Commit 768ddb1e authored by David Howells's avatar David Howells
Browse files

netfs: Limit subrequest by size or number of segments 



Limit a subrequest to a maximum size and/or a maximum number of contiguous
physical regions.  This permits, for instance, an subreq's iterator to be
limited to the number of DMA'able segments that a large RDMA request can
handle.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
parent cae932d3

fs/netfs/io.c

+18 −0
Original line number Diff line number Diff line
@@ -525,6 +525,7 @@ netfs_rreq_prepare_read(struct netfs_io_request *rreq, 
			struct iov_iter *io_iter)

{

	enum netfs_io_source source;

	size_t lsize;



	_enter("%llx-%llx,%llx", subreq->start, subreq->start + subreq->len, rreq->i_size);
@@ -547,13 +548,30 @@ netfs_rreq_prepare_read(struct netfs_io_request *rreq, 
			source = NETFS_INVALID_READ;

			goto out;

		}



		if (subreq->max_nr_segs) {

			lsize = netfs_limit_iter(io_iter, 0, subreq->len,

						 subreq->max_nr_segs);

			if (subreq->len > lsize) {

				subreq->len = lsize;

				trace_netfs_sreq(subreq, netfs_sreq_trace_limited);

			}

		}

	}



	if (subreq->len > rreq->len)

		pr_warn("R=%08x[%u] SREQ>RREQ %zx > %zx\n",

			rreq->debug_id, subreq->debug_index,

			subreq->len, rreq->len);



	if (WARN_ON(subreq->len == 0)) {

		source = NETFS_INVALID_READ;

		goto out;

	}



	subreq->source = source;

	trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);



	subreq->io_iter = *io_iter;

	iov_iter_truncate(&subreq->io_iter, subreq->len);

	iov_iter_advance(io_iter, subreq->len);

include/linux/netfs.h

+1 −0
Original line number Diff line number Diff line
@@ -161,6 +161,7 @@ struct netfs_io_subrequest { 
	refcount_t		ref;

	short			error;		/* 0 or error that occurred */

	unsigned short		debug_index;	/* Index in list (for debugging output) */

	unsigned int		max_nr_segs;	/* 0 or max number of segments in an iterator */

	enum netfs_io_source	source;		/* Where to read from/write to */

	unsigned long		flags;

#define NETFS_SREQ_COPY_TO_CACHE	0	/* Set if should copy the data to the cache */

include/trace/events/netfs.h

+1 −0
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ 
#define netfs_sreq_traces					\

	EM(netfs_sreq_trace_download_instead,	"RDOWN")	\

	EM(netfs_sreq_trace_free,		"FREE ")	\

	EM(netfs_sreq_trace_limited,		"LIMIT")	\

	EM(netfs_sreq_trace_prepare,		"PREP ")	\

	EM(netfs_sreq_trace_resubmit_short,	"SHORT")	\

	EM(netfs_sreq_trace_submit,		"SUBMT")	\