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33 #define DEBUG_SUBSYSTEM S_LOV
35 #include "../../include/linux/libcfs/libcfs.h"
37 #include "../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 int magic = lsm->lsm_magic;
53 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
55 /* lov_do_div64(a, b) returns a % b, and a = a / b */
56 stripe_size = lov_do_div64(ost_size, ssize);
58 lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
60 lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
66 * Compute file level page index by stripe level page offset
68 pgoff_t lov_stripe_pgoff(struct lov_stripe_md *lsm, pgoff_t stripe_index,
73 offset = lov_stripe_size(lsm, (stripe_index << PAGE_SHIFT) + 1, stripe);
74 return offset >> PAGE_SHIFT;
77 /* we have an offset in file backed by an lov and want to find out where
78 * that offset lands in our given stripe of the file. for the easy
79 * case where the offset is within the stripe, we just have to scale the
80 * offset down to make it relative to the stripe instead of the lov.
82 * the harder case is what to do when the offset doesn't intersect the
83 * stripe. callers will want start offsets clamped ahead to the start
84 * of the nearest stripe in the file. end offsets similarly clamped to the
85 * nearest ending byte of a stripe in the file:
87 * all this function does is move offsets to the nearest region of the
88 * stripe, and it does its work "mod" the full length of all the stripes.
89 * consider a file with 3 stripes:
92 * ---------------------------------------------------------------------
93 * | 0 | 1 | 2 | 0 | 1 | 2 |
94 * ---------------------------------------------------------------------
96 * to find stripe 1's offsets for S and E, it divides by the full stripe
97 * width and does its math in the context of a single set of stripes:
100 * -----------------------------------
102 * -----------------------------------
104 * it'll notice that E is outside stripe 1 and clamp it to the end of the
105 * stripe, then multiply it back out by lov_off to give the real offsets in
109 * ---------------------------------------------------------------------
110 * | 1 | 1 | 1 | 1 | 1 | 1 |
111 * ---------------------------------------------------------------------
113 * it would have done similarly and pulled S forward to the start of a 1
114 * stripe if, say, S had landed in a 0 stripe.
116 * this rounding isn't always correct. consider an E lov offset that lands
117 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
118 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
119 * of a previous 1 stripe. this logic is handled by callers and this is why:
121 * this function returns < 0 when the offset was "before" the stripe and
122 * was moved forward to the start of the stripe in question; 0 when it
123 * falls in the stripe and no shifting was done; > 0 when the offset
124 * was outside the stripe and was pulled back to its final byte.
126 int lov_stripe_offset(struct lov_stripe_md *lsm, u64 lov_off,
127 int stripeno, u64 *obdoff)
129 unsigned long ssize = lsm->lsm_stripe_size;
130 u64 stripe_off, this_stripe, swidth;
131 int magic = lsm->lsm_magic;
134 if (lov_off == OBD_OBJECT_EOF) {
135 *obdoff = OBD_OBJECT_EOF;
139 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
142 /* lov_do_div64(a, b) returns a % b, and a = a / b */
143 stripe_off = lov_do_div64(lov_off, swidth);
145 this_stripe = (u64)stripeno * ssize;
146 if (stripe_off < this_stripe) {
150 stripe_off -= this_stripe;
152 if (stripe_off >= ssize) {
158 *obdoff = lov_off * ssize + stripe_off;
162 /* Given a whole-file size and a stripe number, give the file size which
163 * corresponds to the individual object of that stripe.
165 * This behaves basically in the same was as lov_stripe_offset, except that
166 * file sizes falling before the beginning of a stripe are clamped to the end
167 * of the previous stripe, not the beginning of the next:
170 * ---------------------------------------------------------------------
171 * | 0 | 1 | 2 | 0 | 1 | 2 |
172 * ---------------------------------------------------------------------
174 * if clamped to stripe 2 becomes:
177 * ---------------------------------------------------------------------
178 * | 0 | 1 | 2 | 0 | 1 | 2 |
179 * ---------------------------------------------------------------------
181 u64 lov_size_to_stripe(struct lov_stripe_md *lsm, u64 file_size,
184 unsigned long ssize = lsm->lsm_stripe_size;
185 u64 stripe_off, this_stripe, swidth;
186 int magic = lsm->lsm_magic;
188 if (file_size == OBD_OBJECT_EOF)
189 return OBD_OBJECT_EOF;
191 lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
194 /* lov_do_div64(a, b) returns a % b, and a = a / b */
195 stripe_off = lov_do_div64(file_size, swidth);
197 this_stripe = (u64)stripeno * ssize;
198 if (stripe_off < this_stripe) {
199 /* Move to end of previous stripe, or zero */
207 stripe_off -= this_stripe;
209 if (stripe_off >= ssize) {
210 /* Clamp to end of this stripe */
215 return (file_size * ssize + stripe_off);
218 /* given an extent in an lov and a stripe, calculate the extent of the stripe
219 * that is contained within the lov extent. this returns true if the given
220 * stripe does intersect with the lov extent.
222 int lov_stripe_intersects(struct lov_stripe_md *lsm, int stripeno,
223 u64 start, u64 end, u64 *obd_start, u64 *obd_end)
225 int start_side, end_side;
227 start_side = lov_stripe_offset(lsm, start, stripeno, obd_start);
228 end_side = lov_stripe_offset(lsm, end, stripeno, obd_end);
230 CDEBUG(D_INODE, "[%llu->%llu] -> [(%d) %llu->%llu (%d)]\n",
231 start, end, start_side, *obd_start, *obd_end, end_side);
233 /* this stripe doesn't intersect the file extent when neither
234 * start or the end intersected the stripe and obd_start and
235 * obd_end got rounded up to the save value.
237 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
240 /* as mentioned in the lov_stripe_offset commentary, end
241 * might have been shifted in the wrong direction. This
242 * happens when an end offset is before the stripe when viewed
243 * through the "mod stripe size" math. we detect it being shifted
244 * in the wrong direction and touch it up.
245 * interestingly, this can't underflow since end must be > start
246 * if we passed through the previous check.
247 * (should we assert for that somewhere?)
255 /* compute which stripe number "lov_off" will be written into */
256 int lov_stripe_number(struct lov_stripe_md *lsm, u64 lov_off)
258 unsigned long ssize = lsm->lsm_stripe_size;
259 u64 stripe_off, swidth;
260 int magic = lsm->lsm_magic;
262 lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
264 stripe_off = lov_do_div64(lov_off, swidth);
266 /* Puts stripe_off/ssize result into stripe_off */
267 lov_do_div64(stripe_off, ssize);