From: Coly Li <email@example.com> To: NeilBrown <firstname.lastname@example.org> Cc: email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, Dan Williams <firstname.lastname@example.org>, Hannes Reinecke <email@example.com>, Jens Axboe <firstname.lastname@example.org>, Richard Fan <email@example.com>, Vishal L Verma <firstname.lastname@example.org>, Greg Kroah-Hartman <email@example.com>, firstname.lastname@example.org Subject: Re: Too large badblocks sysfs file (was: [PATCH v3 0/7] badblocks improvement for multiple bad block ranges) Date: Thu, 23 Sep 2021 20:55:42 +0800 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <firstname.lastname@example.org> On 9/23/21 6:09 PM, NeilBrown wrote: > On Thu, 23 Sep 2021, Coly Li wrote: >> Hi all the kernel gurus, and folks in mailing lists, >> >> This is a question about exporting 4KB+ text information via sysfs >> interface. I need advice on how to handle the problem. Hi Neil, > Why do you think there is a problem? > As documented in Documentation/admin-guide/md.rst, the truncation at 1 > page is expected and by design. Oh, thanks for letting me know this. Yes this is as-designed, so I will not worry more about this. > > The "unacknowledge-bad-blocks" file is the important one that is needed > for correct behaviour. Being able to read a single block is sufficient, > though being able to read more than one could provide better performance > in some cases. > > The "bad-blocks" file primarily exist to provide visibility into the > state of the system - useful during development. It can be written to > to add bad blocks. I never *needs* to be read from. Thanks for the hint. > > The authoritative source of information about the set of bad blocks is > the on-disk data the can be and should be read directly... The reply is informative. It is more clear for me. Coly Li > > Except that mdadm does. That was a mistake. check_for_cleared_bb() is > wrong. I wonder why it was added. The commit message doesn't give any > justification. > > NeilBrown > > >> Recently I work on the bad blocks API (block/badblocks.c) improvement, >> there is a sysfs file to export the bad block ranges for me raid. E.g >> for a md raid1 device, file >> /sys/block/md0/md/rd0/bad_blocks >> may contain the following text content, >> 64 32 >> 128 8 >> The above lines mean there are two bad block ranges, one starts at LBA >> 64, length 32 sectors, another one starts at LBA 128 and length 8 >> sectors. All the content is generated from the internal bad block >> records with 512 elements. In my testing the worst case only 185 from >> 512 records can be displayed via the sysfs file if the LBA string is >> very long, e.g.the following content, >> 17668164135030776 512 >> 17668164135029776 512 >> 17668164135028776 512 >> 17668164135027776 512 >> ... ... >> The bad block ranges stored in internal bad blocks array are correct, >> but the output message is truncated. This is the problem I encountered. >> >> I don't see sysfs has seq_file support (correct me if I am wrong), and I >> know it is improper to transfer 4KB+ text via sysfs interface, but the >> code is here already for long time. >> >> There are 2 ideas to fix showing up in my brain, >> 1) Do not fix the problem >> Normally it is rare that a storage media has 100+ bad block ranges, >> maybe in real world all the existing bad blocks information won't exceed >> the page size limitation of sysfs file. >> 2) Add seq_file support to sysfs interface if there is no >> >> It is probably there is other better solution to fix. So I do want to >> get hint/advice from you. >> >> Thanks in advance for any comment :-) >> >> Coly Li >> >> On 9/14/21 12:36 AM, Coly Li wrote: >>> This is the second effort to improve badblocks code APIs to handle >>> multiple ranges in bad block table. >>> >>> There are 2 changes from previous version, >>> - Fixes 2 bugs in front_overwrite() which are detected by the user >>> space testing code. >>> - Provide the user space testing code in last patch. >>> >>> There is NO in-memory or on-disk format change in the whole series, all >>> existing API and data structures are consistent. This series just only >>> improve the code algorithm to handle more corner cases, the interfaces >>> are same and consistency to all existing callers (md raid and nvdimm >>> drivers). >>> >>> The original motivation of the change is from the requirement from our >>> customer, that current badblocks routines don't handle multiple ranges. >>> For example if the bad block setting range covers multiple ranges from >>> bad block table, only the first two bad block ranges merged and rested >>> ranges are intact. The expected behavior should be all the covered >>> ranges to be handled. >>> >>> All the patches are tested by modified user space code and the code >>> logic works as expected. The modified user space testing code is >>> provided in last patch. The testing code detects 2 defects in helper >>> front_overwrite() and fixed in this version. >>> >>> The whole change is divided into 6 patches to make the code review more >>> clear and easier. If people prefer, I'd like to post a single large >>> patch finally after the code review accomplished. >>> >>> This version is seriously tested, and so far no more defect observed. >>> >>> >>> Coly Li >>> >>> Cc: Dan Williams <email@example.com> >>> Cc: Hannes Reinecke <firstname.lastname@example.org> >>> Cc: Jens Axboe <email@example.com> >>> Cc: NeilBrown <firstname.lastname@example.org> >>> Cc: Richard Fan <email@example.com> >>> Cc: Vishal L Verma <firstname.lastname@example.org> >>> --- >>> Changelog: >>> v3: add tester Richard Fan <email@example.com> >>> v2: the improved version, and with testing code. >>> v1: the first completed version. >>> >>> >>> Coly Li (6): >>> badblocks: add more helper structure and routines in badblocks.h >>> badblocks: add helper routines for badblock ranges handling >>> badblocks: improvement badblocks_set() for multiple ranges handling >>> badblocks: improve badblocks_clear() for multiple ranges handling >>> badblocks: improve badblocks_check() for multiple ranges handling >>> badblocks: switch to the improved badblock handling code >>> Coly Li (1): >>> test: user space code to test badblocks APIs >>> >>> block/badblocks.c | 1599 ++++++++++++++++++++++++++++++------- >>> include/linux/badblocks.h | 32 + >>> 2 files changed, 1340 insertions(+), 291 deletions(-) >>> >>
prev parent reply other threads:[~2021-09-23 12:55 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-09-13 16:36 [PATCH v3 0/7] badblocks improvement for multiple bad block ranges Coly Li 2021-09-13 16:36 ` [PATCH v3 1/6] badblocks: add more helper structure and routines in badblocks.h Coly Li 2021-09-27 7:23 ` Geliang Tang 2021-09-27 8:23 ` Coly Li 2021-09-13 16:36 ` [PATCH v3 2/6] badblocks: add helper routines for badblock ranges handling Coly Li 2021-09-27 7:25 ` Geliang Tang 2021-09-27 8:17 ` Coly Li 2021-09-13 16:36 ` [PATCH v3 3/6] badblocks: improvement badblocks_set() for multiple " Coly Li 2021-09-27 7:30 ` Geliang Tang 2021-09-27 8:16 ` Coly Li 2021-09-13 16:36 ` [PATCH v3 4/6] badblocks: improve badblocks_clear() " Coly Li 2021-09-13 16:36 ` [PATCH v3 5/6] badblocks: improve badblocks_check() " Coly Li 2021-09-13 16:36 ` [PATCH v3 6/6] badblocks: switch to the improved badblock handling code Coly Li 2021-09-13 16:36 ` [PATCH] test: user space code to test badblocks APIs Coly Li 2021-09-23 5:59 ` Too large badblocks sysfs file (was: [PATCH v3 0/7] badblocks improvement for multiple bad block ranges) Coly Li 2021-09-23 6:08 ` Greg Kroah-Hartman 2021-09-23 6:14 ` Coly Li 2021-09-23 6:47 ` Greg Kroah-Hartman 2021-09-23 7:13 ` Coly Li 2021-09-23 9:40 ` Hannes Reinecke 2021-09-23 9:57 ` Greg Kroah-Hartman 2021-09-23 10:09 ` NeilBrown 2021-09-23 10:39 ` Greg Kroah-Hartman 2021-09-23 12:55 ` Coly Li [this message]
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