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37 #define DEBUG_SUBSYSTEM S_LOV
39 #include <libcfs/libcfs.h>
41 #include <obd_class.h>
43 #include "lov_internal.h"
45 /* compute object size given "stripeno" and the ost size */
46 obd_size lov_stripe_size(struct lov_stripe_md *lsm, obd_size ost_size,
49 unsigned long ssize = lsm->lsm_stripe_size;
50 unsigned long stripe_size;
53 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;
73 * Compute file level page index by stripe level page offset
75 pgoff_t lov_stripe_pgoff(struct lov_stripe_md *lsm, pgoff_t stripe_index,
80 offset = lov_stripe_size(lsm, stripe_index << PAGE_CACHE_SHIFT,
82 return offset >> PAGE_CACHE_SHIFT;
85 /* we have an offset in file backed by an lov and want to find out where
86 * that offset lands in our given stripe of the file. for the easy
87 * case where the offset is within the stripe, we just have to scale the
88 * offset down to make it relative to the stripe instead of the lov.
90 * the harder case is what to do when the offset doesn't intersect the
91 * stripe. callers will want start offsets clamped ahead to the start
92 * of the nearest stripe in the file. end offsets similarly clamped to the
93 * nearest ending byte of a stripe in the file:
95 * all this function does is move offsets to the nearest region of the
96 * stripe, and it does its work "mod" the full length of all the stripes.
97 * consider a file with 3 stripes:
100 * ---------------------------------------------------------------------
101 * | 0 | 1 | 2 | 0 | 1 | 2 |
102 * ---------------------------------------------------------------------
104 * to find stripe 1's offsets for S and E, it divides by the full stripe
105 * width and does its math in the context of a single set of stripes:
108 * -----------------------------------
110 * -----------------------------------
112 * it'll notice that E is outside stripe 1 and clamp it to the end of the
113 * stripe, then multiply it back out by lov_off to give the real offsets in
117 * ---------------------------------------------------------------------
118 * | 1 | 1 | 1 | 1 | 1 | 1 |
119 * ---------------------------------------------------------------------
121 * it would have done similarly and pulled S forward to the start of a 1
122 * stripe if, say, S had landed in a 0 stripe.
124 * this rounding isn't always correct. consider an E lov offset that lands
125 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
126 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
127 * of a previous 1 stripe. this logic is handled by callers and this is why:
129 * this function returns < 0 when the offset was "before" the stripe and
130 * was moved forward to the start of the stripe in question; 0 when it
131 * falls in the stripe and no shifting was done; > 0 when the offset
132 * was outside the stripe and was pulled back to its final byte. */
133 int lov_stripe_offset(struct lov_stripe_md *lsm, obd_off lov_off,
134 int stripeno, obd_off *obdoff)
136 unsigned long ssize = lsm->lsm_stripe_size;
137 obd_off stripe_off, this_stripe, swidth;
138 int magic = lsm->lsm_magic;
141 if (lov_off == OBD_OBJECT_EOF) {
142 *obdoff = OBD_OBJECT_EOF;
146 LASSERT(lsm_op_find(magic) != NULL);
148 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
151 /* lov_do_div64(a, b) returns a % b, and a = a / b */
152 stripe_off = lov_do_div64(lov_off, swidth);
154 this_stripe = (obd_off)stripeno * ssize;
155 if (stripe_off < this_stripe) {
159 stripe_off -= this_stripe;
161 if (stripe_off >= ssize) {
167 *obdoff = lov_off * ssize + stripe_off;
171 /* Given a whole-file size and a stripe number, give the file size which
172 * corresponds to the individual object of that stripe.
174 * This behaves basically in the same was as lov_stripe_offset, except that
175 * file sizes falling before the beginning of a stripe are clamped to the end
176 * of the previous stripe, not the beginning of the next:
179 * ---------------------------------------------------------------------
180 * | 0 | 1 | 2 | 0 | 1 | 2 |
181 * ---------------------------------------------------------------------
183 * if clamped to stripe 2 becomes:
186 * ---------------------------------------------------------------------
187 * | 0 | 1 | 2 | 0 | 1 | 2 |
188 * ---------------------------------------------------------------------
190 obd_off lov_size_to_stripe(struct lov_stripe_md *lsm, obd_off file_size,
193 unsigned long ssize = lsm->lsm_stripe_size;
194 obd_off stripe_off, this_stripe, swidth;
195 int magic = lsm->lsm_magic;
197 if (file_size == OBD_OBJECT_EOF)
198 return OBD_OBJECT_EOF;
200 LASSERT(lsm_op_find(magic) != NULL);
201 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
204 /* lov_do_div64(a, b) returns a % b, and a = a / b */
205 stripe_off = lov_do_div64(file_size, swidth);
207 this_stripe = (obd_off)stripeno * ssize;
208 if (stripe_off < this_stripe) {
209 /* Move to end of previous stripe, or zero */
217 stripe_off -= this_stripe;
219 if (stripe_off >= ssize) {
220 /* Clamp to end of this stripe */
225 return (file_size * ssize + stripe_off);
228 /* given an extent in an lov and a stripe, calculate the extent of the stripe
229 * that is contained within the lov extent. this returns true if the given
230 * stripe does intersect with the lov extent. */
231 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
232 obd_off start, obd_off end,
233 obd_off *obd_start, obd_off *obd_end)
235 int start_side, end_side;
237 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
238 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
240 CDEBUG(D_INODE, "["LPU64"->"LPU64"] -> [(%d) "LPU64"->"LPU64" (%d)]\n",
241 start, end, start_side, *obd_start, *obd_end, end_side);
243 /* this stripe doesn't intersect the file extent when neither
244 * start or the end intersected the stripe and obd_start and
245 * obd_end got rounded up to the save value. */
246 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
249 /* as mentioned in the lov_stripe_offset commentary, end
250 * might have been shifted in the wrong direction. This
251 * happens when an end offset is before the stripe when viewed
252 * through the "mod stripe size" math. we detect it being shifted
253 * in the wrong direction and touch it up.
254 * interestingly, this can't underflow since end must be > start
255 * if we passed through the previous check.
256 * (should we assert for that somewhere?) */
263 /* compute which stripe number "lov_off" will be written into */
264 int lov_stripe_number(struct lov_stripe_md *lsm, obd_off lov_off)
266 unsigned long ssize = lsm->lsm_stripe_size;
267 obd_off stripe_off, swidth;
268 int magic = lsm->lsm_magic;
270 LASSERT(lsm_op_find(magic) != NULL);
271 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
273 stripe_off = lov_do_div64(lov_off, swidth);
275 /* Puts stripe_off/ssize result into stripe_off */
276 lov_do_div64(stripe_off, ssize);