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35 #define DEBUG_SUBSYSTEM S_LOV
38 #include <libcfs/libcfs.h>
40 #include <liblustre.h>
43 #include <obd_class.h>
46 #include "lov_internal.h"
48 /* compute object size given "stripeno" and the ost size */
49 obd_size lov_stripe_size(struct lov_stripe_md *lsm, obd_size ost_size,
52 unsigned long ssize = lsm->lsm_stripe_size;
53 unsigned long stripe_size;
56 int magic = lsm->lsm_magic;
62 LASSERT(lsm_op_find(magic) != NULL);
63 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
65 /* lov_do_div64(a, b) returns a % b, and a = a / b */
66 stripe_size = lov_do_div64(ost_size, ssize);
68 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
70 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
75 /* we have an offset in file backed by an lov and want to find out where
76 * that offset lands in our given stripe of the file. for the easy
77 * case where the offset is within the stripe, we just have to scale the
78 * offset down to make it relative to the stripe instead of the lov.
80 * the harder case is what to do when the offset doesn't intersect the
81 * stripe. callers will want start offsets clamped ahead to the start
82 * of the nearest stripe in the file. end offsets similarly clamped to the
83 * nearest ending byte of a stripe in the file:
85 * all this function does is move offsets to the nearest region of the
86 * stripe, and it does its work "mod" the full length of all the stripes.
87 * consider a file with 3 stripes:
90 * ---------------------------------------------------------------------
91 * | 0 | 1 | 2 | 0 | 1 | 2 |
92 * ---------------------------------------------------------------------
94 * to find stripe 1's offsets for S and E, it divides by the full stripe
95 * width and does its math in the context of a single set of stripes:
98 * -----------------------------------
100 * -----------------------------------
102 * it'll notice that E is outside stripe 1 and clamp it to the end of the
103 * stripe, then multiply it back out by lov_off to give the real offsets in
107 * ---------------------------------------------------------------------
108 * | 1 | 1 | 1 | 1 | 1 | 1 |
109 * ---------------------------------------------------------------------
111 * it would have done similarly and pulled S forward to the start of a 1
112 * stripe if, say, S had landed in a 0 stripe.
114 * this rounding isn't always correct. consider an E lov offset that lands
115 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
116 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
117 * of a previous 1 stripe. this logic is handled by callers and this is why:
119 * this function returns < 0 when the offset was "before" the stripe and
120 * was moved forward to the start of the stripe in question; 0 when it
121 * falls in the stripe and no shifting was done; > 0 when the offset
122 * was outside the stripe and was pulled back to its final byte. */
123 int lov_stripe_offset(struct lov_stripe_md *lsm, obd_off lov_off,
124 int stripeno, obd_off *obdoff)
126 unsigned long ssize = lsm->lsm_stripe_size;
127 obd_off stripe_off, this_stripe, swidth;
128 int magic = lsm->lsm_magic;
131 if (lov_off == OBD_OBJECT_EOF) {
132 *obdoff = OBD_OBJECT_EOF;
136 LASSERT(lsm_op_find(magic) != NULL);
138 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
141 /* lov_do_div64(a, b) returns a % b, and a = a / b */
142 stripe_off = lov_do_div64(lov_off, swidth);
144 this_stripe = (obd_off)stripeno * ssize;
145 if (stripe_off < this_stripe) {
149 stripe_off -= this_stripe;
151 if (stripe_off >= ssize) {
157 *obdoff = lov_off * ssize + stripe_off;
161 /* Given a whole-file size and a stripe number, give the file size which
162 * corresponds to the individual object of that stripe.
164 * This behaves basically in the same was as lov_stripe_offset, except that
165 * file sizes falling before the beginning of a stripe are clamped to the end
166 * of the previous stripe, not the beginning of the next:
169 * ---------------------------------------------------------------------
170 * | 0 | 1 | 2 | 0 | 1 | 2 |
171 * ---------------------------------------------------------------------
173 * if clamped to stripe 2 becomes:
176 * ---------------------------------------------------------------------
177 * | 0 | 1 | 2 | 0 | 1 | 2 |
178 * ---------------------------------------------------------------------
180 obd_off lov_size_to_stripe(struct lov_stripe_md *lsm, obd_off file_size,
183 unsigned long ssize = lsm->lsm_stripe_size;
184 obd_off stripe_off, this_stripe, swidth;
185 int magic = lsm->lsm_magic;
187 if (file_size == OBD_OBJECT_EOF)
188 return OBD_OBJECT_EOF;
190 LASSERT(lsm_op_find(magic) != NULL);
191 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
194 /* lov_do_div64(a, b) returns a % b, and a = a / b */
195 stripe_off = lov_do_div64(file_size, swidth);
197 this_stripe = (obd_off)stripeno * ssize;
198 if (stripe_off < this_stripe) {
199 /* Move to end of previous stripe, or zero */
207 stripe_off -= this_stripe;
209 if (stripe_off >= ssize) {
210 /* Clamp to end of this stripe */
215 return (file_size * ssize + stripe_off);
218 /* given an extent in an lov and a stripe, calculate the extent of the stripe
219 * that is contained within the lov extent. this returns true if the given
220 * stripe does intersect with the lov extent. */
221 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
222 obd_off start, obd_off end,
223 obd_off *obd_start, obd_off *obd_end)
225 int start_side, end_side;
227 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
228 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
230 CDEBUG(D_INODE, "["LPU64"->"LPU64"] -> [(%d) "LPU64"->"LPU64" (%d)]\n",
231 start, end, start_side, *obd_start, *obd_end, end_side);
233 /* this stripe doesn't intersect the file extent when neither
234 * start or the end intersected the stripe and obd_start and
235 * obd_end got rounded up to the save value. */
236 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
239 /* as mentioned in the lov_stripe_offset commentary, end
240 * might have been shifted in the wrong direction. This
241 * happens when an end offset is before the stripe when viewed
242 * through the "mod stripe size" math. we detect it being shifted
243 * in the wrong direction and touch it up.
244 * interestingly, this can't underflow since end must be > start
245 * if we passed through the previous check.
246 * (should we assert for that somewhere?) */
253 /* compute which stripe number "lov_off" will be written into */
254 int lov_stripe_number(struct lov_stripe_md *lsm, obd_off lov_off)
256 unsigned long ssize = lsm->lsm_stripe_size;
257 obd_off stripe_off, swidth;
258 int magic = lsm->lsm_magic;
260 LASSERT(lsm_op_find(magic) != NULL);
261 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
263 stripe_off = lov_do_div64(lov_off, swidth);
265 /* Puts stripe_off/ssize result into stripe_off */
266 lov_do_div64(stripe_off, ssize);