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37 #define DEBUG_SUBSYSTEM S_LOV
39 #include "../../include/linux/libcfs/libcfs.h"
41 #include "../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 int magic = lsm->lsm_magic;
57 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
59 /* lov_do_div64(a, b) returns a % b, and a = a / b */
60 stripe_size = lov_do_div64(ost_size, ssize);
62 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
64 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
70 * Compute file level page index by stripe level page offset
72 pgoff_t lov_stripe_pgoff(struct lov_stripe_md *lsm, pgoff_t stripe_index,
77 offset = lov_stripe_size(lsm, stripe_index << PAGE_SHIFT, stripe);
78 return offset >> PAGE_SHIFT;
81 /* we have an offset in file backed by an lov and want to find out where
82 * that offset lands in our given stripe of the file. for the easy
83 * case where the offset is within the stripe, we just have to scale the
84 * offset down to make it relative to the stripe instead of the lov.
86 * the harder case is what to do when the offset doesn't intersect the
87 * stripe. callers will want start offsets clamped ahead to the start
88 * of the nearest stripe in the file. end offsets similarly clamped to the
89 * nearest ending byte of a stripe in the file:
91 * all this function does is move offsets to the nearest region of the
92 * stripe, and it does its work "mod" the full length of all the stripes.
93 * consider a file with 3 stripes:
96 * ---------------------------------------------------------------------
97 * | 0 | 1 | 2 | 0 | 1 | 2 |
98 * ---------------------------------------------------------------------
100 * to find stripe 1's offsets for S and E, it divides by the full stripe
101 * width and does its math in the context of a single set of stripes:
104 * -----------------------------------
106 * -----------------------------------
108 * it'll notice that E is outside stripe 1 and clamp it to the end of the
109 * stripe, then multiply it back out by lov_off to give the real offsets in
113 * ---------------------------------------------------------------------
114 * | 1 | 1 | 1 | 1 | 1 | 1 |
115 * ---------------------------------------------------------------------
117 * it would have done similarly and pulled S forward to the start of a 1
118 * stripe if, say, S had landed in a 0 stripe.
120 * this rounding isn't always correct. consider an E lov offset that lands
121 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
122 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
123 * of a previous 1 stripe. this logic is handled by callers and this is why:
125 * this function returns < 0 when the offset was "before" the stripe and
126 * was moved forward to the start of the stripe in question; 0 when it
127 * falls in the stripe and no shifting was done; > 0 when the offset
128 * was outside the stripe and was pulled back to its final byte.
130 int lov_stripe_offset(struct lov_stripe_md *lsm, u64 lov_off,
131 int stripeno, u64 *obdoff)
133 unsigned long ssize = lsm->lsm_stripe_size;
134 u64 stripe_off, this_stripe, swidth;
135 int magic = lsm->lsm_magic;
138 if (lov_off == OBD_OBJECT_EOF) {
139 *obdoff = OBD_OBJECT_EOF;
143 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
146 /* lov_do_div64(a, b) returns a % b, and a = a / b */
147 stripe_off = lov_do_div64(lov_off, swidth);
149 this_stripe = (u64)stripeno * ssize;
150 if (stripe_off < this_stripe) {
154 stripe_off -= this_stripe;
156 if (stripe_off >= ssize) {
162 *obdoff = lov_off * ssize + stripe_off;
166 /* Given a whole-file size and a stripe number, give the file size which
167 * corresponds to the individual object of that stripe.
169 * This behaves basically in the same was as lov_stripe_offset, except that
170 * file sizes falling before the beginning of a stripe are clamped to the end
171 * of the previous stripe, not the beginning of the next:
174 * ---------------------------------------------------------------------
175 * | 0 | 1 | 2 | 0 | 1 | 2 |
176 * ---------------------------------------------------------------------
178 * if clamped to stripe 2 becomes:
181 * ---------------------------------------------------------------------
182 * | 0 | 1 | 2 | 0 | 1 | 2 |
183 * ---------------------------------------------------------------------
185 u64 lov_size_to_stripe(struct lov_stripe_md *lsm, u64 file_size,
188 unsigned long ssize = lsm->lsm_stripe_size;
189 u64 stripe_off, this_stripe, swidth;
190 int magic = lsm->lsm_magic;
192 if (file_size == OBD_OBJECT_EOF)
193 return OBD_OBJECT_EOF;
195 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
198 /* lov_do_div64(a, b) returns a % b, and a = a / b */
199 stripe_off = lov_do_div64(file_size, swidth);
201 this_stripe = (u64)stripeno * ssize;
202 if (stripe_off < this_stripe) {
203 /* Move to end of previous stripe, or zero */
211 stripe_off -= this_stripe;
213 if (stripe_off >= ssize) {
214 /* Clamp to end of this stripe */
219 return (file_size * ssize + stripe_off);
222 /* given an extent in an lov and a stripe, calculate the extent of the stripe
223 * that is contained within the lov extent. this returns true if the given
224 * stripe does intersect with the lov extent.
226 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
227 u64 start, u64 end, u64 *obd_start, u64 *obd_end)
229 int start_side, end_side;
231 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
232 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
234 CDEBUG(D_INODE, "[%llu->%llu] -> [(%d) %llu->%llu (%d)]\n",
235 start, end, start_side, *obd_start, *obd_end, end_side);
237 /* this stripe doesn't intersect the file extent when neither
238 * start or the end intersected the stripe and obd_start and
239 * obd_end got rounded up to the save value.
241 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
244 /* as mentioned in the lov_stripe_offset commentary, end
245 * might have been shifted in the wrong direction. This
246 * happens when an end offset is before the stripe when viewed
247 * through the "mod stripe size" math. we detect it being shifted
248 * in the wrong direction and touch it up.
249 * interestingly, this can't underflow since end must be > start
250 * if we passed through the previous check.
251 * (should we assert for that somewhere?)
259 /* compute which stripe number "lov_off" will be written into */
260 int lov_stripe_number(struct lov_stripe_md *lsm, u64 lov_off)
262 unsigned long ssize = lsm->lsm_stripe_size;
263 u64 stripe_off, swidth;
264 int magic = lsm->lsm_magic;
266 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
268 stripe_off = lov_do_div64(lov_off, swidth);
270 /* Puts stripe_off/ssize result into stripe_off */
271 lov_do_div64(stripe_off, ssize);