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md: tidy up status_resync to handle large arrays.

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Two problems in status_resync.
1/ It still used Kilobytes as the basic block unit, while most code
   now uses sectors uniformly.
2/ It doesn't allow for the possibility that max_sectors exceeds
   the range of "unsigned long".

So
 - change "max_blocks" to "max_sectors", and store sector numbers
   in there and in 'resync'
 - Make 'rt' a 'sector_t' so it can temporarily hold the number of
   remaining sectors.
 - use sector_div rather than normal division.
 - change the magic '100' used to preserve precision to '32'.
   + making it a power of 2 makes division easier
   + it doesn't need to be as large as it was chosen when we averaged
     speed over the entire run.  Now we average speed over the last 30
     seconds or so.

Reported-by: "Mario 'BitKoenig' Holbe" <Mario.Holbe@TU-Ilmenau.DE>
Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2009-05-07 12:49:35 +10:00
parent db305e507d
commit dd71cf6b27
1 changed files with 28 additions and 17 deletions
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45
drivers/md/md.c
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@ -5705,37 +5705,38 @@ static void status_unused(struct seq_file *seq)
static void status_resync(struct seq_file *seq, mddev_t * mddev)
{
sector_t max_blocks, resync, res;
unsigned long dt, db, rt;
sector_t max_sectors, resync, res;
unsigned long dt, db;
sector_t rt;
int scale;
unsigned int per_milli;
resync = (mddev->curr_resync - atomic_read(&mddev->recovery_active))/2;
resync = mddev->curr_resync - atomic_read(&mddev->recovery_active);
if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
max_blocks = mddev->resync_max_sectors >> 1;
max_sectors = mddev->resync_max_sectors;
else
max_blocks = mddev->dev_sectors / 2;
max_sectors = mddev->dev_sectors;
/*
* Should not happen.
*/
if (!max_blocks) {
if (!max_sectors) {
MD_BUG();
return;
}
/* Pick 'scale' such that (resync>>scale)*1000 will fit
* in a sector_t, and (max_blocks>>scale) will fit in a
* in a sector_t, and (max_sectors>>scale) will fit in a
* u32, as those are the requirements for sector_div.
* Thus 'scale' must be at least 10
*/
scale = 10;
if (sizeof(sector_t) > sizeof(unsigned long)) {
while ( max_blocks/2 > (1ULL<<(scale+32)))
while ( max_sectors/2 > (1ULL<<(scale+32)))
scale++;
}
res = (resync>>scale)*1000;
sector_div(res, (u32)((max_blocks>>scale)+1));
sector_div(res, (u32)((max_sectors>>scale)+1));
per_milli = res;
{
@ -5756,25 +5757,35 @@ static void status_resync(struct seq_file *seq, mddev_t * mddev)
(test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ?
"resync" : "recovery"))),
per_milli/10, per_milli % 10,
(unsigned long long) resync,
(unsigned long long) max_blocks);
(unsigned long long) resync/2,
(unsigned long long) max_sectors/2);
/*
* We do not want to overflow, so the order of operands and
* the * 100 / 100 trick are important. We do a +1 to be
* safe against division by zero. We only estimate anyway.
*
* dt: time from mark until now
* db: blocks written from mark until now
* rt: remaining time
*
* rt is a sector_t, so could be 32bit or 64bit.
* So we divide before multiply in case it is 32bit and close
* to the limit.
* We scale the divisor (db) by 32 to avoid loosing precision
* near the end of resync when the number of remaining sectors
* is close to 'db'.
* We then divide rt by 32 after multiplying by db to compensate.
* The '+1' avoids division by zero if db is very small.
*/
dt = ((jiffies - mddev->resync_mark) / HZ);
if (!dt) dt++;
db = (mddev->curr_mark_cnt - atomic_read(&mddev->recovery_active))
- mddev->resync_mark_cnt;
rt = (dt * ((unsigned long)(max_blocks-resync) / (db/2/100+1)))/100;
seq_printf(seq, " finish=%lu.%lumin", rt / 60, (rt % 60)/6);
rt = max_sectors - resync; /* number of remaining sectors */
sector_div(rt, db/32+1);
rt *= dt;
rt >>= 5;
seq_printf(seq, " finish=%lu.%lumin", (unsigned long)rt / 60,
((unsigned long)rt % 60)/6);
seq_printf(seq, " speed=%ldK/sec", db/2/dt);
}