Re: [PATCH v2] fs: global sync to not clear error status of individual inodes

From	Tejun Heo <tj@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] fs: global sync to not clear error status of individual inodes
Date	2015-09-16 19:50 +0200
Message-ID	<q9p0e-309-15@gated-at.bofh.it> (permalink)
References	<q8VbQ-1dV-3@gated-at.bofh.it> <q8VbQ-1dV-1@gated-at.bofh.it> <q90lc-mc-33@gated-at.bofh.it> <q99ou-5Xi-15@gated-at.bofh.it> <q9gzE-7Lr-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, Sep 16, 2015 at 08:39:09AM +0000, Junichi Nomura wrote:
> filemap_fdatawait() is a function to wait for on-going writeback
> to complete but also consume and clear error status of the mapping
> set during writeback.
> The latter functionality is critical for applications to detect
> writeback error with system calls like fsync(2)/fdatasync(2).
> 
> However filemap_fdatawait() is also used by sync(2) or FIFREEZE
> ioctl, which don't check error status of individual mappings.
> 
> As a result, fsync() may not be able to detect writeback error
> if events happen in the following order:
> 
>    Application                    System admin
>    ----------------------------------------------------------
>    write data on page cache
>                                   Run sync command
>                                   writeback completes with error
>                                   filemap_fdatawait() clears error
>    fsync returns success
>    (but the data is not on disk)
> 
> This patch adds filemap_fdatawait_keep_errors() for call sites where
> writeback error is not handled so that they don't clear error status.
> 
> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
> Acked-by: Andi Kleen <ak@linux.intel.com>

Reviewed-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun
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[PATCH 1/1] fs: global sync to not clear error status of individual  inodes Junichi Nomura <j-nomura@ce.jp.nec.com> - 2015-09-15 12:00 +0200
  Re: [PATCH 1/1] fs: global sync to not clear error status of  individual inodes Andi Kleen <andi@firstfloor.org> - 2015-09-15 16:40 +0200
    Re: [PATCH 1/1] fs: global sync to not clear error status of  individual inodes Andrew Morton <akpm@linux-foundation.org> - 2015-09-16 00:10 +0200
      Re: [PATCH 1/1] fs: global sync to not clear error status of  individual inodes Junichi Nomura <j-nomura@ce.jp.nec.com> - 2015-09-16 03:10 +0200
        xfstests: test data-writeback error detection with fsync Junichi Nomura <j-nomura@ce.jp.nec.com> - 2015-09-16 12:50 +0200
  Re: [PATCH 1/1] fs: global sync to not clear error status of  individual inodes Tejun Heo <tj@kernel.org> - 2015-09-15 17:30 +0200
    Re: [PATCH 1/1] fs: global sync to not clear error status of  individual inodes Andi Kleen <andi@firstfloor.org> - 2015-09-15 19:00 +0200
    Re: [PATCH 1/1] fs: global sync to not clear error status of  individual inodes Junichi Nomura <j-nomura@ce.jp.nec.com> - 2015-09-16 03:10 +0200
      [PATCH v2] fs: global sync to not clear error status of individual  inodes Junichi Nomura <j-nomura@ce.jp.nec.com> - 2015-09-16 10:50 +0200
        Re: [PATCH v2] fs: global sync to not clear error status of  individual inodes Tejun Heo <tj@kernel.org> - 2015-09-16 19:50 +0200

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