linux-kernel - RE: BUG REPORT - IDR wraps around at 30-bits

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Date:	Tue, 13 Aug 2013 13:04:21 +0530
From:	Shyam Kaushik <shyam@...arastorage.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: RE: BUG REPORT - IDR wraps around at 30-bits - works very bad with NFSD/SCTP

Sorry I added this later, but realized I couldn’t compile.

Working version of the example is

#include <linux/module.h>
#include <linux/init.h>
#include <linux/version.h>
#include <linux/idr.h>

static int log_idr_entry(int id, void *ptr, void *data)
{
        int     *expected_val = (int *)ptr;

        pr_info("\tIDR Actual ID[%d] %s Expected Value[%d]\n", id, (id ==
*expected_val)?"==":"!=", *expected_val);
        return 0;
}

static void process_idr_entry(struct idr *stateids, int min_stateid)
{
        int             new_stid;
        int             error;

        pr_info("\nProcessing for min_stateid[%d]\n", min_stateid);
        if (!idr_pre_get(stateids, GFP_KERNEL)) {
                pr_info("Failed to pre-get\n");
                return;
        }

        error = idr_get_new_above(stateids, &new_stid, min_stateid,
&new_stid);
        if (error) {
                pr_info("Failed to get new id\n");
                idr_remove(stateids, new_stid);
                return;
        }

        pr_info("Allocated new_stid[%d]\n", new_stid);

        if (!idr_find(stateids, new_stid))
                pr_info("BUG: Cant find ID[%d]\n", new_stid);

        pr_info("Dumping entries in IDR\n");
        idr_for_each(stateids, &log_idr_entry, NULL);
        idr_remove(stateids, new_stid);
}

void driver_exit(void)
{
}

int driver_init(void)
{
        struct idr      stateids;

        idr_init(&stateids);
        process_idr_entry(&stateids, 0/*min_stateid*/);
        process_idr_entry(&stateids, 1073741823/*min_stateid*/);
        process_idr_entry(&stateids, 1073741824/*min_stateid*/);
        idr_remove_all(&stateids);
        idr_destroy(&stateids);
        return 0;
}

module_init(driver_init);
module_exit(driver_exit);

-----Original Message-----
From: Greg KH [mailto:gregkh@...uxfoundation.org]
Sent: Tuesday, August 13, 2013 1:03 PM
To: Shyam Kaushik
Cc: linux-kernel@...r.kernel.org
Subject: Re: BUG REPORT - IDR wraps around at 30-bits - works very bad
with NFSD/SCTP

On Tue, Aug 13, 2013 at 12:31:29PM +0530, Shyam Kaushik wrote:
>         pr_info("%d\n", MAX_INT);

How did this line build, there is no MAX_INT in the kernel tree.

odd.

greg k-h

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