ENUM(NFS_UNSTABLE);
TRACE_DEFINE_ENUM(NFS_DATA_SYNC);
TRACE_DEFINE_ENUM(NFS_FILE_SYNC);
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 13b22e898116..eb854f1f86e2 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -264,6 +264,8 @@ static void nfs_readpage_retry(struct rpc_task *task,

/* This is a short read! */
nfs_inc_stats(hdr->inode, NFSIOS_SHORTREAD);
+ trace_nfs_readpage_short(task, hdr);
+
/* Has the server at least made some progress? */
if (resp->count == 0) {
nfs_set_pgio_error(hdr, -EIO, argp->offset);