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    SubjectRe: [PATCH 2/3] f2fs: support checkpoint error injection
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    On 2016/9/25 2:10, Jaegeuk Kim wrote:
    > On Sat, Sep 24, 2016 at 11:32:08AM +0800, Chao Yu wrote:
    >> On 2016/9/24 8:52, Jaegeuk Kim wrote:
    >>> On Sat, Sep 24, 2016 at 08:46:54AM +0800, Chao Yu wrote:
    >>>> Hi Jaegeuk,
    >>>>
    >>>> On 2016/9/24 7:53, Jaegeuk Kim wrote:
    >>>>> Hi Chao,
    >>>>>
    >>>>> The basic rule is to stop every operations once CP_ERROR_FLAG is set.
    >>>>> But, this patch simply breaks the rule.
    >>>>> For example, f2fs_write_data_page() currently exits with mapping_set_error().
    >>>>> So this patch incurs missing dentry blocks in a valid checkpoint.
    >>>>
    >>>> Yes, that's right.
    >>>>
    >>>> How about triggering checkpoint error in f2fs_stop_checkpoint?
    >>>
    >>> Let's just use src/godown in xfstests, since we don't need to trigger this
    >>> multiple times in runtime.
    >>
    >> After we inject checkpoint error into f2fs at first time, all write IOs will be
    >> refused to be writebacked to storage, meanwhile read IOs can continuously go
    >> through f2fs, so with checkpoint error injection being supported, we can support
    >> to trigger random analogously power off by f2fs itself, instead of using tools.
    >> It means it doesn't needs specified test cases where we must use godown ioctl,
    >> but with normal testcases in xfstest/fsstress/lkp, in CP error injection enabled
    >> f2fs, we can test power off cases.
    >
    > But, in this approach, the test coverage would be quite limited.
    > In my testcase, I'm randomly injecting godown while fsstress is running, which
    > mimics really random power failures, as I believe. I'm running this infinitely
    > with fscking at every run.
    >
    > Anyway, in order to do this without godown, how about background_gc thread to
    > trigger f2fs_stop_checkpoint?

    Yeap, better.

    What do you think of adding random f2fs_stop_checkpoint in f2fs_balance_fs?
    power off can be triggered if gc thread is not running.

    Thanks,

    >
    >>
    >> Thanks,
    >
    > .
    >

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