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 void netfs_dispatch_unbuffered_reads(struct netfs_io_request *rreq) 49 { 50 ssize_t size = rreq->len; 51 uoff_t start = rreq->start; 52 int ret; 53 54 do { 55 struct netfs_io_subrequest *subreq; 56 ssize_t slice; 57 58 subreq = netfs_alloc_subrequest(rreq, NETFS_DOWNLOAD_FROM_SERVER); 59 if (!subreq) { 60 /* Stash the error in the request if there's not 61 * already an error set. 62 */ 63 cmpxchg(&rreq->error, 0, -ENOMEM); 64 break; 65 } 66 67 subreq->start = start; 68 subreq->len = size; 69 70 netfs_queue_read(rreq, subreq); 71 72 netfs_stat(&netfs_n_rh_download); 73 if (rreq->netfs_ops->prepare_read) { 74 ret = rreq->netfs_ops->prepare_read(subreq); 75 if (ret < 0) { 76 netfs_cancel_read(subreq, ret); 77 break; 78 } 79 } 80 81 netfs_prepare_dio_read_iterator(subreq); 82 slice = subreq->len; 83 size -= slice; 84 start += slice; 85 rreq->submitted += slice; 86 if (size <= 0) 87 netfs_all_subreqs_queued(rreq); 88 89 rreq->netfs_ops->issue_read(subreq); 90 91 if (test_bit(NETFS_RREQ_PAUSE, &rreq->flags)) 92 netfs_wait_for_paused_read(rreq); 93 if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) 94 break; 95 cond_resched(); 96 } while (size > 0); 97 98 if (unlikely(size > 0)) { 99 netfs_all_subreqs_queued(rreq); 100 netfs_wake_collector(rreq); 101 } 102 } 103 104 /* 105 * Perform a read to an application buffer, bypassing the pagecache and the 106 * local disk cache. 107 */ 108 static ssize_t netfs_unbuffered_read(struct netfs_io_request *rreq, bool sync) 109 { 110 ssize_t ret; 111 112 _enter("R=%x %llx-%llx", 113 rreq->debug_id, rreq->start, rreq->start + rreq->len - 1); 114 115 if (rreq->len == 0) { 116 pr_err("Zero-sized read [R=%x]\n", rreq->debug_id); 117 netfs_put_request(rreq, netfs_rreq_trace_put_discard); 118 return -EIO; 119 } 120 121 // TODO: Use bounce buffer if requested 122 123 inode_dio_begin(rreq->inode); 124 netfs_dispatch_unbuffered_reads(rreq); 125 126 /* The collector will get run, even if we don't manage to submit any 127 * subreqs, so we shouldn't call inode_dio_end() here. 128 */ 129 130 if (sync) 131 ret = netfs_wait_for_read(rreq); 132 else 133 ret = -EIOCBQUEUED; 134 135 _leave(" = %zd", ret); 136 return ret; 137 } 138 139 /** 140 * netfs_unbuffered_read_iter_locked - Perform an unbuffered or direct I/O read 141 * @iocb: The I/O control descriptor describing the read 142 * @iter: The output buffer (also specifies read length) 143 * 144 * Perform an unbuffered I/O or direct I/O from the file in @iocb to the 145 * output buffer. No use is made of the pagecache. 146 * 147 * The caller must hold any appropriate locks. 148 */ 149 ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter) 150 { 151 struct netfs_io_request *rreq; 152 ssize_t ret; 153 size_t orig_count = iov_iter_count(iter); 154 bool sync = is_sync_kiocb(iocb); 155 156 _enter(""); 157 158 if (!orig_count) 159 return 0; /* Don't update atime */ 160 161 ret = kiocb_write_and_wait(iocb, orig_count); 162 if (ret < 0) 163 return ret; 164 file_accessed(iocb->ki_filp); 165 166 rreq = netfs_alloc_request(iocb->ki_filp->f_mapping, iocb->ki_filp, 167 iocb->ki_pos, orig_count, 168 iocb->ki_flags & IOCB_DIRECT ? 169 NETFS_DIO_READ : NETFS_UNBUFFERED_READ); 170 if (IS_ERR(rreq)) 171 return PTR_ERR(rreq); 172 173 netfs_stat(&netfs_n_rh_dio_read); 174 trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_dio_read); 175 176 /* If this is an async op, we have to keep track of the destination 177 * buffer for ourselves as the caller's iterator will be trashed when 178 * we return. 179 * 180 * In such a case, extract an iterator to represent as much of the the 181 * output buffer as we can manage. Note that the extraction might not 182 * be able to allocate a sufficiently large bvec array and may shorten 183 * the request. 184 */ 185 if (user_backed_iter(iter)) { 186 ret = netfs_extract_user_iter(iter, rreq->len, &rreq->buffer.iter, 0); 187 if (ret < 0) 188 goto error_put; 189 rreq->direct_bv = (struct bio_vec *)rreq->buffer.iter.bvec; 190 rreq->direct_bv_count = ret; 191 rreq->direct_bv_unpin = iov_iter_extract_will_pin(iter); 192 rreq->len = iov_iter_count(&rreq->buffer.iter); 193 } else { 194 rreq->buffer.iter = *iter; 195 rreq->len = orig_count; 196 rreq->direct_bv_unpin = false; 197 iov_iter_advance(iter, orig_count); 198 } 199 200 // TODO: Set up bounce buffer if needed 201 202 if (!sync) { 203 rreq->iocb = iocb; 204 __set_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &rreq->flags); 205 } 206 207 ret = netfs_unbuffered_read(rreq, sync); 208 if (ret < 0) 209 goto out; /* May be -EIOCBQUEUED */ 210 if (sync) { 211 // TODO: Copy from bounce buffer 212 iocb->ki_pos += rreq->transferred; 213 ret = rreq->transferred; 214 } 215 216 out: 217 netfs_put_request(rreq, netfs_rreq_trace_put_return); 218 if (ret > 0) 219 orig_count -= ret; 220 return ret; 221 222 error_put: 223 netfs_put_failed_request(rreq); 224 return ret; 225 } 226 EXPORT_SYMBOL(netfs_unbuffered_read_iter_locked); 227 228 /** 229 * netfs_unbuffered_read_iter - Perform an unbuffered or direct I/O read 230 * @iocb: The I/O control descriptor describing the read 231 * @iter: The output buffer (also specifies read length) 232 * 233 * Perform an unbuffered I/O or direct I/O from the file in @iocb to the 234 * output buffer. No use is made of the pagecache. 235 */ 236 ssize_t netfs_unbuffered_read_iter(struct kiocb *iocb, struct iov_iter *iter) 237 { 238 struct inode *inode = file_inode(iocb->ki_filp); 239 ssize_t ret; 240 241 if (!iter->count) 242 return 0; /* Don't update atime */ 243 244 ret = netfs_start_io_direct(inode); 245 if (ret == 0) { 246 ret = netfs_unbuffered_read_iter_locked(iocb, iter); 247 netfs_end_io_direct(inode); 248 } 249 return ret; 250 } 251 EXPORT_SYMBOL(netfs_unbuffered_read_iter); 252