1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (c) 2006-2007 Silicon Graphics, Inc.
4  * Copyright (c) 2014 Christoph Hellwig.
5  * All Rights Reserved.
6  */
7 #include "xfs.h"
8 #include "xfs_format.h"
9 #include "xfs_log_format.h"
10 #include "xfs_trans_resv.h"
11 #include "xfs_sb.h"
12 #include "xfs_mount.h"
13 #include "xfs_defer.h"
14 #include "xfs_inode.h"
15 #include "xfs_bmap.h"
16 #include "xfs_bmap_util.h"
17 #include "xfs_alloc.h"
18 #include "xfs_mru_cache.h"
19 #include "xfs_filestream.h"
20 #include "xfs_trace.h"
21 #include "xfs_ag_resv.h"
22 #include "xfs_trans.h"
23 #include "xfs_shared.h"
24 
25 struct xfs_fstrm_item {
26 	struct xfs_mru_cache_elem	mru;
27 	xfs_agnumber_t			ag; /* AG in use for this directory */
28 };
29 
30 enum xfs_fstrm_alloc {
31 	XFS_PICK_USERDATA = 1,
32 	XFS_PICK_LOWSPACE = 2,
33 };
34 
35 /*
36  * Allocation group filestream associations are tracked with per-ag atomic
37  * counters.  These counters allow xfs_filestream_pick_ag() to tell whether a
38  * particular AG already has active filestreams associated with it. The mount
39  * point's m_peraglock is used to protect these counters from per-ag array
40  * re-allocation during a growfs operation.  When xfs_growfs_data_private() is
41  * about to reallocate the array, it calls xfs_filestream_flush() with the
42  * m_peraglock held in write mode.
43  *
44  * Since xfs_mru_cache_flush() guarantees that all the free functions for all
45  * the cache elements have finished executing before it returns, it's safe for
46  * the free functions to use the atomic counters without m_peraglock protection.
47  * This allows the implementation of xfs_fstrm_free_func() to be agnostic about
48  * whether it was called with the m_peraglock held in read mode, write mode or
49  * not held at all.  The race condition this addresses is the following:
50  *
51  *  - The work queue scheduler fires and pulls a filestream directory cache
52  *    element off the LRU end of the cache for deletion, then gets pre-empted.
53  *  - A growfs operation grabs the m_peraglock in write mode, flushes all the
54  *    remaining items from the cache and reallocates the mount point's per-ag
55  *    array, resetting all the counters to zero.
56  *  - The work queue thread resumes and calls the free function for the element
57  *    it started cleaning up earlier.  In the process it decrements the
58  *    filestreams counter for an AG that now has no references.
59  *
60  * With a shrinkfs feature, the above scenario could panic the system.
61  *
62  * All other uses of the following macros should be protected by either the
63  * m_peraglock held in read mode, or the cache's internal locking exposed by the
64  * interval between a call to xfs_mru_cache_lookup() and a call to
65  * xfs_mru_cache_done().  In addition, the m_peraglock must be held in read mode
66  * when new elements are added to the cache.
67  *
68  * Combined, these locking rules ensure that no associations will ever exist in
69  * the cache that reference per-ag array elements that have since been
70  * reallocated.
71  */
72 int
xfs_filestream_peek_ag(xfs_mount_t * mp,xfs_agnumber_t agno)73 xfs_filestream_peek_ag(
74 	xfs_mount_t	*mp,
75 	xfs_agnumber_t	agno)
76 {
77 	struct xfs_perag *pag;
78 	int		ret;
79 
80 	pag = xfs_perag_get(mp, agno);
81 	ret = atomic_read(&pag->pagf_fstrms);
82 	xfs_perag_put(pag);
83 	return ret;
84 }
85 
86 static int
xfs_filestream_get_ag(xfs_mount_t * mp,xfs_agnumber_t agno)87 xfs_filestream_get_ag(
88 	xfs_mount_t	*mp,
89 	xfs_agnumber_t	agno)
90 {
91 	struct xfs_perag *pag;
92 	int		ret;
93 
94 	pag = xfs_perag_get(mp, agno);
95 	ret = atomic_inc_return(&pag->pagf_fstrms);
96 	xfs_perag_put(pag);
97 	return ret;
98 }
99 
100 static void
xfs_filestream_put_ag(xfs_mount_t * mp,xfs_agnumber_t agno)101 xfs_filestream_put_ag(
102 	xfs_mount_t	*mp,
103 	xfs_agnumber_t	agno)
104 {
105 	struct xfs_perag *pag;
106 
107 	pag = xfs_perag_get(mp, agno);
108 	atomic_dec(&pag->pagf_fstrms);
109 	xfs_perag_put(pag);
110 }
111 
112 static void
xfs_fstrm_free_func(void * data,struct xfs_mru_cache_elem * mru)113 xfs_fstrm_free_func(
114 	void			*data,
115 	struct xfs_mru_cache_elem *mru)
116 {
117 	struct xfs_mount	*mp = data;
118 	struct xfs_fstrm_item	*item =
119 		container_of(mru, struct xfs_fstrm_item, mru);
120 
121 	xfs_filestream_put_ag(mp, item->ag);
122 	trace_xfs_filestream_free(mp, mru->key, item->ag);
123 
124 	kmem_free(item);
125 }
126 
127 /*
128  * Scan the AGs starting at startag looking for an AG that isn't in use and has
129  * at least minlen blocks free.
130  */
131 static int
xfs_filestream_pick_ag(struct xfs_inode * ip,xfs_agnumber_t startag,xfs_agnumber_t * agp,int flags,xfs_extlen_t minlen)132 xfs_filestream_pick_ag(
133 	struct xfs_inode	*ip,
134 	xfs_agnumber_t		startag,
135 	xfs_agnumber_t		*agp,
136 	int			flags,
137 	xfs_extlen_t		minlen)
138 {
139 	struct xfs_mount	*mp = ip->i_mount;
140 	struct xfs_fstrm_item	*item;
141 	struct xfs_perag	*pag;
142 	xfs_extlen_t		longest, free = 0, minfree, maxfree = 0;
143 	xfs_agnumber_t		ag, max_ag = NULLAGNUMBER;
144 	int			err, trylock, nscan;
145 
146 	ASSERT(S_ISDIR(VFS_I(ip)->i_mode));
147 
148 	/* 2% of an AG's blocks must be free for it to be chosen. */
149 	minfree = mp->m_sb.sb_agblocks / 50;
150 
151 	ag = startag;
152 	*agp = NULLAGNUMBER;
153 
154 	/* For the first pass, don't sleep trying to init the per-AG. */
155 	trylock = XFS_ALLOC_FLAG_TRYLOCK;
156 
157 	for (nscan = 0; 1; nscan++) {
158 		trace_xfs_filestream_scan(mp, ip->i_ino, ag);
159 
160 		pag = xfs_perag_get(mp, ag);
161 
162 		if (!pag->pagf_init) {
163 			err = xfs_alloc_pagf_init(mp, NULL, ag, trylock);
164 			if (err && !trylock) {
165 				xfs_perag_put(pag);
166 				return err;
167 			}
168 		}
169 
170 		/* Might fail sometimes during the 1st pass with trylock set. */
171 		if (!pag->pagf_init)
172 			goto next_ag;
173 
174 		/* Keep track of the AG with the most free blocks. */
175 		if (pag->pagf_freeblks > maxfree) {
176 			maxfree = pag->pagf_freeblks;
177 			max_ag = ag;
178 		}
179 
180 		/*
181 		 * The AG reference count does two things: it enforces mutual
182 		 * exclusion when examining the suitability of an AG in this
183 		 * loop, and it guards against two filestreams being established
184 		 * in the same AG as each other.
185 		 */
186 		if (xfs_filestream_get_ag(mp, ag) > 1) {
187 			xfs_filestream_put_ag(mp, ag);
188 			goto next_ag;
189 		}
190 
191 		longest = xfs_alloc_longest_free_extent(pag,
192 				xfs_alloc_min_freelist(mp, pag),
193 				xfs_ag_resv_needed(pag, XFS_AG_RESV_NONE));
194 		if (((minlen && longest >= minlen) ||
195 		     (!minlen && pag->pagf_freeblks >= minfree)) &&
196 		    (!pag->pagf_metadata || !(flags & XFS_PICK_USERDATA) ||
197 		     (flags & XFS_PICK_LOWSPACE))) {
198 
199 			/* Break out, retaining the reference on the AG. */
200 			free = pag->pagf_freeblks;
201 			xfs_perag_put(pag);
202 			*agp = ag;
203 			break;
204 		}
205 
206 		/* Drop the reference on this AG, it's not usable. */
207 		xfs_filestream_put_ag(mp, ag);
208 next_ag:
209 		xfs_perag_put(pag);
210 		/* Move to the next AG, wrapping to AG 0 if necessary. */
211 		if (++ag >= mp->m_sb.sb_agcount)
212 			ag = 0;
213 
214 		/* If a full pass of the AGs hasn't been done yet, continue. */
215 		if (ag != startag)
216 			continue;
217 
218 		/* Allow sleeping in xfs_alloc_pagf_init() on the 2nd pass. */
219 		if (trylock != 0) {
220 			trylock = 0;
221 			continue;
222 		}
223 
224 		/* Finally, if lowspace wasn't set, set it for the 3rd pass. */
225 		if (!(flags & XFS_PICK_LOWSPACE)) {
226 			flags |= XFS_PICK_LOWSPACE;
227 			continue;
228 		}
229 
230 		/*
231 		 * Take the AG with the most free space, regardless of whether
232 		 * it's already in use by another filestream.
233 		 */
234 		if (max_ag != NULLAGNUMBER) {
235 			xfs_filestream_get_ag(mp, max_ag);
236 			free = maxfree;
237 			*agp = max_ag;
238 			break;
239 		}
240 
241 		/* take AG 0 if none matched */
242 		trace_xfs_filestream_pick(ip, *agp, free, nscan);
243 		*agp = 0;
244 		return 0;
245 	}
246 
247 	trace_xfs_filestream_pick(ip, *agp, free, nscan);
248 
249 	if (*agp == NULLAGNUMBER)
250 		return 0;
251 
252 	err = -ENOMEM;
253 	item = kmem_alloc(sizeof(*item), KM_MAYFAIL);
254 	if (!item)
255 		goto out_put_ag;
256 
257 	item->ag = *agp;
258 
259 	err = xfs_mru_cache_insert(mp->m_filestream, ip->i_ino, &item->mru);
260 	if (err) {
261 		if (err == -EEXIST)
262 			err = 0;
263 		goto out_free_item;
264 	}
265 
266 	return 0;
267 
268 out_free_item:
269 	kmem_free(item);
270 out_put_ag:
271 	xfs_filestream_put_ag(mp, *agp);
272 	return err;
273 }
274 
275 static struct xfs_inode *
xfs_filestream_get_parent(struct xfs_inode * ip)276 xfs_filestream_get_parent(
277 	struct xfs_inode	*ip)
278 {
279 	struct inode		*inode = VFS_I(ip), *dir = NULL;
280 	struct dentry		*dentry, *parent;
281 
282 	dentry = d_find_alias(inode);
283 	if (!dentry)
284 		goto out;
285 
286 	parent = dget_parent(dentry);
287 	if (!parent)
288 		goto out_dput;
289 
290 	dir = igrab(d_inode(parent));
291 	dput(parent);
292 
293 out_dput:
294 	dput(dentry);
295 out:
296 	return dir ? XFS_I(dir) : NULL;
297 }
298 
299 /*
300  * Find the right allocation group for a file, either by finding an
301  * existing file stream or creating a new one.
302  *
303  * Returns NULLAGNUMBER in case of an error.
304  */
305 xfs_agnumber_t
xfs_filestream_lookup_ag(struct xfs_inode * ip)306 xfs_filestream_lookup_ag(
307 	struct xfs_inode	*ip)
308 {
309 	struct xfs_mount	*mp = ip->i_mount;
310 	struct xfs_inode	*pip = NULL;
311 	xfs_agnumber_t		startag, ag = NULLAGNUMBER;
312 	struct xfs_mru_cache_elem *mru;
313 
314 	ASSERT(S_ISREG(VFS_I(ip)->i_mode));
315 
316 	pip = xfs_filestream_get_parent(ip);
317 	if (!pip)
318 		return NULLAGNUMBER;
319 
320 	mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino);
321 	if (mru) {
322 		ag = container_of(mru, struct xfs_fstrm_item, mru)->ag;
323 		xfs_mru_cache_done(mp->m_filestream);
324 
325 		trace_xfs_filestream_lookup(mp, ip->i_ino, ag);
326 		goto out;
327 	}
328 
329 	/*
330 	 * Set the starting AG using the rotor for inode32, otherwise
331 	 * use the directory inode's AG.
332 	 */
333 	if (mp->m_flags & XFS_MOUNT_32BITINODES) {
334 		xfs_agnumber_t	 rotorstep = xfs_rotorstep;
335 		startag = (mp->m_agfrotor / rotorstep) % mp->m_sb.sb_agcount;
336 		mp->m_agfrotor = (mp->m_agfrotor + 1) %
337 		                 (mp->m_sb.sb_agcount * rotorstep);
338 	} else
339 		startag = XFS_INO_TO_AGNO(mp, pip->i_ino);
340 
341 	if (xfs_filestream_pick_ag(pip, startag, &ag, 0, 0))
342 		ag = NULLAGNUMBER;
343 out:
344 	xfs_irele(pip);
345 	return ag;
346 }
347 
348 /*
349  * Pick a new allocation group for the current file and its file stream.
350  *
351  * This is called when the allocator can't find a suitable extent in the
352  * current AG, and we have to move the stream into a new AG with more space.
353  */
354 int
xfs_filestream_new_ag(struct xfs_bmalloca * ap,xfs_agnumber_t * agp)355 xfs_filestream_new_ag(
356 	struct xfs_bmalloca	*ap,
357 	xfs_agnumber_t		*agp)
358 {
359 	struct xfs_inode	*ip = ap->ip, *pip;
360 	struct xfs_mount	*mp = ip->i_mount;
361 	xfs_extlen_t		minlen = ap->length;
362 	xfs_agnumber_t		startag = 0;
363 	int			flags = 0;
364 	int			err = 0;
365 	struct xfs_mru_cache_elem *mru;
366 
367 	*agp = NULLAGNUMBER;
368 
369 	pip = xfs_filestream_get_parent(ip);
370 	if (!pip)
371 		goto exit;
372 
373 	mru = xfs_mru_cache_remove(mp->m_filestream, pip->i_ino);
374 	if (mru) {
375 		struct xfs_fstrm_item *item =
376 			container_of(mru, struct xfs_fstrm_item, mru);
377 		startag = (item->ag + 1) % mp->m_sb.sb_agcount;
378 	}
379 
380 	if (xfs_alloc_is_userdata(ap->datatype))
381 		flags |= XFS_PICK_USERDATA;
382 	if (ap->tp->t_flags & XFS_TRANS_LOWMODE)
383 		flags |= XFS_PICK_LOWSPACE;
384 
385 	err = xfs_filestream_pick_ag(pip, startag, agp, flags, minlen);
386 
387 	/*
388 	 * Only free the item here so we skip over the old AG earlier.
389 	 */
390 	if (mru)
391 		xfs_fstrm_free_func(mp, mru);
392 
393 	xfs_irele(pip);
394 exit:
395 	if (*agp == NULLAGNUMBER)
396 		*agp = 0;
397 	return err;
398 }
399 
400 void
xfs_filestream_deassociate(struct xfs_inode * ip)401 xfs_filestream_deassociate(
402 	struct xfs_inode	*ip)
403 {
404 	xfs_mru_cache_delete(ip->i_mount->m_filestream, ip->i_ino);
405 }
406 
407 int
xfs_filestream_mount(xfs_mount_t * mp)408 xfs_filestream_mount(
409 	xfs_mount_t	*mp)
410 {
411 	/*
412 	 * The filestream timer tunable is currently fixed within the range of
413 	 * one second to four minutes, with five seconds being the default.  The
414 	 * group count is somewhat arbitrary, but it'd be nice to adhere to the
415 	 * timer tunable to within about 10 percent.  This requires at least 10
416 	 * groups.
417 	 */
418 	return xfs_mru_cache_create(&mp->m_filestream, mp,
419 			xfs_fstrm_centisecs * 10, 10, xfs_fstrm_free_func);
420 }
421 
422 void
xfs_filestream_unmount(xfs_mount_t * mp)423 xfs_filestream_unmount(
424 	xfs_mount_t	*mp)
425 {
426 	xfs_mru_cache_destroy(mp->m_filestream);
427 }
428