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Subject[patch 06/29] raid5: fix unending write sequence

2.6.23-stable review patch. If anyone has any objections, please let us
know.

------------------
From: Dan Williams <dan.j.williams@intel.com>
patch 6c55be8b962f1bdc592d579e81fc27b11ea53dfc in mainline.

<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: Dan Williams <dan.j.williams@intel.com>
Tested-by: Joel Bertrand <joel.bertrand@systella.fr>
Cc: <stable@kernel.org>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/md/raid5.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -689,7 +689,8 @@ ops_run_prexor(struct stripe_head *sh, s
}

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;
@@ -697,7 +698,7 @@ ops_run_biodrain(struct stripe_head *sh,
/* 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);
@@ -774,7 +775,8 @@ static void ops_complete_write(void *str
}

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;
@@ -782,7 +784,7 @@ ops_run_postxor(struct stripe_head *sh,

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;

@@ -809,7 +811,7 @@ ops_run_postxor(struct stripe_head *sh,
}

/* 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
@@ -897,12 +899,12 @@ static void raid5_run_ops(struct stripe_
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);
--
-
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