reiserfs: add comment to explain endianness issue in xattr_hash
csum_partial() gives different results for little-endian and big-endian hosts. This causes images created on little-endian hosts and mounted on big endian hosts to see csum mismatches. This causes an endianness bug. Sparse gives a warning as csum_partial returns a restricted integer type __wsum_t and xattr_hash expects __u32. This warning acts as a reminder for this bug and should not be suppressed. This comment aims to convey these endianness issues. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/20190423161831.GA15387@bharath12345-Inspiron-5559 Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Jann Horn <jannh@google.com> Cc: Jeff Mahoney <jeffm@suse.com> Cc: Jan Kara <jack@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -450,6 +450,15 @@ fail:
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static inline __u32 xattr_hash(const char *msg, int len)
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{
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/*
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* csum_partial() gives different results for little-endian and
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* big endian hosts. Images created on little-endian hosts and
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* mounted on big-endian hosts(and vice versa) will see csum mismatches
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* when trying to fetch xattrs. Treating the hash as __wsum_t would
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* lower the frequency of mismatch. This is an endianness bug in
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* reiserfs. The return statement would result in a sparse warning. Do
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* not fix the sparse warning so as to not hide a reminder of the bug.
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*/
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return csum_partial(msg, len, 0);
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}
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