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29 * This file is part of Lustre, http://www.lustre.org/
32 #define DEBUG_SUBSYSTEM S_LOV
34 #include <libcfs/libcfs.h>
36 #include <obd_class.h>
38 #include "lov_internal.h"
40 loff_t stripe_width(struct lov_stripe_md *lsm, unsigned int index)
42 struct lov_stripe_md_entry *entry = lsm->lsm_entries[index];
44 LASSERT(index < lsm->lsm_entry_count);
46 if (lsme_is_dom(entry))
47 return (loff_t)entry->lsme_stripe_size;
49 return (loff_t)entry->lsme_stripe_size * entry->lsme_stripe_count;
52 /* compute object size given "stripeno" and the ost size */
53 u64 lov_stripe_size(struct lov_stripe_md *lsm, int index, u64 ost_size,
56 unsigned long ssize = lsm->lsm_entries[index]->lsme_stripe_size;
57 unsigned long stripe_size;
66 swidth = stripe_width(lsm, index);
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;
79 * Compute file level page index by stripe level page offset
81 pgoff_t lov_stripe_pgoff(struct lov_stripe_md *lsm, int index,
82 pgoff_t stripe_index, int stripe)
86 offset = lov_stripe_size(lsm, index,
87 (stripe_index << PAGE_SHIFT) + 1,
89 return offset >> PAGE_SHIFT;
93 * we have an offset in file backed by an lov and want to find out where
94 * that offset lands in our given stripe of the file. for the easy
95 * case where the offset is within the stripe, we just have to scale the
96 * offset down to make it relative to the stripe instead of the lov.
98 * the harder case is what to do when the offset doesn't intersect the
99 * stripe. callers will want start offsets clamped ahead to the start
100 * of the nearest stripe in the file. end offsets similarly clamped to the
101 * nearest ending byte of a stripe in the file:
103 * all this function does is move offsets to the nearest region of the
104 * stripe, and it does its work "mod" the full length of all the stripes.
105 * consider a file with 3 stripes:
108 * ---------------------------------------------------------------------
109 * | 0 | 1 | 2 | 0 | 1 | 2 |
110 * ---------------------------------------------------------------------
112 * to find stripe 1's offsets for S and E, it divides by the full stripe
113 * width and does its math in the context of a single set of stripes:
116 * -----------------------------------
118 * -----------------------------------
120 * it'll notice that E is outside stripe 1 and clamp it to the end of the
121 * stripe, then multiply it back out by lov_off to give the real offsets in
125 * ---------------------------------------------------------------------
126 * | 1 | 1 | 1 | 1 | 1 | 1 |
127 * ---------------------------------------------------------------------
129 * it would have done similarly and pulled S forward to the start of a 1
130 * stripe if, say, S had landed in a 0 stripe.
132 * this rounding isn't always correct. consider an E lov offset that lands
133 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
134 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
135 * of a previous 1 stripe. this logic is handled by callers and this is why:
137 * this function returns < 0 when the offset was "before" the stripe and
138 * was moved forward to the start of the stripe in question; 0 when it
139 * falls in the stripe and no shifting was done; > 0 when the offset
140 * was outside the stripe and was pulled back to its final byte.
142 int lov_stripe_offset(struct lov_stripe_md *lsm, int index, loff_t lov_off,
143 int stripeno, loff_t *obdoff)
145 unsigned long ssize = lsm->lsm_entries[index]->lsme_stripe_size;
151 if (lov_off == OBD_OBJECT_EOF) {
152 *obdoff = OBD_OBJECT_EOF;
156 swidth = stripe_width(lsm, index);
158 /* lov_do_div64(a, b) returns a % b, and a = a / b */
159 stripe_off = lov_do_div64(lov_off, swidth);
161 this_stripe = (loff_t)stripeno * ssize;
162 if (stripe_off < this_stripe) {
166 stripe_off -= this_stripe;
168 if (stripe_off >= ssize) {
174 *obdoff = lov_off * ssize + stripe_off;
179 * Given a whole-file size and a stripe number, give the file size which
180 * corresponds to the individual object of that stripe.
182 * This behaves basically in the same was as lov_stripe_offset, except that
183 * file sizes falling before the beginning of a stripe are clamped to the end
184 * of the previous stripe, not the beginning of the next:
187 * ---------------------------------------------------------------------
188 * | 0 | 1 | 2 | 0 | 1 | 2 |
189 * ---------------------------------------------------------------------
191 * if clamped to stripe 2 becomes:
194 * ---------------------------------------------------------------------
195 * | 0 | 1 | 2 | 0 | 1 | 2 |
196 * ---------------------------------------------------------------------
198 loff_t lov_size_to_stripe(struct lov_stripe_md *lsm, int index, u64 file_size,
201 unsigned long ssize = lsm->lsm_entries[index]->lsme_stripe_size;
206 if (file_size == OBD_OBJECT_EOF)
207 return OBD_OBJECT_EOF;
209 swidth = stripe_width(lsm, index);
211 /* lov_do_div64(a, b) returns a % b, and a = a / b */
212 stripe_off = lov_do_div64(file_size, swidth);
214 this_stripe = (loff_t)stripeno * ssize;
215 if (stripe_off < this_stripe) {
216 /* Move to end of previous stripe, or zero */
224 stripe_off -= this_stripe;
226 if (stripe_off >= ssize) {
227 /* Clamp to end of this stripe */
232 return (file_size * ssize + stripe_off);
236 * given an extent in an lov and a stripe, calculate the extent of the stripe
237 * that is contained within the lov extent. this returns true if the given
238 * stripe does intersect with the lov extent.
240 * Closed interval [@obd_start, @obd_end] will be returned if caller needs them.
242 int lov_stripe_intersects(struct lov_stripe_md *lsm, int index, int stripeno,
243 struct lu_extent *ext, u64 *obd_start, u64 *obd_end)
245 struct lov_stripe_md_entry *entry = lsm->lsm_entries[index];
247 int start_side, end_side;
248 u64 loc_start, loc_end;
250 if (!lu_extent_is_overlapped(ext, &entry->lsme_extent))
254 obd_start = &loc_start;
258 start = max_t(__u64, ext->e_start, entry->lsme_extent.e_start);
259 end = min_t(__u64, ext->e_end, entry->lsme_extent.e_end);
260 if (end != OBD_OBJECT_EOF)
263 start_side = lov_stripe_offset(lsm, index, start, stripeno, obd_start);
264 end_side = lov_stripe_offset(lsm, index, end, stripeno, obd_end);
266 CDEBUG(D_INODE, "[%lld->%lld] -> [(%d) %lld->%lld (%d)]\n",
267 start, end, start_side, *obd_start, *obd_end, end_side);
270 * this stripe doesn't intersect the file extent when neither
271 * start or the end intersected the stripe and obd_start and
272 * obd_end got rounded up to the save value.
274 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
278 * as mentioned in the lov_stripe_offset commentary, end
279 * might have been shifted in the wrong direction. This
280 * happens when an end offset is before the stripe when viewed
281 * through the "mod stripe size" math. we detect it being shifted
282 * in the wrong direction and touch it up.
283 * interestingly, this can't underflow since end must be > start
284 * if we passed through the previous check.
285 * (should we assert for that somewhere?)
293 /* compute which stripe number "lov_off" will be written into */
294 int lov_stripe_number(struct lov_stripe_md *lsm, int index, loff_t lov_off)
296 unsigned long ssize = lsm->lsm_entries[index]->lsme_stripe_size;
300 swidth = stripe_width(lsm, index);
302 stripe_off = lov_do_div64(lov_off, swidth);
304 /* Puts stripe_off/ssize result into stripe_off */
305 lov_do_div64(stripe_off, ssize);