On Thu, 29 Jan 2015 12:24:00 +0100 Heinz Mauelshagen <heinzm@xxxxxxxxxx> wrote: > > Neil, > > the patch worked fine in overnight test runs without the previous livelock. > No regressions have been triggered. > > Yes, tidying up that optimization logic (e.g. in fetch_block()) is very > much appreciated :-) > Thanks! The following is what should appear in -next soonish. If there are any *-by: tags to be added or changed, please let me know. NeilBrown From: NeilBrown <neilb@xxxxxxx> Date: Mon, 2 Feb 2015 10:44:29 +1100 Subject: [PATCH] md/raid5: fix another livelock caused by non-aligned writes. If a non-page-aligned write is destined for a device which is missing/faulty, we can deadlock. As the target device is missing, a read-modify-write cycle is not possible. As the write is not for a full-page, a recontruct-write cycle is not possible. This should be handled by logic in fetch_block() which notices there is a non-R5_OVERWRITE write to a missing device, and so loads all blocks. However since commit 67f455486d2ea2, that code requires STRIPE_PREREAD_ACTIVE before it will active, and those circumstances never set STRIPE_PREREAD_ACTIVE. So: in handle_stripe_dirtying, if neither rmw or rcw was possible, set STRIPE_DELAYED, which will cause STRIPE_PREREAD_ACTIVE be set after a suitable delay. Fixes: 67f455486d2ea20b2d94d6adf5b9b783d079e321 Cc: stable@xxxxxxxxxxxxxxx (v3.16+) Reported-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> Tested-by: Heinz Mauelshagen <heinzm@xxxxxxxxxx> Signed-off-by: NeilBrown <neilb@xxxxxxx> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 41494d904859..274db1834d43 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -3192,6 +3192,11 @@ static void handle_stripe_dirtying(struct r5conf *conf, (unsigned long long)sh->sector, rcw, qread, test_bit(STRIPE_DELAYED, &sh->state)); } + + if (rcw > disks && rmw > disks && + !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) + set_bit(STRIPE_DELAYED, &sh->state); + /* now if nothing is locked, and if we have enough data, * we can start a write request */
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