fs/netfs/write_retry.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Network filesystem write retrying.
   3  *
   4  * Copyright (C) 2024 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/fs.h>
   9 #include <linux/mm.h>
  10 #include <linux/pagemap.h>
  11 #include <linux/slab.h>
  12 #include "internal.h"
  13
  14 /*
  15  * Perform retries on the streams that need it.
  16  */
  17 static void netfs_retry_write_stream(struct netfs_io_request *wreq,
  18                                      struct netfs_io_stream *stream)
  19 {
  20         struct list_head *next;
  21
  22         _enter("R=%x[%x:]", wreq->debug_id, stream->stream_nr);
  23
  24         if (list_empty(&stream->subrequests))
  25                 return;
  26
  27         if (stream->source == NETFS_UPLOAD_TO_SERVER &&
  28             wreq->netfs_ops->retry_request)
  29                 wreq->netfs_ops->retry_request(wreq, stream);
  30
  31         if (unlikely(stream->failed))
  32                 return;
  33
  34         /* If there's no renegotiation to do, just resend each failed subreq. */
  35         if (!stream->prepare_write) {
  36                 struct netfs_io_subrequest *subreq;
  37
  38                 list_for_each_entry(subreq, &stream->subrequests, rreq_link) {
  39                         if (test_bit(NETFS_SREQ_FAILED, &subreq->flags))
  40                                 break;
  41                         if (__test_and_clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags)) {
  42                                 struct iov_iter source = subreq->io_iter;
  43
  44                                 iov_iter_revert(&source, subreq->len - source.count);
  45                                 netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit);
  46                                 netfs_reissue_write(stream, subreq, &source);
  47                         }
  48                 }
  49                 return;
  50         }
  51
  52         next = stream->subrequests.next;
  53
  54         do {
  55                 struct netfs_io_subrequest *subreq = NULL, *from, *to, *tmp;
  56                 struct iov_iter source;
  57                 unsigned long long start, len;
  58                 size_t part;
  59                 bool boundary = false;
  60
  61                 /* Go through the stream and find the next span of contiguous
  62                  * data that we then rejig (cifs, for example, needs the wsize
  63                  * renegotiating) and reissue.
  64                  */
  65                 from = list_entry(next, struct netfs_io_subrequest, rreq_link);
  66                 to = from;
  67                 start = from->start + from->transferred;
  68                 len   = from->len   - from->transferred;
  69
  70                 if (test_bit(NETFS_SREQ_FAILED, &from->flags) ||
  71                     !test_bit(NETFS_SREQ_NEED_RETRY, &from->flags))
  72                         return;
  73
  74                 list_for_each_continue(next, &stream->subrequests) {
  75                         subreq = list_entry(next, struct netfs_io_subrequest, rreq_link);
  76                         if (subreq->start + subreq->transferred != start + len ||
  77                             test_bit(NETFS_SREQ_BOUNDARY, &subreq->flags) ||
  78                             !test_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags))
  79                                 break;
  80                         to = subreq;
  81                         len += to->len;
  82                 }
  83
  84                 /* Determine the set of buffers we're going to use.  Each
  85                  * subreq gets a subset of a single overall contiguous buffer.
  86                  */
  87                 netfs_reset_iter(from);
  88                 source = from->io_iter;
  89                 source.count = len;
  90
  91                 /* Work through the sublist. */
  92                 subreq = from;
  93                 list_for_each_entry_from(subreq, &stream->subrequests, rreq_link) {
  94                         if (!len)
  95                                 break;
  96
  97                         subreq->start   = start;
  98                         subreq->len     = len;
  99                         __clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
 100                         subreq->retry_count++;
 101                         trace_netfs_sreq(subreq, netfs_sreq_trace_retry);
 102
 103                         /* Renegotiate max_len (wsize) */
 104                         stream->sreq_max_len = len;
 105                         stream->prepare_write(subreq);
 106
 107                         part = umin(len, stream->sreq_max_len);
 108                         if (unlikely(stream->sreq_max_segs))
 109                                 part = netfs_limit_iter(&source, 0, part, stream->sreq_max_segs);
 110                         subreq->len = part;
 111                         subreq->transferred = 0;
 112                         len -= part;
 113                         start += part;
 114                         if (len && subreq == to &&
 115                             __test_and_clear_bit(NETFS_SREQ_BOUNDARY, &to->flags))
 116                                 boundary = true;
 117
 118                         netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit);
 119                         netfs_reissue_write(stream, subreq, &source);
 120                         if (subreq == to)
 121                                 break;
 122                 }
 123
 124                 /* If we managed to use fewer subreqs, we can discard the
 125                  * excess; if we used the same number, then we're done.
 126                  */
 127                 if (!len) {
 128                         if (subreq == to)
 129                                 continue;
 130                         list_for_each_entry_safe_from(subreq, tmp,
 131                                                       &stream->subrequests, rreq_link) {
 132                                 trace_netfs_sreq(subreq, netfs_sreq_trace_discard);
 133                                 list_del(&subreq->rreq_link);
 134                                 netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_done);
 135                                 if (subreq == to)
 136                                         break;
 137                         }
 138                         continue;
 139                 }
 140
 141                 /* We ran out of subrequests, so we need to allocate some more
 142                  * and insert them after.
 143                  */
 144                 do {
 145                         subreq = netfs_alloc_subrequest(wreq);
 146                         subreq->source          = to->source;
 147                         subreq->start           = start;
 148                         subreq->debug_index     = atomic_inc_return(&wreq->subreq_counter);
 149                         subreq->stream_nr       = to->stream_nr;
 150                         subreq->retry_count     = 1;
 151
 152                         trace_netfs_sreq_ref(wreq->debug_id, subreq->debug_index,
 153                                              refcount_read(&subreq->ref),
 154                                              netfs_sreq_trace_new);
 155                         netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit);
 156
 157                         list_add(&subreq->rreq_link, &to->rreq_link);
 158                         to = list_next_entry(to, rreq_link);
 159                         trace_netfs_sreq(subreq, netfs_sreq_trace_retry);
 160
 161                         stream->sreq_max_len    = len;
 162                         stream->sreq_max_segs   = INT_MAX;
 163                         switch (stream->source) {
 164                         case NETFS_UPLOAD_TO_SERVER:
 165                                 netfs_stat(&netfs_n_wh_upload);
 166                                 stream->sreq_max_len = umin(len, wreq->wsize);
 167                                 break;
 168                         case NETFS_WRITE_TO_CACHE:
 169                                 netfs_stat(&netfs_n_wh_write);
 170                                 break;
 171                         default:
 172                                 WARN_ON_ONCE(1);
 173                         }
 174
 175                         stream->prepare_write(subreq);
 176
 177                         part = umin(len, stream->sreq_max_len);
 178                         subreq->len = subreq->transferred + part;
 179                         len -= part;
 180                         start += part;
 181                         if (!len && boundary) {
 182                                 __set_bit(NETFS_SREQ_BOUNDARY, &to->flags);
 183                                 boundary = false;
 184                         }
 185
 186                         netfs_reissue_write(stream, subreq, &source);
 187                         if (!len)
 188                                 break;
 189
 190                 } while (len);
 191
 192         } while (!list_is_head(next, &stream->subrequests));
 193 }
 194
 195 /*
 196  * Perform retries on the streams that need it.  If we're doing content
 197  * encryption and the server copy changed due to a third-party write, we may
 198  * need to do an RMW cycle and also rewrite the data to the cache.
 199  */
 200 void netfs_retry_writes(struct netfs_io_request *wreq)
 201 {
 202         struct netfs_io_subrequest *subreq;
 203         struct netfs_io_stream *stream;
 204         int s;
 205
 206         /* Wait for all outstanding I/O to quiesce before performing retries as
 207          * we may need to renegotiate the I/O sizes.
 208          */
 209         for (s = 0; s < NR_IO_STREAMS; s++) {
 210                 stream = &wreq->io_streams[s];
 211                 if (!stream->active)
 212                         continue;
 213
 214                 list_for_each_entry(subreq, &stream->subrequests, rreq_link) {
 215                         wait_on_bit(&subreq->flags, NETFS_SREQ_IN_PROGRESS,
 216                                     TASK_UNINTERRUPTIBLE);
 217                 }
 218         }
 219
 220         // TODO: Enc: Fetch changed partial pages
 221         // TODO: Enc: Reencrypt content if needed.
 222         // TODO: Enc: Wind back transferred point.
 223         // TODO: Enc: Mark cache pages for retry.
 224
 225         for (s = 0; s < NR_IO_STREAMS; s++) {
 226                 stream = &wreq->io_streams[s];
 227                 if (stream->need_retry) {
 228                         stream->need_retry = false;
 229                         netfs_retry_write_stream(wreq, stream);
 230                 }
 231         }
 232 }