* Re: [Bug 2995] New: madvise runs sucessfully for non-file mapped pages
[not found] <200407011338.i61DcD1B011203@fire-2.osdl.org>
@ 2004-07-02 21:42 ` Andrew Morton
0 siblings, 0 replies; only message in thread
From: Andrew Morton @ 2004-07-02 21:42 UTC (permalink / raw)
To: susharma; +Cc: linux-mm
Unless this is very new behaviour, I don't think we can fix this until 2.7. Changing
madvise's behaviour against anonymous memory addresses could break existing
applications.
bugme-daemon@osdl.org wrote:
>
> http://bugme.osdl.org/show_bug.cgi?id=2995
>
> Summary: madvise runs sucessfully for non-file mapped pages.
> Kernel Version: 2.6.5-7.81
> Status: NEW
> Severity: high
> Owner: akpm@digeo.com
> Submitter: susharma@in.ibm.com
>
>
> Distribution: SLES-9 [RC-2]
> Hardware Environment: x330, 2-Way, 1.0 GHz, 1.2 GB RAM
> Software Environment: SLES-9 [RC-2], Kernel - 2.6.5-7.81
> Problem Description: When you call madvise for a memory mapped area (allocated using
> malloc) which is not part of any file, it gets PASSED without giving EBADF error.
>
> Steps to reproduce:
> 1. Write a small program, in which allocate some memory (eg. 5 pages) like this :-
>
> char *ptr=NULL;
> ptr = (char *) malloc(5 * PAGE_SIZE);
>
> Now, call madvise for this malloced memory area (which is a part of any file) :-
>
> ptr = (char *)(((int) ptr + PAGE_SIZE-1) & ~(PAGE_SIZE-1)); // Alignment
> if (madvise(ptr, 5 * PAGE_SIZE, MADV_NORMAL) < 0)
> {
> perror("madvise failed");
> }
> else
> {
> printf("madvise passed\n");
> }
>
> Here, if you run this code you will find that madvise is getting PASSED even when you have
> passed a memory area which is nowhere a part of file-mapped area. Actually, it should give
> error with error code EBADF.
>
> Additional Information : Please refer to the manpage of madvise for the condition when EBADF
> error code should be generated.
>
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