commit 86aa1397ddfde563b3692adadb8b8e32e97b4e5e
author Song Liu <songliubraving@fb.com> Thu Jan 12 17:22:41 2017 -0800
committer Shaohua Li <shli@fb.com> Tue Jan 24 11:20:14 2017 -0800
tree 866e94b5411650b70561ea663ce3680a6d4a364f
parent d46d29f072accb069cb42b5fbebcc77d9094a785

md/r5cache: read data into orig_page for prexor of cached data

With write back cache, we use orig_page to do prexor. This patch
makes sure we read data into orig_page for it.

Flag R5_OrigPageUPTDODATE is added to show whether orig_page
has the latest data from raid disk.

We introduce a helper function uptodate_for_rmw() to simplify
the a couple conditions in handle_stripe_dirtying().

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>