xref: /openbmc/linux/fs/xfs/xfs_filestream.c (revision 4f205687)
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