1 /* 2 * Copyright (c) 2006-2007 Silicon Graphics, Inc. 3 * Copyright (c) 2014 Christoph Hellwig. 4 * All Rights Reserved. 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License as 8 * published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope that it would be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, write the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 18 */ 19 #include "xfs.h" 20 #include "xfs_format.h" 21 #include "xfs_log_format.h" 22 #include "xfs_trans_resv.h" 23 #include "xfs_sb.h" 24 #include "xfs_mount.h" 25 #include "xfs_inode.h" 26 #include "xfs_bmap.h" 27 #include "xfs_bmap_util.h" 28 #include "xfs_alloc.h" 29 #include "xfs_mru_cache.h" 30 #include "xfs_filestream.h" 31 #include "xfs_trace.h" 32 33 struct xfs_fstrm_item { 34 struct xfs_mru_cache_elem mru; 35 struct xfs_inode *ip; 36 xfs_agnumber_t ag; /* AG in use for this directory */ 37 }; 38 39 enum xfs_fstrm_alloc { 40 XFS_PICK_USERDATA = 1, 41 XFS_PICK_LOWSPACE = 2, 42 }; 43 44 /* 45 * Allocation group filestream associations are tracked with per-ag atomic 46 * counters. These counters allow xfs_filestream_pick_ag() to tell whether a 47 * particular AG already has active filestreams associated with it. The mount 48 * point's m_peraglock is used to protect these counters from per-ag array 49 * re-allocation during a growfs operation. When xfs_growfs_data_private() is 50 * about to reallocate the array, it calls xfs_filestream_flush() with the 51 * m_peraglock held in write mode. 52 * 53 * Since xfs_mru_cache_flush() guarantees that all the free functions for all 54 * the cache elements have finished executing before it returns, it's safe for 55 * the free functions to use the atomic counters without m_peraglock protection. 56 * This allows the implementation of xfs_fstrm_free_func() to be agnostic about 57 * whether it was called with the m_peraglock held in read mode, write mode or 58 * not held at all. The race condition this addresses is the following: 59 * 60 * - The work queue scheduler fires and pulls a filestream directory cache 61 * element off the LRU end of the cache for deletion, then gets pre-empted. 62 * - A growfs operation grabs the m_peraglock in write mode, flushes all the 63 * remaining items from the cache and reallocates the mount point's per-ag 64 * array, resetting all the counters to zero. 65 * - The work queue thread resumes and calls the free function for the element 66 * it started cleaning up earlier. In the process it decrements the 67 * filestreams counter for an AG that now has no references. 68 * 69 * With a shrinkfs feature, the above scenario could panic the system. 70 * 71 * All other uses of the following macros should be protected by either the 72 * m_peraglock held in read mode, or the cache's internal locking exposed by the 73 * interval between a call to xfs_mru_cache_lookup() and a call to 74 * xfs_mru_cache_done(). In addition, the m_peraglock must be held in read mode 75 * when new elements are added to the cache. 76 * 77 * Combined, these locking rules ensure that no associations will ever exist in 78 * the cache that reference per-ag array elements that have since been 79 * reallocated. 80 */ 81 int 82 xfs_filestream_peek_ag( 83 xfs_mount_t *mp, 84 xfs_agnumber_t agno) 85 { 86 struct xfs_perag *pag; 87 int ret; 88 89 pag = xfs_perag_get(mp, agno); 90 ret = atomic_read(&pag->pagf_fstrms); 91 xfs_perag_put(pag); 92 return ret; 93 } 94 95 static int 96 xfs_filestream_get_ag( 97 xfs_mount_t *mp, 98 xfs_agnumber_t agno) 99 { 100 struct xfs_perag *pag; 101 int ret; 102 103 pag = xfs_perag_get(mp, agno); 104 ret = atomic_inc_return(&pag->pagf_fstrms); 105 xfs_perag_put(pag); 106 return ret; 107 } 108 109 static void 110 xfs_filestream_put_ag( 111 xfs_mount_t *mp, 112 xfs_agnumber_t agno) 113 { 114 struct xfs_perag *pag; 115 116 pag = xfs_perag_get(mp, agno); 117 atomic_dec(&pag->pagf_fstrms); 118 xfs_perag_put(pag); 119 } 120 121 static void 122 xfs_fstrm_free_func( 123 struct xfs_mru_cache_elem *mru) 124 { 125 struct xfs_fstrm_item *item = 126 container_of(mru, struct xfs_fstrm_item, mru); 127 128 xfs_filestream_put_ag(item->ip->i_mount, item->ag); 129 130 trace_xfs_filestream_free(item->ip, item->ag); 131 132 kmem_free(item); 133 } 134 135 /* 136 * Scan the AGs starting at startag looking for an AG that isn't in use and has 137 * at least minlen blocks free. 138 */ 139 static int 140 xfs_filestream_pick_ag( 141 struct xfs_inode *ip, 142 xfs_agnumber_t startag, 143 xfs_agnumber_t *agp, 144 int flags, 145 xfs_extlen_t minlen) 146 { 147 struct xfs_mount *mp = ip->i_mount; 148 struct xfs_fstrm_item *item; 149 struct xfs_perag *pag; 150 xfs_extlen_t longest, free = 0, minfree, maxfree = 0; 151 xfs_agnumber_t ag, max_ag = NULLAGNUMBER; 152 int err, trylock, nscan; 153 154 ASSERT(S_ISDIR(ip->i_d.di_mode)); 155 156 /* 2% of an AG's blocks must be free for it to be chosen. */ 157 minfree = mp->m_sb.sb_agblocks / 50; 158 159 ag = startag; 160 *agp = NULLAGNUMBER; 161 162 /* For the first pass, don't sleep trying to init the per-AG. */ 163 trylock = XFS_ALLOC_FLAG_TRYLOCK; 164 165 for (nscan = 0; 1; nscan++) { 166 trace_xfs_filestream_scan(ip, ag); 167 168 pag = xfs_perag_get(mp, ag); 169 170 if (!pag->pagf_init) { 171 err = xfs_alloc_pagf_init(mp, NULL, ag, trylock); 172 if (err && !trylock) { 173 xfs_perag_put(pag); 174 return err; 175 } 176 } 177 178 /* Might fail sometimes during the 1st pass with trylock set. */ 179 if (!pag->pagf_init) 180 goto next_ag; 181 182 /* Keep track of the AG with the most free blocks. */ 183 if (pag->pagf_freeblks > maxfree) { 184 maxfree = pag->pagf_freeblks; 185 max_ag = ag; 186 } 187 188 /* 189 * The AG reference count does two things: it enforces mutual 190 * exclusion when examining the suitability of an AG in this 191 * loop, and it guards against two filestreams being established 192 * in the same AG as each other. 193 */ 194 if (xfs_filestream_get_ag(mp, ag) > 1) { 195 xfs_filestream_put_ag(mp, ag); 196 goto next_ag; 197 } 198 199 longest = xfs_alloc_longest_free_extent(mp, pag); 200 if (((minlen && longest >= minlen) || 201 (!minlen && pag->pagf_freeblks >= minfree)) && 202 (!pag->pagf_metadata || !(flags & XFS_PICK_USERDATA) || 203 (flags & XFS_PICK_LOWSPACE))) { 204 205 /* Break out, retaining the reference on the AG. */ 206 free = pag->pagf_freeblks; 207 xfs_perag_put(pag); 208 *agp = ag; 209 break; 210 } 211 212 /* Drop the reference on this AG, it's not usable. */ 213 xfs_filestream_put_ag(mp, ag); 214 next_ag: 215 xfs_perag_put(pag); 216 /* Move to the next AG, wrapping to AG 0 if necessary. */ 217 if (++ag >= mp->m_sb.sb_agcount) 218 ag = 0; 219 220 /* If a full pass of the AGs hasn't been done yet, continue. */ 221 if (ag != startag) 222 continue; 223 224 /* Allow sleeping in xfs_alloc_pagf_init() on the 2nd pass. */ 225 if (trylock != 0) { 226 trylock = 0; 227 continue; 228 } 229 230 /* Finally, if lowspace wasn't set, set it for the 3rd pass. */ 231 if (!(flags & XFS_PICK_LOWSPACE)) { 232 flags |= XFS_PICK_LOWSPACE; 233 continue; 234 } 235 236 /* 237 * Take the AG with the most free space, regardless of whether 238 * it's already in use by another filestream. 239 */ 240 if (max_ag != NULLAGNUMBER) { 241 xfs_filestream_get_ag(mp, max_ag); 242 free = maxfree; 243 *agp = max_ag; 244 break; 245 } 246 247 /* take AG 0 if none matched */ 248 trace_xfs_filestream_pick(ip, *agp, free, nscan); 249 *agp = 0; 250 return 0; 251 } 252 253 trace_xfs_filestream_pick(ip, *agp, free, nscan); 254 255 if (*agp == NULLAGNUMBER) 256 return 0; 257 258 err = -ENOMEM; 259 item = kmem_alloc(sizeof(*item), KM_MAYFAIL); 260 if (!item) 261 goto out_put_ag; 262 263 item->ag = *agp; 264 item->ip = ip; 265 266 err = xfs_mru_cache_insert(mp->m_filestream, ip->i_ino, &item->mru); 267 if (err) { 268 if (err == -EEXIST) 269 err = 0; 270 goto out_free_item; 271 } 272 273 return 0; 274 275 out_free_item: 276 kmem_free(item); 277 out_put_ag: 278 xfs_filestream_put_ag(mp, *agp); 279 return err; 280 } 281 282 static struct xfs_inode * 283 xfs_filestream_get_parent( 284 struct xfs_inode *ip) 285 { 286 struct inode *inode = VFS_I(ip), *dir = NULL; 287 struct dentry *dentry, *parent; 288 289 dentry = d_find_alias(inode); 290 if (!dentry) 291 goto out; 292 293 parent = dget_parent(dentry); 294 if (!parent) 295 goto out_dput; 296 297 dir = igrab(parent->d_inode); 298 dput(parent); 299 300 out_dput: 301 dput(dentry); 302 out: 303 return dir ? XFS_I(dir) : NULL; 304 } 305 306 /* 307 * Find the right allocation group for a file, either by finding an 308 * existing file stream or creating a new one. 309 * 310 * Returns NULLAGNUMBER in case of an error. 311 */ 312 xfs_agnumber_t 313 xfs_filestream_lookup_ag( 314 struct xfs_inode *ip) 315 { 316 struct xfs_mount *mp = ip->i_mount; 317 struct xfs_inode *pip = NULL; 318 xfs_agnumber_t startag, ag = NULLAGNUMBER; 319 struct xfs_mru_cache_elem *mru; 320 321 ASSERT(S_ISREG(ip->i_d.di_mode)); 322 323 pip = xfs_filestream_get_parent(ip); 324 if (!pip) 325 return NULLAGNUMBER; 326 327 mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino); 328 if (mru) { 329 ag = container_of(mru, struct xfs_fstrm_item, mru)->ag; 330 xfs_mru_cache_done(mp->m_filestream); 331 332 trace_xfs_filestream_lookup(ip, ag); 333 goto out; 334 } 335 336 /* 337 * Set the starting AG using the rotor for inode32, otherwise 338 * use the directory inode's AG. 339 */ 340 if (mp->m_flags & XFS_MOUNT_32BITINODES) { 341 xfs_agnumber_t rotorstep = xfs_rotorstep; 342 startag = (mp->m_agfrotor / rotorstep) % mp->m_sb.sb_agcount; 343 mp->m_agfrotor = (mp->m_agfrotor + 1) % 344 (mp->m_sb.sb_agcount * rotorstep); 345 } else 346 startag = XFS_INO_TO_AGNO(mp, pip->i_ino); 347 348 if (xfs_filestream_pick_ag(pip, startag, &ag, 0, 0)) 349 ag = NULLAGNUMBER; 350 out: 351 IRELE(pip); 352 return ag; 353 } 354 355 /* 356 * Pick a new allocation group for the current file and its file stream. 357 * 358 * This is called when the allocator can't find a suitable extent in the 359 * current AG, and we have to move the stream into a new AG with more space. 360 */ 361 int 362 xfs_filestream_new_ag( 363 struct xfs_bmalloca *ap, 364 xfs_agnumber_t *agp) 365 { 366 struct xfs_inode *ip = ap->ip, *pip; 367 struct xfs_mount *mp = ip->i_mount; 368 xfs_extlen_t minlen = ap->length; 369 xfs_agnumber_t startag = 0; 370 int flags, err = 0; 371 struct xfs_mru_cache_elem *mru; 372 373 *agp = NULLAGNUMBER; 374 375 pip = xfs_filestream_get_parent(ip); 376 if (!pip) 377 goto exit; 378 379 mru = xfs_mru_cache_remove(mp->m_filestream, pip->i_ino); 380 if (mru) { 381 struct xfs_fstrm_item *item = 382 container_of(mru, struct xfs_fstrm_item, mru); 383 startag = (item->ag + 1) % mp->m_sb.sb_agcount; 384 } 385 386 flags = (ap->userdata ? XFS_PICK_USERDATA : 0) | 387 (ap->flist->xbf_low ? XFS_PICK_LOWSPACE : 0); 388 389 err = xfs_filestream_pick_ag(pip, startag, agp, flags, minlen); 390 391 /* 392 * Only free the item here so we skip over the old AG earlier. 393 */ 394 if (mru) 395 xfs_fstrm_free_func(mru); 396 397 IRELE(pip); 398 exit: 399 if (*agp == NULLAGNUMBER) 400 *agp = 0; 401 return err; 402 } 403 404 void 405 xfs_filestream_deassociate( 406 struct xfs_inode *ip) 407 { 408 xfs_mru_cache_delete(ip->i_mount->m_filestream, ip->i_ino); 409 } 410 411 int 412 xfs_filestream_mount( 413 xfs_mount_t *mp) 414 { 415 /* 416 * The filestream timer tunable is currently fixed within the range of 417 * one second to four minutes, with five seconds being the default. The 418 * group count is somewhat arbitrary, but it'd be nice to adhere to the 419 * timer tunable to within about 10 percent. This requires at least 10 420 * groups. 421 */ 422 return xfs_mru_cache_create(&mp->m_filestream, xfs_fstrm_centisecs * 10, 423 10, xfs_fstrm_free_func); 424 } 425 426 void 427 xfs_filestream_unmount( 428 xfs_mount_t *mp) 429 { 430 xfs_mru_cache_destroy(mp->m_filestream); 431 } 432