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37 #define DEBUG_SUBSYSTEM S_LOV
39 #include <linux/libcfs/libcfs.h>
41 #include <obd_class.h>
44 #include "lov_internal.h"
46 /* compute object size given "stripeno" and the ost size */
47 obd_size lov_stripe_size(struct lov_stripe_md *lsm, obd_size ost_size,
50 unsigned long ssize = lsm->lsm_stripe_size;
51 unsigned long stripe_size;
54 int magic = lsm->lsm_magic;
59 LASSERT(lsm_op_find(magic) != NULL);
60 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
62 /* lov_do_div64(a, b) returns a % b, and a = a / b */
63 stripe_size = lov_do_div64(ost_size, ssize);
65 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
67 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
72 /* we have an offset in file backed by an lov and want to find out where
73 * that offset lands in our given stripe of the file. for the easy
74 * case where the offset is within the stripe, we just have to scale the
75 * offset down to make it relative to the stripe instead of the lov.
77 * the harder case is what to do when the offset doesn't intersect the
78 * stripe. callers will want start offsets clamped ahead to the start
79 * of the nearest stripe in the file. end offsets similarly clamped to the
80 * nearest ending byte of a stripe in the file:
82 * all this function does is move offsets to the nearest region of the
83 * stripe, and it does its work "mod" the full length of all the stripes.
84 * consider a file with 3 stripes:
87 * ---------------------------------------------------------------------
88 * | 0 | 1 | 2 | 0 | 1 | 2 |
89 * ---------------------------------------------------------------------
91 * to find stripe 1's offsets for S and E, it divides by the full stripe
92 * width and does its math in the context of a single set of stripes:
95 * -----------------------------------
97 * -----------------------------------
99 * it'll notice that E is outside stripe 1 and clamp it to the end of the
100 * stripe, then multiply it back out by lov_off to give the real offsets in
104 * ---------------------------------------------------------------------
105 * | 1 | 1 | 1 | 1 | 1 | 1 |
106 * ---------------------------------------------------------------------
108 * it would have done similarly and pulled S forward to the start of a 1
109 * stripe if, say, S had landed in a 0 stripe.
111 * this rounding isn't always correct. consider an E lov offset that lands
112 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
113 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
114 * of a previous 1 stripe. this logic is handled by callers and this is why:
116 * this function returns < 0 when the offset was "before" the stripe and
117 * was moved forward to the start of the stripe in question; 0 when it
118 * falls in the stripe and no shifting was done; > 0 when the offset
119 * was outside the stripe and was pulled back to its final byte. */
120 int lov_stripe_offset(struct lov_stripe_md *lsm, obd_off lov_off,
121 int stripeno, obd_off *obdoff)
123 unsigned long ssize = lsm->lsm_stripe_size;
124 obd_off stripe_off, this_stripe, swidth;
125 int magic = lsm->lsm_magic;
128 if (lov_off == OBD_OBJECT_EOF) {
129 *obdoff = OBD_OBJECT_EOF;
133 LASSERT(lsm_op_find(magic) != NULL);
135 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
138 /* lov_do_div64(a, b) returns a % b, and a = a / b */
139 stripe_off = lov_do_div64(lov_off, swidth);
141 this_stripe = (obd_off)stripeno * ssize;
142 if (stripe_off < this_stripe) {
146 stripe_off -= this_stripe;
148 if (stripe_off >= ssize) {
154 *obdoff = lov_off * ssize + stripe_off;
158 /* Given a whole-file size and a stripe number, give the file size which
159 * corresponds to the individual object of that stripe.
161 * This behaves basically in the same was as lov_stripe_offset, except that
162 * file sizes falling before the beginning of a stripe are clamped to the end
163 * of the previous stripe, not the beginning of the next:
166 * ---------------------------------------------------------------------
167 * | 0 | 1 | 2 | 0 | 1 | 2 |
168 * ---------------------------------------------------------------------
170 * if clamped to stripe 2 becomes:
173 * ---------------------------------------------------------------------
174 * | 0 | 1 | 2 | 0 | 1 | 2 |
175 * ---------------------------------------------------------------------
177 obd_off lov_size_to_stripe(struct lov_stripe_md *lsm, obd_off file_size,
180 unsigned long ssize = lsm->lsm_stripe_size;
181 obd_off stripe_off, this_stripe, swidth;
182 int magic = lsm->lsm_magic;
184 if (file_size == OBD_OBJECT_EOF)
185 return OBD_OBJECT_EOF;
187 LASSERT(lsm_op_find(magic) != NULL);
188 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
191 /* lov_do_div64(a, b) returns a % b, and a = a / b */
192 stripe_off = lov_do_div64(file_size, swidth);
194 this_stripe = (obd_off)stripeno * ssize;
195 if (stripe_off < this_stripe) {
196 /* Move to end of previous stripe, or zero */
204 stripe_off -= this_stripe;
206 if (stripe_off >= ssize) {
207 /* Clamp to end of this stripe */
212 return (file_size * ssize + stripe_off);
215 /* given an extent in an lov and a stripe, calculate the extent of the stripe
216 * that is contained within the lov extent. this returns true if the given
217 * stripe does intersect with the lov extent. */
218 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
219 obd_off start, obd_off end,
220 obd_off *obd_start, obd_off *obd_end)
222 int start_side, end_side;
224 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
225 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
227 CDEBUG(D_INODE, "["LPU64"->"LPU64"] -> [(%d) "LPU64"->"LPU64" (%d)]\n",
228 start, end, start_side, *obd_start, *obd_end, end_side);
230 /* this stripe doesn't intersect the file extent when neither
231 * start or the end intersected the stripe and obd_start and
232 * obd_end got rounded up to the save value. */
233 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
236 /* as mentioned in the lov_stripe_offset commentary, end
237 * might have been shifted in the wrong direction. This
238 * happens when an end offset is before the stripe when viewed
239 * through the "mod stripe size" math. we detect it being shifted
240 * in the wrong direction and touch it up.
241 * interestingly, this can't underflow since end must be > start
242 * if we passed through the previous check.
243 * (should we assert for that somewhere?) */
250 /* compute which stripe number "lov_off" will be written into */
251 int lov_stripe_number(struct lov_stripe_md *lsm, obd_off lov_off)
253 unsigned long ssize = lsm->lsm_stripe_size;
254 obd_off stripe_off, swidth;
255 int magic = lsm->lsm_magic;
257 LASSERT(lsm_op_find(magic) != NULL);
258 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
260 stripe_off = lov_do_div64(lov_off, swidth);
262 /* Puts stripe_off/ssize result into stripe_off */
263 lov_do_div64(stripe_off, ssize);