Commit 9642fa73 authored by Mariusz Tkaczyk's avatar Mariusz Tkaczyk Committed by Song Liu
Browse files

md: fix for divide error in status_resync 



Stopping external metadata arrays during resync/recovery causes
retries, loop of interrupting and starting reconstruction, until it
hit at good moment to stop completely. While these retries
curr_mark_cnt can be small- especially on HDD drives, so subtraction
result can be smaller than 0. However it is casted to uint without
checking. As a result of it the status bar in /proc/mdstat while stopping
is strange (it jumps between 0% and 99%).

The real problem occurs here after commit 72deb455 ("block: remove
CONFIG_LBDAF"). Sector_div() macro has been changed, now the
divisor is casted to uint32. For db = -8 the divisior(db/32-1) becomes 0.

Check if db value can be really counted and replace these macro by
div64_u64() inline.

Signed-off-by: default avatarMariusz Tkaczyk <mariusz.tkaczyk@intel.com>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
parent 45691804

drivers/md/md.c

+22 −14
Original line number Diff line number Diff line
@@ -7607,9 +7607,9 @@ static void status_unused(struct seq_file *seq) 
static int status_resync(struct seq_file *seq, struct mddev *mddev)

{

	sector_t max_sectors, resync, res;

	unsigned long dt, db;

	sector_t rt;

	int scale;

	unsigned long dt, db = 0;

	sector_t rt, curr_mark_cnt, resync_mark_cnt;

	int scale, recovery_active;

	unsigned int per_milli;



	if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ||
@@ -7698,7 +7698,10 @@ static int status_resync(struct seq_file *seq, struct mddev *mddev) 
	 * db: blocks written from mark until now

	 * rt: remaining time

	 *

	 * rt is a sector_t, so could be 32bit or 64bit.

	 * rt is a sector_t, which is always 64bit now. We are keeping

	 * the original algorithm, but it is not really necessary.

	 *

	 * Original algorithm:

	 *   So we divide before multiply in case it is 32bit and close

	 *   to the limit.

	 *   We scale the divisor (db) by 32 to avoid losing precision
@@ -7709,11 +7712,16 @@ static int status_resync(struct seq_file *seq, struct mddev *mddev) 
	 */

	dt = ((jiffies - mddev->resync_mark) / HZ);

	if (!dt) dt++;

	db = (mddev->curr_mark_cnt - atomic_read(&mddev->recovery_active))

		- mddev->resync_mark_cnt;



	curr_mark_cnt = mddev->curr_mark_cnt;

	recovery_active = atomic_read(&mddev->recovery_active);

	resync_mark_cnt = mddev->resync_mark_cnt;



	if (curr_mark_cnt >= (recovery_active + resync_mark_cnt))

		db = curr_mark_cnt - (recovery_active + resync_mark_cnt);



	rt = max_sectors - resync;    /* number of remaining sectors */

	sector_div(rt, db/32+1);

	rt = div64_u64(rt, db/32+1);

	rt *= dt;

	rt >>= 5;

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