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Message-ID: <CACQ1gAgz+nko3S4=KC=fAa8-V0gEchB05W6y1edOxYRmB9W0UQ@mail.gmail.com> Date: Fri, 1 Mar 2013 09:10:50 +0100 From: Richard Genoud <richard.genoud@...il.com> To: Brian Norris <computersforpeace@...il.com> Cc: "Velykokhatko, Sergey" <Sergey.Velykokhatko@...-med.de>, "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "artem.bityutskiy@...ux.intel.com" <artem.bityutskiy@...ux.intel.com> Subject: Re: Bug in mtd_get_device_size()? 2013/2/28 Brian Norris <computersforpeace@...il.com>: > + Richard > > On Thu, Feb 28, 2013 at 4:30 AM, Velykokhatko, Sergey > <Sergey.Velykokhatko@...-med.de> wrote: >> I got today such case: >> >> * Kernel 3.8 >> >> * We are using M29F2G16 NAND chip with 4096 blocks, each has 128k >> >> * Configured with CONFIG_MTD_UBI_BEB_LIMIT=100 > > This is your problem. See below for more comments. > >> * Our rootfs partition contains 640 EBs >> >> * At system start comes following error message: >> >> Feb 28 09:23:09 (none) kern.notice kernel: [ 0.375000] Creating 6 MTD >> partitions on "atmel_nand": >> >> Feb 28 09:23:09 (none) kern.notice kernel: [ 0.375000] >> 0x000000000000-0x000000020000 : "obsolete_bootstrap" >> >> Feb 28 09:23:09 (none) kern.notice kernel: [ 0.381000] >> 0x000000020000-0x000000320000 : "kernel_a" >> >> Feb 28 09:23:09 (none) kern.notice kernel: [ 0.386000] >> 0x000000320000-0x000000620000 : "kernel_b" >> >> Feb 28 09:23:09 (none) kern.notice kernel: [ 0.392000] >> 0x000000620000-0x000005620000 : "rootfs_a" >> >> Feb 28 09:23:09 (none) kern.notice kernel: [ 0.399000] >> 0x000005620000-0x00000a620000 : "rootfs_b" >> >> Feb 28 09:23:09 (none) kern.notice kernel: [ 0.406000] >> 0x00000a620000-0x000020000000 : "config_data" >> >> ... >> >> >> >> Feb 28 09:23:10 (none) kern.info kernel: [ 0.546000] NET: Registered >> protocol family 17 >> >> Feb 28 09:23:10 (none) kern.notice kernel: [ 0.557000] UBI: attaching >> mtd3 to ubi0 >> >> Feb 28 09:23:10 (none) kern.info kernel: [ 0.748000] usb 1-2: new >> high-speed USB device number 2 using atmel-ehci >> >> Feb 28 09:23:10 (none) kern.notice kernel: [ 0.810000] UBI: scanning is >> finished >> >> Feb 28 09:23:10 (none) kern.warn kernel: [ 0.821000] UBI warning: >> print_rsvd_warning: cannot reserve enough PEBs for bad PEB handling, >> reserved 115, need 400 >> >> Feb 28 09:23:10 (none) kern.notice kernel: [ 0.826000] UBI: attached mtd3 >> (name "rootfs_a", size 80 MiB) to ubi0 >> >> Feb 28 09:23:10 (none) kern.notice kernel: [ 0.826000] UBI: PEB size: >> 131072 bytes (128 KiB), LEB size: 129024 bytes >> >> Feb 28 09:23:10 (none) kern.notice kernel: [ 0.826000] UBI: min./max. I/O >> unit sizes: 2048/2048, sub-page size 512 >> >> Feb 28 09:23:10 (none) kern.notice kernel: [ 0.826000] UBI: VID header >> offset: 512 (aligned 512), data offset: 2048 >> >> Feb 28 09:23:10 (none) kern.notice kernel: [ 0.826000] UBI: good PEBs: >> 640, bad PEBs: 0, corrupted PEBs: 0 >> >> Feb 28 09:23:10 (none) kern.notice kernel: [ 0.826000] UBI: user volume: >> 1, internal volumes: 1, max. volumes count: 128 >> >> Feb 28 09:23:10 (none) kern.notice kernel: [ 0.826000] UBI: max/mean >> erase counter: 399/202, WL threshold: 4096, image sequence number: 548304255 >> >> Feb 28 09:23:10 (none) kern.notice kernel: [ 0.826000] UBI: available >> PEBs: 0, total reserved PEBs: 640, PEBs reserved for bad PEB handling: 115 >> >> Feb 28 09:23:10 (none) kern.notice kernel: [ 0.827000] UBI: background >> thread "ubi_bgt0d" started, PID 288 >> >> UBI wanted to reserve 400 blocks on MTD with 640. Hm... During debugging I >> found that mtd_get_device_size() gives the size of whole flash memory back >> (4096 blocks * 128kB). I guess that I found small error. With micro patch >> the problem seems to be corrected for my case > > Your patch is wrong, actually. mtd_get_device_size() should get "the > size of the entire flash chip", so if mtd is a partition, you *want* > to return the size of its 'master'. > > In fact, everything is behaving as expected (by the designers; not by > you). Because your BEB_LIMIT=100, you are reserving 100*size/1024 > (that is 9.8% of your total size, or 400 blocks) in *every* partition. > I don't see why you need that high of a limit, though. Check your NAND > data sheet, but the limit defaults reasonably to 20 (or, about 2%). > That would reserve only 80 blocks on your system, and you would not > see these warnings/errors, since you already have 115 blocks reserved. That's rigth ! There's also some documentation on how the overhead is calculated here : http://www.linux-mtd.infradead.org/doc/ubi.html#L_overhead and some more explanations a little bellow, in the "Reserved blocks for bad block handling" section > > You might want to read the comments in this commit: > > commit ba4087e956d336488c6df9dfca65d1e70cf480f1 > Author: Richard Genoud <richard.genoud@...il.com> > Date: Tue Jul 10 18:23:41 2012 +0200 > > UBI: use the whole MTD device size to get bad_peb_limit > > It might be worth revisiting the conclusions of those arguments; it > essentially limits your partitions to a certain minimum size. But as > far as I can tell, the code works as documented. > > Brian -- for me, ck means con kolivas and not calvin klein... does it mean I'm a geek ? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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