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Date: Mon, 23 Jul 2007 18:17:01 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Fengguang Wu <fengguang.wu@...il.com>
Cc: Nick Piggin <nickpiggin@...oo.com.au>,
Rusty Russell <rusty@...tcorp.com.au>,
Dave Jones <davej@...hat.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
linux-kernel <linux-kernel@...r.kernel.org>,
riel <riel@...hat.com>, Tim Pepper <lnxninja@...ibm.com>,
Chris Snook <csnook@...hat.com>,
Jens Axboe <jens.axboe@...cle.com>, linux-ext4@...r.kernel.org,
Mingming Cao <cmm@...ibm.com>,
Bjorn Helgaas <bjorn.helgaas@...com>,
Chris Ahna <christopher.j.ahna@...el.com>,
David Mosberger-Tang <davidm@....hp.com>,
Kyle McMartin <kyle@...isc-linux.org>,
Dave Jones <davej@...emonkey.org.uk>,
Dave Airlie <airlied@...ux.ie>
Subject: Re: [PATCH 0/3] readahead drop behind and size adjustment
On Tue, 24 Jul 2007 08:47:28 +0800
Fengguang Wu <fengguang.wu@...il.com> wrote:
> Subject: convert ill defined log2() to ilog2()
>
> It's *wrong* to have
> #define log2(n) ffz(~(n))
> It should be *reversed*:
> #define log2(n) flz(~(n))
> or
> #define log2(n) fls(n)
> or just use
> ilog2(n) defined in linux/log2.h.
>
> This patch follows the last solution, recommended by Andrew Morton.
>
> //Or are they simply the wrong naming, and is in fact correct in behavior?
>
> Cc: linux-ext4@...r.kernel.org
> Cc: Mingming Cao <cmm@...ibm.com>
> Cc: Bjorn Helgaas <bjorn.helgaas@...com>
> Cc: Chris Ahna <christopher.j.ahna@...el.com>
> Cc: David Mosberger-Tang <davidm@....hp.com>
> Cc: Kyle McMartin <kyle@...isc-linux.org>
> Signed-off-by: Fengguang Wu <wfg@...l.ustc.edu.cn>
> ---
> drivers/char/agp/hp-agp.c | 9 +++------
> drivers/char/agp/i460-agp.c | 5 ++---
> drivers/char/agp/parisc-agp.c | 7 ++-----
> fs/ext4/super.c | 6 ++----
> 4 files changed, 9 insertions(+), 18 deletions(-)
hm, yes, there is a risk that the code was accidentally correct. Or the
code has only ever dealt with power-of-2 inputs, in which case it happens
to work either way.
David(s) and ext4-people: could we please have a close review of these
changes?
Thanks.
> --- linux-2.6.22-rc6-mm1.orig/drivers/char/agp/hp-agp.c
> +++ linux-2.6.22-rc6-mm1/drivers/char/agp/hp-agp.c
> @@ -14,15 +14,12 @@
> #include <linux/pci.h>
> #include <linux/init.h>
> #include <linux/agp_backend.h>
> +#include <linux/log2.h>
>
> #include <asm/acpi-ext.h>
>
> #include "agp.h"
>
> -#ifndef log2
> -#define log2(x) ffz(~(x))
> -#endif
> -
> #define HP_ZX1_IOC_OFFSET 0x1000 /* ACPI reports SBA, we want IOC */
>
> /* HP ZX1 IOC registers */
> @@ -256,7 +253,7 @@ hp_zx1_configure (void)
> readl(hp->ioc_regs+HP_ZX1_IMASK);
> writel(hp->iova_base|1, hp->ioc_regs+HP_ZX1_IBASE);
> readl(hp->ioc_regs+HP_ZX1_IBASE);
> - writel(hp->iova_base|log2(HP_ZX1_IOVA_SIZE), hp->ioc_regs+HP_ZX1_PCOM);
> + writel(hp->iova_base|ilog2(HP_ZX1_IOVA_SIZE), hp->ioc_regs+HP_ZX1_PCOM);
> readl(hp->ioc_regs+HP_ZX1_PCOM);
> }
>
> @@ -284,7 +281,7 @@ hp_zx1_tlbflush (struct agp_memory *mem)
> {
> struct _hp_private *hp = &hp_private;
>
> - writeq(hp->gart_base | log2(hp->gart_size), hp->ioc_regs+HP_ZX1_PCOM);
> + writeq(hp->gart_base | ilog2(hp->gart_size), hp->ioc_regs+HP_ZX1_PCOM);
> readq(hp->ioc_regs+HP_ZX1_PCOM);
> }
>
> --- linux-2.6.22-rc6-mm1.orig/drivers/char/agp/i460-agp.c
> +++ linux-2.6.22-rc6-mm1/drivers/char/agp/i460-agp.c
> @@ -13,6 +13,7 @@
> #include <linux/string.h>
> #include <linux/slab.h>
> #include <linux/agp_backend.h>
> +#include <linux/log2.h>
>
> #include "agp.h"
>
> @@ -59,8 +60,6 @@
> */
> #define WR_FLUSH_GATT(index) RD_GATT(index)
>
> -#define log2(x) ffz(~(x))
> -
> static struct {
> void *gatt; /* ioremap'd GATT area */
>
> @@ -148,7 +147,7 @@ static int i460_fetch_size (void)
> * values[i].size.
> */
> values[i].num_entries = (values[i].size << 8) >> (I460_IO_PAGE_SHIFT - 12);
> - values[i].page_order = log2((sizeof(u32)*values[i].num_entries) >> PAGE_SHIFT);
> + values[i].page_order = ilog2((sizeof(u32)*values[i].num_entries) >> PAGE_SHIFT);
> }
>
> for (i = 0; i < agp_bridge->driver->num_aperture_sizes; i++) {
> --- linux-2.6.22-rc6-mm1.orig/drivers/char/agp/parisc-agp.c
> +++ linux-2.6.22-rc6-mm1/drivers/char/agp/parisc-agp.c
> @@ -18,6 +18,7 @@
> #include <linux/init.h>
> #include <linux/klist.h>
> #include <linux/agp_backend.h>
> +#include <linux/log2.h>
>
> #include <asm-parisc/parisc-device.h>
> #include <asm-parisc/ropes.h>
> @@ -27,10 +28,6 @@
> #define DRVNAME "quicksilver"
> #define DRVPFX DRVNAME ": "
>
> -#ifndef log2
> -#define log2(x) ffz(~(x))
> -#endif
> -
> #define AGP8X_MODE_BIT 3
> #define AGP8X_MODE (1 << AGP8X_MODE_BIT)
>
> @@ -92,7 +89,7 @@ parisc_agp_tlbflush(struct agp_memory *m
> {
> struct _parisc_agp_info *info = &parisc_agp_info;
>
> - writeq(info->gart_base | log2(info->gart_size), info->ioc_regs+IOC_PCOM);
> + writeq(info->gart_base | ilog2(info->gart_size), info->ioc_regs+IOC_PCOM);
> readq(info->ioc_regs+IOC_PCOM); /* flush */
> }
>
> --- linux-2.6.22-rc6-mm1.orig/fs/ext4/super.c
> +++ linux-2.6.22-rc6-mm1/fs/ext4/super.c
> @@ -1433,8 +1433,6 @@ static void ext4_orphan_cleanup (struct
> sb->s_flags = s_flags; /* Restore MS_RDONLY status */
> }
>
> -#define log2(n) ffz(~(n))
> -
> /*
> * Maximal file size. There is a direct, and {,double-,triple-}indirect
> * block limit, and also a limit of (2^32 - 1) 512-byte sectors in i_blocks.
> @@ -1706,8 +1704,8 @@ static int ext4_fill_super (struct super
> sbi->s_desc_per_block = blocksize / EXT4_DESC_SIZE(sb);
> sbi->s_sbh = bh;
> sbi->s_mount_state = le16_to_cpu(es->s_state);
> - sbi->s_addr_per_block_bits = log2(EXT4_ADDR_PER_BLOCK(sb));
> - sbi->s_desc_per_block_bits = log2(EXT4_DESC_PER_BLOCK(sb));
> + sbi->s_addr_per_block_bits = ilog2(EXT4_ADDR_PER_BLOCK(sb));
> + sbi->s_desc_per_block_bits = ilog2(EXT4_DESC_PER_BLOCK(sb));
> for (i=0; i < 4; i++)
> sbi->s_hash_seed[i] = le32_to_cpu(es->s_hash_seed[i]);
> sbi->s_def_hash_version = es->s_def_hash_version;
-
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