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37 #define DEBUG_SUBSYSTEM S_LOV
40 #include <libcfs/libcfs.h>
42 #include <liblustre.h>
45 #include <obd_class.h>
48 #include "lov_internal.h"
50 /* compute object size given "stripeno" and the ost size */
51 obd_size lov_stripe_size(struct lov_stripe_md *lsm, obd_size ost_size,
54 unsigned long ssize = lsm->lsm_stripe_size;
55 unsigned long stripe_size;
58 int magic = lsm->lsm_magic;
64 LASSERT(lsm_op_find(magic) != NULL);
65 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
67 /* lov_do_div64(a, b) returns a % b, and a = a / b */
68 stripe_size = lov_do_div64(ost_size, ssize);
70 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
72 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
78 * Compute file level page index by stripe level page offset
80 pgoff_t lov_stripe_pgoff(struct lov_stripe_md *lsm, pgoff_t stripe_index,
85 offset = lov_stripe_size(lsm, stripe_index << PAGE_CACHE_SHIFT,
87 return offset >> PAGE_CACHE_SHIFT;
90 /* we have an offset in file backed by an lov and want to find out where
91 * that offset lands in our given stripe of the file. for the easy
92 * case where the offset is within the stripe, we just have to scale the
93 * offset down to make it relative to the stripe instead of the lov.
95 * the harder case is what to do when the offset doesn't intersect the
96 * stripe. callers will want start offsets clamped ahead to the start
97 * of the nearest stripe in the file. end offsets similarly clamped to the
98 * nearest ending byte of a stripe in the file:
100 * all this function does is move offsets to the nearest region of the
101 * stripe, and it does its work "mod" the full length of all the stripes.
102 * consider a file with 3 stripes:
105 * ---------------------------------------------------------------------
106 * | 0 | 1 | 2 | 0 | 1 | 2 |
107 * ---------------------------------------------------------------------
109 * to find stripe 1's offsets for S and E, it divides by the full stripe
110 * width and does its math in the context of a single set of stripes:
113 * -----------------------------------
115 * -----------------------------------
117 * it'll notice that E is outside stripe 1 and clamp it to the end of the
118 * stripe, then multiply it back out by lov_off to give the real offsets in
122 * ---------------------------------------------------------------------
123 * | 1 | 1 | 1 | 1 | 1 | 1 |
124 * ---------------------------------------------------------------------
126 * it would have done similarly and pulled S forward to the start of a 1
127 * stripe if, say, S had landed in a 0 stripe.
129 * this rounding isn't always correct. consider an E lov offset that lands
130 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
131 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
132 * of a previous 1 stripe. this logic is handled by callers and this is why:
134 * this function returns < 0 when the offset was "before" the stripe and
135 * was moved forward to the start of the stripe in question; 0 when it
136 * falls in the stripe and no shifting was done; > 0 when the offset
137 * was outside the stripe and was pulled back to its final byte. */
138 int lov_stripe_offset(struct lov_stripe_md *lsm, obd_off lov_off,
139 int stripeno, obd_off *obdoff)
141 unsigned long ssize = lsm->lsm_stripe_size;
142 obd_off stripe_off, this_stripe, swidth;
143 int magic = lsm->lsm_magic;
146 if (lov_off == OBD_OBJECT_EOF) {
147 *obdoff = OBD_OBJECT_EOF;
151 LASSERT(lsm_op_find(magic) != NULL);
153 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
156 /* lov_do_div64(a, b) returns a % b, and a = a / b */
157 stripe_off = lov_do_div64(lov_off, swidth);
159 this_stripe = (obd_off)stripeno * ssize;
160 if (stripe_off < this_stripe) {
164 stripe_off -= this_stripe;
166 if (stripe_off >= ssize) {
172 *obdoff = lov_off * ssize + stripe_off;
176 /* Given a whole-file size and a stripe number, give the file size which
177 * corresponds to the individual object of that stripe.
179 * This behaves basically in the same was as lov_stripe_offset, except that
180 * file sizes falling before the beginning of a stripe are clamped to the end
181 * of the previous stripe, not the beginning of the next:
184 * ---------------------------------------------------------------------
185 * | 0 | 1 | 2 | 0 | 1 | 2 |
186 * ---------------------------------------------------------------------
188 * if clamped to stripe 2 becomes:
191 * ---------------------------------------------------------------------
192 * | 0 | 1 | 2 | 0 | 1 | 2 |
193 * ---------------------------------------------------------------------
195 obd_off lov_size_to_stripe(struct lov_stripe_md *lsm, obd_off file_size,
198 unsigned long ssize = lsm->lsm_stripe_size;
199 obd_off stripe_off, this_stripe, swidth;
200 int magic = lsm->lsm_magic;
202 if (file_size == OBD_OBJECT_EOF)
203 return OBD_OBJECT_EOF;
205 LASSERT(lsm_op_find(magic) != NULL);
206 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
209 /* lov_do_div64(a, b) returns a % b, and a = a / b */
210 stripe_off = lov_do_div64(file_size, swidth);
212 this_stripe = (obd_off)stripeno * ssize;
213 if (stripe_off < this_stripe) {
214 /* Move to end of previous stripe, or zero */
222 stripe_off -= this_stripe;
224 if (stripe_off >= ssize) {
225 /* Clamp to end of this stripe */
230 return (file_size * ssize + stripe_off);
233 /* given an extent in an lov and a stripe, calculate the extent of the stripe
234 * that is contained within the lov extent. this returns true if the given
235 * stripe does intersect with the lov extent. */
236 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
237 obd_off start, obd_off end,
238 obd_off *obd_start, obd_off *obd_end)
240 int start_side, end_side;
242 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
243 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
245 CDEBUG(D_INODE, "["LPU64"->"LPU64"] -> [(%d) "LPU64"->"LPU64" (%d)]\n",
246 start, end, start_side, *obd_start, *obd_end, end_side);
248 /* this stripe doesn't intersect the file extent when neither
249 * start or the end intersected the stripe and obd_start and
250 * obd_end got rounded up to the save value. */
251 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
254 /* as mentioned in the lov_stripe_offset commentary, end
255 * might have been shifted in the wrong direction. This
256 * happens when an end offset is before the stripe when viewed
257 * through the "mod stripe size" math. we detect it being shifted
258 * in the wrong direction and touch it up.
259 * interestingly, this can't underflow since end must be > start
260 * if we passed through the previous check.
261 * (should we assert for that somewhere?) */
268 /* compute which stripe number "lov_off" will be written into */
269 int lov_stripe_number(struct lov_stripe_md *lsm, obd_off lov_off)
271 unsigned long ssize = lsm->lsm_stripe_size;
272 obd_off stripe_off, swidth;
273 int magic = lsm->lsm_magic;
275 LASSERT(lsm_op_find(magic) != NULL);
276 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
278 stripe_off = lov_do_div64(lov_off, swidth);
280 /* Puts stripe_off/ssize result into stripe_off */
281 lov_do_div64(stripe_off, ssize);