From: Joe Thornber Introduce dm_bm_set_read_only to switch the block manager into a read-only mode. To be used when dm-thin degrades due to io errors on the metadata device. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon --- drivers/md/persistent-data/dm-block-manager.c | 18 ++++++++++++++++++ drivers/md/persistent-data/dm-block-manager.h | 13 +++++++++++++ 2 files changed, 31 insertions(+) Index: linux-3.5/drivers/md/persistent-data/dm-block-manager.c =================================================================== --- linux-3.5.orig/drivers/md/persistent-data/dm-block-manager.c +++ linux-3.5/drivers/md/persistent-data/dm-block-manager.c @@ -364,6 +364,7 @@ static void dm_block_manager_write_callb *--------------------------------------------------------------*/ struct dm_block_manager { struct dm_bufio_client *bufio; + bool read_only:1; }; struct dm_block_manager *dm_block_manager_create(struct block_device *bdev, @@ -390,6 +391,8 @@ struct dm_block_manager *dm_block_manage goto bad; } + bm->read_only = false; + return bm; bad: @@ -481,6 +484,9 @@ int dm_bm_write_lock(struct dm_block_man void *p; int r; + if (bm->read_only) + return -EPERM; + p = dm_bufio_read(bm->bufio, b, (struct dm_buffer **) result); if (unlikely(IS_ERR(p))) return PTR_ERR(p); @@ -547,6 +553,9 @@ int dm_bm_write_lock_zero(struct dm_bloc struct buffer_aux *aux; void *p; + if (bm->read_only) + return -EPERM; + p = dm_bufio_new(bm->bufio, b, (struct dm_buffer **) result); if (unlikely(IS_ERR(p))) return PTR_ERR(p); @@ -589,6 +598,9 @@ int dm_bm_flush_and_unlock(struct dm_blo { int r; + if (bm->read_only) + return -EPERM; + r = dm_bufio_write_dirty_buffers(bm->bufio); if (unlikely(r)) { dm_bm_unlock(superblock); @@ -600,6 +612,12 @@ int dm_bm_flush_and_unlock(struct dm_blo return dm_bufio_write_dirty_buffers(bm->bufio); } +void dm_bm_set_read_only(struct dm_block_manager *bm) +{ + bm->read_only = true; +} +EXPORT_SYMBOL_GPL(dm_bm_set_read_only); + u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor) { return crc32c(~(u32) 0, data, len) ^ init_xor; Index: linux-3.5/drivers/md/persistent-data/dm-block-manager.h =================================================================== --- linux-3.5.orig/drivers/md/persistent-data/dm-block-manager.h +++ linux-3.5/drivers/md/persistent-data/dm-block-manager.h @@ -108,6 +108,19 @@ int dm_bm_unlock(struct dm_block *b); int dm_bm_flush_and_unlock(struct dm_block_manager *bm, struct dm_block *superblock); +/* + * Switches the bm to a read only mode. Once read-only mode + * has been entered the following functions will return -EPERM. + * + * dm_bm_write_lock + * dm_bm_write_lock_zero + * dm_bm_flush_and_unlock + * + * Additionally you should not use dm_bm_unlock_move, however no error will + * be returned if you do. + */ +void dm_bm_set_read_only(struct dm_block_manager *bm); + u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor); /*----------------------------------------------------------------*/