1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* Direct I/O support. 3 * 4 * Copyright (C) 2023 Red Hat, Inc. All Rights Reserved. 5 * Written by David Howells (dhowells@redhat.com) 6 */ 7 8 #include <linux/export.h> 9 #include <linux/fs.h> 10 #include <linux/mm.h> 11 #include <linux/pagemap.h> 12 #include <linux/slab.h> 13 #include <linux/uio.h> 14 #include <linux/sched/mm.h> 15 #include <linux/task_io_accounting_ops.h> 16 #include <linux/netfs.h> 17 #include "internal.h" 18 19 static void netfs_prepare_dio_read_iterator(struct netfs_io_subrequest *subreq) 20 { 21 struct netfs_io_request *rreq = subreq->rreq; 22 size_t rsize; 23 24 rsize = umin(subreq->len, rreq->io_streams[0].sreq_max_len); 25 subreq->len = rsize; 26 27 if (unlikely(rreq->io_streams[0].sreq_max_segs)) { 28 size_t limit = netfs_limit_iter(&rreq->buffer.iter, 0, rsize, 29 rreq->io_streams[0].sreq_max_segs); 30 31 if (limit < rsize) { 32 subreq->len = limit; 33 trace_netfs_sreq(subreq, netfs_sreq_trace_limited); 34 } 35 } 36 37 trace_netfs_sreq(subreq, netfs_sreq_trace_prepare); 38 39 subreq->io_iter = rreq->buffer.iter; 40 iov_iter_truncate(&subreq->io_iter, subreq->len); 41 iov_iter_advance(&rreq->buffer.iter, subreq->len); 42 } 43 44 /* 45 * Perform a read to a buffer from the server, slicing up the region to be read 46 * according to the network rsize. 47 */ 48 static int netfs_dispatch_unbuffered_reads(struct netfs_io_request *rreq) 49 { 50 struct netfs_io_stream *stream = &rreq->io_streams[0]; 51 unsigned long long start = rreq->start; 52 ssize_t size = rreq->len; 53 int ret = 0; 54 55 do { 56 struct netfs_io_subrequest *subreq; 57 ssize_t slice; 58 59 subreq = netfs_alloc_subrequest(rreq); 60 if (!subreq) { 61 ret = -ENOMEM; 62 break; 63 } 64 65 subreq->source = NETFS_DOWNLOAD_FROM_SERVER; 66 subreq->start = start; 67 subreq->len = size; 68 69 __set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags); 70 71 spin_lock(&rreq->lock); 72 list_add_tail(&subreq->rreq_link, &stream->subrequests); 73 if (list_is_first(&subreq->rreq_link, &stream->subrequests)) { 74 stream->front = subreq; 75 if (!stream->active) { 76 stream->collected_to = stream->front->start; 77 /* Store list pointers before active flag */ 78 smp_store_release(&stream->active, true); 79 } 80 } 81 trace_netfs_sreq(subreq, netfs_sreq_trace_added); 82 spin_unlock(&rreq->lock); 83 84 netfs_stat(&netfs_n_rh_download); 85 if (rreq->netfs_ops->prepare_read) { 86 ret = rreq->netfs_ops->prepare_read(subreq); 87 if (ret < 0) { 88 netfs_put_subrequest(subreq, netfs_sreq_trace_put_cancel); 89 break; 90 } 91 } 92 93 netfs_prepare_dio_read_iterator(subreq); 94 slice = subreq->len; 95 size -= slice; 96 start += slice; 97 rreq->submitted += slice; 98 if (size <= 0) { 99 smp_wmb(); /* Write lists before ALL_QUEUED. */ 100 set_bit(NETFS_RREQ_ALL_QUEUED, &rreq->flags); 101 } 102 103 rreq->netfs_ops->issue_read(subreq); 104 105 if (test_bit(NETFS_RREQ_PAUSE, &rreq->flags)) 106 netfs_wait_for_paused_read(rreq); 107 if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) 108 break; 109 cond_resched(); 110 } while (size > 0); 111 112 if (unlikely(size > 0)) { 113 smp_wmb(); /* Write lists before ALL_QUEUED. */ 114 set_bit(NETFS_RREQ_ALL_QUEUED, &rreq->flags); 115 netfs_wake_collector(rreq); 116 } 117 118 return ret; 119 } 120 121 /* 122 * Perform a read to an application buffer, bypassing the pagecache and the 123 * local disk cache. 124 */ 125 static ssize_t netfs_unbuffered_read(struct netfs_io_request *rreq, bool sync) 126 { 127 ssize_t ret; 128 129 _enter("R=%x %llx-%llx", 130 rreq->debug_id, rreq->start, rreq->start + rreq->len - 1); 131 132 if (rreq->len == 0) { 133 pr_err("Zero-sized read [R=%x]\n", rreq->debug_id); 134 netfs_put_request(rreq, netfs_rreq_trace_put_discard); 135 return -EIO; 136 } 137 138 // TODO: Use bounce buffer if requested 139 140 inode_dio_begin(rreq->inode); 141 142 ret = netfs_dispatch_unbuffered_reads(rreq); 143 144 if (!rreq->submitted) { 145 netfs_put_request(rreq, netfs_rreq_trace_put_no_submit); 146 inode_dio_end(rreq->inode); 147 ret = 0; 148 goto out; 149 } 150 151 if (sync) 152 ret = netfs_wait_for_read(rreq); 153 else 154 ret = -EIOCBQUEUED; 155 out: 156 _leave(" = %zd", ret); 157 return ret; 158 } 159 160 /** 161 * netfs_unbuffered_read_iter_locked - Perform an unbuffered or direct I/O read 162 * @iocb: The I/O control descriptor describing the read 163 * @iter: The output buffer (also specifies read length) 164 * 165 * Perform an unbuffered I/O or direct I/O from the file in @iocb to the 166 * output buffer. No use is made of the pagecache. 167 * 168 * The caller must hold any appropriate locks. 169 */ 170 ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter) 171 { 172 struct netfs_io_request *rreq; 173 ssize_t ret; 174 size_t orig_count = iov_iter_count(iter); 175 bool sync = is_sync_kiocb(iocb); 176 177 _enter(""); 178 179 if (!orig_count) 180 return 0; /* Don't update atime */ 181 182 ret = kiocb_write_and_wait(iocb, orig_count); 183 if (ret < 0) 184 return ret; 185 file_accessed(iocb->ki_filp); 186 187 rreq = netfs_alloc_request(iocb->ki_filp->f_mapping, iocb->ki_filp, 188 iocb->ki_pos, orig_count, 189 iocb->ki_flags & IOCB_DIRECT ? 190 NETFS_DIO_READ : NETFS_UNBUFFERED_READ); 191 if (IS_ERR(rreq)) 192 return PTR_ERR(rreq); 193 194 netfs_stat(&netfs_n_rh_dio_read); 195 trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_dio_read); 196 197 /* If this is an async op, we have to keep track of the destination 198 * buffer for ourselves as the caller's iterator will be trashed when 199 * we return. 200 * 201 * In such a case, extract an iterator to represent as much of the the 202 * output buffer as we can manage. Note that the extraction might not 203 * be able to allocate a sufficiently large bvec array and may shorten 204 * the request. 205 */ 206 if (user_backed_iter(iter)) { 207 ret = netfs_extract_user_iter(iter, rreq->len, &rreq->buffer.iter, 0); 208 if (ret < 0) 209 goto error_put; 210 rreq->direct_bv = (struct bio_vec *)rreq->buffer.iter.bvec; 211 rreq->direct_bv_count = ret; 212 rreq->direct_bv_unpin = iov_iter_extract_will_pin(iter); 213 rreq->len = iov_iter_count(&rreq->buffer.iter); 214 } else { 215 rreq->buffer.iter = *iter; 216 rreq->len = orig_count; 217 rreq->direct_bv_unpin = false; 218 iov_iter_advance(iter, orig_count); 219 } 220 221 // TODO: Set up bounce buffer if needed 222 223 if (!sync) { 224 rreq->iocb = iocb; 225 __set_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &rreq->flags); 226 } 227 228 ret = netfs_unbuffered_read(rreq, sync); 229 if (ret < 0) 230 goto out; /* May be -EIOCBQUEUED */ 231 if (sync) { 232 // TODO: Copy from bounce buffer 233 iocb->ki_pos += rreq->transferred; 234 ret = rreq->transferred; 235 } 236 237 out: 238 netfs_put_request(rreq, netfs_rreq_trace_put_return); 239 if (ret > 0) 240 orig_count -= ret; 241 return ret; 242 243 error_put: 244 netfs_put_failed_request(rreq); 245 return ret; 246 } 247 EXPORT_SYMBOL(netfs_unbuffered_read_iter_locked); 248 249 /** 250 * netfs_unbuffered_read_iter - Perform an unbuffered or direct I/O read 251 * @iocb: The I/O control descriptor describing the read 252 * @iter: The output buffer (also specifies read length) 253 * 254 * Perform an unbuffered I/O or direct I/O from the file in @iocb to the 255 * output buffer. No use is made of the pagecache. 256 */ 257 ssize_t netfs_unbuffered_read_iter(struct kiocb *iocb, struct iov_iter *iter) 258 { 259 struct inode *inode = file_inode(iocb->ki_filp); 260 ssize_t ret; 261 262 if (!iter->count) 263 return 0; /* Don't update atime */ 264 265 ret = netfs_start_io_direct(inode); 266 if (ret == 0) { 267 ret = netfs_unbuffered_read_iter_locked(iocb, iter); 268 netfs_end_io_direct(inode); 269 } 270 return ret; 271 } 272 EXPORT_SYMBOL(netfs_unbuffered_read_iter); 273