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TOMOYO Linux Cross Reference
Linux/fs/xfs/xfs_filestream.c

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  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(VFS_I(ip)->i_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                                         xfs_alloc_min_freelist(mp, pag));
201                 if (((minlen && longest >= minlen) ||
202                      (!minlen && pag->pagf_freeblks >= minfree)) &&
203                     (!pag->pagf_metadata || !(flags & XFS_PICK_USERDATA) ||
204                      (flags & XFS_PICK_LOWSPACE))) {
205 
206                         /* Break out, retaining the reference on the AG. */
207                         free = pag->pagf_freeblks;
208                         xfs_perag_put(pag);
209                         *agp = ag;
210                         break;
211                 }
212 
213                 /* Drop the reference on this AG, it's not usable. */
214                 xfs_filestream_put_ag(mp, ag);
215 next_ag:
216                 xfs_perag_put(pag);
217                 /* Move to the next AG, wrapping to AG 0 if necessary. */
218                 if (++ag >= mp->m_sb.sb_agcount)
219                         ag = 0;
220 
221                 /* If a full pass of the AGs hasn't been done yet, continue. */
222                 if (ag != startag)
223                         continue;
224 
225                 /* Allow sleeping in xfs_alloc_pagf_init() on the 2nd pass. */
226                 if (trylock != 0) {
227                         trylock = 0;
228                         continue;
229                 }
230 
231                 /* Finally, if lowspace wasn't set, set it for the 3rd pass. */
232                 if (!(flags & XFS_PICK_LOWSPACE)) {
233                         flags |= XFS_PICK_LOWSPACE;
234                         continue;
235                 }
236 
237                 /*
238                  * Take the AG with the most free space, regardless of whether
239                  * it's already in use by another filestream.
240                  */
241                 if (max_ag != NULLAGNUMBER) {
242                         xfs_filestream_get_ag(mp, max_ag);
243                         free = maxfree;
244                         *agp = max_ag;
245                         break;
246                 }
247 
248                 /* take AG 0 if none matched */
249                 trace_xfs_filestream_pick(ip, *agp, free, nscan);
250                 *agp = 0;
251                 return 0;
252         }
253 
254         trace_xfs_filestream_pick(ip, *agp, free, nscan);
255 
256         if (*agp == NULLAGNUMBER)
257                 return 0;
258 
259         err = -ENOMEM;
260         item = kmem_alloc(sizeof(*item), KM_MAYFAIL);
261         if (!item)
262                 goto out_put_ag;
263 
264         item->ag = *agp;
265         item->ip = ip;
266 
267         err = xfs_mru_cache_insert(mp->m_filestream, ip->i_ino, &item->mru);
268         if (err) {
269                 if (err == -EEXIST)
270                         err = 0;
271                 goto out_free_item;
272         }
273 
274         return 0;
275 
276 out_free_item:
277         kmem_free(item);
278 out_put_ag:
279         xfs_filestream_put_ag(mp, *agp);
280         return err;
281 }
282 
283 static struct xfs_inode *
284 xfs_filestream_get_parent(
285         struct xfs_inode        *ip)
286 {
287         struct inode            *inode = VFS_I(ip), *dir = NULL;
288         struct dentry           *dentry, *parent;
289 
290         dentry = d_find_alias(inode);
291         if (!dentry)
292                 goto out;
293 
294         parent = dget_parent(dentry);
295         if (!parent)
296                 goto out_dput;
297 
298         dir = igrab(d_inode(parent));
299         dput(parent);
300 
301 out_dput:
302         dput(dentry);
303 out:
304         return dir ? XFS_I(dir) : NULL;
305 }
306 
307 /*
308  * Find the right allocation group for a file, either by finding an
309  * existing file stream or creating a new one.
310  *
311  * Returns NULLAGNUMBER in case of an error.
312  */
313 xfs_agnumber_t
314 xfs_filestream_lookup_ag(
315         struct xfs_inode        *ip)
316 {
317         struct xfs_mount        *mp = ip->i_mount;
318         struct xfs_inode        *pip = NULL;
319         xfs_agnumber_t          startag, ag = NULLAGNUMBER;
320         struct xfs_mru_cache_elem *mru;
321 
322         ASSERT(S_ISREG(VFS_I(ip)->i_mode));
323 
324         pip = xfs_filestream_get_parent(ip);
325         if (!pip)
326                 return NULLAGNUMBER;
327 
328         mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino);
329         if (mru) {
330                 ag = container_of(mru, struct xfs_fstrm_item, mru)->ag;
331                 xfs_mru_cache_done(mp->m_filestream);
332 
333                 trace_xfs_filestream_lookup(ip, ag);
334                 goto out;
335         }
336 
337         /*
338          * Set the starting AG using the rotor for inode32, otherwise
339          * use the directory inode's AG.
340          */
341         if (mp->m_flags & XFS_MOUNT_32BITINODES) {
342                 xfs_agnumber_t   rotorstep = xfs_rotorstep;
343                 startag = (mp->m_agfrotor / rotorstep) % mp->m_sb.sb_agcount;
344                 mp->m_agfrotor = (mp->m_agfrotor + 1) %
345                                  (mp->m_sb.sb_agcount * rotorstep);
346         } else
347                 startag = XFS_INO_TO_AGNO(mp, pip->i_ino);
348 
349         if (xfs_filestream_pick_ag(pip, startag, &ag, 0, 0))
350                 ag = NULLAGNUMBER;
351 out:
352         IRELE(pip);
353         return ag;
354 }
355 
356 /*
357  * Pick a new allocation group for the current file and its file stream.
358  *
359  * This is called when the allocator can't find a suitable extent in the
360  * current AG, and we have to move the stream into a new AG with more space.
361  */
362 int
363 xfs_filestream_new_ag(
364         struct xfs_bmalloca     *ap,
365         xfs_agnumber_t          *agp)
366 {
367         struct xfs_inode        *ip = ap->ip, *pip;
368         struct xfs_mount        *mp = ip->i_mount;
369         xfs_extlen_t            minlen = ap->length;
370         xfs_agnumber_t          startag = 0;
371         int                     flags, err = 0;
372         struct xfs_mru_cache_elem *mru;
373 
374         *agp = NULLAGNUMBER;
375 
376         pip = xfs_filestream_get_parent(ip);
377         if (!pip)
378                 goto exit;
379 
380         mru = xfs_mru_cache_remove(mp->m_filestream, pip->i_ino);
381         if (mru) {
382                 struct xfs_fstrm_item *item =
383                         container_of(mru, struct xfs_fstrm_item, mru);
384                 startag = (item->ag + 1) % mp->m_sb.sb_agcount;
385         }
386 
387         flags = (ap->userdata ? XFS_PICK_USERDATA : 0) |
388                 (ap->flist->xbf_low ? XFS_PICK_LOWSPACE : 0);
389 
390         err = xfs_filestream_pick_ag(pip, startag, agp, flags, minlen);
391 
392         /*
393          * Only free the item here so we skip over the old AG earlier.
394          */
395         if (mru)
396                 xfs_fstrm_free_func(mru);
397 
398         IRELE(pip);
399 exit:
400         if (*agp == NULLAGNUMBER)
401                 *agp = 0;
402         return err;
403 }
404 
405 void
406 xfs_filestream_deassociate(
407         struct xfs_inode        *ip)
408 {
409         xfs_mru_cache_delete(ip->i_mount->m_filestream, ip->i_ino);
410 }
411 
412 int
413 xfs_filestream_mount(
414         xfs_mount_t     *mp)
415 {
416         /*
417          * The filestream timer tunable is currently fixed within the range of
418          * one second to four minutes, with five seconds being the default.  The
419          * group count is somewhat arbitrary, but it'd be nice to adhere to the
420          * timer tunable to within about 10 percent.  This requires at least 10
421          * groups.
422          */
423         return xfs_mru_cache_create(&mp->m_filestream, xfs_fstrm_centisecs * 10,
424                                     10, xfs_fstrm_free_func);
425 }
426 
427 void
428 xfs_filestream_unmount(
429         xfs_mount_t     *mp)
430 {
431         xfs_mru_cache_destroy(mp->m_filestream);
432 }
433 

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