1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
2 * vim:expandtab:shiftwidth=8:tabstop=8:
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
8 * This program is free software; you can redistribute it and/or modify
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13 * WITHOUT ANY WARRANTY; without even the implied warranty of
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15 * General Public License version 2 for more details (a copy is included
16 * in the LICENSE file that accompanied this code).
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23 * CA 95054 USA or visit www.sun.com if you need additional information or
29 * Copyright 2008 Sun Microsystems, Inc. All rights reserved
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33 * This file is part of Lustre, http://www.lustre.org/
34 * Lustre is a trademark of Sun Microsystems, Inc.
38 # define EXPORT_SYMTAB
40 #define DEBUG_SUBSYSTEM S_LOV
43 #include <libcfs/libcfs.h>
45 #include <liblustre.h>
48 #include <obd_class.h>
51 #include "lov_internal.h"
53 /* compute object size given "stripeno" and the ost size */
54 obd_size lov_stripe_size(struct lov_stripe_md *lsm, obd_size ost_size,
57 unsigned long ssize = lsm->lsm_stripe_size;
58 unsigned long stripe_size;
61 int magic = lsm->lsm_magic;
67 LASSERT(lsm_op_find(magic) != NULL);
68 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
70 /* do_div(a, b) returns a % b, and a = a / b */
71 stripe_size = do_div(ost_size, ssize);
73 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
75 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
80 /* we have an offset in file backed by an lov and want to find out where
81 * that offset lands in our given stripe of the file. for the easy
82 * case where the offset is within the stripe, we just have to scale the
83 * offset down to make it relative to the stripe instead of the lov.
85 * the harder case is what to do when the offset doesn't intersect the
86 * stripe. callers will want start offsets clamped ahead to the start
87 * of the nearest stripe in the file. end offsets similarly clamped to the
88 * nearest ending byte of a stripe in the file:
90 * all this function does is move offsets to the nearest region of the
91 * stripe, and it does its work "mod" the full length of all the stripes.
92 * consider a file with 3 stripes:
95 * ---------------------------------------------------------------------
96 * | 0 | 1 | 2 | 0 | 1 | 2 |
97 * ---------------------------------------------------------------------
99 * to find stripe 1's offsets for S and E, it divides by the full stripe
100 * width and does its math in the context of a single set of stripes:
103 * -----------------------------------
105 * -----------------------------------
107 * it'll notice that E is outside stripe 1 and clamp it to the end of the
108 * stripe, then multiply it back out by lov_off to give the real offsets in
112 * ---------------------------------------------------------------------
113 * | 1 | 1 | 1 | 1 | 1 | 1 |
114 * ---------------------------------------------------------------------
116 * it would have done similarly and pulled S forward to the start of a 1
117 * stripe if, say, S had landed in a 0 stripe.
119 * this rounding isn't always correct. consider an E lov offset that lands
120 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
121 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
122 * of a previous 1 stripe. this logic is handled by callers and this is why:
124 * this function returns < 0 when the offset was "before" the stripe and
125 * was moved forward to the start of the stripe in question; 0 when it
126 * falls in the stripe and no shifting was done; > 0 when the offset
127 * was outside the stripe and was pulled back to its final byte. */
128 int lov_stripe_offset(struct lov_stripe_md *lsm, obd_off lov_off,
129 int stripeno, obd_off *obdoff)
131 unsigned long ssize = lsm->lsm_stripe_size;
132 obd_off stripe_off, this_stripe, swidth;
133 int magic = lsm->lsm_magic;
136 if (lov_off == OBD_OBJECT_EOF) {
137 *obdoff = OBD_OBJECT_EOF;
141 LASSERT(lsm_op_find(magic) != NULL);
143 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
146 /* ll_do_div64(a, b) returns a % b, and a = a / b */
147 stripe_off = ll_do_div64(lov_off, swidth);
149 this_stripe = (obd_off)stripeno * ssize;
150 if (stripe_off < this_stripe) {
154 stripe_off -= this_stripe;
156 if (stripe_off >= ssize) {
162 *obdoff = lov_off * ssize + stripe_off;
166 /* Given a whole-file size and a stripe number, give the file size which
167 * corresponds to the individual object of that stripe.
169 * This behaves basically in the same was as lov_stripe_offset, except that
170 * file sizes falling before the beginning of a stripe are clamped to the end
171 * of the previous stripe, not the beginning of the next:
174 * ---------------------------------------------------------------------
175 * | 0 | 1 | 2 | 0 | 1 | 2 |
176 * ---------------------------------------------------------------------
178 * if clamped to stripe 2 becomes:
181 * ---------------------------------------------------------------------
182 * | 0 | 1 | 2 | 0 | 1 | 2 |
183 * ---------------------------------------------------------------------
185 obd_off lov_size_to_stripe(struct lov_stripe_md *lsm, obd_off file_size,
188 unsigned long ssize = lsm->lsm_stripe_size;
189 obd_off stripe_off, this_stripe, swidth;
190 int magic = lsm->lsm_magic;
192 if (file_size == OBD_OBJECT_EOF)
193 return OBD_OBJECT_EOF;
195 LASSERT(lsm_op_find(magic) != NULL);
196 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
199 /* ll_do_div64(a, b) returns a % b, and a = a / b */
200 stripe_off = ll_do_div64(file_size, swidth);
202 this_stripe = (obd_off)stripeno * ssize;
203 if (stripe_off < this_stripe) {
204 /* Move to end of previous stripe, or zero */
212 stripe_off -= this_stripe;
214 if (stripe_off >= ssize) {
215 /* Clamp to end of this stripe */
220 return (file_size * ssize + stripe_off);
223 /* given an extent in an lov and a stripe, calculate the extent of the stripe
224 * that is contained within the lov extent. this returns true if the given
225 * stripe does intersect with the lov extent. */
226 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
227 obd_off start, obd_off end,
228 obd_off *obd_start, obd_off *obd_end)
230 int start_side, end_side;
232 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
233 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
235 CDEBUG(D_INODE, "["LPU64"->"LPU64"] -> [(%d) "LPU64"->"LPU64" (%d)]\n",
236 start, end, start_side, *obd_start, *obd_end, end_side);
238 /* this stripe doesn't intersect the file extent when neither
239 * start or the end intersected the stripe and obd_start and
240 * obd_end got rounded up to the save value. */
241 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
244 /* as mentioned in the lov_stripe_offset commentary, end
245 * might have been shifted in the wrong direction. This
246 * happens when an end offset is before the stripe when viewed
247 * through the "mod stripe size" math. we detect it being shifted
248 * in the wrong direction and touch it up.
249 * interestingly, this can't underflow since end must be > start
250 * if we passed through the previous check.
251 * (should we assert for that somewhere?) */
258 /* compute which stripe number "lov_off" will be written into */
259 int lov_stripe_number(struct lov_stripe_md *lsm, obd_off lov_off)
261 unsigned long ssize = lsm->lsm_stripe_size;
262 obd_off stripe_off, swidth;
263 int magic = lsm->lsm_magic;
265 LASSERT(lsm_op_find(magic) != NULL);
266 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
268 stripe_off = ll_do_div64(lov_off, swidth);
270 /* Puts stripe_off/ssize result into stripe_off */
271 do_div(stripe_off, ssize);