Hi Greg, Unfortunately we dont have a 3.9/3.10 environment here. So if IDR developers can try the example code, it should show if the bug is still present in there. Thanks.
--Shyam -----Original Message----- From: Greg KH [mailto:[email protected]] Sent: Tuesday, August 13, 2013 12:50 PM To: Shyam Kaushik Cc: Tejun Heo; Andrew Morton; [email protected] 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: > Hi Folks, > > We are using Ubuntu linux kernel 3.2.0-25-generic & 3.8.13-030813-generic > in our environments, but I think this bug is still present in mainline > kernel. Clients of IDR rollover at MAX_INT (NFSD & SCTP in kernel do this) > & others on MAX_IDR_MASK. This is ideally 2^31. But there is some BUG > within IDR that it wraps over at 2^30. > > NFSD uses IDR for maintaining its stateids & tracks min_stateid with a > static variable which keeps incrementing. So over a period of time NFSD > could run into the issue that it allocates an ID with IDR, but IDR cant > locate this ID, resulting in NFSD constantly sending BAD_STATEIDS to all > its clients. > > Following short driver (which closely resembles NFSD usage of IDR) shows > the BUG within IDR: The IDR code was rewritten very recently (3.9 or 3.10), so could you test 3.10.6 out and let us know if this is still an issue there? And if so, cc: the idr developers (on cc:) would help out a lot. Example left below for them... thanks, greg k-h > > #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; > > pr_info("%d\n", MAX_INT); > 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); > > > Upon loading the driver, the following message shows up > [71641.440846] Processing for min_stateid[0] > [71641.440857] Allocated new_stid[0] > [71641.440859] Dumping entries in IDR > [71641.440861] IDR Actual ID[0] == Expected Value[0] > [71641.440864] > [71641.440864] Processing for min_stateid[1073741823] > [71641.440867] Allocated new_stid[1073741823] > [71641.440868] Dumping entries in IDR > [71641.440876] IDR Actual ID[1073741823] == Expected Value[1073741823] > [71641.440878] > [71641.440878] Processing for min_stateid[1073741824] > [71641.440883] Allocated new_stid[1073741824] > [71641.440884] BUG: Cant find ID[1073741824] > [71641.440886] Dumping entries in IDR > [71641.440887] IDR Actual ID[0] != Expected Value[1073741824] > > i.e. when we allocate a stated==1073741824, IDR internally has it as 0. > > --Shyam > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2013.0.2904 / Virus Database: 3211/6571 - Release Date: 08/12/13 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
