diff options
author | Zach Brown <zach.brown@oracle.com> | 2007-10-30 11:45:46 -0700 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-30 12:14:06 -0700 |
commit | bdb76ef5a4bc8676a81034a443f1eda450b4babb (patch) | |
tree | b4ec8736e6d4bed26f96c94d5c7c8eec0896fcd0 /arch/s390/math-emu | |
parent | e58b7dab272ecee09cd7bafb89d6b224cd17bbe3 (diff) |
dio: fix cache invalidation after sync writes
Commit commit 65b8291c4000e5f38fc94fb2ca0cb7e8683c8a1b ("dio: invalidate
clean pages before dio write") introduced a bug which stopped dio from
ever invalidating the page cache after writes. It still invalidated it
before writes so most users were fine.
Karl Schendel reported ( http://lkml.org/lkml/2007/10/26/481 ) hitting
this bug when he had a buffered reader immediately reading file data
after an O_DIRECT wirter had written the data. The kernel issued
read-ahead beyond the position of the reader which overlapped with the
O_DIRECT writer. The failure to invalidate after writes caused the
reader to see stale data from the read-ahead.
The following patch is originally from Karl. The following commentary
is his:
The below 3rd try takes on your suggestion of just invalidating
no matter what the retval from the direct_IO call. I ran it
thru the test-case several times and it has worked every time.
The post-invalidate is probably still too early for async-directio,
but I don't have a testcase for that; just sync. And, this
won't be any worse in the async case.
I added a test to the aio-dio-regress repository which mimics Karl's IO
pattern. It verifed the bad behaviour and that the patch fixed it. I
agree with Karl, this still doesn't help the case where a buffered
reader follows an AIO O_DIRECT writer. That will require a bit more
work.
This gives up on the idea of returning EIO to indicate to userspace that
stale data remains if the invalidation failed.
Signed-off-by: Zach Brown <zach.brown@oracle.com>
Cc: Karl Schendel <kschendel@datallegro.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Leonid Ananiev <leonid.i.ananiev@linux.intel.com>
Cc: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/s390/math-emu')
0 files changed, 0 insertions, 0 deletions