From: Greg KH <gregkh@suse.de>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org,
alan@lxorguk.ukuu.org.uk, Dmitry Torokhov <dtor@vmware.com>
Subject: [29/53] linux/log2.h: Fix rounddown_pow_of_two(1)
Date: Fri, 16 Dec 2011 11:45:26 -0800 [thread overview]
Message-ID: <20111216194558.749862947@clark.kroah.org> (raw)
In-Reply-To: <20111216194613.GA18395@kroah.com>
3.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Linus Torvalds <torvalds@linux-foundation.org>
commit 13c07b0286d340275f2d97adf085cecda37ede37 upstream.
Exactly like roundup_pow_of_two(1), the rounddown version was buggy for
the case of a compile-time constant '1' argument. Probably because it
originated from the same code, sharing history with the roundup version
from before the bugfix (for that one, see commit 1a06a52ee1b0: "Fix
roundup_pow_of_two(1)").
However, unlike the roundup version, the fix for rounddown is to just
remove the broken special case entirely. It's simply not needed - the
generic code
1UL << ilog2(n)
does the right thing for the constant '1' argment too. The only reason
roundup needed that special case was because rounding up does so by
subtracting one from the argument (and then adding one to the result)
causing the obvious problems with "ilog2(0)".
But rounddown doesn't do any of that, since ilog2() naturally truncates
(ie "rounds down") to the right rounded down value. And without the
ilog2(0) case, there's no reason for the special case that had the wrong
value.
tl;dr: rounddown_pow_of_two(1) should be 1, not 0.
Acked-by: Dmitry Torokhov <dtor@vmware.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
include/linux/log2.h | 1 -
1 file changed, 1 deletion(-)
--- a/include/linux/log2.h
+++ b/include/linux/log2.h
@@ -185,7 +185,6 @@ unsigned long __rounddown_pow_of_two(uns
#define rounddown_pow_of_two(n) \
( \
__builtin_constant_p(n) ? ( \
- (n == 1) ? 0 : \
(1UL << ilog2(n))) : \
__rounddown_pow_of_two(n) \
)
next prev parent reply other threads:[~2011-12-16 19:52 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-16 19:46 [00/53] 3.1.6-stable review Greg KH
2011-12-16 19:44 ` [01/53] ALSA: sis7019 - give slow codecs more time to reset Greg KH
2011-12-16 19:44 ` [02/53] ALSA: hda/realtek - Fix Oops in alc_mux_select() Greg KH
2011-12-16 19:45 ` [03/53] ALSA: hda - Fix GPIO LED setup for IDT 92HD75 codecs Greg KH
2011-12-16 19:45 ` [04/53] alarmtimers: Fix time comparison Greg KH
2011-12-16 19:45 ` [05/53] ARM: davinci: da850 evm: change audio edma event queue to EVENTQ_0 Greg KH
2011-12-16 19:45 ` [06/53] arm: mx23: recognise stmp378x as mx23 Greg KH
2011-12-16 19:45 ` [07/53] ARM: at91: fix clock conid for atmel_tcb.1 on 9260/9g20 Greg KH
2011-12-16 19:45 ` [08/53] ARM: at91: Fix USB AT91 gadget registration Greg KH
2011-12-16 19:45 ` [09/53] ARM: davinci: dm646x evm: wrong register used in setup_vpif_input_channel_mode Greg KH
2011-12-16 19:45 ` [10/53] ASoC: Provide a more complete DMA driver stub Greg KH
2011-12-16 19:45 ` [11/53] drivers/rtc/rtc-s3c.c: fix driver clock enable/disable balance issues Greg KH
2011-12-16 19:45 ` [12/53] fs/proc/meminfo.c: fix compilation error Greg KH
2011-12-16 19:45 ` [13/53] thp: add compound tail page _mapcount when mapped Greg KH
2011-12-16 19:45 ` [14/53] thp: set compound tail page _count to zero Greg KH
2011-12-16 19:45 ` [15/53] lockdep, kmemcheck: Annotate ->lock in lockdep_init_map() Greg KH
2011-12-16 19:45 ` [16/53] ptp: Fix clock_getres() implementation Greg KH
2011-12-16 19:45 ` [17/53] mm: Ensure that pfn_valid() is called once per pageblock when reserving pageblocks Greg KH
2011-12-16 19:45 ` [18/53] mm: vmalloc: check for page allocation failure before vmlist insertion Greg KH
2011-12-16 19:45 ` [19/53] fix apparmor dereferencing potentially freed dentry, sanitize __d_path() API Greg KH
2011-12-16 19:45 ` [20/53] TOMOYO: Fix pathname handling of disconnected paths Greg KH
2011-12-16 19:45 ` [21/53] target: Reject SCSI data overflow for fabrics using transport_generic_map_mem_to_cmd Greg KH
2011-12-16 19:45 ` [22/53] iscsi-target: Fix residual count hanlding + remove iscsi_cmd->residual_count Greg KH
2011-12-16 19:45 ` [23/53] target: Handle 0 correctly in transport_get_sectors_6() Greg KH
2011-12-16 19:45 ` [24/53] target: Fix page length in emulated INQUIRY VPD page 86h Greg KH
2011-12-16 19:45 ` [25/53] iscsi-target: Add missing F_BIT for iscsi_tm_rsp Greg KH
2011-12-16 19:45 ` [26/53] target/file: walk properly over sg list Greg KH
2011-12-16 19:45 ` [27/53] percpu: fix chunk range calculation Greg KH
2011-12-16 19:45 ` [28/53] cifs: check for NULL last_entry before calling cifs_save_resume_key Greg KH
2011-12-16 19:45 ` Greg KH [this message]
2011-12-16 19:45 ` [30/53] hwmon: (jz4740) fix signedness bug Greg KH
2011-12-16 19:45 ` [31/53] ARM: 7204/1: arch/arm/kernel/setup.c: initialize arm_dma_zone_size earlier Greg KH
2011-12-16 19:45 ` [32/53] mmc: mxcmmc: fix falling back to PIO Greg KH
2011-12-16 19:45 ` [33/53] xen/pm_idle: Make pm_idle be default_idle under Xen Greg KH
2011-12-16 19:45 ` [34/53] x86, hpet: Immediately disable HPET timer 1 if rtc irq is masked Greg KH
2011-12-16 19:45 ` [35/53] jbd/jbd2: validate sb->s_first in journal_get_superblock() Greg KH
2011-12-16 19:45 ` [36/53] hfs: fix hfs_find_init() sb->ext_tree NULL ptr oops Greg KH
2011-12-16 19:45 ` [37/53] drm/radeon/kms: cleanup atombios_adjust_pll() Greg KH
2011-12-16 19:45 ` [38/53] drm/radeon/kms: rework DP bridge checks Greg KH
2011-12-16 19:45 ` [39/53] drm/radeon/kms: fix DP setup on TRAVIS bridges Greg KH
2011-12-16 19:45 ` [40/53] xen: only limit memory map to maximum reservation for domain 0 Greg KH
2011-12-16 19:45 ` [41/53] ext4: fix ext4_end_io_dio() racing against fsync() Greg KH
2011-12-16 19:45 ` [42/53] ext4: display the correct mount option in /proc/mounts for [no]init_itable Greg KH
2011-12-16 19:45 ` [43/53] ext4: avoid hangs in ext4_da_should_update_i_disksize() Greg KH
2011-12-16 19:45 ` [44/53] ext4: avoid potential hang in mpage_submit_io() when blocksize < pagesize Greg KH
2011-12-16 19:45 ` [45/53] ext4: handle EOF correctly in ext4_bio_write_page() Greg KH
2011-12-16 19:45 ` [46/53] fuse: fix fuse_retrieve Greg KH
2011-12-16 19:45 ` [47/53] fuse: fix llseek bug Greg KH
2011-12-16 19:45 ` [48/53] staging: r8712u: Add new USB ID Greg KH
2011-12-16 19:45 ` [49/53] drm/radeon/kms: add some new pci ids Greg KH
2011-12-16 19:45 ` [50/53] ibft: Fix finding IBFT ACPI table on UEFI Greg KH
2011-12-16 19:45 ` [51/53] USB: cdc-acm: add IDs for Motorola H24 HSPA USB module Greg KH
2011-12-16 19:45 ` [52/53] usb: option: Add Huawei E398 controlling interfaces Greg KH
2011-12-16 19:45 ` [53/53] USB: option: Removing one bogus and adding some new Huawei combinations Greg KH
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