linux-toradex.git/drivers/md/dm-thin-metadata.h, branch v4.9.123

dm thin: fix a race condition between discarding and provisioning a block

2016-07-20T16:43:35+00:00

The discard passdown was being issued after the block was unmapped,
which meant the block could be reprovisioned whilst the passdown discard
was still in flight.

We can only identify unshared blocks (safe to do a passdown a discard
to) once they're unmapped and their ref count hits zero.  Block ref
counts are now used to guard against concurrent allocation of these
blocks that are being discarded.  So now we unmap the block, issue
passdown discards, and the immediately increment ref counts for regions
that have been discarded via passed down (this is safe because
allocation occurs within the same thread).  We then decrement ref counts
once the passdown discard IO is complete -- signaling these blocks may
now be allocated.

This fixes the potential for corruption that was reported here:
https://www.redhat.com/archives/dm-devel/2016-June/msg00311.html

Reported-by: Dennis Yang 
Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer

dm thin metadata: add dm_thin_remove_range()

2015-06-11T21:13:04+00:00

Removes a range of blocks from the btree.

Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer

dm thin metadata: add dm_thin_find_mapped_range()

2015-06-11T21:13:03+00:00

Retrieve the next run of contiguously mapped blocks.  Useful for working
out where to break up IO.

Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer

dm thin metadata: remove unused dm_pool_get_data_block_size()

2015-02-09T18:06:49+00:00

The thin-pool target doesn't display the data block size as part of
its table status, unlike the dm-cache target, so there is no need for
dm_pool_get_data_block_size().

This was found using cppcheck.

Signed-off-by: Rickard Strandqvist 
Signed-off-by: Mike Snitzer

dm thin: prefetch missing metadata pages

2014-11-10T20:25:27+00:00

Prefetch metadata at the start of the worker thread and then again every
128th bio processed from the deferred list.

Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer

dm thin metadata: change dm_thin_find_block to allow blocking, but not issuing, IO

2014-11-10T20:25:26+00:00

This change is a prerequisite for allowing metadata to be prefetched.

Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer

dm thin: ensure user takes action to validate data and metadata consistency

2014-03-05T20:25:35+00:00

If a thin metadata operation fails the current transaction will abort,
whereby causing potential for IO layers up the stack (e.g. filesystems)
to have data loss.  As such, set THIN_METADATA_NEEDS_CHECK_FLAG in the
thin metadata's superblock which:
1) requires the user verify the thin metadata is consistent (e.g. use
   thin_check, etc)
2) suggests the user verify the thin data is consistent (e.g. use fsck)

The only way to clear the superblock's THIN_METADATA_NEEDS_CHECK_FLAG is
to run thin_repair.

On metadata operation failure: abort current metadata transaction, set
pool in read-only mode, and now set the needs_check flag.

As part of this change, constraints are introduced or relaxed:
* don't allow a pool to transition to write mode if needs_check is set
* don't allow data or metadata space to be resized if needs_check is set
* if a thin pool's metadata space is exhausted: the kernel will now
  force the user to take the pool offline for repair before the kernel
  will allow the metadata space to be extended.

Also, update Documentation to include information about when the thin
provisioning target commits metadata, how it handles metadata failures
and running out of space.

Signed-off-by: Mike Snitzer 
Signed-off-by: Joe Thornber

dm thin: allow metadata space larger than supported to go unused

2014-02-27T16:49:08+00:00

It was always intended that a user could provide a thin metadata device
that is larger than the max supported by the on-disk format.  The extra
space would just go unused.

Unfortunately that never worked.  If the user attempted to use a larger
metadata device on creation they would get an error like the following:

 device-mapper: space map common: space map too large
 device-mapper: transaction manager: couldn't create metadata space map
 device-mapper: thin metadata: tm_create_with_sm failed
 device-mapper: table: 252:17: thin-pool: Error creating metadata object
 device-mapper: ioctl: error adding target to table

Fix this by allowing the initial metadata space map creation to cap its
size at the max number of blocks supported (DM_SM_METADATA_MAX_BLOCKS).
get_metadata_dev_size() must also impose DM_SM_METADATA_MAX_BLOCKS (via
THIN_METADATA_MAX_SECTORS), otherwise extending metadata would cap at
THIN_METADATA_MAX_SECTORS_WARNING (which is larger than supported).

Also, the calculation for THIN_METADATA_MAX_SECTORS didn't account for
the sizeof the disk_bitmap_header.  So the supported maximum metadata
size is a bit smaller (reduced from 33423360 to 33292800 sectors).

Lastly, remove the "excess space will not be used" warning message from
get_metadata_dev_size(); it resulted in printing the warning multiple
times.  Factor out warn_if_metadata_device_too_big(), call it from
pool_ctr() and maybe_resize_metadata_dev().

Signed-off-by: Mike Snitzer 
Acked-by: Joe Thornber

dm thin: avoid metadata commit if a pool's thin devices haven't changed

2014-02-17T16:00:05+00:00

Commit 905e51b ("dm thin: commit outstanding data every second")
introduced a periodic commit.  This commit occurs regardless of whether
any thin devices have made changes.

Fix the periodic commit to check if any of a pool's thin devices have
changed using dm_pool_changed_this_transaction().

Reported-by: Alexander Larsson 
Signed-off-by: Mike Snitzer 
Acked-by: Joe Thornber 
Cc: stable@vger.kernel.org

dm thin: use bool rather than unsigned for flags in structures

2014-01-07T15:14:18+00:00

Also, move 'err' member in dm_thin_new_mapping structure to eliminate 4
byte hole (reduces size from 88 bytes to 80).

Signed-off-by: Mike Snitzer 
Acked-by: Joe Thornber