linux-toradex.git/drivers/md/dm-core.h, branch v6.11

dm: optimize flushes

2024-06-26T15:32:39+00:00

Device mapper sends flush bios to all the targets and the targets send it
to the underlying device. That may be inefficient, for example if a table
contains 10 linear targets pointing to the same physical device, then
device mapper would send 10 flush bios to that device - despite the fact
that only one bio would be sufficient.

This commit optimizes the flush behavior. It introduces a per-target
variable flush_bypasses_map - it is set when the target supports flush
optimization - currently, the dm-linear and dm-stripe targets support it.
When all the targets in a table have flush_bypasses_map,
flush_bypasses_map on the table is set. __send_empty_flush tests if the
table has flush_bypasses_map - and if it has, no flush bios are sent to
the targets via the "map" method and the list dm_table->devices is
iterated and the flush bios are sent to each member of the list.

Signed-off-by: Mikulas Patocka 
Reviewed-by: Mike Snitzer 
Suggested-by: Yang Yang

block: move integrity information into queue_limits

2024-06-14T16:20:07+00:00

Move the integrity information into the queue limits so that it can be
set atomically with other queue limits, and that the sysfs changes to
the read_verify and write_generate flags are properly synchronized.
This also allows to provide a more useful helper to stack the integrity
fields, although it still is separate from the main stacking function
as not all stackable devices want to inherit the integrity settings.
Even with that it greatly simplifies the code in md and dm.

Note that the integrity field is moved as-is into the queue limits.
While there are good arguments for removing the separate blk_integrity
structure, this would cause a lot of churn and might better be done at a
later time if desired.  However the integrity field in the queue_limits
structure is now unconditional so that various ifdefs can be avoided or
replaced with IS_ENABLED().  Given that tiny size of it that seems like
a worthwhile trade off.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Hannes Reinecke 
Reviewed-by: Martin K. Petersen 
Link: https://lore.kernel.org/r/20240613084839.1044015-13-hch@lst.de
Signed-off-by: Jens Axboe

dm: Use the block layer zone append emulation

2024-04-17T14:44:03+00:00

For targets requiring zone append operation emulation with regular
writes (e.g. dm-crypt), we can use the block layer emulation provided by
zone write plugging. Remove DM implemented zone append emulation and
enable the block layer one.

This is done by setting the max_zone_append_sectors limit of the
mapped device queue to 0 for mapped devices that have a target table
that cannot support native zone append operations (e.g. dm-crypt).
Such mapped devices are flagged with the DMF_EMULATE_ZONE_APPEND flag.
dm_split_and_process_bio() is modified to execute
blk_zone_write_plug_bio() for such device to let the block layer
transform zone append operations into regular writes.  This is done
after ensuring that the submitted BIO is split if it straddles zone
boundaries. Both changes are implemented unsing the inline helpers
dm_zone_write_plug_bio() and dm_zone_bio_needs_split() respectively.

dm_revalidate_zones() is also modified to use the block layer provided
function blk_revalidate_disk_zones() so that all zone resources needed
for zone append emulation are initialized by the block layer without DM
core needing to do anything. Since the device table is not yet live when
dm_revalidate_zones() is executed, enabling the use of
blk_revalidate_disk_zones() requires adding a pointer to the device
table in struct mapped_device. This avoids errors in
dm_blk_report_zones() trying to get the table with dm_get_live_table().
The mapped device table pointer is set to the table passed as argument
to dm_revalidate_zones() before calling blk_revalidate_disk_zones() and
reset to NULL after this function returns to restore the live table
handling for user call of report zones.

All the code related to zone append emulation is removed from
dm-zone.c. This leads to simplifications of the functions __map_bio()
and dm_zone_endio(). This later function now only needs to deal with
completions of real zone append operations for targets that support it.

Signed-off-by: Damien Le Moal 
Reviewed-by: Mike Snitzer 
Reviewed-by: Hannes Reinecke 
Tested-by: Hans Holmberg 
Tested-by: Dennis Maisenbacher 
Reviewed-by: Martin K. Petersen 
Link: https://lore.kernel.org/r/20240408014128.205141-13-dlemoal@kernel.org
Signed-off-by: Jens Axboe

dm: limit the number of targets and parameter size area

2024-01-30T19:05:02+00:00

The kvmalloc function fails with a warning if the size is larger than
INT_MAX. The warning was triggered by a syscall testing robot.

In order to avoid the warning, this commit limits the number of targets to
1048576 and the size of the parameter area to 1073741824.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm: fix a race condition in retrieve_deps

2023-09-14T15:18:29+00:00

There's a race condition in the multipath target when retrieve_deps
races with multipath_message calling dm_get_device and dm_put_device.
retrieve_deps walks the list of open devices without holding any lock
but multipath may add or remove devices to the list while it is
running. The end result may be memory corruption or use-after-free
memory access.

See this description of a UAF with multipath_message():
https://listman.redhat.com/archives/dm-devel/2022-October/052373.html

Fix this bug by introducing a new rw semaphore "devices_lock". We grab
devices_lock for read in retrieve_deps and we grab it for write in
dm_get_device and dm_put_device.

Reported-by: Luo Meng 
Signed-off-by: Mikulas Patocka 
Cc: stable@vger.kernel.org
Tested-by: Li Lingfeng 
Signed-off-by: Mike Snitzer

dm: support turning off block-core's io stats accounting

2023-06-16T22:24:13+00:00

Commit bc58ba9468d9 ("block: add sysfs file for controlling io stats
accounting") allowed users to turn off disk stat accounting completely
by checking if queue flag QUEUE_FLAG_IO_STAT is set. In dm, this flag
is neither set nor checked: so block-core's io stats are continuously
counted and cannot be turned off.

Add support for turning off block-core's io stats accounting for dm.
Set QUEUE_FLAG_IO_STAT for dm's request_queue. If QUEUE_FLAG_IO_STAT
is set when an io starts, record the need for block core's io stats by
setting the DM_IO_BLK_STAT dm_io flag to avoid io stats being disabled
in the middle of the io.

DM statistics (dm-stats) is independent of block-core's io stats and
remains unchanged.

Signed-off-by: Li Nan 
Signed-off-by: Mike Snitzer

block: replace fmode_t with a block-specific type for block open flags

2023-06-12T14:04:05+00:00

The only overlap between the block open flags mapped into the fmode_t and
other uses of fmode_t are FMODE_READ and FMODE_WRITE.  Define a new
blk_mode_t instead for use in blkdev_get_by_{dev,path}, ->open and
->ioctl and stop abusing fmode_t.

Signed-off-by: Christoph Hellwig 
Acked-by: Jack Wang 		[rnbd]
Reviewed-by: Hannes Reinecke 
Reviewed-by: Christian Brauner 
Link: https://lore.kernel.org/r/20230608110258.189493-28-hch@lst.de
Signed-off-by: Jens Axboe

dm: add argument identifier names

2023-02-14T19:23:06+00:00

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Mike Snitzer

dm: change "unsigned" to "unsigned int"

2023-02-14T19:23:06+00:00

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Mike Snitzer

dm: add missing SPDX-License-Indentifiers

2023-02-14T19:23:06+00:00

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

Suggested-by: John Wiele 
Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Mike Snitzer