/* compute object size given "stripeno" and the ost size */
obd_size lov_stripe_size(struct lov_stripe_md *lsm, obd_size ost_size,
int stripeno)
{
unsigned long ssize = lsm->lsm_stripe_size;
unsigned long stripe_size;
obd_off swidth;
obd_size lov_size;
int magic = lsm->lsm_magic;
ENTRY;
if (ost_size == 0)
RETURN(0);
LASSERT(lsm_op_find(magic) != NULL);
lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, NULL, &swidth);
/* lov_do_div64(a, b) returns a % b, and a = a / b */
stripe_size = lov_do_div64(ost_size, ssize);
if (stripe_size)
lov_size = ost_size * swidth + stripeno * ssize + stripe_size;
else
lov_size = (ost_size - 1) * swidth + (stripeno + 1) * ssize;
RETURN(lov_size);
}
/* compute which stripe number "lov_off" will be written into */
int lov_stripe_number(struct lov_stripe_md *lsm, obd_off lov_off)
{
unsigned long ssize = lsm->lsm_stripe_size;
obd_off stripe_off, swidth;
int magic = lsm->lsm_magic;
LASSERT(lsm_op_find(magic) != NULL);
lsm_op_find(magic)->lsm_stripe_by_offset(lsm, NULL, &lov_off, &swidth);
stripe_off = lov_do_div64(lov_off, swidth);
/* Puts stripe_off/ssize result into stripe_off */
lov_do_div64(stripe_off, ssize);
return stripe_off;
}
/* Given a whole-file size and a stripe number, give the file size which
* corresponds to the individual object of that stripe.
*
* This behaves basically in the same was as lov_stripe_offset, except that
* file sizes falling before the beginning of a stripe are clamped to the end
* of the previous stripe, not the beginning of the next:
*
* S
* ---------------------------------------------------------------------
* | 0 | 1 | 2 | 0 | 1 | 2 |
* ---------------------------------------------------------------------
*
* if clamped to stripe 2 becomes:
*
* S
* ---------------------------------------------------------------------
* | 0 | 1 | 2 | 0 | 1 | 2 |
* ---------------------------------------------------------------------
*/
loff_t lov_size_to_stripe(struct lov_stripe_md *lsm, u64 file_size,
int stripeno)
{
unsigned long ssize = lsm->lsm_stripe_size;
loff_t stripe_off;
loff_t this_stripe;
loff_t swidth;
u32 magic = lsm->lsm_magic;
if (file_size == OBD_OBJECT_EOF)
return OBD_OBJECT_EOF;
LASSERT(lsm_op_find(magic) != NULL);
lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &file_size,
&swidth);
/* lov_do_div64(a, b) returns a % b, and a = a / b */
stripe_off = lov_do_div64(file_size, swidth);
this_stripe = (loff_t)stripeno * ssize;
if (stripe_off < this_stripe) {
/* Move to end of previous stripe, or zero */
if (file_size > 0) {
file_size--;
stripe_off = ssize;
} else {
stripe_off = 0;
}
} else {
stripe_off -= this_stripe;
if (stripe_off >= ssize) {
/* Clamp to end of this stripe */
stripe_off = ssize;
}
}
return (file_size * ssize + stripe_off);
}
/* we have an offset in file backed by an lov and want to find out where
* that offset lands in our given stripe of the file. for the easy
* case where the offset is within the stripe, we just have to scale the
* offset down to make it relative to the stripe instead of the lov.
*
* the harder case is what to do when the offset doesn't intersect the
* stripe. callers will want start offsets clamped ahead to the start
* of the nearest stripe in the file. end offsets similarly clamped to the
* nearest ending byte of a stripe in the file:
*
* all this function does is move offsets to the nearest region of the
* stripe, and it does its work "mod" the full length of all the stripes.
* consider a file with 3 stripes:
*
* S E
* ---------------------------------------------------------------------
* | 0 | 1 | 2 | 0 | 1 | 2 |
* ---------------------------------------------------------------------
*
* to find stripe 1's offsets for S and E, it divides by the full stripe
* width and does its math in the context of a single set of stripes:
*
* S E
* -----------------------------------
* | 0 | 1 | 2 |
* -----------------------------------
*
* it'll notice that E is outside stripe 1 and clamp it to the end of the
* stripe, then multiply it back out by lov_off to give the real offsets in
* the stripe:
*
* S E
* ---------------------------------------------------------------------
* | 1 | 1 | 1 | 1 | 1 | 1 |
* ---------------------------------------------------------------------
*
* it would have done similarly and pulled S forward to the start of a 1
* stripe if, say, S had landed in a 0 stripe.
*
* this rounding isn't always correct. consider an E lov offset that lands
* on a 0 stripe, the "mod stripe width" math will pull it forward to the
* start of a 1 stripe, when in fact it wanted to be rounded back to the end
* of a previous 1 stripe. this logic is handled by callers and this is why:
*
* this function returns < 0 when the offset was "before" the stripe and
* was moved forward to the start of the stripe in question; 0 when it
* falls in the stripe and no shifting was done; > 0 when the offset
* was outside the stripe and was pulled back to its final byte. */
int lov_stripe_offset(struct lov_stripe_md *lsm, loff_t lov_off, int stripeno,
loff_t *obdoff)
{
unsigned long ssize = lsm->lsm_stripe_size;
loff_t stripe_off;
loff_t this_stripe;
loff_t swidth;
u32 magic = lsm->lsm_magic;
int ret = 0;
if (lov_off == OBD_OBJECT_EOF) {
*obdoff = OBD_OBJECT_EOF;
return 0;
}
LASSERT(lsm_op_find(magic) != NULL);
lsm_op_find(magic)->lsm_stripe_by_index(lsm, &stripeno, &lov_off,
&swidth);
/* lov_do_div64(a, b) returns a % b, and a = a / b */
stripe_off = lov_do_div64(lov_off, swidth);
this_stripe = (loff_t)stripeno * ssize;
if (stripe_off < this_stripe) {
stripe_off = 0;
ret = -1;
} else {
stripe_off -= this_stripe;
if (stripe_off >= ssize) {
stripe_off = ssize;
ret = 1;
}
}
*obdoff = lov_off * ssize + stripe_off;
return ret;
}
