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 unsigned long long start = rreq->start; 51 ssize_t size = rreq->len; 52 int ret; 53 54 do { 55 struct netfs_io_subrequest *subreq; 56 ssize_t slice; 57 58 subreq = netfs_alloc_subrequest(rreq); 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->source = NETFS_DOWNLOAD_FROM_SERVER; 68 subreq->start = start; 69 subreq->len = size; 70 71 netfs_queue_read(rreq, subreq); 72 73 netfs_stat(&netfs_n_rh_download); 74 if (rreq->netfs_ops->prepare_read) { 75 ret = rreq->netfs_ops->prepare_read(subreq); 76 if (ret < 0) { 77 netfs_cancel_read(subreq, ret); 78 break; 79 } 80 } 81 82 netfs_prepare_dio_read_iterator(subreq); 83 slice = subreq->len; 84 size -= slice; 85 start += slice; 86 rreq->submitted += slice; 87 if (size <= 0) { 88 smp_wmb(); /* Write lists before ALL_QUEUED. */ 89 set_bit(NETFS_RREQ_ALL_QUEUED, &rreq->flags); 90 } 91 92 rreq->netfs_ops->issue_read(subreq); 93 94 if (test_bit(NETFS_RREQ_PAUSE, &rreq->flags)) 95 netfs_wait_for_paused_read(rreq); 96 if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) 97 break; 98 cond_resched(); 99 } while (size > 0); 100 101 if (unlikely(size > 0)) { 102 smp_wmb(); /* Write lists before ALL_QUEUED. */ 103 set_bit(NETFS_RREQ_ALL_QUEUED, &rreq->flags); 104 netfs_wake_collector(rreq); 105 } 106 } 107 108 /* 109 * Perform a read to an application buffer, bypassing the pagecache and the 110 * local disk cache. 111 */ 112 static ssize_t netfs_unbuffered_read(struct netfs_io_request *rreq, bool sync) 113 { 114 ssize_t ret; 115 116 _enter("R=%x %llx-%llx", 117 rreq->debug_id, rreq->start, rreq->start + rreq->len - 1); 118 119 if (rreq->len == 0) { 120 pr_err("Zero-sized read [R=%x]\n", rreq->debug_id); 121 netfs_put_request(rreq, netfs_rreq_trace_put_discard); 122 return -EIO; 123 } 124 125 // TODO: Use bounce buffer if requested 126 127 inode_dio_begin(rreq->inode); 128 netfs_dispatch_unbuffered_reads(rreq); 129 130 /* The collector will get run, even if we don't manage to submit any 131 * subreqs, so we shouldn't call inode_dio_end() here. 132 */ 133 134 if (sync) 135 ret = netfs_wait_for_read(rreq); 136 else 137 ret = -EIOCBQUEUED; 138 139 _leave(" = %zd", ret); 140 return ret; 141 } 142 143 /** 144 * netfs_unbuffered_read_iter_locked - Perform an unbuffered or direct I/O read 145 * @iocb: The I/O control descriptor describing the read 146 * @iter: The output buffer (also specifies read length) 147 * 148 * Perform an unbuffered I/O or direct I/O from the file in @iocb to the 149 * output buffer. No use is made of the pagecache. 150 * 151 * The caller must hold any appropriate locks. 152 */ 153 ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter) 154 { 155 struct netfs_io_request *rreq; 156 ssize_t ret; 157 size_t orig_count = iov_iter_count(iter); 158 bool sync = is_sync_kiocb(iocb); 159 160 _enter(""); 161 162 if (!orig_count) 163 return 0; /* Don't update atime */ 164 165 ret = kiocb_write_and_wait(iocb, orig_count); 166 if (ret < 0) 167 return ret; 168 file_accessed(iocb->ki_filp); 169 170 rreq = netfs_alloc_request(iocb->ki_filp->f_mapping, iocb->ki_filp, 171 iocb->ki_pos, orig_count, 172 iocb->ki_flags & IOCB_DIRECT ? 173 NETFS_DIO_READ : NETFS_UNBUFFERED_READ); 174 if (IS_ERR(rreq)) 175 return PTR_ERR(rreq); 176 177 netfs_stat(&netfs_n_rh_dio_read); 178 trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_dio_read); 179 180 /* If this is an async op, we have to keep track of the destination 181 * buffer for ourselves as the caller's iterator will be trashed when 182 * we return. 183 * 184 * In such a case, extract an iterator to represent as much of the the 185 * output buffer as we can manage. Note that the extraction might not 186 * be able to allocate a sufficiently large bvec array and may shorten 187 * the request. 188 */ 189 if (user_backed_iter(iter)) { 190 ret = netfs_extract_user_iter(iter, rreq->len, &rreq->buffer.iter, 0); 191 if (ret < 0) 192 goto error_put; 193 rreq->direct_bv = (struct bio_vec *)rreq->buffer.iter.bvec; 194 rreq->direct_bv_count = ret; 195 rreq->direct_bv_unpin = iov_iter_extract_will_pin(iter); 196 rreq->len = iov_iter_count(&rreq->buffer.iter); 197 } else { 198 rreq->buffer.iter = *iter; 199 rreq->len = orig_count; 200 rreq->direct_bv_unpin = false; 201 iov_iter_advance(iter, orig_count); 202 } 203 204 // TODO: Set up bounce buffer if needed 205 206 if (!sync) { 207 rreq->iocb = iocb; 208 __set_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &rreq->flags); 209 } 210 211 ret = netfs_unbuffered_read(rreq, sync); 212 if (ret < 0) 213 goto out; /* May be -EIOCBQUEUED */ 214 if (sync) { 215 // TODO: Copy from bounce buffer 216 iocb->ki_pos += rreq->transferred; 217 ret = rreq->transferred; 218 } 219 220 out: 221 netfs_put_request(rreq, netfs_rreq_trace_put_return); 222 if (ret > 0) 223 orig_count -= ret; 224 return ret; 225 226 error_put: 227 netfs_put_failed_request(rreq); 228 return ret; 229 } 230 EXPORT_SYMBOL(netfs_unbuffered_read_iter_locked); 231 232 /** 233 * netfs_unbuffered_read_iter - Perform an unbuffered or direct I/O read 234 * @iocb: The I/O control descriptor describing the read 235 * @iter: The output buffer (also specifies read length) 236 * 237 * Perform an unbuffered I/O or direct I/O from the file in @iocb to the 238 * output buffer. No use is made of the pagecache. 239 */ 240 ssize_t netfs_unbuffered_read_iter(struct kiocb *iocb, struct iov_iter *iter) 241 { 242 struct inode *inode = file_inode(iocb->ki_filp); 243 ssize_t ret; 244 245 if (!iter->count) 246 return 0; /* Don't update atime */ 247 248 ret = netfs_start_io_direct(inode); 249 if (ret == 0) { 250 ret = netfs_unbuffered_read_iter_locked(iocb, iter); 251 netfs_end_io_direct(inode); 252 } 253 return ret; 254 } 255 EXPORT_SYMBOL(netfs_unbuffered_read_iter); 256