diff options
Diffstat (limited to 'drivers/md/dm-table.c')
| -rw-r--r-- | drivers/md/dm-table.c | 28 |
1 files changed, 23 insertions, 5 deletions
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index ebaaf72cd82..2fd66c30f7f 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -1,6 +1,6 @@ /* * Copyright (C) 2001 Sistina Software (UK) Limited. - * Copyright (C) 2004 Red Hat, Inc. All rights reserved. + * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved. * * This file is released under the GPL. */ @@ -15,6 +15,7 @@ #include <linux/slab.h> #include <linux/interrupt.h> #include <linux/mutex.h> +#include <linux/delay.h> #include <asm/atomic.h> #define DM_MSG_PREFIX "table" @@ -24,6 +25,19 @@ #define KEYS_PER_NODE (NODE_SIZE / sizeof(sector_t)) #define CHILDREN_PER_NODE (KEYS_PER_NODE + 1) +/* + * The table has always exactly one reference from either mapped_device->map + * or hash_cell->new_map. This reference is not counted in table->holders. + * A pair of dm_create_table/dm_destroy_table functions is used for table + * creation/destruction. + * + * Temporary references from the other code increase table->holders. A pair + * of dm_table_get/dm_table_put functions is used to manipulate it. + * + * When the table is about to be destroyed, we wait for table->holders to + * drop to zero. + */ + struct dm_table { struct mapped_device *md; atomic_t holders; @@ -228,7 +242,7 @@ int dm_table_create(struct dm_table **result, fmode_t mode, return -ENOMEM; INIT_LIST_HEAD(&t->devices); - atomic_set(&t->holders, 1); + atomic_set(&t->holders, 0); t->barriers_supported = 1; if (!num_targets) @@ -259,10 +273,14 @@ static void free_devices(struct list_head *devices) } } -static void table_destroy(struct dm_table *t) +void dm_table_destroy(struct dm_table *t) { unsigned int i; + while (atomic_read(&t->holders)) + msleep(1); + smp_mb(); + /* free the indexes (see dm_table_complete) */ if (t->depth >= 2) vfree(t->index[t->depth - 2]); @@ -300,8 +318,8 @@ void dm_table_put(struct dm_table *t) if (!t) return; - if (atomic_dec_and_test(&t->holders)) - table_destroy(t); + smp_mb__before_atomic_dec(); + atomic_dec(&t->holders); } /* |