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.
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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
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29 * Copyright 2008 Sun Microsystems, Inc. All rights reserved
30 * Use is subject to license terms.
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 swidth, stripe_size;
59 int sindex = stripeno;
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;
77 lov_size += lsm_op_find(magic)->lsm_stripe_offset_by_index(lsm, sindex);
81 /* we have an offset in file backed by an lov and want to find out where
82 * that offset lands in our given stripe of the file. for the easy
83 * case where the offset is within the stripe, we just have to scale the
84 * offset down to make it relative to the stripe instead of the lov.
86 * the harder case is what to do when the offset doesn't intersect the
87 * stripe. callers will want start offsets clamped ahead to the start
88 * of the nearest stripe in the file. end offsets similarly clamped to the
89 * nearest ending byte of a stripe in the file:
91 * all this function does is move offsets to the nearest region of the
92 * stripe, and it does its work "mod" the full length of all the stripes.
93 * consider a file with 3 stripes:
96 * ---------------------------------------------------------------------
97 * | 0 | 1 | 2 | 0 | 1 | 2 |
98 * ---------------------------------------------------------------------
100 * to find stripe 1's offsets for S and E, it divides by the full stripe
101 * width and does its math in the context of a single set of stripes:
104 * -----------------------------------
106 * -----------------------------------
108 * it'll notice that E is outside stripe 1 and clamp it to the end of the
109 * stripe, then multiply it back out by lov_off to give the real offsets in
113 * ---------------------------------------------------------------------
114 * | 1 | 1 | 1 | 1 | 1 | 1 |
115 * ---------------------------------------------------------------------
117 * it would have done similarly and pulled S forward to the start of a 1
118 * stripe if, say, S had landed in a 0 stripe.
120 * this rounding isn't always correct. consider an E lov offset that lands
121 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
122 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
123 * of a previous 1 stripe. this logic is handled by callers and this is why:
125 * this function returns < 0 when the offset was "before" the stripe and
126 * was moved forward to the start of the stripe in question; 0 when it
127 * falls in the stripe and no shifting was done; > 0 when the offset
128 * was outside the stripe and was pulled back to its final byte. */
129 int lov_stripe_offset(struct lov_stripe_md *lsm, obd_off lov_off,
130 int stripeno, obd_off *obd_off)
132 unsigned long ssize = lsm->lsm_stripe_size;
133 unsigned long swidth, stripe_off, this_stripe;
135 int magic = lsm->lsm_magic;
138 if (lov_off == OBD_OBJECT_EOF) {
139 *obd_off = OBD_OBJECT_EOF;
143 LASSERT(lsm_op_find(magic) != NULL);
144 /*It will check whether the lov_off and stripeno
145 *are in the same extent.
146 *1) lov_off extent < stripeno extent, ret = -1, obd_off = 0
147 *2) lov_off extent > stripeno extent, ret = 1,
148 * obd_off = lov_off extent offset*/
149 l_off = lsm_op_find(magic)->lsm_stripe_offset_by_index(lsm, stripeno);
150 s_off = lsm_op_find(magic)->lsm_stripe_offset_by_offset(lsm, lov_off);
155 } else if (s_off > l_off) {
160 /*If they are in the same extent, original logic*/
161 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
164 /* do_div(a, b) returns a % b, and a = a / b */
165 stripe_off = do_div(lov_off, swidth);
167 this_stripe = stripeno * ssize;
168 if (stripe_off < this_stripe) {
172 stripe_off -= this_stripe;
174 if (stripe_off >= ssize) {
180 *obd_off = lov_off * ssize + stripe_off;
184 /* Given a whole-file size and a stripe number, give the file size which
185 * corresponds to the individual object of that stripe.
187 * This behaves basically in the same was as lov_stripe_offset, except that
188 * file sizes falling before the beginning of a stripe are clamped to the end
189 * of the previous stripe, not the beginning of the next:
192 * ---------------------------------------------------------------------
193 * | 0 | 1 | 2 | 0 | 1 | 2 |
194 * ---------------------------------------------------------------------
196 * if clamped to stripe 2 becomes:
199 * ---------------------------------------------------------------------
200 * | 0 | 1 | 2 | 0 | 1 | 2 |
201 * ---------------------------------------------------------------------
203 obd_off lov_size_to_stripe(struct lov_stripe_md *lsm, obd_off file_size,
206 unsigned long ssize = lsm->lsm_stripe_size;
207 unsigned long swidth, stripe_off, this_stripe;
208 int magic = lsm->lsm_magic;
210 if (file_size == OBD_OBJECT_EOF)
211 return OBD_OBJECT_EOF;
213 LASSERT(lsm_op_find(magic) != NULL);
214 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
217 /* do_div(a, b) returns a % b, and a = a / b */
218 stripe_off = do_div(file_size, swidth);
220 this_stripe = stripeno * ssize;
221 if (stripe_off < this_stripe) {
222 /* Move to end of previous stripe, or zero */
230 stripe_off -= this_stripe;
232 if (stripe_off >= ssize) {
233 /* Clamp to end of this stripe */
238 return (file_size * ssize + stripe_off);
241 /* given an extent in an lov and a stripe, calculate the extent of the stripe
242 * that is contained within the lov extent. this returns true if the given
243 * stripe does intersect with the lov extent. */
244 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
245 obd_off start, obd_off end,
246 obd_off *obd_start, obd_off *obd_end)
248 int start_side, end_side;
250 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
251 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
253 CDEBUG(D_INODE, "["LPU64"->"LPU64"] -> [(%d) "LPU64"->"LPU64" (%d)]\n",
254 start, end, start_side, *obd_start, *obd_end, end_side);
256 /* this stripe doesn't intersect the file extent when neither
257 * start or the end intersected the stripe and obd_start and
258 * obd_end got rounded up to the save value. */
259 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
262 /* as mentioned in the lov_stripe_offset commentary, end
263 * might have been shifted in the wrong direction. This
264 * happens when an end offset is before the stripe when viewed
265 * through the "mod stripe size" math. we detect it being shifted
266 * in the wrong direction and touch it up.
267 * interestingly, this can't underflow since end must be > start
268 * if we passed through the previous check.
269 * (should we assert for that somewhere?) */
276 /* compute which stripe number "lov_off" will be written into */
277 int lov_stripe_number(struct lov_stripe_md *lsm, obd_off lov_off)
279 unsigned long ssize = lsm->lsm_stripe_size;
280 unsigned long swidth, stripe_off;
281 obd_off offset = lov_off;
282 int magic = lsm->lsm_magic;
284 LASSERT(lsm_op_find(magic) != NULL);
285 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
287 stripe_off = do_div(lov_off, swidth);
289 return (stripe_off/ssize +
290 lsm_op_find(magic)->lsm_stripe_index_by_offset(lsm, offset));