drbd: Fix a potential write ordering issue on SyncTarget nodes
drbd: Fix a potential write ordering issue on SyncTarget nodes

If a SyncTarget node gets a P_RS_DATA_REPLY before a P_DATA packet
for the same sector, it simply submits these two IO requests.

  This is be possible because on the SyncSource node, the data of the
  P_RS_DATA_REPLY packet was read from disk.  Immediately after that a
  write request from upper layers came in.

The disk scheduler or even the "hardware" queues on the disk drive might
reorder these writes.

Signed-off-by: Philipp Reisner <35a55a4ac466b5abd81eb66f3f7d6a972dd0dc24@linbit.com>
Signed-off-by: Lars Ellenberg <31df9cacdc65c624cc60c2dcd22bbf92dc230e16@linbit.com>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas