Commit 7b19b8d45b (zram: Prevent overflow
in logical block size) introduced ZRAM_LOGICAL_BLOCK_SIZE constant to
prevent overflow of logical block size on 64k page kernel.
However, the current implementation of zram only allow operation on block
of the same size as a page. That makes theorically legit 4k requests fail
on 64k page kernel.
This patch makes zram allow operation on partial pages. Basically, it
means we still do operations on full pages internally, but only copy the
relevent segments from/to the user memory.
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
On a 64K page kernel, the value PAGE_SIZE passed to
blk_queue_logical_block_size would overflow the logical block size
argument (resulting in setting it to 0).
This patch sets the logical block size to 4096, using a new
ZRAM_LOGICAL_BLOCK_SIZE constant.
Signed-off-by: Robert Jennings <rcj@linux.vnet.ibm.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Currently, the user has to explicitly write a positive value to
initstate sysfs node before the device can be used. This event
triggers allocation of per-device metadata like memory pool,
table array and so on.
We do not pre-initialize all zram devices since the 'table' array,
mapping disk blocks to compressed chunks, takes considerable amount
of memory (8 bytes per page). So, pre-initializing all devices will
be quite wasteful if only few or none of the devices are actually
used.
This explicit device initialization from user is an odd requirement and
can be easily avoided. We now initialize the device when first write is
done to the device.
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Creates per-device sysfs nodes in /sys/block/zram<id>/
Currently following stats are exported:
- disksize
- num_reads
- num_writes
- invalid_io
- zero_pages
- orig_data_size
- compr_data_size
- mem_used_total
By default, disksize is set to 0. So, to start using
a zram device, fist write a disksize value and then
initialize device by writing any positive value to
initstate. For example:
# initialize /dev/zram0 with 50MB disksize
echo 50*1024*1024 | bc > /sys/block/zram0/disksize
echo 1 > /sys/block/zram0/initstate
When done using a disk, issue reset to free its memory
by writing any positive value to reset node:
echo 1 > /sys/block/zram0/reset
This change also obviates the need for 'rzscontrol' utility.
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Related changes:
- Modify revelant Kconfig and Makefile accordingly.
- Change include filenames in code.
- Remove dependency on CONFIG_SWAP in Kconfig as zram usage
is no longer limited to swap disks.
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Jerome Marchand