| Message ID | 1305751647-3122-1-git-send-email-bengardiner@nanometrics.ca |
|---|---|
| State | New, archived |
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On Wed, May 18, 2011 at 4:47 PM, Ben Gardiner <bengardiner@nanometrics.ca> wrote: > + /* > + * Don't fail on -EBADMSG since these are precisely the error codes that > + * are returned by ubi_red in the cases where free-space fix-ups are > + * required. > + */ Hi Ben, Off-hand, I don't see how this comment can be true. It seems like we'll have 2 cases: 1. The pages in question are actually erased, in which case they'll be 0xff-filled by ubi_read() without error, or 2. The pages were programmed with all 0xff data, in which case the ECC info should be correct There's a third possibility, that the ECC info is bad because there's a real error, but that's not something we can reliably recover from. Am I overlooking another scenario?
Hi Matthew, On Wed, May 18, 2011 at 5:41 PM, Matthew L. Creech <mlcreech@gmail.com> wrote: > On Wed, May 18, 2011 at 4:47 PM, Ben Gardiner > <bengardiner@nanometrics.ca> wrote: >> + /* >> + * Don't fail on -EBADMSG since these are precisely the error codes that >> + * are returned by ubi_red in the cases where free-space fix-ups are >> + * required. >> + */ > > Hi Ben, > > Off-hand, I don't see how this comment can be true. It seems like > we'll have 2 cases: > > 1. The pages in question are actually erased, in which case they'll be > 0xff-filled by ubi_read() without error, or > 2. The pages were programmed with all 0xff data, in which case the ECC > info should be correct > > There's a third possibility, that the ECC info is bad because there's > a real error, but that's not something we can reliably recover from. > Am I overlooking another scenario? Perhaps I am running into a nuance of the davinci nand driver. Back when you started the 'Programming ubinized images' thread [1] some of you problem description caught me eye: On Mon, Apr 25, 2011 at 2:37 PM, Matthew L. Creech <mlcreech@gmail.com> wrote: > We encountered one case in which we were re-flashing a device for > testing using U-Boot's "nand erase", and got the "ubi_io_read: error > -74" error from the FAQ. That's no big deal, since we never do this > in the field, and clearly "nand erase" isn't something we'd want to do > even without this problem since it loses erase-counter info. Because the "ubi_io_read: error -74 (ECC error)" is precisely what I am encountering on my hardware when I do not flash with a utility that drops empty pages at the end of eraseblocks. I imagined that this was also the case for you. But I have also read that there are peculiarities of the davinci nand driver (both in u-boot and linux). So, at least on my hardware, the -74 error is expected when the 0xff pages are not dropped and so without the 'err != -EBADMSG' exception the free space fixup will cause the volume to fail mount for me: UBIFS: start fixing up free space UBI error: ubi_io_read: error -74 (ECC error) while reading 4096 bytes from PEB 18:4096, read 4096 bytes VFS: Cannot open root device "ubi0:rootfs" or unknown-block(0,0) [...] Whereas, when the same image is flashed using a u-boot 'nand write' variant that drops 0xff pages [2] there are no such -74 errors encountered. UBIFS: start fixing up free space UBIFS: free space fixup complete UBIFS: mounted UBI device 0, volume 1, name "rootfs" [...] The nand I am using is the micron part that ships with the da850evm; it has eraseblocks of 128KiB and pages of 2048. Here is a dump of eraseblock 18 from the ubinized image: 00240000 55 42 49 23 01 00 00 00 00 00 00 00 00 00 00 00 |UBI#............| 00240010 00 00 08 00 00 00 10 00 04 6c 24 45 00 00 00 00 |.........l$E....| 00240020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 00240030 00 00 00 00 00 00 00 00 00 00 00 00 38 be e8 75 |............8..u| 00240040 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................| * 00240800 55 42 49 21 01 01 00 00 00 00 00 01 00 00 00 01 |UBI!............| 00240810 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00240830 00 00 00 00 00 00 00 00 00 00 00 00 5f 7f ac 08 |............_...| 00240840 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................| * 00241000 31 18 10 06 5f 3f 84 94 65 32 01 00 00 00 00 00 |1..._?..e2......| 00241010 00 02 00 00 07 00 00 00 53 2a 00 00 00 00 00 00 |........S*......| 00241020 00 00 00 00 00 00 00 00 02 00 00 00 03 00 00 00 |................| 00241030 f0 01 00 00 e0 8a 01 00 44 00 00 00 e3 01 00 00 |........D.......| 00241040 f0 01 00 00 00 90 01 00 b0 c7 18 00 00 00 00 00 |................| 00241050 00 18 05 00 00 00 00 00 00 49 05 00 00 00 00 00 |.........I......| 00241060 50 77 8a 03 00 00 00 00 78 fc 04 00 00 00 00 00 |Pw......x.......| 00241070 78 b8 01 00 00 00 00 00 08 00 00 00 12 0a 00 00 |x...............| 00241080 08 00 00 00 00 10 00 00 08 00 00 00 1e 0a 00 00 |................| 00241090 00 00 00 00 00 00 00 00 0b 00 00 00 01 00 00 00 |................| 002410a0 0d 00 00 00 f1 01 00 00 00 00 00 00 00 00 00 00 |................| 002410b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00241200 31 18 10 06 ef de 0e ee 00 00 00 00 00 00 00 00 |1...............| 00241210 1c 00 00 00 05 00 00 00 e4 05 00 00 00 00 00 00 |................| 00241220 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00241800 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................| * 00260000 55 42 49 23 01 00 00 00 00 00 00 00 00 00 00 00 |UBI#............| 00260010 00 00 08 00 00 00 10 00 04 6c 24 45 00 00 00 00 |.........l$E....| 00260020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 00260030 00 00 00 00 00 00 00 00 00 00 00 00 38 be e8 75 |............8..u| 00260040 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................| * 00260800 55 42 49 21 01 01 00 00 00 00 00 01 00 00 00 02 |UBI!............| [...] The data between 0x00241800 and 0x00260000 is all 0xff, so there are trailing empty pages in this block. Here is a u-boot nand-dump of eraseblock 18 + 0x1800 when flashed using the usual u-boot 'nand write': ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff [...] ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff OOB: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 3f 27 56 f5 29 d8 61 d9 9d 14 3f 27 56 f5 29 d8 61 d9 9d 14 3f 27 56 f5 29 d8 61 d9 9d 14 3f 27 56 f5 29 d8 61 d9 9d 14 and here it is again when flashed with the 'nand write' variant that drops 0xff pages [2]: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff [...] ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff OOB: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff The former state of eraseblock 18 causes "ubi_io_read: error -74 (ECC error)" during free-space-fixup and the latter does not. So I guess my particular situation is a problem with the davinci nand driver's ECC for 0xFF data and is _not_ covered by the free space fixup? It would be really nice if the free space fixup supported both 1) setups that are such that the flash cannot be written to more than once and 2) setups that are such that they return bogus -74 errors. Both are caused by not dropping trailing 0xff pages when writing. Best Regards, Ben Gardiner [1] http://article.gmane.org/gmane.linux.drivers.mtd/34890 [2] http://article.gmane.org/gmane.comp.boot-loaders.u-boot/98740 --- Nanometrics Inc. http://www.nanometrics.ca
On Thu, May 19, 2011 at 9:28 AM, Ben Gardiner <bengardiner@nanometrics.ca> wrote: > > So I guess my particular situation is a problem with the davinci nand > driver's ECC for 0xFF data and is _not_ covered by the free space > fixup? > Yeah, that's what it sounds like. Can you reproduce the -EBADMSG with a simpler test case that leaves UBI/UBIFS out of the equation? Maybe enable write-verify in U-Boot and try using "nand write" again, or use mtd-utils "nandwrite" from an initramfs image then try to read back the data -- that should give a simpler test case that shows whether the ECC handling of empty space is wrong. If so, that probably needs to be fixed at the MTD level, since it will affect more than this particular UBIFS case.
[Rmoving Adiran Hunter from CC - he's left Nokia and his e-mail does not work anyway] Hi, On Thu, 2011-05-19 at 09:28 -0400, Ben Gardiner wrote: > On Mon, Apr 25, 2011 at 2:37 PM, Matthew L. Creech <mlcreech@gmail.com> wrote: > > We encountered one case in which we were re-flashing a device for > > testing using U-Boot's "nand erase", and got the "ubi_io_read: error > > -74" error from the FAQ. That's no big deal, since we never do this > > in the field, and clearly "nand erase" isn't something we'd want to do > > even without this problem since it loses erase-counter info. > > Because the "ubi_io_read: error -74 (ECC error)" is precisely what I > am encountering on my hardware when I do not flash with a utility that > drops empty pages at the end of eraseblocks. I imagined that this was > also the case for you. But I have also read that there are > peculiarities of the davinci nand driver (both in u-boot and linux). > > So, at least on my hardware, the -74 error is expected when the 0xff > pages are not dropped and so without the 'err != -EBADMSG' exception > the free space fixup will cause the volume to fail mount for me: I am confused. The fix Matthew made is about the following situation: 1. You have completely erased flash (MTD partition) - no one has ever written there. If you now read the flash, you'll get all 0xFFs with no errors. 2. You use a "dumb" flasher to program an UBI image. This flasher will write empty NAND pages "as is". If you now read the flash after the "dumb" programming, you should have no errors. 3. You mount UBIFS for the very first time. It tries to fix up your flash. Whatever eraseblock UBIFS reads, it should not encounter any error. Isn't it weird that a freshly programmed flash cannot be read without -EBADMSG (ECC correction failure). Why Matthew's patches are needed then? They are needed to _prevent_ UBIFS from writing to the NAND pages which have been programmed with all 0xFFs.
On Thu, 2011-05-19 at 09:28 -0400, Ben Gardiner wrote: > So, at least on my hardware, the -74 error is expected when the 0xff > pages are not dropped and so without the 'err != -EBADMSG' exception > the free space fixup will cause the volume to fail mount for me: Still confused. If you have empty and erased flash, then you program it with all 0xFFs, you should be able to read it with no errors. If this is not the case for you, you should fix the driver. UBIFS cannot help in this case - we consider it as "broken flash driver" case. I have not read your e-mail carefully because of limited amount of time, but with quick reading I became confused - too much information :-)
Hi Artem, On Fri, May 20, 2011 at 2:21 AM, Artem Bityutskiy <dedekind1@gmail.com> wrote: > On Thu, 2011-05-19 at 09:28 -0400, Ben Gardiner wrote: >> [...] >> >> Because the "ubi_io_read: error -74 (ECC error)" is precisely what I >> am encountering on my hardware when I do not flash with a utility that >> drops empty pages at the end of eraseblocks. I imagined that this was >> also the case for you. But I have also read that there are >> peculiarities of the davinci nand driver (both in u-boot and linux). >> >> So, at least on my hardware, the -74 error is expected when the 0xff >> pages are not dropped and so without the 'err != -EBADMSG' exception >> the free space fixup will cause the volume to fail mount for me: > > I am confused. The fix Matthew made is about the following situation: Sorry for the confusion. In the first 'Programming ubinized images' thread I saw that Matthew mentioned seeing lots of -74 errors so I was assuming that his and my problems are one and the same. Now that I have tested his patch I am seeing that this is not the case. > 1. You have completely erased flash (MTD partition) - no one has ever > written there. If you now read the flash, you'll get all 0xFFs with no > errors. > > 2. You use a "dumb" flasher to program an UBI image. This flasher will > write empty NAND pages "as is". If you now read the flash after the > "dumb" programming, you should have no errors. > > 3. You mount UBIFS for the very first time. It tries to fix up your > flash. Whatever eraseblock UBIFS reads, it should not encounter any > error. Yes I agree with the context for the patch. I can say so far that on da850evm 1. occurs as you described whereas for 2. and 3. ECC errors are encountered on read. > Isn't it weird that a freshly programmed flash cannot be read without > -EBADMSG (ECC correction failure). Yes it is very weird. :) I had been assuming up to this point that the -74 errors were the result of writing the 0xff pages when they should be dropped. I can see now that this is not the case. On Fri, May 20, 2011 at 2:29 AM, Artem Bityutskiy <dedekind1@gmail.com> wrote: > On Thu, 2011-05-19 at 09:28 -0400, Ben Gardiner wrote: >> So, at least on my hardware, the -74 error is expected when the 0xff >> pages are not dropped and so without the 'err != -EBADMSG' exception >> the free space fixup will cause the volume to fail mount for me: > > Still confused. If you have empty and erased flash, then you program it > with all 0xFFs, you should be able to read it with no errors. Right. In retrospect this seems to be a self-evident statement :) I had been previously attributing the -74 errors to a combination of 1) writing 0xff pages when one should not and 2) lack of subpage writing support workaround with -O 2048. But it is clearly (to me now) a reading operation failure. > If this is > not the case for you, you should fix the driver. UBIFS cannot help in > this case - we consider it as "broken flash driver" case. Thank you. Yes, this appears to be the case and I'm glad to hear confirmation of this from an expert such as yourself. > I have not read your e-mail carefully because of limited amount of time, > but with quick reading I became confused - too much information :-) No problem. Thank you very much for what you have read and for your insights into the ongoing NAND flash problems on da850evm. Best Regards, Ben Gardiner --- Nanometrics Inc. http://www.nanometrics.ca
diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c index c606f01..6e7da54 100644 --- a/fs/ubifs/sb.c +++ b/fs/ubifs/sb.c @@ -1,3 +1,4 @@ +#define DEBUG /* * This file is part of UBIFS. * @@ -679,7 +680,12 @@ static int fixup_leb(struct ubifs_info *c, int lnum, int len) dbg_mnt("fixup LEB %d, data len %d", lnum, len); err = ubi_read(c->ubi, lnum, c->sbuf, 0, len); - if (err) + /* + * Don't fail on -EBADMSG since these are precisely the error codes that + * are returned by ubi_red in the cases where free-space fix-ups are + * required. + */ + if (err && err != -EBADMSG) return err; return ubi_leb_change(c->ubi, lnum, c->sbuf, len, UBI_UNKNOWN);
The free space fixup was introduced so that UBIFS on NAND flashes where the empty pages at the end need to be dropped when flashing or else -74 (aka -EBADMSG) failures will occur -- but due to the limited functionality of flash-programming facilities the emtpy pages cannot be dropped. In fixup_leb, which is called during free space fixup, the now-expected return code of -EBADMSG is treated as a failure. Don't fail when -EBADMSG is encountered during ubi_read. Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca> CC: Matthew L. Creech <mlcreech@gmail.com> --- I tested this patch on-top-of l2 head : 'bbf2b37 UBIFS: fix extremely rare mount failure' using Matthew's 'mkfs.ubifs: add "-F" option for "free-space fixup"' patch to create the UBIFS image with the flag set. The test system was a da850evm, the image was flashed with U-boot's plain-old 'nand write' and the rootfs is mounted with 'ubi.mtd=X,2048 root=ubi0:rootfs rootfstype=ubifs' bootargs. Without this patch the first attemp to start fixing free space fails with -EBADMSG: UBIFS: start fixing up free space UBI error: ubi_io_read: error -74 (ECC error) while reading 4096 bytes from PEB 18:4096, read 4096 bytes VFS: Cannot open root device "ubi0:rootfs" or unknown-block(0,0) [...] --- fs/ubifs/sb.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-)