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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 u64 lov_stripe_size(struct lov_stripe_md *lsm, u64 ost_size, int stripeno)
48 unsigned long ssize = lsm->lsm_stripe_size;
49 unsigned long stripe_size;
52 u32 magic = lsm->lsm_magic;
58 LASSERT(lsm_op_find(magic) != NULL);
59 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
61 /* lov_do_div64(a, b) returns a % b, and a = a / b */
62 stripe_size = lov_do_div64(ost_size, ssize);
64 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
66 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
72 * Compute file level page index by stripe level page offset
74 pgoff_t lov_stripe_pgoff(struct lov_stripe_md *lsm, pgoff_t stripe_index,
79 offset = lov_stripe_size(lsm, stripe_index << PAGE_CACHE_SHIFT,
81 return offset >> PAGE_CACHE_SHIFT;
84 /* we have an offset in file backed by an lov and want to find out where
85 * that offset lands in our given stripe of the file. for the easy
86 * case where the offset is within the stripe, we just have to scale the
87 * offset down to make it relative to the stripe instead of the lov.
89 * the harder case is what to do when the offset doesn't intersect the
90 * stripe. callers will want start offsets clamped ahead to the start
91 * of the nearest stripe in the file. end offsets similarly clamped to the
92 * nearest ending byte of a stripe in the file:
94 * all this function does is move offsets to the nearest region of the
95 * stripe, and it does its work "mod" the full length of all the stripes.
96 * consider a file with 3 stripes:
99 * ---------------------------------------------------------------------
100 * | 0 | 1 | 2 | 0 | 1 | 2 |
101 * ---------------------------------------------------------------------
103 * to find stripe 1's offsets for S and E, it divides by the full stripe
104 * width and does its math in the context of a single set of stripes:
107 * -----------------------------------
109 * -----------------------------------
111 * it'll notice that E is outside stripe 1 and clamp it to the end of the
112 * stripe, then multiply it back out by lov_off to give the real offsets in
116 * ---------------------------------------------------------------------
117 * | 1 | 1 | 1 | 1 | 1 | 1 |
118 * ---------------------------------------------------------------------
120 * it would have done similarly and pulled S forward to the start of a 1
121 * stripe if, say, S had landed in a 0 stripe.
123 * this rounding isn't always correct. consider an E lov offset that lands
124 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
125 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
126 * of a previous 1 stripe. this logic is handled by callers and this is why:
128 * this function returns < 0 when the offset was "before" the stripe and
129 * was moved forward to the start of the stripe in question; 0 when it
130 * falls in the stripe and no shifting was done; > 0 when the offset
131 * was outside the stripe and was pulled back to its final byte. */
132 int lov_stripe_offset(struct lov_stripe_md *lsm, loff_t lov_off, int stripeno,
135 unsigned long ssize = lsm->lsm_stripe_size;
139 u32 magic = lsm->lsm_magic;
142 if (lov_off == OBD_OBJECT_EOF) {
143 *obdoff = OBD_OBJECT_EOF;
147 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 = (loff_t)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 loff_t lov_size_to_stripe(struct lov_stripe_md *lsm, u64 file_size,
193 unsigned long ssize = lsm->lsm_stripe_size;
197 u32 magic = lsm->lsm_magic;
199 if (file_size == OBD_OBJECT_EOF)
200 return OBD_OBJECT_EOF;
202 LASSERT(lsm_op_find(magic) != NULL);
203 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
206 /* lov_do_div64(a, b) returns a % b, and a = a / b */
207 stripe_off = lov_do_div64(file_size, swidth);
209 this_stripe = (loff_t)stripeno * ssize;
210 if (stripe_off < this_stripe) {
211 /* Move to end of previous stripe, or zero */
219 stripe_off -= this_stripe;
221 if (stripe_off >= ssize) {
222 /* Clamp to end of this stripe */
227 return (file_size * ssize + stripe_off);
230 /* given an extent in an lov and a stripe, calculate the extent of the stripe
231 * that is contained within the lov extent. this returns true if the given
232 * stripe does intersect with the lov extent. */
233 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
234 loff_t start, loff_t end,
235 loff_t *obd_start, loff_t *obd_end)
237 int start_side, end_side;
239 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
240 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
242 CDEBUG(D_INODE, "["LPD64"->"LPD64"] -> [(%d) "LPD64"->"LPD64" (%d)]\n",
243 start, end, start_side, *obd_start, *obd_end, end_side);
245 /* this stripe doesn't intersect the file extent when neither
246 * start or the end intersected the stripe and obd_start and
247 * obd_end got rounded up to the save value. */
248 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
251 /* as mentioned in the lov_stripe_offset commentary, end
252 * might have been shifted in the wrong direction. This
253 * happens when an end offset is before the stripe when viewed
254 * through the "mod stripe size" math. we detect it being shifted
255 * in the wrong direction and touch it up.
256 * interestingly, this can't underflow since end must be > start
257 * if we passed through the previous check.
258 * (should we assert for that somewhere?) */
265 /* compute which stripe number "lov_off" will be written into */
266 int lov_stripe_number(struct lov_stripe_md *lsm, loff_t lov_off)
268 unsigned long ssize = lsm->lsm_stripe_size;
271 u32 magic = lsm->lsm_magic;
273 LASSERT(lsm_op_find(magic) != NULL);
274 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
276 stripe_off = lov_do_div64(lov_off, swidth);
278 /* Puts stripe_off/ssize result into stripe_off */
279 lov_do_div64(stripe_off, ssize);