1// SPDX-License-Identifier: GPL-2.0 2/* 3 * Copyright (C) 2010, 2023 Red Hat, Inc. 4 * All Rights Reserved. 5 */ 6#include "xfs.h" 7#include "xfs_shared.h" 8#include "xfs_format.h" 9#include "xfs_log_format.h" 10#include "xfs_trans_resv.h" 11#include "xfs_trans.h" 12#include "xfs_mount.h" 13#include "xfs_btree.h" 14#include "xfs_alloc_btree.h" 15#include "xfs_alloc.h" 16#include "xfs_discard.h" 17#include "xfs_error.h" 18#include "xfs_extent_busy.h" 19#include "xfs_trace.h" 20#include "xfs_log.h" 21#include "xfs_ag.h" 22#include "xfs_health.h" 23 24/* 25 * Notes on an efficient, low latency fstrim algorithm 26 * 27 * We need to walk the filesystem free space and issue discards on the free 28 * space that meet the search criteria (size and location). We cannot issue 29 * discards on extents that might be in use, or are so recently in use they are 30 * still marked as busy. To serialise against extent state changes whilst we are 31 * gathering extents to trim, we must hold the AGF lock to lock out other 32 * allocations and extent free operations that might change extent state. 33 * 34 * However, we cannot just hold the AGF for the entire AG free space walk whilst 35 * we issue discards on each free space that is found. Storage devices can have 36 * extremely slow discard implementations (e.g. ceph RBD) and so walking a 37 * couple of million free extents and issuing synchronous discards on each 38 * extent can take a *long* time. Whilst we are doing this walk, nothing else 39 * can access the AGF, and we can stall transactions and hence the log whilst 40 * modifications wait for the AGF lock to be released. This can lead hung tasks 41 * kicking the hung task timer and rebooting the system. This is bad. 42 * 43 * Hence we need to take a leaf from the bulkstat playbook. It takes the AGI 44 * lock, gathers a range of inode cluster buffers that are allocated, drops the 45 * AGI lock and then reads all the inode cluster buffers and processes them. It 46 * loops doing this, using a cursor to keep track of where it is up to in the AG 47 * for each iteration to restart the INOBT lookup from. 48 * 49 * We can't do this exactly with free space - once we drop the AGF lock, the 50 * state of the free extent is out of our control and we cannot run a discard 51 * safely on it in this situation. Unless, of course, we've marked the free 52 * extent as busy and undergoing a discard operation whilst we held the AGF 53 * locked. 54 * 55 * This is exactly how online discard works - free extents are marked busy when 56 * they are freed, and once the extent free has been committed to the journal, 57 * the busy extent record is marked as "undergoing discard" and the discard is 58 * then issued on the free extent. Once the discard completes, the busy extent 59 * record is removed and the extent is able to be allocated again. 60 * 61 * In the context of fstrim, if we find a free extent we need to discard, we 62 * don't have to discard it immediately. All we need to do it record that free 63 * extent as being busy and under discard, and all the allocation routines will 64 * now avoid trying to allocate it. Hence if we mark the extent as busy under 65 * the AGF lock, we can safely discard it without holding the AGF lock because 66 * nothing will attempt to allocate that free space until the discard completes. 67 * 68 * This also allows us to issue discards asynchronously like we do with online 69 * discard, and so for fast devices fstrim will run much faster as we can have 70 * multiple discard operations in flight at once, as well as pipeline the free 71 * extent search so that it overlaps in flight discard IO. 72 */ 73 74struct workqueue_struct *xfs_discard_wq; 75 76static void 77xfs_discard_endio_work( 78 struct work_struct *work) 79{ 80 struct xfs_busy_extents *extents = 81 container_of(work, struct xfs_busy_extents, endio_work); 82 83 xfs_extent_busy_clear(extents->mount, &extents->extent_list, false); 84 kfree(extents->owner); 85} 86 87/* 88 * Queue up the actual completion to a thread to avoid IRQ-safe locking for 89 * pagb_lock. 90 */ 91static void 92xfs_discard_endio( 93 struct bio *bio) 94{ 95 struct xfs_busy_extents *extents = bio->bi_private; 96 97 INIT_WORK(&extents->endio_work, xfs_discard_endio_work); 98 queue_work(xfs_discard_wq, &extents->endio_work); 99 bio_put(bio); 100} 101 102/* 103 * Walk the discard list and issue discards on all the busy extents in the 104 * list. We plug and chain the bios so that we only need a single completion 105 * call to clear all the busy extents once the discards are complete. 106 */ 107int 108xfs_discard_extents( 109 struct xfs_mount *mp, 110 struct xfs_busy_extents *extents) 111{ 112 struct xfs_extent_busy *busyp; 113 struct bio *bio = NULL; 114 struct blk_plug plug; 115 int error = 0; 116 117 blk_start_plug(&plug); 118 list_for_each_entry(busyp, &extents->extent_list, list) { 119 trace_xfs_discard_extent(mp, busyp->agno, busyp->bno, 120 busyp->length); 121 122 error = __blkdev_issue_discard(mp->m_ddev_targp->bt_bdev, 123 XFS_AGB_TO_DADDR(mp, busyp->agno, busyp->bno), 124 XFS_FSB_TO_BB(mp, busyp->length), 125 GFP_KERNEL, &bio); 126 if (error && error != -EOPNOTSUPP) { 127 xfs_info(mp, 128 "discard failed for extent [0x%llx,%u], error %d", 129 (unsigned long long)busyp->bno, 130 busyp->length, 131 error); 132 break; 133 } 134 } 135 136 if (bio) { 137 bio->bi_private = extents; 138 bio->bi_end_io = xfs_discard_endio; 139 submit_bio(bio); 140 } else { 141 xfs_discard_endio_work(&extents->endio_work); 142 } 143 blk_finish_plug(&plug); 144 145 return error; 146} 147 148 149static int 150xfs_trim_gather_extents( 151 struct xfs_perag *pag, 152 xfs_daddr_t start, 153 xfs_daddr_t end, 154 xfs_daddr_t minlen, 155 struct xfs_alloc_rec_incore *tcur, 156 struct xfs_busy_extents *extents, 157 uint64_t *blocks_trimmed) 158{ 159 struct xfs_mount *mp = pag->pag_mount; 160 struct xfs_trans *tp; 161 struct xfs_btree_cur *cur; 162 struct xfs_buf *agbp; 163 int error; 164 int i; 165 int batch = 100; 166 167 /* 168 * Force out the log. This means any transactions that might have freed 169 * space before we take the AGF buffer lock are now on disk, and the 170 * volatile disk cache is flushed. 171 */ 172 xfs_log_force(mp, XFS_LOG_SYNC); 173 174 error = xfs_trans_alloc_empty(mp, &tp); 175 if (error) 176 return error; 177 178 error = xfs_alloc_read_agf(pag, tp, 0, &agbp); 179 if (error) 180 goto out_trans_cancel; 181 182 cur = xfs_cntbt_init_cursor(mp, tp, agbp, pag); 183 184 /* 185 * Look up the extent length requested in the AGF and start with it. 186 */ 187 if (tcur->ar_startblock == NULLAGBLOCK) 188 error = xfs_alloc_lookup_ge(cur, 0, tcur->ar_blockcount, &i); 189 else 190 error = xfs_alloc_lookup_le(cur, tcur->ar_startblock, 191 tcur->ar_blockcount, &i); 192 if (error) 193 goto out_del_cursor; 194 if (i == 0) { 195 /* nothing of that length left in the AG, we are done */ 196 tcur->ar_blockcount = 0; 197 goto out_del_cursor; 198 } 199 200 /* 201 * Loop until we are done with all extents that are large 202 * enough to be worth discarding or we hit batch limits. 203 */ 204 while (i) { 205 xfs_agblock_t fbno; 206 xfs_extlen_t flen; 207 xfs_daddr_t dbno; 208 xfs_extlen_t dlen; 209 210 error = xfs_alloc_get_rec(cur, &fbno, &flen, &i); 211 if (error) 212 break; 213 if (XFS_IS_CORRUPT(mp, i != 1)) { 214 xfs_btree_mark_sick(cur); 215 error = -EFSCORRUPTED; 216 break; 217 } 218 219 if (--batch <= 0) { 220 /* 221 * Update the cursor to point at this extent so we 222 * restart the next batch from this extent. 223 */ 224 tcur->ar_startblock = fbno; 225 tcur->ar_blockcount = flen; 226 break; 227 } 228 229 /* 230 * use daddr format for all range/len calculations as that is 231 * the format the range/len variables are supplied in by 232 * userspace. 233 */ 234 dbno = XFS_AGB_TO_DADDR(mp, pag->pag_agno, fbno); 235 dlen = XFS_FSB_TO_BB(mp, flen); 236 237 /* 238 * Too small? Give up. 239 */ 240 if (dlen < minlen) { 241 trace_xfs_discard_toosmall(mp, pag->pag_agno, fbno, flen); 242 tcur->ar_blockcount = 0; 243 break; 244 } 245 246 /* 247 * If the extent is entirely outside of the range we are 248 * supposed to discard skip it. Do not bother to trim 249 * down partially overlapping ranges for now. 250 */ 251 if (dbno + dlen < start || dbno > end) { 252 trace_xfs_discard_exclude(mp, pag->pag_agno, fbno, flen); 253 goto next_extent; 254 } 255 256 /* 257 * If any blocks in the range are still busy, skip the 258 * discard and try again the next time. 259 */ 260 if (xfs_extent_busy_search(mp, pag, fbno, flen)) { 261 trace_xfs_discard_busy(mp, pag->pag_agno, fbno, flen); 262 goto next_extent; 263 } 264 265 xfs_extent_busy_insert_discard(pag, fbno, flen, 266 &extents->extent_list); 267 *blocks_trimmed += flen; 268next_extent: 269 error = xfs_btree_decrement(cur, 0, &i); 270 if (error) 271 break; 272 273 /* 274 * If there's no more records in the tree, we are done. Set the 275 * cursor block count to 0 to indicate to the caller that there 276 * is no more extents to search. 277 */ 278 if (i == 0) 279 tcur->ar_blockcount = 0; 280 } 281 282 /* 283 * If there was an error, release all the gathered busy extents because 284 * we aren't going to issue a discard on them any more. 285 */ 286 if (error) 287 xfs_extent_busy_clear(mp, &extents->extent_list, false); 288out_del_cursor: 289 xfs_btree_del_cursor(cur, error); 290out_trans_cancel: 291 xfs_trans_cancel(tp); 292 return error; 293} 294 295static bool 296xfs_trim_should_stop(void) 297{ 298 return fatal_signal_pending(current) || freezing(current); 299} 300 301/* 302 * Iterate the free list gathering extents and discarding them. We need a cursor 303 * for the repeated iteration of gather/discard loop, so use the longest extent 304 * we found in the last batch as the key to start the next. 305 */ 306static int 307xfs_trim_extents( 308 struct xfs_perag *pag, 309 xfs_daddr_t start, 310 xfs_daddr_t end, 311 xfs_daddr_t minlen, 312 uint64_t *blocks_trimmed) 313{ 314 struct xfs_alloc_rec_incore tcur = { 315 .ar_blockcount = pag->pagf_longest, 316 .ar_startblock = NULLAGBLOCK, 317 }; 318 int error = 0; 319 320 do { 321 struct xfs_busy_extents *extents; 322 323 extents = kzalloc(sizeof(*extents), GFP_KERNEL); 324 if (!extents) { 325 error = -ENOMEM; 326 break; 327 } 328 329 extents->mount = pag->pag_mount; 330 extents->owner = extents; 331 INIT_LIST_HEAD(&extents->extent_list); 332 333 error = xfs_trim_gather_extents(pag, start, end, minlen, 334 &tcur, extents, blocks_trimmed); 335 if (error) { 336 kfree(extents); 337 break; 338 } 339 340 /* 341 * We hand the extent list to the discard function here so the 342 * discarded extents can be removed from the busy extent list. 343 * This allows the discards to run asynchronously with gathering 344 * the next round of extents to discard. 345 * 346 * However, we must ensure that we do not reference the extent 347 * list after this function call, as it may have been freed by 348 * the time control returns to us. 349 */ 350 error = xfs_discard_extents(pag->pag_mount, extents); 351 if (error) 352 break; 353 354 if (xfs_trim_should_stop()) 355 break; 356 357 } while (tcur.ar_blockcount != 0); 358 359 return error; 360 361} 362 363/* 364 * trim a range of the filesystem. 365 * 366 * Note: the parameters passed from userspace are byte ranges into the 367 * filesystem which does not match to the format we use for filesystem block 368 * addressing. FSB addressing is sparse (AGNO|AGBNO), while the incoming format 369 * is a linear address range. Hence we need to use DADDR based conversions and 370 * comparisons for determining the correct offset and regions to trim. 371 */ 372int 373xfs_ioc_trim( 374 struct xfs_mount *mp, 375 struct fstrim_range __user *urange) 376{ 377 struct xfs_perag *pag; 378 unsigned int granularity = 379 bdev_discard_granularity(mp->m_ddev_targp->bt_bdev); 380 struct fstrim_range range; 381 xfs_daddr_t start, end, minlen; 382 xfs_agnumber_t agno; 383 uint64_t blocks_trimmed = 0; 384 int error, last_error = 0; 385 386 if (!capable(CAP_SYS_ADMIN)) 387 return -EPERM; 388 if (!bdev_max_discard_sectors(mp->m_ddev_targp->bt_bdev)) 389 return -EOPNOTSUPP; 390 391 /* 392 * We haven't recovered the log, so we cannot use our bnobt-guided 393 * storage zapping commands. 394 */ 395 if (xfs_has_norecovery(mp)) 396 return -EROFS; 397 398 if (copy_from_user(&range, urange, sizeof(range))) 399 return -EFAULT; 400 401 range.minlen = max_t(u64, granularity, range.minlen); 402 minlen = BTOBB(range.minlen); 403 /* 404 * Truncating down the len isn't actually quite correct, but using 405 * BBTOB would mean we trivially get overflows for values 406 * of ULLONG_MAX or slightly lower. And ULLONG_MAX is the default 407 * used by the fstrim application. In the end it really doesn't 408 * matter as trimming blocks is an advisory interface. 409 */ 410 if (range.start >= XFS_FSB_TO_B(mp, mp->m_sb.sb_dblocks) || 411 range.minlen > XFS_FSB_TO_B(mp, mp->m_ag_max_usable) || 412 range.len < mp->m_sb.sb_blocksize) 413 return -EINVAL; 414 415 start = BTOBB(range.start); 416 end = start + BTOBBT(range.len) - 1; 417 418 if (end > XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks) - 1) 419 end = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks) - 1; 420 421 agno = xfs_daddr_to_agno(mp, start); 422 for_each_perag_range(mp, agno, xfs_daddr_to_agno(mp, end), pag) { 423 error = xfs_trim_extents(pag, start, end, minlen, 424 &blocks_trimmed); 425 if (error) 426 last_error = error; 427 428 if (xfs_trim_should_stop()) { 429 xfs_perag_rele(pag); 430 break; 431 } 432 } 433 434 if (last_error) 435 return last_error; 436 437 range.len = XFS_FSB_TO_B(mp, blocks_trimmed); 438 if (copy_to_user(urange, &range, sizeof(range))) 439 return -EFAULT; 440 return 0; 441} 442