fs/xfs/xfs_filestream.c

   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_ag.h"
  24 #include "xfs_sb.h"
  25 #include "xfs_mount.h"
  26 #include "xfs_inum.h"
  27 #include "xfs_inode.h"
  28 #include "xfs_bmap.h"
  29 #include "xfs_bmap_util.h"
  30 #include "xfs_alloc.h"
  31 #include "xfs_mru_cache.h"
  32 #include "xfs_dinode.h"
  33 #include "xfs_filestream.h"
  34 #include "xfs_trace.h"
  35
  36 struct xfs_fstrm_item {
  37         struct xfs_mru_cache_elem       mru;
  38         struct xfs_inode                *ip;
  39         xfs_agnumber_t                  ag; /* AG in use for this directory */
  40 };
  41
  42 enum xfs_fstrm_alloc {
  43         XFS_PICK_USERDATA = 1,
  44         XFS_PICK_LOWSPACE = 2,
  45 };
  46
  47 /*
  48  * Allocation group filestream associations are tracked with per-ag atomic
  49  * counters.  These counters allow xfs_filestream_pick_ag() to tell whether a
  50  * particular AG already has active filestreams associated with it. The mount
  51  * point's m_peraglock is used to protect these counters from per-ag array
  52  * re-allocation during a growfs operation.  When xfs_growfs_data_private() is
  53  * about to reallocate the array, it calls xfs_filestream_flush() with the
  54  * m_peraglock held in write mode.
  55  *
  56  * Since xfs_mru_cache_flush() guarantees that all the free functions for all
  57  * the cache elements have finished executing before it returns, it's safe for
  58  * the free functions to use the atomic counters without m_peraglock protection.
  59  * This allows the implementation of xfs_fstrm_free_func() to be agnostic about
  60  * whether it was called with the m_peraglock held in read mode, write mode or
  61  * not held at all.  The race condition this addresses is the following:
  62  *
  63  *  - The work queue scheduler fires and pulls a filestream directory cache
  64  *    element off the LRU end of the cache for deletion, then gets pre-empted.
  65  *  - A growfs operation grabs the m_peraglock in write mode, flushes all the
  66  *    remaining items from the cache and reallocates the mount point's per-ag
  67  *    array, resetting all the counters to zero.
  68  *  - The work queue thread resumes and calls the free function for the element
  69  *    it started cleaning up earlier.  In the process it decrements the
  70  *    filestreams counter for an AG that now has no references.
  71  *
  72  * With a shrinkfs feature, the above scenario could panic the system.
  73  *
  74  * All other uses of the following macros should be protected by either the
  75  * m_peraglock held in read mode, or the cache's internal locking exposed by the
  76  * interval between a call to xfs_mru_cache_lookup() and a call to
  77  * xfs_mru_cache_done().  In addition, the m_peraglock must be held in read mode
  78  * when new elements are added to the cache.
  79  *
  80  * Combined, these locking rules ensure that no associations will ever exist in
  81  * the cache that reference per-ag array elements that have since been
  82  * reallocated.
  83  */
  84 int
  85 xfs_filestream_peek_ag(
  86         xfs_mount_t     *mp,
  87         xfs_agnumber_t  agno)
  88 {
  89         struct xfs_perag *pag;
  90         int             ret;
  91
  92         pag = xfs_perag_get(mp, agno);
  93         ret = atomic_read(&pag->pagf_fstrms);
  94         xfs_perag_put(pag);
  95         return ret;
  96 }
  97
  98 static int
  99 xfs_filestream_get_ag(
 100         xfs_mount_t     *mp,
 101         xfs_agnumber_t  agno)
 102 {
 103         struct xfs_perag *pag;
 104         int             ret;
 105
 106         pag = xfs_perag_get(mp, agno);
 107         ret = atomic_inc_return(&pag->pagf_fstrms);
 108         xfs_perag_put(pag);
 109         return ret;
 110 }
 111
 112 static void
 113 xfs_filestream_put_ag(
 114         xfs_mount_t     *mp,
 115         xfs_agnumber_t  agno)
 116 {
 117         struct xfs_perag *pag;
 118
 119         pag = xfs_perag_get(mp, agno);
 120         atomic_dec(&pag->pagf_fstrms);
 121         xfs_perag_put(pag);
 122 }
 123
 124 static void
 125 xfs_fstrm_free_func(
 126         struct xfs_mru_cache_elem *mru)
 127 {
 128         struct xfs_fstrm_item   *item =
 129                 container_of(mru, struct xfs_fstrm_item, mru);
 130
 131         xfs_filestream_put_ag(item->ip->i_mount, item->ag);
 132
 133         trace_xfs_filestream_free(item->ip, item->ag);
 134
 135         kmem_free(item);
 136 }
 137
 138 /*
 139  * Scan the AGs starting at startag looking for an AG that isn't in use and has
 140  * at least minlen blocks free.
 141  */
 142 static int
 143 xfs_filestream_pick_ag(
 144         struct xfs_inode        *ip,
 145         xfs_agnumber_t          startag,
 146         xfs_agnumber_t          *agp,
 147         int                     flags,
 148         xfs_extlen_t            minlen)
 149 {
 150         struct xfs_mount        *mp = ip->i_mount;
 151         struct xfs_fstrm_item   *item;
 152         struct xfs_perag        *pag;
 153         xfs_extlen_t            longest, free = 0, minfree, maxfree = 0;
 154         xfs_agnumber_t          ag, max_ag = NULLAGNUMBER;
 155         int                     err, trylock, nscan;
 156
 157         ASSERT(S_ISDIR(ip->i_d.di_mode));
 158
 159         /* 2% of an AG's blocks must be free for it to be chosen. */
 160         minfree = mp->m_sb.sb_agblocks / 50;
 161
 162         ag = startag;
 163         *agp = NULLAGNUMBER;
 164
 165         /* For the first pass, don't sleep trying to init the per-AG. */
 166         trylock = XFS_ALLOC_FLAG_TRYLOCK;
 167
 168         for (nscan = 0; 1; nscan++) {
 169                 trace_xfs_filestream_scan(ip, ag);
 170
 171                 pag = xfs_perag_get(mp, ag);
 172
 173                 if (!pag->pagf_init) {
 174                         err = xfs_alloc_pagf_init(mp, NULL, ag, trylock);
 175                         if (err && !trylock) {
 176                                 xfs_perag_put(pag);
 177                                 return err;
 178                         }
 179                 }
 180
 181                 /* Might fail sometimes during the 1st pass with trylock set. */
 182                 if (!pag->pagf_init)
 183                         goto next_ag;
 184
 185                 /* Keep track of the AG with the most free blocks. */
 186                 if (pag->pagf_freeblks > maxfree) {
 187                         maxfree = pag->pagf_freeblks;
 188                         max_ag = ag;
 189                 }
 190
 191                 /*
 192                  * The AG reference count does two things: it enforces mutual
 193                  * exclusion when examining the suitability of an AG in this
 194                  * loop, and it guards against two filestreams being established
 195                  * in the same AG as each other.
 196                  */
 197                 if (xfs_filestream_get_ag(mp, ag) > 1) {
 198                         xfs_filestream_put_ag(mp, ag);
 199                         goto next_ag;
 200                 }
 201
 202                 longest = xfs_alloc_longest_free_extent(mp, pag);
 203                 if (((minlen && longest >= minlen) ||
 204                      (!minlen && pag->pagf_freeblks >= minfree)) &&
 205                     (!pag->pagf_metadata || !(flags & XFS_PICK_USERDATA) ||
 206                      (flags & XFS_PICK_LOWSPACE))) {
 207
 208                         /* Break out, retaining the reference on the AG. */
 209                         free = pag->pagf_freeblks;
 210                         xfs_perag_put(pag);
 211                         *agp = ag;
 212                         break;
 213                 }
 214
 215                 /* Drop the reference on this AG, it's not usable. */
 216                 xfs_filestream_put_ag(mp, ag);
 217 next_ag:
 218                 xfs_perag_put(pag);
 219                 /* Move to the next AG, wrapping to AG 0 if necessary. */
 220                 if (++ag >= mp->m_sb.sb_agcount)
 221                         ag = 0;
 222
 223                 /* If a full pass of the AGs hasn't been done yet, continue. */
 224                 if (ag != startag)
 225                         continue;
 226
 227                 /* Allow sleeping in xfs_alloc_pagf_init() on the 2nd pass. */
 228                 if (trylock != 0) {
 229                         trylock = 0;
 230                         continue;
 231                 }
 232
 233                 /* Finally, if lowspace wasn't set, set it for the 3rd pass. */
 234                 if (!(flags & XFS_PICK_LOWSPACE)) {
 235                         flags |= XFS_PICK_LOWSPACE;
 236                         continue;
 237                 }
 238
 239                 /*
 240                  * Take the AG with the most free space, regardless of whether
 241                  * it's already in use by another filestream.
 242                  */
 243                 if (max_ag != NULLAGNUMBER) {
 244                         xfs_filestream_get_ag(mp, max_ag);
 245                         free = maxfree;
 246                         *agp = max_ag;
 247                         break;
 248                 }
 249
 250                 /* take AG 0 if none matched */
 251                 trace_xfs_filestream_pick(ip, *agp, free, nscan);
 252                 *agp = 0;
 253                 return 0;
 254         }
 255
 256         trace_xfs_filestream_pick(ip, *agp, free, nscan);
 257
 258         if (*agp == NULLAGNUMBER)
 259                 return 0;
 260
 261         err = -ENOMEM;
 262         item = kmem_alloc(sizeof(*item), KM_MAYFAIL);
 263         if (!item)
 264                 goto out_put_ag;
 265
 266         item->ag = *agp;
 267         item->ip = ip;
 268
 269         err = xfs_mru_cache_insert(mp->m_filestream, ip->i_ino, &item->mru);
 270         if (err) {
 271                 if (err == -EEXIST)
 272                         err = 0;
 273                 goto out_free_item;
 274         }
 275
 276         return 0;
 277
 278 out_free_item:
 279         kmem_free(item);
 280 out_put_ag:
 281         xfs_filestream_put_ag(mp, *agp);
 282         return err;
 283 }
 284
 285 static struct xfs_inode *
 286 xfs_filestream_get_parent(
 287         struct xfs_inode        *ip)
 288 {
 289         struct inode            *inode = VFS_I(ip), *dir = NULL;
 290         struct dentry           *dentry, *parent;
 291
 292         dentry = d_find_alias(inode);
 293         if (!dentry)
 294                 goto out;
 295
 296         parent = dget_parent(dentry);
 297         if (!parent)
 298                 goto out_dput;
 299
 300         dir = igrab(parent->d_inode);
 301         dput(parent);
 302
 303 out_dput:
 304         dput(dentry);
 305 out:
 306         return dir ? XFS_I(dir) : NULL;
 307 }
 308
 309 /*
 310  * Find the right allocation group for a file, either by finding an
 311  * existing file stream or creating a new one.
 312  *
 313  * Returns NULLAGNUMBER in case of an error.
 314  */
 315 xfs_agnumber_t
 316 xfs_filestream_lookup_ag(
 317         struct xfs_inode        *ip)
 318 {
 319         struct xfs_mount        *mp = ip->i_mount;
 320         struct xfs_inode        *pip = NULL;
 321         xfs_agnumber_t          startag, ag = NULLAGNUMBER;
 322         struct xfs_mru_cache_elem *mru;
 323
 324         ASSERT(S_ISREG(ip->i_d.di_mode));
 325
 326         pip = xfs_filestream_get_parent(ip);
 327         if (!pip)
 328                 goto out;
 329
 330         mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino);
 331         if (mru) {
 332                 ag = container_of(mru, struct xfs_fstrm_item, mru)->ag;
 333                 xfs_mru_cache_done(mp->m_filestream);
 334
 335                 trace_xfs_filestream_lookup(ip, ag);
 336                 goto out;
 337         }
 338
 339         /*
 340          * Set the starting AG using the rotor for inode32, otherwise
 341          * use the directory inode's AG.
 342          */
 343         if (mp->m_flags & XFS_MOUNT_32BITINODES) {
 344                 xfs_agnumber_t   rotorstep = xfs_rotorstep;
 345                 startag = (mp->m_agfrotor / rotorstep) % mp->m_sb.sb_agcount;
 346                 mp->m_agfrotor = (mp->m_agfrotor + 1) %
 347                                  (mp->m_sb.sb_agcount * rotorstep);
 348         } else
 349                 startag = XFS_INO_TO_AGNO(mp, pip->i_ino);
 350
 351         if (xfs_filestream_pick_ag(pip, startag, &ag, 0, 0))
 352                 ag = NULLAGNUMBER;
 353 out:
 354         IRELE(pip);
 355         return ag;
 356 }
 357
 358 /*
 359  * Pick a new allocation group for the current file and its file stream.
 360  *
 361  * This is called when the allocator can't find a suitable extent in the
 362  * current AG, and we have to move the stream into a new AG with more space.
 363  */
 364 int
 365 xfs_filestream_new_ag(
 366         struct xfs_bmalloca     *ap,
 367         xfs_agnumber_t          *agp)
 368 {
 369         struct xfs_inode        *ip = ap->ip, *pip;
 370         struct xfs_mount        *mp = ip->i_mount;
 371         xfs_extlen_t            minlen = ap->length;
 372         xfs_agnumber_t          startag = 0;
 373         int                     flags, err = 0;
 374         struct xfs_mru_cache_elem *mru;
 375
 376         *agp = NULLAGNUMBER;
 377
 378         pip = xfs_filestream_get_parent(ip);
 379         if (!pip)
 380                 goto exit;
 381
 382         mru = xfs_mru_cache_remove(mp->m_filestream, pip->i_ino);
 383         if (mru) {
 384                 struct xfs_fstrm_item *item =
 385                         container_of(mru, struct xfs_fstrm_item, mru);
 386                 startag = (item->ag + 1) % mp->m_sb.sb_agcount;
 387         }
 388
 389         flags = (ap->userdata ? XFS_PICK_USERDATA : 0) |
 390                 (ap->flist->xbf_low ? XFS_PICK_LOWSPACE : 0);
 391
 392         err = xfs_filestream_pick_ag(pip, startag, agp, flags, minlen);
 393
 394         /*
 395          * Only free the item here so we skip over the old AG earlier.
 396          */
 397         if (mru)
 398                 xfs_fstrm_free_func(mru);
 399
 400         IRELE(pip);
 401 exit:
 402         if (*agp == NULLAGNUMBER)
 403                 *agp = 0;
 404         return err;
 405 }
 406
 407 void
 408 xfs_filestream_deassociate(
 409         struct xfs_inode        *ip)
 410 {
 411         xfs_mru_cache_delete(ip->i_mount->m_filestream, ip->i_ino);
 412 }
 413
 414 int
 415 xfs_filestream_mount(
 416         xfs_mount_t     *mp)
 417 {
 418         /*
 419          * The filestream timer tunable is currently fixed within the range of
 420          * one second to four minutes, with five seconds being the default.  The
 421          * group count is somewhat arbitrary, but it'd be nice to adhere to the
 422          * timer tunable to within about 10 percent.  This requires at least 10
 423          * groups.
 424          */
 425         return xfs_mru_cache_create(&mp->m_filestream, xfs_fstrm_centisecs * 10,
 426                                     10, xfs_fstrm_free_func);
 427 }
 428
 429 void
 430 xfs_filestream_unmount(
 431         xfs_mount_t     *mp)
 432 {
 433         xfs_mru_cache_destroy(mp->m_filestream);
 434 }