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Date: Wed, 21 Jul 2021 13:43:47 -0400
From: Jeff Layton <jlayton@...hat.com>
To: David Howells <dhowells@...hat.com>, linux-fsdevel@...r.kernel.org
Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>,
Anna Schumaker <anna.schumaker@...app.com>,
Steve French <sfrench@...ba.org>,
Dominique Martinet <asmadeus@...ewreck.org>,
Mike Marshall <hubcap@...ibond.com>,
David Wysochanski <dwysocha@...hat.com>,
Shyam Prasad N <nspmangalore@...il.com>,
Miklos Szeredi <miklos@...redi.hu>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-cachefs@...hat.com, linux-afs@...ts.infradead.org,
linux-nfs@...r.kernel.org, linux-cifs@...r.kernel.org,
ceph-devel@...r.kernel.org, v9fs-developer@...ts.sourceforge.net,
devel@...ts.orangefs.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 03/12] netfs: Remove
netfs_read_subrequest::transferred
On Wed, 2021-07-21 at 14:45 +0100, David Howells wrote:
> Remove netfs_read_subrequest::transferred as it's redundant as the count on
> the iterator added to the subrequest can be used instead.
>
> Signed-off-by: David Howells <dhowells@...hat.com>
> ---
>
> fs/afs/file.c | 4 ++--
> fs/netfs/read_helper.c | 26 ++++----------------------
> include/linux/netfs.h | 1 -
> include/trace/events/netfs.h | 12 ++++++------
> 4 files changed, 12 insertions(+), 31 deletions(-)
>
> diff --git a/fs/afs/file.c b/fs/afs/file.c
> index ca529f23515a..82e945dbe379 100644
> --- a/fs/afs/file.c
> +++ b/fs/afs/file.c
> @@ -315,8 +315,8 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
> return netfs_subreq_terminated(subreq, -ENOMEM, false);
>
> fsreq->subreq = subreq;
> - fsreq->pos = subreq->start + subreq->transferred;
> - fsreq->len = subreq->len - subreq->transferred;
> + fsreq->pos = subreq->start + subreq->len - iov_iter_count(&subreq->iter);
> + fsreq->len = iov_iter_count(&subreq->iter);
> fsreq->key = subreq->rreq->netfs_priv;
> fsreq->vnode = vnode;
> fsreq->iter = &subreq->iter;
> diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
> index 715f3e9c380d..5e1a9be48130 100644
> --- a/fs/netfs/read_helper.c
> +++ b/fs/netfs/read_helper.c
> @@ -148,12 +148,7 @@ static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq,
> */
> static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
> {
> - struct iov_iter iter;
> -
> - iov_iter_xarray(&iter, READ, &subreq->rreq->mapping->i_pages,
> - subreq->start + subreq->transferred,
> - subreq->len - subreq->transferred);
> - iov_iter_zero(iov_iter_count(&iter), &iter);
> + iov_iter_zero(iov_iter_count(&subreq->iter), &subreq->iter);
> }
>
> static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
> @@ -173,14 +168,9 @@ static void netfs_read_from_cache(struct netfs_read_request *rreq,
> bool seek_data)
> {
> struct netfs_cache_resources *cres = &rreq->cache_resources;
> - struct iov_iter iter;
>
> netfs_stat(&netfs_n_rh_read);
> - iov_iter_xarray(&iter, READ, &rreq->mapping->i_pages,
> - subreq->start + subreq->transferred,
> - subreq->len - subreq->transferred);
> -
> - cres->ops->read(cres, subreq->start, &iter, seek_data,
> + cres->ops->read(cres, subreq->start, &subreq->iter, seek_data,
> netfs_cache_read_terminated, subreq);
> }
>
The above two deltas seem like they should have been in patch #2.
> @@ -419,7 +409,7 @@ static void netfs_rreq_unlock(struct netfs_read_request *rreq)
> if (pgend < iopos + subreq->len)
> break;
>
> - account += subreq->transferred;
> + account += subreq->len - iov_iter_count(&subreq->iter);
> iopos += subreq->len;
> if (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) {
> subreq = list_next_entry(subreq, rreq_link);
> @@ -635,15 +625,8 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
> goto failed;
> }
>
> - if (WARN(transferred_or_error > subreq->len - subreq->transferred,
> - "Subreq overread: R%x[%x] %zd > %zu - %zu",
> - rreq->debug_id, subreq->debug_index,
> - transferred_or_error, subreq->len, subreq->transferred))
> - transferred_or_error = subreq->len - subreq->transferred;
> -
> subreq->error = 0;
> - subreq->transferred += transferred_or_error;
> - if (subreq->transferred < subreq->len)
> + if (iov_iter_count(&subreq->iter))
> goto incomplete;
>
I must be missing it, but where does subreq->iter get advanced to the
end of the current read? If you're getting rid of subreq->transferred
then I think that has to happen above, no?
> complete:
> @@ -667,7 +650,6 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
> incomplete:
> if (test_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags)) {
> netfs_clear_unread(subreq);
> - subreq->transferred = subreq->len;
> goto complete;
> }
>
> diff --git a/include/linux/netfs.h b/include/linux/netfs.h
> index 5e4fafcc9480..45d40c622205 100644
> --- a/include/linux/netfs.h
> +++ b/include/linux/netfs.h
> @@ -116,7 +116,6 @@ struct netfs_read_subrequest {
> struct iov_iter iter; /* Iterator for this subrequest */
> loff_t start; /* Where to start the I/O */
> size_t len; /* Size of the I/O */
> - size_t transferred; /* Amount of data transferred */
> refcount_t usage;
> short error; /* 0 or error that occurred */
> unsigned short debug_index; /* Index in list (for debugging output) */
> diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
> index 4d470bffd9f1..04ac29fc700f 100644
> --- a/include/trace/events/netfs.h
> +++ b/include/trace/events/netfs.h
> @@ -190,7 +190,7 @@ TRACE_EVENT(netfs_sreq,
> __field(enum netfs_read_source, source )
> __field(enum netfs_sreq_trace, what )
> __field(size_t, len )
> - __field(size_t, transferred )
> + __field(size_t, remain )
> __field(loff_t, start )
> ),
>
> @@ -202,7 +202,7 @@ TRACE_EVENT(netfs_sreq,
> __entry->source = sreq->source;
> __entry->what = what;
> __entry->len = sreq->len;
> - __entry->transferred = sreq->transferred;
> + __entry->remain = iov_iter_count(&sreq->iter);
> __entry->start = sreq->start;
> ),
>
> @@ -211,7 +211,7 @@ TRACE_EVENT(netfs_sreq,
> __print_symbolic(__entry->what, netfs_sreq_traces),
> __print_symbolic(__entry->source, netfs_sreq_sources),
> __entry->flags,
> - __entry->start, __entry->transferred, __entry->len,
> + __entry->start, __entry->len - __entry->remain, __entry->len,
> __entry->error)
> );
>
> @@ -230,7 +230,7 @@ TRACE_EVENT(netfs_failure,
> __field(enum netfs_read_source, source )
> __field(enum netfs_failure, what )
> __field(size_t, len )
> - __field(size_t, transferred )
> + __field(size_t, remain )
> __field(loff_t, start )
> ),
>
> @@ -242,7 +242,7 @@ TRACE_EVENT(netfs_failure,
> __entry->source = sreq ? sreq->source : NETFS_INVALID_READ;
> __entry->what = what;
> __entry->len = sreq ? sreq->len : 0;
> - __entry->transferred = sreq ? sreq->transferred : 0;
> + __entry->remain = sreq ? iov_iter_count(&sreq->iter) : 0;
> __entry->start = sreq ? sreq->start : 0;
> ),
>
> @@ -250,7 +250,7 @@ TRACE_EVENT(netfs_failure,
> __entry->rreq, __entry->index,
> __print_symbolic(__entry->source, netfs_sreq_sources),
> __entry->flags,
> - __entry->start, __entry->transferred, __entry->len,
> + __entry->start, __entry->len - __entry->remain, __entry->len,
> __print_symbolic(__entry->what, netfs_failures),
> __entry->error)
> );
>
>
--
Jeff Layton <jlayton@...hat.com>
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