linux-kernel - bitmap_find_free_region and bitmap

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Message-ID: <3a5b1be00611300733y121ef089m66bf46852ec0866d@mail.gmail.com>
Date:	Thu, 30 Nov 2006 17:33:35 +0200
From:	"Komal Shah" <komal.shah802003@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...l.org, lethal@...ux-sh.org
Subject: bitmap_find_free_region and bitmap_full arg doubts

Hi,

I was writing the test module, for layered bitmaps, specific to my
requirement such that I want to have control/track of 2GB virtual
address space. As per the discussion with Paul Mundt, I have taken the
approach of segmenting the virt. space with 128MB of blocks and then
to do find_next_zero_bit followed by bitmap_find_free_region on the
bitmaps.

I have attached the test module code. I have confusion about the what
to pass as second argument of bitmap_find_free_region for 2nd layer
bitmap.

Do we have to pass "total size of the block...here 128MB" as the
second argument or no. of bits in that block, which 32768 (128 >>
PAGE_SHIFT) ?

This confusion arised as store queue implementation (sq.c) of sh arch,
passes total size of the bitmap (64M) as the second argument instead
of bits.

Same is the case with bitmap_full, where I have to pass total size of
the block (here 128MB) instead of no. of bits, in-order it to make my
test module work correctly.

--
Link: sq.c
http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;h=7bcc73f9b8df535ad8887383aeac71a8b2491ef5;hb=0215ffb08ce99e2bb59eca114a99499a4d06e704;f=arch/sh/kernel/cpu/sh4/sq.c

-- 
---Komal Shah
http://komalshah.blogspot.com

View attachment "bitmap.c" of type "text/x-csrc" (2512 bytes)