Re: [PATCH 3/4] Staging: zram: allow partial page operations
From: Nitin Gupta
Date: Wed Jul 13 2011 - 23:20:48 EST
On 07/01/2011 02:47 AM, Jerome Marchand wrote:
On 06/10/2011 06:41 PM, Nitin Gupta wrote:
On 06/10/2011 06:28 AM, Jerome Marchand wrote:
Commit 7b19b8d45b216ff3186f066b31937bdbde066f08 (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.
Couldn't we just change struct queue_limits.logical_block_size type to
unsigned int or something so it could hold value of 64K? Then we could
avoid making all these changes to handle partial page requests.
I've finally done some tests. At least FAT filesystems are unable to cope
with 64k logical blocks. Probably some other fs are affected too. I we want
to support them, zram need to handle operation on partial pages.
Sorry for late reply.
If this is the case, we surely need partial page operations. I also
looked into these patches and they look good (though I've have not
tested them).
Thanks,
Nitin
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