Re: [PATCH v2 15/18] nfsd: Add I/O trace points in the NFSv4 read proc

[Bruce Fields <bfields@fieldses.org>]

On Tue, Mar 27, 2018 at 05:22:28PM -0400, Chuck Lever wrote:
> 
> 
> > On Mar 27, 2018, at 4:14 PM, Bruce Fields <bfields@fieldses.org> wrote:
> > 
> > Could you check that I got this right in
> > 
> > 	git://linux-nfs.org/~bfields/linux.git nfsd-next
> 
> You changed it correctly.
> 
> However, the patch description says "Also, we want to record any local I/O error that occurs, and the total count of bytes that were actually moved."
> 
> Therefore I think we want to pass host_err rather than maxcount to trace_nfsd_read_io_done, in both NFSv4 read helpers.
> 
> Do you want me to resend with these fixes?

Sure, thanks!--b.

> 
> 
> > --b.
> > 
> > On Tue, Mar 27, 2018 at 12:57:17PM -0400, Chuck Lever wrote:
> >> 
> >> 
> >>> On Mar 27, 2018, at 10:53 AM, Chuck Lever <chuck.lever@oracle.com> wrote:
> >>> 
> >>> NFSv4 read compound processing invokes nfsd_splice_read and
> >>> nfs_readv directly, so the trace points currently in nfsd_read are
> >>> not effective for NFSv4 reads.
> >>> 
> >>> Move and copy the trace points so that NFSv4 reads are captured.
> >>> Also, we want to record any local I/O error that occurs, and
> >>> the total count of bytes that were actually moved. And, also
> >>> whether splice or vectored read was used.
> >>> 
> >>> The svc_fh is not passed to the read helpers, so some code
> >>> duplication is necessary.
> >>> 
> >>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> >>> ---
> >>> fs/nfsd/nfs4proc.c |    5 +++++
> >>> fs/nfsd/nfs4xdr.c  |   56 +++++++++++++++++++++++++++++++++++++---------------
> >>> fs/nfsd/trace.h    |    4 +++-
> >>> fs/nfsd/vfs.c      |   54 ++++++++++++++++++++++----------------------------
> >>> fs/nfsd/vfs.h      |    8 ++++---
> >>> 5 files changed, 76 insertions(+), 51 deletions(-)
> >>> 
> >>> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> >>> index b93673e..39016b6 100644
> >>> --- a/fs/nfsd/nfs4proc.c
> >>> +++ b/fs/nfsd/nfs4proc.c
> >>> @@ -751,6 +751,9 @@ static __be32 nfsd4_do_lookupp(struct svc_rqst *rqstp, struct svc_fh *fh)
> >>> 	if (read->rd_offset >= OFFSET_MAX)
> >>> 		return nfserr_inval;
> >>> 
> >>> +	trace_nfsd_read_start(rqstp, &cstate->current_fh,
> >>> +			      read->rd_offset, read->rd_length);
> >>> +
> >>> 	/*
> >>> 	 * If we do a zero copy read, then a client will see read data
> >>> 	 * that reflects the state of the file *after* performing the
> >>> @@ -783,6 +786,8 @@ static __be32 nfsd4_do_lookupp(struct svc_rqst *rqstp, struct svc_fh *fh)
> >>> {
> >>> 	if (u->read.rd_filp)
> >>> 		fput(u->read.rd_filp);
> >>> +	trace_nfsd_read_done(u->read.rd_rqstp, u->read.rd_fhp,
> >>> +			     u->read.rd_offset, u->read.rd_length);
> >>> }
> >>> 
> >>> static __be32
> >>> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> >>> index e502fd1..d03059a 100644
> >>> --- a/fs/nfsd/nfs4xdr.c
> >>> +++ b/fs/nfsd/nfs4xdr.c
> >>> @@ -37,6 +37,7 @@
> >>> #include <linux/file.h>
> >>> #include <linux/slab.h>
> >>> #include <linux/namei.h>
> >>> +#include <linux/fsnotify.h>
> >>> #include <linux/statfs.h>
> >>> #include <linux/utsname.h>
> >>> #include <linux/pagemap.h>
> >>> @@ -50,6 +51,7 @@
> >>> #include "cache.h"
> >>> #include "netns.h"
> >>> #include "pnfs.h"
> >>> +#include "trace.h"
> >>> 
> >>> #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
> >>> #include <linux/security.h>
> >>> @@ -3416,28 +3418,28 @@ static __be32 nfsd4_encode_splice_read(
> >>> {
> >>> 	struct xdr_stream *xdr = &resp->xdr;
> >>> 	struct xdr_buf *buf = xdr->buf;
> >>> +	int host_err;
> >>> 	u32 eof;
> >>> 	long len;
> >>> 	int space_left;
> >>> -	__be32 nfserr;
> >>> 	__be32 *p = xdr->p - 2;
> >>> 
> >>> 	/* Make sure there will be room for padding if needed */
> >>> 	if (xdr->end - xdr->p < 1)
> >>> 		return nfserr_resource;
> >>> 
> >>> +	trace_nfsd_read_splice(resp->rqstp, read->rd_fhp,
> >>> +			       read->rd_offset, maxcount);
> >>> 	len = maxcount;
> >>> -	nfserr = nfsd_splice_read(read->rd_rqstp, file,
> >>> +	host_err = nfsd_splice_read(read->rd_rqstp, file,
> >>> 				  read->rd_offset, &maxcount);
> >>> -	if (nfserr) {
> >>> -		/*
> >>> -		 * nfsd_splice_actor may have already messed with the
> >>> -		 * page length; reset it so as not to confuse
> >>> -		 * xdr_truncate_encode:
> >>> -		 */
> >>> -		buf->page_len = 0;
> >>> -		return nfserr;
> >>> -	}
> >>> +	if (host_err < 0)
> >>> +		goto err;
> >>> +	trace_nfsd_read_io_done(read->rd_rqstp, read->rd_fhp,
> >>> +				read->rd_offset, maxcount);
> >>> +	maxcount = host_err;
> >>> +	nfsdstats.io_read += maxcount;
> >>> +	fsnotify_access(file);
> >>> 
> >>> 	eof = nfsd_eof_on_read(len, maxcount, read->rd_offset,
> >>> 				d_inode(read->rd_fhp->fh_dentry)->i_size);
> >>> @@ -3470,6 +3472,17 @@ static __be32 nfsd4_encode_splice_read(
> >>> 	xdr->end = (__be32 *)((void *)xdr->end + space_left);
> >>> 
> >>> 	return 0;
> >>> +
> >>> +err:
> >>> +	/*
> >>> +	 * nfsd_splice_actor may have already messed with the
> >>> +	 * page length; reset it so as not to confuse
> >>> +	 * xdr_truncate_encode:
> >>> +	 */
> >>> +	buf->page_len = 0;
> >>> +	trace_nfsd_read_err(read->rd_rqstp, read->rd_fhp,
> >>> +			    read->rd_offset, host_err);
> >>> +	return nfserrno(host_err);
> >>> }
> >>> 
> >>> static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
> >>> @@ -3477,12 +3490,12 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
> >>> 				 struct file *file, unsigned long maxcount)
> >>> {
> >>> 	struct xdr_stream *xdr = &resp->xdr;
> >>> +	int host_err;
> >>> 	u32 eof;
> >>> 	int v;
> >>> 	int starting_len = xdr->buf->len - 8;
> >>> 	long len;
> >>> 	int thislen;
> >>> -	__be32 nfserr;
> >>> 	__be32 tmp;
> >>> 	__be32 *p;
> >>> 	u32 zzz = 0;
> >>> @@ -3510,11 +3523,18 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
> >>> 	}
> >>> 	read->rd_vlen = v;
> >>> 
> >>> +	trace_nfsd_read_vector(resp->rqstp, read->rd_fhp,
> >>> +			       read->rd_offset, maxcount);
> >>> 	len = maxcount;
> >>> -	nfserr = nfsd_readv(file, read->rd_offset, resp->rqstp->rq_vec,
> >>> -			read->rd_vlen, &maxcount);
> >>> -	if (nfserr)
> >>> -		return nfserr;
> >>> +	host_err = nfsd_readv(file, read->rd_offset, resp->rqstp->rq_vec,
> >>> +			      read->rd_vlen, &maxcount);
> >>> +	if (host_err < 0)
> >>> +		goto err;
> >>> +	trace_nfsd_read_io_done(resp->rqstp, read->rd_fhp,
> >>> +				read->rd_offset, maxcount);
> >> 
> >> I missed a spot.
> >> 
> >> +	maxcount = host_err;
> >> 
> >>> +	nfsdstats.io_read += maxcount;
> >>> +	fsnotify_access(file);
> >>> +
> >>> 	xdr_truncate_encode(xdr, starting_len + 8 + ((maxcount+3)&~3));
> >>> 
> >>> 	eof = nfsd_eof_on_read(len, maxcount, read->rd_offset,
> >>> @@ -3530,6 +3550,10 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
> >>> 								&zzz, pad);
> >>> 	return 0;
> >>> 
> >>> +err:
> >>> +	trace_nfsd_read_err(resp->rqstp, read->rd_fhp,
> >>> +			    read->rd_offset, host_err);
> >>> +	return nfserrno(host_err);
> >>> }
> >>> 
> >>> static __be32
> >>> diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> >>> index 653e9ee..a8bbd9d 100644
> >>> --- a/fs/nfsd/trace.h
> >>> +++ b/fs/nfsd/trace.h
> >>> @@ -43,7 +43,8 @@
> >>> 	TP_ARGS(rqstp, fhp, offset, len))
> >>> 
> >>> DEFINE_NFSD_IO_EVENT(read_start);
> >>> -DEFINE_NFSD_IO_EVENT(read_opened);
> >>> +DEFINE_NFSD_IO_EVENT(read_splice);
> >>> +DEFINE_NFSD_IO_EVENT(read_vector);
> >>> DEFINE_NFSD_IO_EVENT(read_io_done);
> >>> DEFINE_NFSD_IO_EVENT(read_done);
> >>> DEFINE_NFSD_IO_EVENT(write_start);
> >>> @@ -82,6 +83,7 @@
> >>> 		 int		len),		\
> >>> 	TP_ARGS(rqstp, fhp, offset, len))
> >>> 
> >>> +DEFINE_NFSD_ERR_EVENT(read_err);
> >>> DEFINE_NFSD_ERR_EVENT(write_err);
> >>> 
> >>> #include "state.h"
> >>> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> >>> index ee59a0b..0fa54b5 100644
> >>> --- a/fs/nfsd/vfs.c
> >>> +++ b/fs/nfsd/vfs.c
> >>> @@ -881,19 +881,7 @@ static int nfsd_direct_splice_actor(struct pipe_inode_info *pipe,
> >>> 	return __splice_from_pipe(pipe, sd, nfsd_splice_actor);
> >>> }
> >>> 
> >>> -static __be32
> >>> -nfsd_finish_read(struct file *file, unsigned long *count, int host_err)
> >>> -{
> >>> -	if (host_err >= 0) {
> >>> -		nfsdstats.io_read += host_err;
> >>> -		*count = host_err;
> >>> -		fsnotify_access(file);
> >>> -		return 0;
> >>> -	} else 
> >>> -		return nfserrno(host_err);
> >>> -}
> >>> -
> >>> -__be32 nfsd_splice_read(struct svc_rqst *rqstp,
> >>> +int nfsd_splice_read(struct svc_rqst *rqstp,
> >>> 		     struct file *file, loff_t offset, unsigned long *count)
> >>> {
> >>> 	struct splice_desc sd = {
> >>> @@ -902,23 +890,18 @@ __be32 nfsd_splice_read(struct svc_rqst *rqstp,
> >>> 		.pos		= offset,
> >>> 		.u.data		= rqstp,
> >>> 	};
> >>> -	int host_err;
> >>> 
> >>> 	rqstp->rq_next_page = rqstp->rq_respages + 1;
> >>> -	host_err = splice_direct_to_actor(file, &sd, nfsd_direct_splice_actor);
> >>> -	return nfsd_finish_read(file, count, host_err);
> >>> +	return splice_direct_to_actor(file, &sd, nfsd_direct_splice_actor);
> >>> }
> >>> 
> >>> -__be32 nfsd_readv(struct file *file, loff_t offset, struct kvec *vec, int vlen,
> >>> -		unsigned long *count)
> >>> +int nfsd_readv(struct file *file, loff_t offset, struct kvec *vec, int vlen,
> >>> +	       unsigned long *count)
> >>> {
> >>> 	struct iov_iter iter;
> >>> -	int host_err;
> >>> 
> >>> 	iov_iter_kvec(&iter, READ | ITER_KVEC, vec, vlen, *count);
> >>> -	host_err = vfs_iter_read(file, &iter, &offset, 0);
> >>> -
> >>> -	return nfsd_finish_read(file, count, host_err);
> >>> +	return vfs_iter_read(file, &iter, &offset, 0);
> >>> }
> >>> 
> >>> /*
> >>> @@ -1025,6 +1008,7 @@ __be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
> >>> {
> >>> 	struct file *file;
> >>> 	struct raparms	*ra;
> >>> +	int host_err;
> >>> 	__be32 err;
> >>> 
> >>> 	trace_nfsd_read_start(rqstp, fhp, offset, *count);
> >>> @@ -1034,14 +1018,24 @@ __be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
> >>> 
> >>> 	ra = nfsd_init_raparms(file);
> >>> 
> >>> -	trace_nfsd_read_opened(rqstp, fhp, offset, *count);
> >>> -
> >>> -	if (file->f_op->splice_read && test_bit(RQ_SPLICE_OK, &rqstp->rq_flags))
> >>> -		err = nfsd_splice_read(rqstp, file, offset, count);
> >>> -	else
> >>> -		err = nfsd_readv(file, offset, vec, vlen, count);
> >>> -
> >>> -	trace_nfsd_read_io_done(rqstp, fhp, offset, *count);
> >>> +	if (file->f_op->splice_read &&
> >>> +	    test_bit(RQ_SPLICE_OK, &rqstp->rq_flags)) {
> >>> +		trace_nfsd_read_splice(rqstp, fhp, offset, *count);
> >>> +		host_err = nfsd_splice_read(rqstp, file, offset, count);
> >>> +	} else {
> >>> +		trace_nfsd_read_vector(rqstp, fhp, offset, *count);
> >>> +		host_err = nfsd_readv(file, offset, vec, vlen, count);
> >>> +	}
> >>> +	if (host_err >= 0) {
> >>> +		trace_nfsd_read_io_done(rqstp, fhp, offset, host_err);
> >>> +		nfsdstats.io_read += host_err;
> >>> +		*count = host_err;
> >>> +		fsnotify_access(file);
> >>> +		err = nfs_ok;
> >>> +	} else  {
> >>> +		trace_nfsd_read_err(rqstp, fhp, offset, host_err);
> >>> +		err = nfserrno(host_err);
> >>> +	}
> >>> 
> >>> 	if (ra)
> >>> 		nfsd_put_raparams(file, ra);
> >>> diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
> >>> index be6d8e0..d9131c3 100644
> >>> --- a/fs/nfsd/vfs.h
> >>> +++ b/fs/nfsd/vfs.h
> >>> @@ -78,10 +78,10 @@ __be32		nfsd_commit(struct svc_rqst *, struct svc_fh *,
> >>> __be32		nfsd_open(struct svc_rqst *, struct svc_fh *, umode_t,
> >>> 				int, struct file **);
> >>> struct raparms;
> >>> -__be32		nfsd_splice_read(struct svc_rqst *,
> >>> -				struct file *, loff_t, unsigned long *);
> >>> -__be32		nfsd_readv(struct file *, loff_t, struct kvec *, int,
> >>> -				unsigned long *);
> >>> +int		nfsd_splice_read(struct svc_rqst *rqstp, struct file *file,
> >>> +				loff_t offset, unsigned long *count);
> >>> +int		nfsd_readv(struct file *file, loff_t offset, struct kvec *vec,
> >>> +				int vlen, unsigned long *count);
> >>> __be32 		nfsd_read(struct svc_rqst *, struct svc_fh *,
> >>> 				loff_t, struct kvec *, int, unsigned long *);
> >>> __be32 		nfsd_write(struct svc_rqst *, struct svc_fh *, loff_t,
> >>> 
> >>> --
> >>> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> >>> the body of a message to majordomo@vger.kernel.org
> >>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >> 
> >> --
> >> Chuck Lever
> >> 
> >> 
> 
> --
> Chuck Lever
> 
>