user/sven/linux.git/drivers/md/persistent-data/dm-space-map-disk.c, branch v6.1.4

dm space maps: improve performance with inc/dec on ranges of blocks

2021-06-04T16:07:22Z

When we break sharing on btree nodes we typically need to increment the reference counts to every value held in the node. This can cause a lot of repeated calls to the space maps. Fix this by changing the interface to the space map inc/dec methods to take ranges of adjacent blocks to be operated on. For installations that are using a lot of snapshots this will reduce cpu overhead of fundamental operations such as provisioning a new block, or deleting a snapshot, by as much as 10 times. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer

dm space maps: don't reset space map allocation cursor when committing

2021-06-04T16:07:21Z

Current commit code resets the place where the search for free blocks will begin back to the start of the metadata device. There are a couple of repercussions to this: - The first allocation after the commit is likely to take longer than normal as it searches for a free block in an area that is likely to have very few free blocks (if any). - Any free blocks it finds will have been recently freed. Reusing them means we have fewer old copies of the metadata to aid recovery from hardware error. Fix these issues by leaving the cursor alone, only resetting when the search hits the end of the metadata device. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer

dm space map disk: remove redundant calls to sm_disk_get_nr_free()

2021-04-19T16:36:46Z

Both sm_disk_new_block and sm_disk_commit are needlessly calling sm_disk_get_nr_free(). Looks like old queries used for some debugging. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer

dm space map common: fix to ensure new block isn't already in use

2020-01-15T01:15:53Z

The space-maps track the reference counts for disk blocks allocated by both the thin-provisioning and cache targets. There are variants for tracking metadata blocks and data blocks. Transactionality is implemented by never touching blocks from the previous transaction, so we can rollback in the event of a crash. When allocating a new block we need to ensure the block is free (has reference count of 0) in both the current and previous transaction. Prior to this fix we were doing this by searching for a free block in the previous transaction, and relying on a 'begin' counter to track where the last allocation in the current transaction was. This 'begin' field was not being updated in all code paths (eg, increment of a data block reference count due to breaking sharing of a neighbour block in the same btree leaf). This fix keeps the 'begin' field, but now it's just a hint to speed up the search. Instead the current transaction is searched for a free block, and then the old transaction is double checked to ensure it's free. Much simpler. This fixes reports of sm_disk_new_block()'s BUG_ON() triggering when DM thin-provisioning's snapshots are heavily used. Reported-by: Eric Wheeler Cc: stable@vger.kernel.org Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer

dm space map disk: fix some book keeping in the disk space map

2017-05-15T19:09:50Z

When decrementing the reference count for a block, the free count wasn't being updated if the reference count went to zero. Cc: stable@vger.kernel.org Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer

dm space map disk: fix sm_disk_count_is_more_than_one()

2015-02-14T00:32:58Z

dm_tm_shadow_block() is the only caller of dm_sm_count_is_more_than_one() which only ever operates on a metadata space-map. So in practice, sm_disk_count_is_more_than_one() isn't actually used (which explains why this bug never amounted to anything). But fix sm_disk_count_is_more_than_one() to properly set *result and return 0. Reported-by: Vivek Goyal Signed-off-by: Mike Snitzer

dm space map disk: optimise sm_disk_dec_block

2013-11-09T23:20:24Z

Don't waste time spotting blocks that have been allocated and then freed in the same transaction. The extra lookup is expensive, and I don't think it really gives us much. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer

dm persistent data: add threshold callback to space map

2013-05-10T13:37:20Z

Add a threshold callback function to the persistent data space map interface for a subsequent patch to use. dm-thin and dm-cache are interested in knowing when they're getting low on metadata or data blocks. This patch introduces a new method for registering a callback against a threshold. Signed-off-by: Joe Thornber Signed-off-by: Alasdair G Kergon

dm persistent data: remove debug space map checker

2012-07-27T14:07:58Z

Remove debug space map checker from dm persistent data. The space map checker is a wrapper for other space maps that double checks the reference counts are correct. It holds all these reference counts in memory rather than on disk, so uses a lot of memory and is thus restricted to small pools. As yet, this checker hasn't found any issues, but has caused a few of its own due to people turning it on by default with larger pools. Removing. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon

dm persistent data: handle space map checker creation failure

2012-07-03T11:55:35Z

If CONFIG_DM_DEBUG_SPACE_MAPS is enabled and dm_sm_checker_create() fails, dm_tm_create_internal() would still return success even though it cleaned up all resources it was supposed to have created. This will lead to a kernel crash: general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC ... RIP: 0010:[] [] dm_bufio_get_block_size+0x9/0x20 Call Trace: [] dm_bm_block_size+0xe/0x10 [] sm_ll_init+0x78/0xd0 [] sm_ll_new_disk+0x16/0xa0 [] dm_sm_disk_create+0xfe/0x160 [] dm_pool_metadata_open+0x16e/0x6a0 [] pool_ctr+0x3f0/0x900 [] dm_table_add_target+0x195/0x450 [] table_load+0xe4/0x330 [] ctl_ioctl+0x15a/0x2c0 [] dm_ctl_ioctl+0x13/0x20 [] do_vfs_ioctl+0x98/0x560 [] sys_ioctl+0x91/0xa0 [] system_call_fastpath+0x16/0x1b Fix the space map checker code to return an appropriate ERR_PTR and have dm_sm_disk_create() and dm_tm_create_internal() check for it with IS_ERR. Reported-by: Vivek Goyal Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org Signed-off-by: Alasdair G Kergon