On 2013/12/11 5:06, Yinghai Lu wrote: > On Tue, Dec 10, 2013 at 1:06 AM, Xishi Qiu <qiuxishi@xxxxxxxxxx> wrote: >> In the following case, e820_all_mapped() will return 1. >> A < start < B-1 and B < end < C, it means <start, end> spans two regions. >> <start, end>: [start - end] >> e820 addr: ...[A - B-1][B - C]... > > should be [start, end) right? > and > [A, B),[B, C) > Hi Yinghai, It is right, in this case the function will return 1. >> >> Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx> >> --- >> arch/x86/kernel/e820.c | 15 +++------------ >> 1 files changed, 3 insertions(+), 12 deletions(-) >> >> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c >> index 174da5f..31ecab2 100644 >> --- a/arch/x86/kernel/e820.c >> +++ b/arch/x86/kernel/e820.c >> @@ -85,20 +85,11 @@ int __init e820_all_mapped(u64 start, u64 end, unsigned type) >> >> if (type && ei->type != type) >> continue; >> - /* is the region (part) in overlap with the current region ?*/ >> + /* is the region (part) in overlap with the current region ? */ >> if (ei->addr >= end || ei->addr + ei->size <= start) >> continue; >> - >> - /* if the region is at the beginning of <start,end> we move >> - * start to the end of the region since it's ok until there >> - */ >> - if (ei->addr <= start) >> - start = ei->addr + ei->size; > > so in your case new start will be B ? > > next run will be C > >> - /* >> - * if start is now at or beyond end, we're done, full >> - * coverage >> - */ >> - if (start >= end) > > >> + /* is the region full coverage of <start, end> ? */ >> + if (ei->addr <= start && ei->addr + ei->size >= end) >> return 1; >> } >> return 0; > > also e820 should be sanitized already to have [A,C). > Yes, it should be sanitized already, but maybe someone will change the e820 to support some feature, so this function will be a potential bomb. > or you are talking about [A,B), [B+1, C) > first run start will be B, and next run with [B+1, ...), that will be > skipped... > will not return 1. > > so old code should be ok. > In this case, old code is right, but I discuss in another one that you wrote above. Thanks, Xishi Qiu > Thanks > > Yinghai > > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>