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33 #define DEBUG_SUBSYSTEM S_LOV
35 #include <libcfs/libcfs.h>
37 #include <obd_class.h>
39 #include "lov_internal.h"
41 /* compute object size given "stripeno" and the ost size */
42 u64 lov_stripe_size(struct lov_stripe_md *lsm, u64 ost_size, int stripeno)
44 unsigned long ssize = lsm->lsm_stripe_size;
45 unsigned long stripe_size;
48 u32 magic = lsm->lsm_magic;
54 LASSERT(lsm_op_find(magic) != NULL);
55 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
57 /* lov_do_div64(a, b) returns a % b, and a = a / b */
58 stripe_size = lov_do_div64(ost_size, ssize);
60 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
62 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
68 * Compute file level page index by stripe level page offset
70 pgoff_t lov_stripe_pgoff(struct lov_stripe_md *lsm, pgoff_t stripe_index,
75 offset = lov_stripe_size(lsm, (stripe_index << PAGE_SHIFT) + 1,
77 return offset >> PAGE_SHIFT;
80 /* we have an offset in file backed by an lov and want to find out where
81 * that offset lands in our given stripe of the file. for the easy
82 * case where the offset is within the stripe, we just have to scale the
83 * offset down to make it relative to the stripe instead of the lov.
85 * the harder case is what to do when the offset doesn't intersect the
86 * stripe. callers will want start offsets clamped ahead to the start
87 * of the nearest stripe in the file. end offsets similarly clamped to the
88 * nearest ending byte of a stripe in the file:
90 * all this function does is move offsets to the nearest region of the
91 * stripe, and it does its work "mod" the full length of all the stripes.
92 * consider a file with 3 stripes:
95 * ---------------------------------------------------------------------
96 * | 0 | 1 | 2 | 0 | 1 | 2 |
97 * ---------------------------------------------------------------------
99 * to find stripe 1's offsets for S and E, it divides by the full stripe
100 * width and does its math in the context of a single set of stripes:
103 * -----------------------------------
105 * -----------------------------------
107 * it'll notice that E is outside stripe 1 and clamp it to the end of the
108 * stripe, then multiply it back out by lov_off to give the real offsets in
112 * ---------------------------------------------------------------------
113 * | 1 | 1 | 1 | 1 | 1 | 1 |
114 * ---------------------------------------------------------------------
116 * it would have done similarly and pulled S forward to the start of a 1
117 * stripe if, say, S had landed in a 0 stripe.
119 * this rounding isn't always correct. consider an E lov offset that lands
120 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
121 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
122 * of a previous 1 stripe. this logic is handled by callers and this is why:
124 * this function returns < 0 when the offset was "before" the stripe and
125 * was moved forward to the start of the stripe in question; 0 when it
126 * falls in the stripe and no shifting was done; > 0 when the offset
127 * was outside the stripe and was pulled back to its final byte. */
128 int lov_stripe_offset(struct lov_stripe_md *lsm, loff_t lov_off, int stripeno,
131 unsigned long ssize = lsm->lsm_stripe_size;
135 u32 magic = lsm->lsm_magic;
138 if (lov_off == OBD_OBJECT_EOF) {
139 *obdoff = OBD_OBJECT_EOF;
143 LASSERT(lsm_op_find(magic) != NULL);
144 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
147 /* lov_do_div64(a, b) returns a % b, and a = a / b */
148 stripe_off = lov_do_div64(lov_off, swidth);
150 this_stripe = (loff_t)stripeno * ssize;
151 if (stripe_off < this_stripe) {
155 stripe_off -= this_stripe;
157 if (stripe_off >= ssize) {
163 *obdoff = lov_off * ssize + stripe_off;
167 /* Given a whole-file size and a stripe number, give the file size which
168 * corresponds to the individual object of that stripe.
170 * This behaves basically in the same was as lov_stripe_offset, except that
171 * file sizes falling before the beginning of a stripe are clamped to the end
172 * of the previous stripe, not the beginning of the next:
175 * ---------------------------------------------------------------------
176 * | 0 | 1 | 2 | 0 | 1 | 2 |
177 * ---------------------------------------------------------------------
179 * if clamped to stripe 2 becomes:
182 * ---------------------------------------------------------------------
183 * | 0 | 1 | 2 | 0 | 1 | 2 |
184 * ---------------------------------------------------------------------
186 loff_t lov_size_to_stripe(struct lov_stripe_md *lsm, u64 file_size,
189 unsigned long ssize = lsm->lsm_stripe_size;
193 u32 magic = lsm->lsm_magic;
195 if (file_size == OBD_OBJECT_EOF)
196 return OBD_OBJECT_EOF;
198 LASSERT(lsm_op_find(magic) != NULL);
199 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
202 /* lov_do_div64(a, b) returns a % b, and a = a / b */
203 stripe_off = lov_do_div64(file_size, swidth);
205 this_stripe = (loff_t)stripeno * ssize;
206 if (stripe_off < this_stripe) {
207 /* Move to end of previous stripe, or zero */
215 stripe_off -= this_stripe;
217 if (stripe_off >= ssize) {
218 /* Clamp to end of this stripe */
223 return (file_size * ssize + stripe_off);
226 /* given an extent in an lov and a stripe, calculate the extent of the stripe
227 * that is contained within the lov extent. this returns true if the given
228 * stripe does intersect with the lov extent. */
229 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
230 loff_t start, loff_t end,
231 loff_t *obd_start, loff_t *obd_end)
233 int start_side, end_side;
235 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
236 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
238 CDEBUG(D_INODE, "[%lld->%lld] -> [(%d) %lld->%lld (%d)]\n",
239 start, end, start_side, *obd_start, *obd_end, end_side);
241 /* this stripe doesn't intersect the file extent when neither
242 * start or the end intersected the stripe and obd_start and
243 * obd_end got rounded up to the save value. */
244 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
247 /* as mentioned in the lov_stripe_offset commentary, end
248 * might have been shifted in the wrong direction. This
249 * happens when an end offset is before the stripe when viewed
250 * through the "mod stripe size" math. we detect it being shifted
251 * in the wrong direction and touch it up.
252 * interestingly, this can't underflow since end must be > start
253 * if we passed through the previous check.
254 * (should we assert for that somewhere?) */
261 /* compute which stripe number "lov_off" will be written into */
262 int lov_stripe_number(struct lov_stripe_md *lsm, loff_t lov_off)
264 unsigned long ssize = lsm->lsm_stripe_size;
267 u32 magic = lsm->lsm_magic;
269 LASSERT(lsm_op_find(magic) != NULL);
270 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
272 stripe_off = lov_do_div64(lov_off, swidth);
274 /* Puts stripe_off/ssize result into stripe_off */
275 lov_do_div64(stripe_off, ssize);