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From: Dave Kleikamp <dave.kleikamp@oracle.com>
To: sparclinux@vger.kernel.org
Subject: return value of __copy_from_user_inatomic()
Date: Fri, 13 Dec 2013 19:04:55 +0000	[thread overview]
Message-ID: <52AB5A57.3010405@oracle.com> (raw)

We're seeing some failing test cases due to sparc64's
__copy_from_user_inatomic returning 1 on an incomplete copy rather than
the number of bytes not copied. This results in
iov_iter_copy_from_user_atomic returning the wrong value to
generic_perform_write().

xfstests generic/246 and LTP writev01 both fail on btrfs and nfs because
of this.

Commit 145e1c00 "sparc64: Fix __copy_{to,from}_user_inatomic defines."
changed the behavior by removing the call to the fixups in
__copy_from_user_inatomic and __copy_to_user_inatomic. I found the
reported problem here: https://lkml.org/lkml/2008/11/1/91 , but I don't
understand why the fixup is the problem. The bzero (memset in the code)
is called against the destination, which is a pagecache page, and the
faulting address is sanity-checked against the boundaries.

reverting commit 145e1c00 fixes those failing test cases, and I wasn't
able to recreate the dbench failure on tmpfs.

Thanks,
Dave

                 reply	other threads:[~2013-12-13 19:04 UTC|newest]

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