1 /*
2 * GPL HEADER START
3 *
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 only,
8 * as published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License version 2 for more details (a copy is included
14 * in the LICENSE file that accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License
17 * version 2 along with this program; If not, see
18 * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
19 *
20 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
21 * CA 95054 USA or visit www.sun.com if you need additional information or
22 * have any questions.
23 *
24 * GPL HEADER END
25 */
26 /*
27 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
28 * Use is subject to license terms.
29 *
30 * Copyright (c) 2011, Intel Corporation.
31 */
32 /*
33 * This file is part of Lustre, http://www.lustre.org/
34 * Lustre is a trademark of Sun Microsystems, Inc.
35 */
36
37 #define DEBUG_SUBSYSTEM S_LOV
38
39 #include "../../include/linux/libcfs/libcfs.h"
40
41 #include "../include/obd_class.h"
42
43 #include "lov_internal.h"
44
45 /* compute object size given "stripeno" and the ost size */
lov_stripe_size(struct lov_stripe_md * lsm,u64 ost_size,int stripeno)46 u64 lov_stripe_size(struct lov_stripe_md *lsm, u64 ost_size,
47 int stripeno)
48 {
49 unsigned long ssize = lsm->lsm_stripe_size;
50 unsigned long stripe_size;
51 u64 swidth;
52 u64 lov_size;
53 int magic = lsm->lsm_magic;
54
55 if (ost_size == 0)
56 return 0;
57
58 LASSERT(lsm_op_find(magic) != NULL);
59 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
60
61 /* lov_do_div64(a, b) returns a % b, and a = a / b */
62 stripe_size = lov_do_div64(ost_size, ssize);
63 if (stripe_size)
64 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
65 else
66 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
67
68 return lov_size;
69 }
70
71 /* we have an offset in file backed by an lov and want to find out where
72 * that offset lands in our given stripe of the file. for the easy
73 * case where the offset is within the stripe, we just have to scale the
74 * offset down to make it relative to the stripe instead of the lov.
75 *
76 * the harder case is what to do when the offset doesn't intersect the
77 * stripe. callers will want start offsets clamped ahead to the start
78 * of the nearest stripe in the file. end offsets similarly clamped to the
79 * nearest ending byte of a stripe in the file:
80 *
81 * all this function does is move offsets to the nearest region of the
82 * stripe, and it does its work "mod" the full length of all the stripes.
83 * consider a file with 3 stripes:
84 *
85 * S E
86 * ---------------------------------------------------------------------
87 * | 0 | 1 | 2 | 0 | 1 | 2 |
88 * ---------------------------------------------------------------------
89 *
90 * to find stripe 1's offsets for S and E, it divides by the full stripe
91 * width and does its math in the context of a single set of stripes:
92 *
93 * S E
94 * -----------------------------------
95 * | 0 | 1 | 2 |
96 * -----------------------------------
97 *
98 * it'll notice that E is outside stripe 1 and clamp it to the end of the
99 * stripe, then multiply it back out by lov_off to give the real offsets in
100 * the stripe:
101 *
102 * S E
103 * ---------------------------------------------------------------------
104 * | 1 | 1 | 1 | 1 | 1 | 1 |
105 * ---------------------------------------------------------------------
106 *
107 * it would have done similarly and pulled S forward to the start of a 1
108 * stripe if, say, S had landed in a 0 stripe.
109 *
110 * this rounding isn't always correct. consider an E lov offset that lands
111 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
112 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
113 * of a previous 1 stripe. this logic is handled by callers and this is why:
114 *
115 * this function returns < 0 when the offset was "before" the stripe and
116 * was moved forward to the start of the stripe in question; 0 when it
117 * falls in the stripe and no shifting was done; > 0 when the offset
118 * was outside the stripe and was pulled back to its final byte. */
lov_stripe_offset(struct lov_stripe_md * lsm,u64 lov_off,int stripeno,u64 * obdoff)119 int lov_stripe_offset(struct lov_stripe_md *lsm, u64 lov_off,
120 int stripeno, u64 *obdoff)
121 {
122 unsigned long ssize = lsm->lsm_stripe_size;
123 u64 stripe_off, this_stripe, swidth;
124 int magic = lsm->lsm_magic;
125 int ret = 0;
126
127 if (lov_off == OBD_OBJECT_EOF) {
128 *obdoff = OBD_OBJECT_EOF;
129 return 0;
130 }
131
132 LASSERT(lsm_op_find(magic) != NULL);
133
134 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
135 &swidth);
136
137 /* lov_do_div64(a, b) returns a % b, and a = a / b */
138 stripe_off = lov_do_div64(lov_off, swidth);
139
140 this_stripe = (u64)stripeno * ssize;
141 if (stripe_off < this_stripe) {
142 stripe_off = 0;
143 ret = -1;
144 } else {
145 stripe_off -= this_stripe;
146
147 if (stripe_off >= ssize) {
148 stripe_off = ssize;
149 ret = 1;
150 }
151 }
152
153 *obdoff = lov_off * ssize + stripe_off;
154 return ret;
155 }
156
157 /* Given a whole-file size and a stripe number, give the file size which
158 * corresponds to the individual object of that stripe.
159 *
160 * This behaves basically in the same was as lov_stripe_offset, except that
161 * file sizes falling before the beginning of a stripe are clamped to the end
162 * of the previous stripe, not the beginning of the next:
163 *
164 * S
165 * ---------------------------------------------------------------------
166 * | 0 | 1 | 2 | 0 | 1 | 2 |
167 * ---------------------------------------------------------------------
168 *
169 * if clamped to stripe 2 becomes:
170 *
171 * S
172 * ---------------------------------------------------------------------
173 * | 0 | 1 | 2 | 0 | 1 | 2 |
174 * ---------------------------------------------------------------------
175 */
lov_size_to_stripe(struct lov_stripe_md * lsm,u64 file_size,int stripeno)176 u64 lov_size_to_stripe(struct lov_stripe_md *lsm, u64 file_size,
177 int stripeno)
178 {
179 unsigned long ssize = lsm->lsm_stripe_size;
180 u64 stripe_off, this_stripe, swidth;
181 int magic = lsm->lsm_magic;
182
183 if (file_size == OBD_OBJECT_EOF)
184 return OBD_OBJECT_EOF;
185
186 LASSERT(lsm_op_find(magic) != NULL);
187 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
188 &swidth);
189
190 /* lov_do_div64(a, b) returns a % b, and a = a / b */
191 stripe_off = lov_do_div64(file_size, swidth);
192
193 this_stripe = (u64)stripeno * ssize;
194 if (stripe_off < this_stripe) {
195 /* Move to end of previous stripe, or zero */
196 if (file_size > 0) {
197 file_size--;
198 stripe_off = ssize;
199 } else {
200 stripe_off = 0;
201 }
202 } else {
203 stripe_off -= this_stripe;
204
205 if (stripe_off >= ssize) {
206 /* Clamp to end of this stripe */
207 stripe_off = ssize;
208 }
209 }
210
211 return (file_size * ssize + stripe_off);
212 }
213
214 /* given an extent in an lov and a stripe, calculate the extent of the stripe
215 * that is contained within the lov extent. this returns true if the given
216 * stripe does intersect with the lov extent. */
lov_stripe_intersects(struct lov_stripe_md * lsm,int stripeno,u64 start,u64 end,u64 * obd_start,u64 * obd_end)217 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
218 u64 start, u64 end, u64 *obd_start, u64 *obd_end)
219 {
220 int start_side, end_side;
221
222 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
223 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
224
225 CDEBUG(D_INODE, "[%llu->%llu] -> [(%d) %llu->%llu (%d)]\n",
226 start, end, start_side, *obd_start, *obd_end, end_side);
227
228 /* this stripe doesn't intersect the file extent when neither
229 * start or the end intersected the stripe and obd_start and
230 * obd_end got rounded up to the save value. */
231 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
232 return 0;
233
234 /* as mentioned in the lov_stripe_offset commentary, end
235 * might have been shifted in the wrong direction. This
236 * happens when an end offset is before the stripe when viewed
237 * through the "mod stripe size" math. we detect it being shifted
238 * in the wrong direction and touch it up.
239 * interestingly, this can't underflow since end must be > start
240 * if we passed through the previous check.
241 * (should we assert for that somewhere?) */
242 if (end_side != 0)
243 (*obd_end)--;
244
245 return 1;
246 }
247
248 /* compute which stripe number "lov_off" will be written into */
lov_stripe_number(struct lov_stripe_md * lsm,u64 lov_off)249 int lov_stripe_number(struct lov_stripe_md *lsm, u64 lov_off)
250 {
251 unsigned long ssize = lsm->lsm_stripe_size;
252 u64 stripe_off, swidth;
253 int magic = lsm->lsm_magic;
254
255 LASSERT(lsm_op_find(magic) != NULL);
256 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
257
258 stripe_off = lov_do_div64(lov_off, swidth);
259
260 /* Puts stripe_off/ssize result into stripe_off */
261 lov_do_div64(stripe_off, ssize);
262
263 return stripe_off;
264 }
265