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-rw-r--r--fs/netfs/write_retry.c234
1 files changed, 234 insertions, 0 deletions
diff --git a/fs/netfs/write_retry.c b/fs/netfs/write_retry.c
new file mode 100644
index 000000000000..545d33079a77
--- /dev/null
+++ b/fs/netfs/write_retry.c
@@ -0,0 +1,234 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Network filesystem write retrying.
+ *
+ * Copyright (C) 2024 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include "internal.h"
+
+/*
+ * Perform retries on the streams that need it.
+ */
+static void netfs_retry_write_stream(struct netfs_io_request *wreq,
+ struct netfs_io_stream *stream)
+{
+ struct list_head *next;
+
+ _enter("R=%x[%x:]", wreq->debug_id, stream->stream_nr);
+
+ if (list_empty(&stream->subrequests))
+ return;
+
+ if (stream->source == NETFS_UPLOAD_TO_SERVER &&
+ wreq->netfs_ops->retry_request)
+ wreq->netfs_ops->retry_request(wreq, stream);
+
+ if (unlikely(stream->failed))
+ return;
+
+ /* If there's no renegotiation to do, just resend each failed subreq. */
+ if (!stream->prepare_write) {
+ struct netfs_io_subrequest *subreq;
+
+ list_for_each_entry(subreq, &stream->subrequests, rreq_link) {
+ if (test_bit(NETFS_SREQ_FAILED, &subreq->flags))
+ break;
+ if (__test_and_clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags)) {
+ struct iov_iter source = subreq->io_iter;
+
+ iov_iter_revert(&source, subreq->len - source.count);
+ netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit);
+ netfs_reissue_write(stream, subreq, &source);
+ }
+ }
+ return;
+ }
+
+ next = stream->subrequests.next;
+
+ do {
+ struct netfs_io_subrequest *subreq = NULL, *from, *to, *tmp;
+ struct iov_iter source;
+ unsigned long long start, len;
+ size_t part;
+ bool boundary = false;
+
+ /* Go through the stream and find the next span of contiguous
+ * data that we then rejig (cifs, for example, needs the wsize
+ * renegotiating) and reissue.
+ */
+ from = list_entry(next, struct netfs_io_subrequest, rreq_link);
+ to = from;
+ start = from->start + from->transferred;
+ len = from->len - from->transferred;
+
+ if (test_bit(NETFS_SREQ_FAILED, &from->flags) ||
+ !test_bit(NETFS_SREQ_NEED_RETRY, &from->flags))
+ return;
+
+ list_for_each_continue(next, &stream->subrequests) {
+ subreq = list_entry(next, struct netfs_io_subrequest, rreq_link);
+ if (subreq->start + subreq->transferred != start + len ||
+ test_bit(NETFS_SREQ_BOUNDARY, &subreq->flags) ||
+ !test_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags))
+ break;
+ to = subreq;
+ len += to->len;
+ }
+
+ /* Determine the set of buffers we're going to use. Each
+ * subreq gets a subset of a single overall contiguous buffer.
+ */
+ netfs_reset_iter(from);
+ source = from->io_iter;
+ source.count = len;
+
+ /* Work through the sublist. */
+ subreq = from;
+ list_for_each_entry_from(subreq, &stream->subrequests, rreq_link) {
+ if (!len)
+ break;
+
+ subreq->start = start;
+ subreq->len = len;
+ __clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
+ subreq->retry_count++;
+ trace_netfs_sreq(subreq, netfs_sreq_trace_retry);
+
+ /* Renegotiate max_len (wsize) */
+ stream->sreq_max_len = len;
+ stream->prepare_write(subreq);
+
+ part = umin(len, stream->sreq_max_len);
+ if (unlikely(stream->sreq_max_segs))
+ part = netfs_limit_iter(&source, 0, part, stream->sreq_max_segs);
+ subreq->len = part;
+ subreq->transferred = 0;
+ len -= part;
+ start += part;
+ if (len && subreq == to &&
+ __test_and_clear_bit(NETFS_SREQ_BOUNDARY, &to->flags))
+ boundary = true;
+
+ netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit);
+ netfs_reissue_write(stream, subreq, &source);
+ if (subreq == to)
+ break;
+ }
+
+ /* If we managed to use fewer subreqs, we can discard the
+ * excess; if we used the same number, then we're done.
+ */
+ if (!len) {
+ if (subreq == to)
+ continue;
+ list_for_each_entry_safe_from(subreq, tmp,
+ &stream->subrequests, rreq_link) {
+ trace_netfs_sreq(subreq, netfs_sreq_trace_discard);
+ list_del(&subreq->rreq_link);
+ netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_done);
+ if (subreq == to)
+ break;
+ }
+ continue;
+ }
+
+ /* We ran out of subrequests, so we need to allocate some more
+ * and insert them after.
+ */
+ do {
+ subreq = netfs_alloc_subrequest(wreq);
+ subreq->source = to->source;
+ subreq->start = start;
+ subreq->debug_index = atomic_inc_return(&wreq->subreq_counter);
+ subreq->stream_nr = to->stream_nr;
+ subreq->retry_count = 1;
+
+ trace_netfs_sreq_ref(wreq->debug_id, subreq->debug_index,
+ refcount_read(&subreq->ref),
+ netfs_sreq_trace_new);
+ netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit);
+
+ list_add(&subreq->rreq_link, &to->rreq_link);
+ to = list_next_entry(to, rreq_link);
+ trace_netfs_sreq(subreq, netfs_sreq_trace_retry);
+
+ stream->sreq_max_len = len;
+ stream->sreq_max_segs = INT_MAX;
+ switch (stream->source) {
+ case NETFS_UPLOAD_TO_SERVER:
+ netfs_stat(&netfs_n_wh_upload);
+ stream->sreq_max_len = umin(len, wreq->wsize);
+ break;
+ case NETFS_WRITE_TO_CACHE:
+ netfs_stat(&netfs_n_wh_write);
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ }
+
+ stream->prepare_write(subreq);
+
+ part = umin(len, stream->sreq_max_len);
+ subreq->len = subreq->transferred + part;
+ len -= part;
+ start += part;
+ if (!len && boundary) {
+ __set_bit(NETFS_SREQ_BOUNDARY, &to->flags);
+ boundary = false;
+ }
+
+ netfs_reissue_write(stream, subreq, &source);
+ if (!len)
+ break;
+
+ } while (len);
+
+ } while (!list_is_head(next, &stream->subrequests));
+}
+
+/*
+ * Perform retries on the streams that need it. If we're doing content
+ * encryption and the server copy changed due to a third-party write, we may
+ * need to do an RMW cycle and also rewrite the data to the cache.
+ */
+void netfs_retry_writes(struct netfs_io_request *wreq)
+{
+ struct netfs_io_subrequest *subreq;
+ struct netfs_io_stream *stream;
+ int s;
+
+ netfs_stat(&netfs_n_wh_retry_write_req);
+
+ /* Wait for all outstanding I/O to quiesce before performing retries as
+ * we may need to renegotiate the I/O sizes.
+ */
+ for (s = 0; s < NR_IO_STREAMS; s++) {
+ stream = &wreq->io_streams[s];
+ if (!stream->active)
+ continue;
+
+ list_for_each_entry(subreq, &stream->subrequests, rreq_link) {
+ wait_on_bit(&subreq->flags, NETFS_SREQ_IN_PROGRESS,
+ TASK_UNINTERRUPTIBLE);
+ }
+ }
+
+ // TODO: Enc: Fetch changed partial pages
+ // TODO: Enc: Reencrypt content if needed.
+ // TODO: Enc: Wind back transferred point.
+ // TODO: Enc: Mark cache pages for retry.
+
+ for (s = 0; s < NR_IO_STREAMS; s++) {
+ stream = &wreq->io_streams[s];
+ if (stream->need_retry) {
+ stream->need_retry = false;
+ netfs_retry_write_stream(wreq, stream);
+ }
+ }
+}
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