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Commit 6c55be8b authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds
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raid5: fix unending write sequence 



<debug output from Joel's system>
handling stripe 7629696, state=0x14 cnt=1, pd_idx=2 ops=0:0:0
check 5: state 0x6 toread 0000000000000000 read 0000000000000000 write fffff800ffcffcc0 written 0000000000000000
check 4: state 0x6 toread 0000000000000000 read 0000000000000000 write fffff800fdd4e360 written 0000000000000000
check 3: state 0x1 toread 0000000000000000 read 0000000000000000 write 0000000000000000 written 0000000000000000
check 2: state 0x1 toread 0000000000000000 read 0000000000000000 write 0000000000000000 written 0000000000000000
check 1: state 0x6 toread 0000000000000000 read 0000000000000000 write fffff800ff517e40 written 0000000000000000
check 0: state 0x6 toread 0000000000000000 read 0000000000000000 write fffff800fd4cae60 written 0000000000000000
locked=4 uptodate=2 to_read=0 to_write=4 failed=0 failed_num=0
for sector 7629696, rmw=0 rcw=0
</debug>

These blocks were prepared to be written out, but were never handled in
ops_run_biodrain(), so they remain locked forever.  The operations flags
are all clear which means handle_stripe() thinks nothing else needs to be
done.

This state suggests that the STRIPE_OP_PREXOR bit was sampled 'set' when it
should not have been.  This patch cleans up cases where the code looks at
sh->ops.pending when it should be looking at the consistent stack-based
snapshot of the operations flags.

Report from Joel:
	Resync done. Patch fix this bug.

Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Tested-by: default avatarJoel Bertrand <joel.bertrand@systella.fr>
Cc: <stable@kernel.org>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5b23dbe8

drivers/md/raid5.c

+9 −7
Original line number Diff line number Diff line
@@ -688,7 +688,8 @@ ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx) 
}



static struct dma_async_tx_descriptor *

ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)

ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,

		 unsigned long pending)

{

	int disks = sh->disks;

	int pd_idx = sh->pd_idx, i;
@@ -696,7 +697,7 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx) 
	/* check if prexor is active which means only process blocks

	 * that are part of a read-modify-write (Wantprexor)

	 */

	int prexor = test_bit(STRIPE_OP_PREXOR, &sh->ops.pending);

	int prexor = test_bit(STRIPE_OP_PREXOR, &pending);



	pr_debug("%s: stripe %llu\n", __FUNCTION__,

		(unsigned long long)sh->sector);
@@ -773,7 +774,8 @@ static void ops_complete_write(void *stripe_head_ref) 
}



static void

ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)

ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,

		unsigned long pending)

{

	/* kernel stack size limits the total number of disks */

	int disks = sh->disks;
@@ -781,7 +783,7 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx) 


	int count = 0, pd_idx = sh->pd_idx, i;

	struct page *xor_dest;

	int prexor = test_bit(STRIPE_OP_PREXOR, &sh->ops.pending);

	int prexor = test_bit(STRIPE_OP_PREXOR, &pending);

	unsigned long flags;

	dma_async_tx_callback callback;
@@ -808,7 +810,7 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx) 
	}



	/* check whether this postxor is part of a write */

	callback = test_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending) ?

	callback = test_bit(STRIPE_OP_BIODRAIN, &pending) ?

		ops_complete_write : ops_complete_postxor;



	/* 1/ if we prexor'd then the dest is reused as a source
@@ -896,12 +898,12 @@ static void raid5_run_ops(struct stripe_head *sh, unsigned long pending) 
		tx = ops_run_prexor(sh, tx);



	if (test_bit(STRIPE_OP_BIODRAIN, &pending)) {

		tx = ops_run_biodrain(sh, tx);

		tx = ops_run_biodrain(sh, tx, pending);

		overlap_clear++;

	}



	if (test_bit(STRIPE_OP_POSTXOR, &pending))

		ops_run_postxor(sh, tx);

		ops_run_postxor(sh, tx, pending);



	if (test_bit(STRIPE_OP_CHECK, &pending))

		ops_run_check(sh);