dm array: fix cursor index when skipping across block boundaries

dm_array_cursor_skip() seeks to the target position by loading array
blocks iteratively until the specified number of entries to skip

dm array: fix cursor index when skipping across block boundaries

dm_array_cursor_skip() seeks to the target position by loading array
blocks iteratively until the specified number of entries to skip is
reached. When seeking across block boundaries, it uses
dm_array_cursor_next() to step into the next block.
dm_array_cursor_skip() must first move the cursor index to the end
of the current block; otherwise, the cursor position could incorrectly
remain in the same block, causing the actual number of skipped entries
to be much smaller than expected.

This bug affects cache resizing in v2 metadata and could lead to data
loss if the fast device is shrunk during the first-time resume. For
example:

1. create a cache metadata consists of 32768 blocks, with a dirty block
assigned to the second bitmap block. cache_restore v1.0 is required.

cat <<EOF >> cmeta.xml
<superblock uuid="" block_size="64" nr_cache_blocks="32768" \
policy="smq" hint_width="4">
<mappings>
<mapping cache_block="32767" origin_block="0" dirty="true"/>
</mappings>
</superblock>
EOF
dmsetup create cmeta --table "0 8192 linear /dev/sdc 0"
cache_restore -i cmeta.xml -o /dev/mapper/cmeta --metadata-version=2

2. bring up the cache while attempt to discard all the blocks belonging
to the second bitmap block (block# 32576 to 32767). The last command
is expected to fail, but it actually succeeds.

dmsetup create cdata --table "0 2084864 linear /dev/sdc 8192"
dmsetup create corig --table "0 65536 linear /dev/sdc 2105344"
dmsetup create cache --table "0 65536 cache /dev/mapper/cmeta \
/dev/mapper/cdata /dev/mapper/corig 64 2 metadata2 writeback smq \
2 migration_threshold 0"

In addition to the reproducer described above, this fix can be
verified using the "array_cursor/skip" tests in dm-unit:
dm-unit run /pdata/array_cursor/skip/ --kernel-dir <KERNEL_DIR>

Signed-off-by: Ming-Hung Tsai <[email protected]>
Fixes: 9b696229aa7d ("dm persistent data: add cursor skip functions to the cursor APIs")
Reviewed-by: Joe Thornber <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

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dm array: fix unreleased btree blocks on closing a faulty array cursor

The cached block pointer in dm_array_cursor might be NULL if it reaches
an unreadable array block, or the array is empty. There

dm array: fix unreleased btree blocks on closing a faulty array cursor

The cached block pointer in dm_array_cursor might be NULL if it reaches
an unreadable array block, or the array is empty. Therefore,
dm_array_cursor_end() should call dm_btree_cursor_end() unconditionally,
to prevent leaving unreleased btree blocks.

This fix can be verified using the "array_cursor/iterate/empty" test
in dm-unit:
dm-unit run /pdata/array_cursor/iterate/empty --kernel-dir <KERNEL_DIR>

Signed-off-by: Ming-Hung Tsai <[email protected]>
Fixes: fdd1315aa5f0 ("dm array: introduce cursor api")
Reviewed-by: Joe Thornber <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

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dm array: fix releasing a faulty array block twice in dm_array_cursor_end

When dm_bm_read_lock() fails due to locking or checksum errors, it
releases the faulty block implicitly while leaving an inv

dm array: fix releasing a faulty array block twice in dm_array_cursor_end

When dm_bm_read_lock() fails due to locking or checksum errors, it
releases the faulty block implicitly while leaving an invalid output
pointer behind. The caller of dm_bm_read_lock() should not operate on
this invalid dm_block pointer, or it will lead to undefined result.
For example, the dm_array_cursor incorrectly caches the invalid pointer
on reading a faulty array block, causing a double release in
dm_array_cursor_end(), then hitting the BUG_ON in dm-bufio cache_put().

Reproduce steps:

1. initialize a cache device

dmsetup create cmeta --table "0 8192 linear /dev/sdc 0"
dmsetup create cdata --table "0 65536 linear /dev/sdc 8192"
dmsetup create corig --table "0 524288 linear /dev/sdc $262144"
dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1
dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta \
/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0"

2. wipe the second array block offline

dmsteup remove cache cmeta cdata corig
mapping_root=$(dd if=/dev/sdc bs=1c count=8 skip=192 \
2>/dev/null | hexdump -e '1/8 "%u\n"')
ablock=$(dd if=/dev/sdc bs=1c count=8 skip=$((4096*mapping_root+2056)) \
2>/dev/null | hexdump -e '1/8 "%u\n"')
dd if=/dev/zero of=/dev/sdc bs=4k count=1 seek=$ablock

3. try reopen the cache device

dmsetup create cmeta --table "0 8192 linear /dev/sdc 0"
dmsetup create cdata --table "0 65536 linear /dev/sdc 8192"
dmsetup create corig --table "0 524288 linear /dev/sdc $262144"
dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta \
/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0"

Kernel logs:

(snip)
device-mapper: array: array_block_check failed: blocknr 0 != wanted 10
device-mapper: block manager: array validator check failed for block 10
device-mapper: array: get_ablock failed
device-mapper: cache metadata: dm_array_cursor_next for mapping failed
------------[ cut here ]------------
kernel BUG at drivers/md/dm-bufio.c:638!

Fix by setting the cached block pointer to NULL on errors.

In addition to the reproducer described above, this fix can be
verified using the "array_cursor/damaged" test in dm-unit:
dm-unit run /pdata/array_cursor/damaged --kernel-dir <KERNEL_DIR>

Signed-off-by: Ming-Hung Tsai <[email protected]>
Fixes: fdd1315aa5f0 ("dm array: introduce cursor api")
Reviewed-by: Joe Thornber <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

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dm: Constify struct dm_block_validator

'struct dm_block_validator' are not modified in these drivers.

Constifying this structure moves some data to a read-only section, so
increase overall security

dm: Constify struct dm_block_validator

'struct dm_block_validator' are not modified in these drivers.

Constifying this structure moves some data to a read-only section, so
increase overall security.

On a x86_64, with allmodconfig, as an example:

Before:
======
text data bss dec hex filename
32047 920 16 32983 80d7 drivers/md/dm-cache-metadata.o

After:
=====
text data bss dec hex filename
32075 896 16 32987 80db drivers/md/dm-cache-metadata.o

Signed-off-by: Christophe JAILLET <[email protected]>
Signed-off-by: Mikulas Patocka <[email protected]>

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dm: add missing blank line after declarations/fix those

Signed-off-by: Heinz Mauelshagen <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

dm: prefer '"%s...", __func__'

Signed-off-by: Heinz Mauelshagen <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

dm: add missing empty lines

Signed-off-by: Heinz Mauelshagen <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

dm: change "unsigned" to "unsigned int"

Signed-off-by: Heinz Mauelshagen <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

dm: add missing SPDX-License-Indentifiers

'GPL-2.0-only' is used instead of 'GPL-2.0' because SPDX has
deprecated its use.

Suggested-by: John Wiele <[email protected]>
Signed-off-by: Heinz Mauelsha

dm: add missing SPDX-License-Indentifiers

'GPL-2.0-only' is used instead of 'GPL-2.0' because SPDX has
deprecated its use.

Suggested-by: John Wiele <[email protected]>
Signed-off-by: Heinz Mauelshagen <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

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

When we break sharing on btree nodes we typically need to increment
the reference counts to every value held in the node. This ca

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

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 <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

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dm persistent data: add cursor skip functions to the cursor APIs

Signed-off-by: Joe Thornber <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

dm array: remove a dead assignment in populate_ablock_with_values()

A value is assigned to 'nr_entries' but is never used, remove it.

Signed-off-by: Bart Van Assche <[email protected]>
Sig

dm array: remove a dead assignment in populate_ablock_with_values()

A value is assigned to 'nr_entries' but is never used, remove it.

Signed-off-by: Bart Van Assche <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

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dm array: introduce cursor api

More efficient way to iterate an array due to prefetching (makes use of
the new dm_btree_cursor_* api).

Signed-off-by: Joe Thornber <[email protected]>
Signed-off-by: Mi

dm array: introduce cursor api

More efficient way to iterate an array due to prefetching (makes use of
the new dm_btree_cursor_* api).

Signed-off-by: Joe Thornber <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

show more ...

dm array: add dm_array_new()

dm_array_new() creates a new, populated array more efficiently than
starting with an empty one and resizing.

Signed-off-by: Joe Thornber <[email protected]>
Signed-off-by:

dm array: add dm_array_new()

dm_array_new() creates a new, populated array more efficiently than
starting with an empty one and resizing.

Signed-off-by: Joe Thornber <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

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dm persistent data: eliminate unnecessary return values

dm_bm_unlock and dm_tm_unlock return an integer value but the returned
value is always 0. The calling code sometimes checks the return value

dm persistent data: eliminate unnecessary return values

dm_bm_unlock and dm_tm_unlock return an integer value but the returned
value is always 0. The calling code sometimes checks the return value
and sometimes doesn't.

Eliminate these unnecessary return values and also the checks for them.

Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

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dm array: if resizing the array is a noop set the new root to the old one

This could've been quite bad (to return success but not update the new
root to point at the old) but in practice the only kn

dm array: if resizing the array is a noop set the new root to the old one

This could've been quite bad (to return success but not update the new
root to point at the old) but in practice the only known consumer of the
dm array code is the DM cache target. And the DM cache target passes in
the same old root to array_resize() anyway.

Signed-off-by: Joe Thornber <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

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dm array: fix a reference counting bug in shadow_ablock

An old array block could have its reference count decremented below
zero when it is being replaced in the btree by a new array block.

The fix

dm array: fix a reference counting bug in shadow_ablock

An old array block could have its reference count decremented below
zero when it is being replaced in the btree by a new array block.

The fix is to increment the old ablock's reference count just before
inserting a new ablock into the btree.

Signed-off-by: Joe Thornber <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
Cc: [email protected] # 3.9+

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dm array: fix bug in growing array

Entries would be lost if the old tail block was partially filled.

Signed-off-by: Joe Thornber <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
Cc

dm array: fix bug in growing array

Entries would be lost if the old tail block was partially filled.

Signed-off-by: Joe Thornber <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
Cc: [email protected] # 3.9+

show more ...

dm persistent data: add transactional array

Add a transactional array.

Signed-off-by: Joe Thornber <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>