From dd71cf6b2773310b01c6fe6c773064c80fd2476b Mon Sep 17 00:00:00 2001
From: NeilBrown
Date: Thu, 7 May 2009 12:49:35 +1000
Subject: md: tidy up status_resync to handle large arrays.
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"
Signed-off-by: NeilBrown
---
drivers/md/md.c | 45 ++++++++++++++++++++++++++++-----------------
1 file changed, 28 insertions(+), 17 deletions(-)
(limited to 'drivers/md')
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 612343fdde94..5eb01a4d27ba 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -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);
}
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