1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
2 * vim:expandtab:shiftwidth=8:tabstop=8:
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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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29 * Copyright 2008 Sun Microsystems, Inc. All rights reserved
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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 obd_size ssize = lsm->lsm_stripe_size;
58 unsigned long stripe_size;
60 int sindex = stripeno;
62 int magic = lsm->lsm_magic;
68 LASSERT(lsm_op_find(magic) != NULL);
69 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
71 /* ll_do_div64(a, b) returns a % b, and a = a / b */
72 stripe_size = ll_do_div64(ost_size, ssize);
74 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
76 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
78 lov_size += lsm_op_find(magic)->lsm_stripe_offset_by_index(lsm, sindex);
82 /* we have an offset in file backed by an lov and want to find out where
83 * that offset lands in our given stripe of the file. for the easy
84 * case where the offset is within the stripe, we just have to scale the
85 * offset down to make it relative to the stripe instead of the lov.
87 * the harder case is what to do when the offset doesn't intersect the
88 * stripe. callers will want start offsets clamped ahead to the start
89 * of the nearest stripe in the file. end offsets similarly clamped to the
90 * nearest ending byte of a stripe in the file:
92 * all this function does is move offsets to the nearest region of the
93 * stripe, and it does its work "mod" the full length of all the stripes.
94 * consider a file with 3 stripes:
97 * ---------------------------------------------------------------------
98 * | 0 | 1 | 2 | 0 | 1 | 2 |
99 * ---------------------------------------------------------------------
101 * to find stripe 1's offsets for S and E, it divides by the full stripe
102 * width and does its math in the context of a single set of stripes:
105 * -----------------------------------
107 * -----------------------------------
109 * it'll notice that E is outside stripe 1 and clamp it to the end of the
110 * stripe, then multiply it back out by lov_off to give the real offsets in
114 * ---------------------------------------------------------------------
115 * | 1 | 1 | 1 | 1 | 1 | 1 |
116 * ---------------------------------------------------------------------
118 * it would have done similarly and pulled S forward to the start of a 1
119 * stripe if, say, S had landed in a 0 stripe.
121 * this rounding isn't always correct. consider an E lov offset that lands
122 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
123 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
124 * of a previous 1 stripe. this logic is handled by callers and this is why:
126 * this function returns < 0 when the offset was "before" the stripe and
127 * was moved forward to the start of the stripe in question; 0 when it
128 * falls in the stripe and no shifting was done; > 0 when the offset
129 * was outside the stripe and was pulled back to its final byte. */
130 int lov_stripe_offset(struct lov_stripe_md *lsm, obd_off lov_off,
131 int stripeno, obd_off *obdoff)
133 unsigned long ssize = lsm->lsm_stripe_size;
134 unsigned long stripe_off, this_stripe;
137 int magic = lsm->lsm_magic;
140 if (lov_off == OBD_OBJECT_EOF) {
141 *obdoff = OBD_OBJECT_EOF;
145 LASSERT(lsm_op_find(magic) != NULL);
146 /*It will check whether the lov_off and stripeno
147 *are in the same extent.
148 *1) lov_off extent < stripeno extent, ret = -1, obdoff = 0
149 *2) lov_off extent > stripeno extent, ret = 1,
150 * obdoff = lov_off extent offset*/
151 l_off = lsm_op_find(magic)->lsm_stripe_offset_by_index(lsm, stripeno);
152 s_off = lsm_op_find(magic)->lsm_stripe_offset_by_offset(lsm, lov_off);
157 } else if (s_off > l_off) {
162 /*If they are in the same extent, original logic*/
163 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
166 /* ll_do_div64(a, b) returns a % b, and a = a / b */
167 stripe_off = ll_do_div64(lov_off, swidth);
169 this_stripe = stripeno * ssize;
170 if (stripe_off < this_stripe) {
174 stripe_off -= this_stripe;
176 if (stripe_off >= ssize) {
182 *obdoff = lov_off * ssize + stripe_off;
186 /* Given a whole-file size and a stripe number, give the file size which
187 * corresponds to the individual object of that stripe.
189 * This behaves basically in the same was as lov_stripe_offset, except that
190 * file sizes falling before the beginning of a stripe are clamped to the end
191 * of the previous stripe, not the beginning of the next:
194 * ---------------------------------------------------------------------
195 * | 0 | 1 | 2 | 0 | 1 | 2 |
196 * ---------------------------------------------------------------------
198 * if clamped to stripe 2 becomes:
201 * ---------------------------------------------------------------------
202 * | 0 | 1 | 2 | 0 | 1 | 2 |
203 * ---------------------------------------------------------------------
205 obd_off lov_size_to_stripe(struct lov_stripe_md *lsm, obd_off file_size,
208 unsigned long ssize = lsm->lsm_stripe_size;
209 unsigned long stripe_off, this_stripe;
211 int magic = lsm->lsm_magic;
213 if (file_size == OBD_OBJECT_EOF)
214 return OBD_OBJECT_EOF;
216 LASSERT(lsm_op_find(magic) != NULL);
217 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
220 /* ll_do_div64(a, b) returns a % b, and a = a / b */
221 stripe_off = ll_do_div64(file_size, swidth);
223 this_stripe = stripeno * ssize;
224 if (stripe_off < this_stripe) {
225 /* Move to end of previous stripe, or zero */
233 stripe_off -= this_stripe;
235 if (stripe_off >= ssize) {
236 /* Clamp to end of this stripe */
241 return (file_size * ssize + stripe_off);
244 /* given an extent in an lov and a stripe, calculate the extent of the stripe
245 * that is contained within the lov extent. this returns true if the given
246 * stripe does intersect with the lov extent. */
247 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
248 obd_off start, obd_off end,
249 obd_off *obd_start, obd_off *obd_end)
251 int start_side, end_side;
253 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
254 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
256 CDEBUG(D_INODE, "["LPU64"->"LPU64"] -> [(%d) "LPU64"->"LPU64" (%d)]\n",
257 start, end, start_side, *obd_start, *obd_end, end_side);
259 /* this stripe doesn't intersect the file extent when neither
260 * start or the end intersected the stripe and obd_start and
261 * obd_end got rounded up to the save value. */
262 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
265 /* as mentioned in the lov_stripe_offset commentary, end
266 * might have been shifted in the wrong direction. This
267 * happens when an end offset is before the stripe when viewed
268 * through the "mod stripe size" math. we detect it being shifted
269 * in the wrong direction and touch it up.
270 * interestingly, this can't underflow since end must be > start
271 * if we passed through the previous check.
272 * (should we assert for that somewhere?) */
279 /* compute which stripe number "lov_off" will be written into */
280 int lov_stripe_number(struct lov_stripe_md *lsm, obd_off lov_off)
282 unsigned long ssize = lsm->lsm_stripe_size;
283 unsigned long stripe_off;
285 obd_off offset = lov_off;
286 int magic = lsm->lsm_magic;
288 LASSERT(lsm_op_find(magic) != NULL);
289 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
291 stripe_off = ll_do_div64(lov_off, swidth);
293 return (stripe_off/ssize +
294 lsm_op_find(magic)->lsm_stripe_index_by_offset(lsm, offset));