From 768ddb1eacf5dd997ecf393e7bab9796bad047e0 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 27 May 2022 13:45:28 +0100 Subject: 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: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- fs/netfs/io.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'fs/netfs') diff --git a/fs/netfs/io.c b/fs/netfs/io.c index e9d408e211b8..e228bfb530ea 100644 --- a/fs/netfs/io.c +++ b/fs/netfs/io.c @@ -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); -- cgit