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36 # define EXPORT_SYMTAB
38 #define DEBUG_SUBSYSTEM S_LOV
41 #include <libcfs/libcfs.h>
43 #include <liblustre.h>
46 #include <obd_class.h>
49 #include "lov_internal.h"
51 /* compute object size given "stripeno" and the ost size */
52 obd_size lov_stripe_size(struct lov_stripe_md *lsm, obd_size ost_size,
55 unsigned long ssize = lsm->lsm_stripe_size;
56 unsigned long stripe_size;
59 int magic = lsm->lsm_magic;
65 LASSERT(lsm_op_find(magic) != NULL);
66 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
68 /* lov_do_div64(a, b) returns a % b, and a = a / b */
69 stripe_size = lov_do_div64(ost_size, ssize);
71 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
73 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
78 /* we have an offset in file backed by an lov and want to find out where
79 * that offset lands in our given stripe of the file. for the easy
80 * case where the offset is within the stripe, we just have to scale the
81 * offset down to make it relative to the stripe instead of the lov.
83 * the harder case is what to do when the offset doesn't intersect the
84 * stripe. callers will want start offsets clamped ahead to the start
85 * of the nearest stripe in the file. end offsets similarly clamped to the
86 * nearest ending byte of a stripe in the file:
88 * all this function does is move offsets to the nearest region of the
89 * stripe, and it does its work "mod" the full length of all the stripes.
90 * consider a file with 3 stripes:
93 * ---------------------------------------------------------------------
94 * | 0 | 1 | 2 | 0 | 1 | 2 |
95 * ---------------------------------------------------------------------
97 * to find stripe 1's offsets for S and E, it divides by the full stripe
98 * width and does its math in the context of a single set of stripes:
101 * -----------------------------------
103 * -----------------------------------
105 * it'll notice that E is outside stripe 1 and clamp it to the end of the
106 * stripe, then multiply it back out by lov_off to give the real offsets in
110 * ---------------------------------------------------------------------
111 * | 1 | 1 | 1 | 1 | 1 | 1 |
112 * ---------------------------------------------------------------------
114 * it would have done similarly and pulled S forward to the start of a 1
115 * stripe if, say, S had landed in a 0 stripe.
117 * this rounding isn't always correct. consider an E lov offset that lands
118 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
119 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
120 * of a previous 1 stripe. this logic is handled by callers and this is why:
122 * this function returns < 0 when the offset was "before" the stripe and
123 * was moved forward to the start of the stripe in question; 0 when it
124 * falls in the stripe and no shifting was done; > 0 when the offset
125 * was outside the stripe and was pulled back to its final byte. */
126 int lov_stripe_offset(struct lov_stripe_md *lsm, obd_off lov_off,
127 int stripeno, obd_off *obdoff)
129 unsigned long ssize = lsm->lsm_stripe_size;
130 obd_off stripe_off, this_stripe, swidth;
131 int magic = lsm->lsm_magic;
134 if (lov_off == OBD_OBJECT_EOF) {
135 *obdoff = OBD_OBJECT_EOF;
139 LASSERT(lsm_op_find(magic) != NULL);
141 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
144 /* lov_do_div64(a, b) returns a % b, and a = a / b */
145 stripe_off = lov_do_div64(lov_off, swidth);
147 this_stripe = (obd_off)stripeno * ssize;
148 if (stripe_off < this_stripe) {
152 stripe_off -= this_stripe;
154 if (stripe_off >= ssize) {
160 *obdoff = lov_off * ssize + stripe_off;
164 /* Given a whole-file size and a stripe number, give the file size which
165 * corresponds to the individual object of that stripe.
167 * This behaves basically in the same was as lov_stripe_offset, except that
168 * file sizes falling before the beginning of a stripe are clamped to the end
169 * of the previous stripe, not the beginning of the next:
172 * ---------------------------------------------------------------------
173 * | 0 | 1 | 2 | 0 | 1 | 2 |
174 * ---------------------------------------------------------------------
176 * if clamped to stripe 2 becomes:
179 * ---------------------------------------------------------------------
180 * | 0 | 1 | 2 | 0 | 1 | 2 |
181 * ---------------------------------------------------------------------
183 obd_off lov_size_to_stripe(struct lov_stripe_md *lsm, obd_off file_size,
186 unsigned long ssize = lsm->lsm_stripe_size;
187 obd_off stripe_off, this_stripe, swidth;
188 int magic = lsm->lsm_magic;
190 if (file_size == OBD_OBJECT_EOF)
191 return OBD_OBJECT_EOF;
193 LASSERT(lsm_op_find(magic) != NULL);
194 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
197 /* lov_do_div64(a, b) returns a % b, and a = a / b */
198 stripe_off = lov_do_div64(file_size, swidth);
200 this_stripe = (obd_off)stripeno * ssize;
201 if (stripe_off < this_stripe) {
202 /* Move to end of previous stripe, or zero */
210 stripe_off -= this_stripe;
212 if (stripe_off >= ssize) {
213 /* Clamp to end of this stripe */
218 return (file_size * ssize + stripe_off);
221 /* given an extent in an lov and a stripe, calculate the extent of the stripe
222 * that is contained within the lov extent. this returns true if the given
223 * stripe does intersect with the lov extent. */
224 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
225 obd_off start, obd_off end,
226 obd_off *obd_start, obd_off *obd_end)
228 int start_side, end_side;
230 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
231 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
233 CDEBUG(D_INODE, "["LPU64"->"LPU64"] -> [(%d) "LPU64"->"LPU64" (%d)]\n",
234 start, end, start_side, *obd_start, *obd_end, end_side);
236 /* this stripe doesn't intersect the file extent when neither
237 * start or the end intersected the stripe and obd_start and
238 * obd_end got rounded up to the save value. */
239 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
242 /* as mentioned in the lov_stripe_offset commentary, end
243 * might have been shifted in the wrong direction. This
244 * happens when an end offset is before the stripe when viewed
245 * through the "mod stripe size" math. we detect it being shifted
246 * in the wrong direction and touch it up.
247 * interestingly, this can't underflow since end must be > start
248 * if we passed through the previous check.
249 * (should we assert for that somewhere?) */
256 /* compute which stripe number "lov_off" will be written into */
257 int lov_stripe_number(struct lov_stripe_md *lsm, obd_off lov_off)
259 unsigned long ssize = lsm->lsm_stripe_size;
260 obd_off stripe_off, swidth;
261 int magic = lsm->lsm_magic;
263 LASSERT(lsm_op_find(magic) != NULL);
264 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
266 stripe_off = lov_do_div64(lov_off, swidth);
268 /* Puts stripe_off/ssize result into stripe_off */
269 lov_do_div64(stripe_off, ssize);