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Subject[PATCH AUTOSEL 5.5 360/542] dm thin: don't allow changing data device during thin-pool reload
Date
From: Mikulas Patocka <mpatocka@redhat.com>

[ Upstream commit 873937e75f9a8ea231a502c3d29d9cb6ad91b3ef ]

The existing code allows changing the data device when the thin-pool
target is reloaded.

This capability is not required and only complicates device lifetime
guarantees. This can cause crashes like the one reported here:
https://bugzilla.redhat.com/show_bug.cgi?id=1788596
where the kernel tries to issue a flush bio located in a structure that
was already freed.

Take the first step to simplifying the thin-pool's data device lifetime
by disallowing changing it. Like the thin-pool's metadata device, the
data device is now set in pool_create() and it cannot be changed for a
given thin-pool.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/dm-thin.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index a2bb2622cdbd5..4fb6e89c87862 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -231,6 +231,7 @@ struct pool {
struct dm_target *ti; /* Only set if a pool target is bound */

struct mapped_device *pool_md;
+ struct block_device *data_dev;
struct block_device *md_dev;
struct dm_pool_metadata *pmd;

@@ -2933,6 +2934,7 @@ static struct kmem_cache *_new_mapping_cache;

static struct pool *pool_create(struct mapped_device *pool_md,
struct block_device *metadata_dev,
+ struct block_device *data_dev,
unsigned long block_size,
int read_only, char **error)
{
@@ -3040,6 +3042,7 @@ static struct pool *pool_create(struct mapped_device *pool_md,
pool->last_commit_jiffies = jiffies;
pool->pool_md = pool_md;
pool->md_dev = metadata_dev;
+ pool->data_dev = data_dev;
__pool_table_insert(pool);

return pool;
@@ -3081,6 +3084,7 @@ static void __pool_dec(struct pool *pool)

static struct pool *__pool_find(struct mapped_device *pool_md,
struct block_device *metadata_dev,
+ struct block_device *data_dev,
unsigned long block_size, int read_only,
char **error, int *created)
{
@@ -3091,19 +3095,23 @@ static struct pool *__pool_find(struct mapped_device *pool_md,
*error = "metadata device already in use by a pool";
return ERR_PTR(-EBUSY);
}
+ if (pool->data_dev != data_dev) {
+ *error = "data device already in use by a pool";
+ return ERR_PTR(-EBUSY);
+ }
__pool_inc(pool);

} else {
pool = __pool_table_lookup(pool_md);
if (pool) {
- if (pool->md_dev != metadata_dev) {
+ if (pool->md_dev != metadata_dev || pool->data_dev != data_dev) {
*error = "different pool cannot replace a pool";
return ERR_PTR(-EINVAL);
}
__pool_inc(pool);

} else {
- pool = pool_create(pool_md, metadata_dev, block_size, read_only, error);
+ pool = pool_create(pool_md, metadata_dev, data_dev, block_size, read_only, error);
*created = 1;
}
}
@@ -3356,7 +3364,7 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
goto out;
}

- pool = __pool_find(dm_table_get_md(ti->table), metadata_dev->bdev,
+ pool = __pool_find(dm_table_get_md(ti->table), metadata_dev->bdev, data_dev->bdev,
block_size, pf.mode == PM_READ_ONLY, &ti->error, &pool_created);
if (IS_ERR(pool)) {
r = PTR_ERR(pool);
@@ -4098,7 +4106,7 @@ static struct target_type pool_target = {
.name = "thin-pool",
.features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |
DM_TARGET_IMMUTABLE,
- .version = {1, 21, 0},
+ .version = {1, 22, 0},
.module = THIS_MODULE,
.ctr = pool_ctr,
.dtr = pool_dtr,
@@ -4475,7 +4483,7 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits)

static struct target_type thin_target = {
.name = "thin",
- .version = {1, 21, 0},
+ .version = {1, 22, 0},
.module = THIS_MODULE,
.ctr = thin_ctr,
.dtr = thin_dtr,
--
2.20.1
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