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33 #define DEBUG_SUBSYSTEM S_LOV
35 #include <libcfs/libcfs.h>
37 #include <obd_class.h>
39 #include "lov_internal.h"
41 static loff_t stripe_width(struct lov_stripe_md *lsm, unsigned int index)
43 struct lov_stripe_md_entry *entry = lsm->lsm_entries[index];
45 LASSERT(index < lsm->lsm_entry_count);
47 if (lsme_is_dom(entry))
48 return (loff_t)entry->lsme_stripe_size;
50 return (loff_t)entry->lsme_stripe_size * entry->lsme_stripe_count;
53 /* compute object size given "stripeno" and the ost size */
54 u64 lov_stripe_size(struct lov_stripe_md *lsm, int index, u64 ost_size,
57 unsigned long ssize = lsm->lsm_entries[index]->lsme_stripe_size;
58 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;
92 /* we have an offset in file backed by an lov and want to find out where
93 * that offset lands in our given stripe of the file. for the easy
94 * case where the offset is within the stripe, we just have to scale the
95 * offset down to make it relative to the stripe instead of the lov.
97 * the harder case is what to do when the offset doesn't intersect the
98 * stripe. callers will want start offsets clamped ahead to the start
99 * of the nearest stripe in the file. end offsets similarly clamped to the
100 * nearest ending byte of a stripe in the file:
102 * all this function does is move offsets to the nearest region of the
103 * stripe, and it does its work "mod" the full length of all the stripes.
104 * consider a file with 3 stripes:
107 * ---------------------------------------------------------------------
108 * | 0 | 1 | 2 | 0 | 1 | 2 |
109 * ---------------------------------------------------------------------
111 * to find stripe 1's offsets for S and E, it divides by the full stripe
112 * width and does its math in the context of a single set of stripes:
115 * -----------------------------------
117 * -----------------------------------
119 * it'll notice that E is outside stripe 1 and clamp it to the end of the
120 * stripe, then multiply it back out by lov_off to give the real offsets in
124 * ---------------------------------------------------------------------
125 * | 1 | 1 | 1 | 1 | 1 | 1 |
126 * ---------------------------------------------------------------------
128 * it would have done similarly and pulled S forward to the start of a 1
129 * stripe if, say, S had landed in a 0 stripe.
131 * this rounding isn't always correct. consider an E lov offset that lands
132 * on a 0 stripe, the "mod stripe width" math will pull it forward to the
133 * start of a 1 stripe, when in fact it wanted to be rounded back to the end
134 * of a previous 1 stripe. this logic is handled by callers and this is why:
136 * this function returns < 0 when the offset was "before" the stripe and
137 * was moved forward to the start of the stripe in question; 0 when it
138 * falls in the stripe and no shifting was done; > 0 when the offset
139 * was outside the stripe and was pulled back to its final byte. */
140 int lov_stripe_offset(struct lov_stripe_md *lsm, int index, loff_t lov_off,
141 int stripeno, loff_t *obdoff)
143 unsigned long ssize = lsm->lsm_entries[index]->lsme_stripe_size;
149 if (lov_off == OBD_OBJECT_EOF) {
150 *obdoff = OBD_OBJECT_EOF;
154 swidth = stripe_width(lsm, index);
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 = (loff_t)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 loff_t lov_size_to_stripe(struct lov_stripe_md *lsm, int index, u64 file_size,
198 unsigned long ssize = lsm->lsm_entries[index]->lsme_stripe_size;
203 if (file_size == OBD_OBJECT_EOF)
204 return OBD_OBJECT_EOF;
206 swidth = stripe_width(lsm, index);
208 /* lov_do_div64(a, b) returns a % b, and a = a / b */
209 stripe_off = lov_do_div64(file_size, swidth);
211 this_stripe = (loff_t)stripeno * ssize;
212 if (stripe_off < this_stripe) {
213 /* Move to end of previous stripe, or zero */
221 stripe_off -= this_stripe;
223 if (stripe_off >= ssize) {
224 /* Clamp to end of this stripe */
229 return (file_size * ssize + stripe_off);
232 /* given an extent in an lov and a stripe, calculate the extent of the stripe
233 * that is contained within the lov extent. this returns true if the given
234 * stripe does intersect with the lov extent. */
235 int lov_stripe_intersects(struct lov_stripe_md *lsm, int index, int stripeno,
236 struct lu_extent *ext, u64 *obd_start, u64 *obd_end)
238 struct lov_stripe_md_entry *entry = lsm->lsm_entries[index];
240 int start_side, end_side;
242 if (!lu_extent_is_overlapped(ext, &entry->lsme_extent))
245 start = max_t(__u64, ext->e_start, entry->lsme_extent.e_start);
246 end = min_t(__u64, ext->e_end, entry->lsme_extent.e_end);
247 if (end != OBD_OBJECT_EOF)
250 start_side = lov_stripe_offset(lsm, index, start, stripeno, obd_start);
251 end_side = lov_stripe_offset(lsm, index, end, stripeno, obd_end);
253 CDEBUG(D_INODE, "[%lld->%lld] -> [(%d) %lld->%lld (%d)]\n",
254 start, end, start_side, *obd_start, *obd_end, end_side);
256 /* this stripe doesn't intersect the file extent when neither
257 * start or the end intersected the stripe and obd_start and
258 * obd_end got rounded up to the save value. */
259 if (start_side != 0 && end_side != 0 && *obd_start == *obd_end)
262 /* as mentioned in the lov_stripe_offset commentary, end
263 * might have been shifted in the wrong direction. This
264 * happens when an end offset is before the stripe when viewed
265 * through the "mod stripe size" math. we detect it being shifted
266 * in the wrong direction and touch it up.
267 * interestingly, this can't underflow since end must be > start
268 * if we passed through the previous check.
269 * (should we assert for that somewhere?) */
276 /* compute which stripe number "lov_off" will be written into */
277 int lov_stripe_number(struct lov_stripe_md *lsm, int index, loff_t lov_off)
279 unsigned long ssize = lsm->lsm_entries[index]->lsme_stripe_size;
283 swidth = stripe_width(lsm, index);
285 stripe_off = lov_do_div64(lov_off, swidth);
287 /* Puts stripe_off/ssize result into stripe_off */
288 lov_do_div64(stripe_off, ssize);