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Grow: Make sure new data-offset is well-aligned 

If we choose a new data-offset, make sure it is rounded to a largest
power of to possible, up to 1Meg

Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2013-06-24 12:55:41 +10:00
parent e09233d048
commit 534f543296
1 changed files with 51 additions and 16 deletions
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67
Grow.c
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@ -2146,6 +2146,47 @@ static int verify_reshape_position(struct mdinfo *info, int level)
return ret_val;
}
static unsigned long long choose_offset(unsigned long long lo,
unsigned long long hi,
unsigned long long min,
unsigned long long max)
{
/* Choose a new offset between hi and lo.
* It must be between min and max, but
* we would prefer something near the middle of hi/lo, and also
* prefer to be aligned to a big power of 2.
*
* So we start with the middle, then for each bit,
* starting at '1' and increasing, if it is set, we either
* add it or subtract it if possible, preferring the option
* which is furthest from the boundary.
*
* We stop once we get a 1MB alignment. As units are in sectors,
* 1MB = 2*1024 sectors.
*/
unsigned long long choice = (lo + hi) / 2;
unsigned long long bit = 1;
for (bit = 1; bit < 2*1024; bit = bit << 1) {
unsigned long long bigger, smaller;
if (! (bit & choice))
continue;
bigger = choice + bit;
smaller = choice - bit;
if (bigger > max && smaller < min)
break;
if (bigger > max)
choice = smaller;
else if (smaller < min)
choice = bigger;
else if (hi - bigger > smaller - lo)
choice = bigger;
else
choice = smaller;
}
return choice;
}
static int set_new_data_offset(struct mdinfo *sra, struct supertype *st,
char *devname, int delta_disks,
unsigned long long data_offset,
@ -2285,14 +2326,11 @@ static int set_new_data_offset(struct mdinfo *sra, struct supertype *st,
}
if (data_offset != INVALID_SECTORS)
new_data_offset = data_offset;
else {
unsigned long long off = after / 2;
off &= ~7ULL;
if (off < min)
off = min;
new_data_offset =
sd->data_offset + off;
}
else
new_data_offset = choose_offset(sd->data_offset,
sd->data_offset + after,
sd->data_offset + min,
sd->data_offset + after);
} else {
/* Decrease data offset */
if (before < min) {
@ -2308,14 +2346,11 @@ static int set_new_data_offset(struct mdinfo *sra, struct supertype *st,
}
if (data_offset != INVALID_SECTORS)
new_data_offset = data_offset;
else {
unsigned long long off = before / 2;
off &= ~7ULL;
if (off < min)
off = min;
new_data_offset =
sd->data_offset - off;
}
else
new_data_offset = choose_offset(sd->data_offset - before,
sd->data_offset,
sd->data_offset - before,
sd->data_offset - min);
}
}
if (sysfs_set_num(sra, sd, "new_offset",