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37 #define DEBUG_SUBSYSTEM S_LOV
40 #include <libcfs/libcfs.h>
42 #include <liblustre.h>
45 #include <obd_class.h>
47 #include "lov_internal.h"
49 /* compute object size given "stripeno" and the ost size */
50 obd_size lov_stripe_size(struct lov_stripe_md *lsm, obd_size ost_size,
53 unsigned long ssize = lsm->lsm_stripe_size;
54 unsigned long stripe_size;
57 int magic = lsm->lsm_magic;
63 LASSERT(lsm_op_find(magic) != NULL);
64 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
66 /* lov_do_div64(a, b) returns a % b, and a = a / b */
67 stripe_size = lov_do_div64(ost_size, ssize);
69 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
71 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
77 * Compute file level page index by stripe level page offset
79 pgoff_t lov_stripe_pgoff(struct lov_stripe_md *lsm, pgoff_t stripe_index,
84 offset = lov_stripe_size(lsm, stripe_index << PAGE_CACHE_SHIFT,
86 return offset >> PAGE_CACHE_SHIFT;
89 /* we have an offset in file backed by an lov and want to find out where
90 * that offset lands in our given stripe of the file. for the easy
91 * case where the offset is within the stripe, we just have to scale the
92 * offset down to make it relative to the stripe instead of the lov.
94 * the harder case is what to do when the offset doesn't intersect the
95 * stripe. callers will want start offsets clamped ahead to the start
96 * of the nearest stripe in the file. end offsets similarly clamped to the
97 * nearest ending byte of a stripe in the file:
99 * all this function does is move offsets to the nearest region of the
100 * stripe, and it does its work "mod" the full length of all the stripes.
101 * consider a file with 3 stripes:
104 * ---------------------------------------------------------------------
105 * | 0 | 1 | 2 | 0 | 1 | 2 |
106 * ---------------------------------------------------------------------
108 * to find stripe 1's offsets for S and E, it divides by the full stripe
109 * width and does its math in the context of a single set of stripes:
112 * -----------------------------------
114 * -----------------------------------
116 * it'll notice that E is outside stripe 1 and clamp it to the end of the
117 * stripe, then multiply it back out by lov_off to give the real offsets in
121 * ---------------------------------------------------------------------
122 * | 1 | 1 | 1 | 1 | 1 | 1 |
123 * ---------------------------------------------------------------------
125 * it would have done similarly and pulled S forward to the start of a 1
126 * stripe if, say, S had landed in a 0 stripe.
128 * this rounding isn't always correct. consider an E lov offset that lands
129 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
130 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
131 * of a previous 1 stripe. this logic is handled by callers and this is why:
133 * this function returns < 0 when the offset was "before" the stripe and
134 * was moved forward to the start of the stripe in question; 0 when it
135 * falls in the stripe and no shifting was done; > 0 when the offset
136 * was outside the stripe and was pulled back to its final byte. */
137 int lov_stripe_offset(struct lov_stripe_md *lsm, obd_off lov_off,
138 int stripeno, obd_off *obdoff)
140 unsigned long ssize = lsm->lsm_stripe_size;
141 obd_off stripe_off, this_stripe, swidth;
142 int magic = lsm->lsm_magic;
145 if (lov_off == OBD_OBJECT_EOF) {
146 *obdoff = OBD_OBJECT_EOF;
150 LASSERT(lsm_op_find(magic) != NULL);
152 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
155 /* lov_do_div64(a, b) returns a % b, and a = a / b */
156 stripe_off = lov_do_div64(lov_off, swidth);
158 this_stripe = (obd_off)stripeno * ssize;
159 if (stripe_off < this_stripe) {
163 stripe_off -= this_stripe;
165 if (stripe_off >= ssize) {
171 *obdoff = lov_off * ssize + stripe_off;
175 /* Given a whole-file size and a stripe number, give the file size which
176 * corresponds to the individual object of that stripe.
178 * This behaves basically in the same was as lov_stripe_offset, except that
179 * file sizes falling before the beginning of a stripe are clamped to the end
180 * of the previous stripe, not the beginning of the next:
183 * ---------------------------------------------------------------------
184 * | 0 | 1 | 2 | 0 | 1 | 2 |
185 * ---------------------------------------------------------------------
187 * if clamped to stripe 2 becomes:
190 * ---------------------------------------------------------------------
191 * | 0 | 1 | 2 | 0 | 1 | 2 |
192 * ---------------------------------------------------------------------
194 obd_off lov_size_to_stripe(struct lov_stripe_md *lsm, obd_off file_size,
197 unsigned long ssize = lsm->lsm_stripe_size;
198 obd_off stripe_off, this_stripe, swidth;
199 int magic = lsm->lsm_magic;
201 if (file_size == OBD_OBJECT_EOF)
202 return OBD_OBJECT_EOF;
204 LASSERT(lsm_op_find(magic) != NULL);
205 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
208 /* lov_do_div64(a, b) returns a % b, and a = a / b */
209 stripe_off = lov_do_div64(file_size, swidth);
211 this_stripe = (obd_off)stripeno * ssize;
212 if (stripe_off < this_stripe) {
213 /* Move to end of previous stripe, or zero */
221 stripe_off -= this_stripe;
223 if (stripe_off >= ssize) {
224 /* Clamp to end of this stripe */
229 return (file_size * ssize + stripe_off);
232 /* given an extent in an lov and a stripe, calculate the extent of the stripe
233 * that is contained within the lov extent. this returns true if the given
234 * stripe does intersect with the lov extent. */
235 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
236 obd_off start, obd_off end,
237 obd_off *obd_start, obd_off *obd_end)
239 int start_side, end_side;
241 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
242 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
244 CDEBUG(D_INODE, "["LPU64"->"LPU64"] -> [(%d) "LPU64"->"LPU64" (%d)]\n",
245 start, end, start_side, *obd_start, *obd_end, end_side);
247 /* this stripe doesn't intersect the file extent when neither
248 * start or the end intersected the stripe and obd_start and
249 * obd_end got rounded up to the save value. */
250 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
253 /* as mentioned in the lov_stripe_offset commentary, end
254 * might have been shifted in the wrong direction. This
255 * happens when an end offset is before the stripe when viewed
256 * through the "mod stripe size" math. we detect it being shifted
257 * in the wrong direction and touch it up.
258 * interestingly, this can't underflow since end must be > start
259 * if we passed through the previous check.
260 * (should we assert for that somewhere?) */
267 /* compute which stripe number "lov_off" will be written into */
268 int lov_stripe_number(struct lov_stripe_md *lsm, obd_off lov_off)
270 unsigned long ssize = lsm->lsm_stripe_size;
271 obd_off stripe_off, swidth;
272 int magic = lsm->lsm_magic;
274 LASSERT(lsm_op_find(magic) != NULL);
275 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
277 stripe_off = lov_do_div64(lov_off, swidth);
279 /* Puts stripe_off/ssize result into stripe_off */
280 lov_do_div64(stripe_off, ssize);