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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 02-29-2012, 01:50 PM
Mike Snitzer
 
Default dm thin: don't use the bi_next field for the holder of a cell

From: Joe Thornber <ejt@redhat.com>

The holder can be passed down to lower devices which may want to use
bi_next themselves. Also add BUG_ON check to confirm fix.

When releasing bios that have been detained in a cell, fix the order in
which the holder and other cellmates are added to the inmates list:
append holder first followed by the other cellmates.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/md/dm-thin.c | 29 +++++++++++++++++------------
1 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index f796afb..a148532 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -125,7 +125,7 @@ struct cell {
struct hlist_node list;
struct bio_prison *prison;
struct cell_key key;
- unsigned count;
+ struct bio *holder;
struct bio_list bios;
};

@@ -221,8 +221,7 @@ static struct cell *__search_bucket(struct hlist_head *bucket,
* This may block if a new cell needs allocating. You must ensure that
* cells will be unlocked even if the calling thread is blocked.
*
- * Returns the number of entries in the cell prior to the new addition
- * or < 0 on failure.
+ * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
*/
static int bio_detain(struct bio_prison *prison, struct cell_key *key,
struct bio *inmate, struct cell **ref)
@@ -257,21 +256,25 @@ static int bio_detain(struct bio_prison *prison, struct cell_key *key,

cell->prison = prison;
memcpy(&cell->key, key, sizeof(cell->key));
- cell->count = 0;
+ cell->holder = inmate;
bio_list_init(&cell->bios);
hlist_add_head(&cell->list, prison->cells + hash);
+ r = 0;
+
+ } else {
+ mempool_free(cell2, prison->cell_pool);
+ cell2 = NULL;
+ r = 1;
+ bio_list_add(&cell->bios, inmate);
}
- }

- r = cell->count++;
- bio_list_add(&cell->bios, inmate);
+ } else {
+ r = 1;
+ bio_list_add(&cell->bios, inmate);
+ }
spin_unlock_irqrestore(&prison->lock, flags);

- if (cell2)
- mempool_free(cell2, prison->cell_pool);
-
*ref = cell;
-
return r;
}

@@ -284,8 +287,10 @@ static void __cell_release(struct cell *cell, struct bio_list *inmates)

hlist_del(&cell->list);

- if (inmates)
+ if (inmates) {
+ bio_list_add(inmates, cell->holder);
bio_list_merge(inmates, &cell->bios);
+ }

mempool_free(cell, prison->cell_pool);
}
--
1.7.1

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