performance/write-behind: fix flush stuck by former failed writes

the issue is happened in this case:
assume a file is opened with fd1 and fd2.
1. some WRITE opto fd1 got error, they were add back to 'todo' queue
   because of those error.
2. fd2 closed, a FLUSH op is send to write-behind.
3. FLUSH can not be unwind because it's not a legal waiter for those
   failed write(as func __wb_request_waiting_on() say). and those failed
   WRITE also can not be ended if fd1 is not closed. fd2 stuck in close
   syscall.

to resolve this issue, we can change the way we determine 2 requests is
'conflict': flush/fsync is not conflict with those write that is not
belonged to them. so __wb_pick_winds() can wind the FLUSH op.

below is some information when the stuck issue happen:
glusterdump logs:
[xlator.performance.write-behind.wb_inode]
path=/ltp-F9eG0ZSOME/rw-buffered-16436
inode=0x7fdbe8039b9c
window_conf=1048576
window_current=249856
transit-size=0
dontsync=0

[.WRITE]
request-ptr=0x7fdbe8020200
refcount=1
wound=no
generation-number=4
req->op_ret=-1
req->op_errno=116
sync-attempts=3
sync-in-progress=no
size=131072
offset=1220608
lied=-1
append=0
fulfilled=0
go=0

[.WRITE]
request-ptr=0x7fdbe8068c30
refcount=1
wound=no
generation-number=5
req->op_ret=-1
req->op_errno=116
sync-attempts=2
sync-in-progress=no
size=118784
offset=1351680
lied=-1
append=0
fulfilled=0
go=0

[.FLUSH]
request-ptr=0x7fdbe8021cd0
refcount=1
wound=no
generation-number=6
req->op_ret=0
req->op_errno=0
sync-attempts=0

gdb detail about above 3 requests:
(gdb) print *((wb_request_t *)0x7fdbe8021cd0)
$2 = {all = {next = 0x7fdbe803a608, prev = 0x7fdbe8068c30}, todo = {next
= 0x7fdbe803a618, prev = 0x7fdbe8068c40}, lie = {next = 0x7fdbe8021cf0,
    prev = 0x7fdbe8021cf0}, winds = {next = 0x7fdbe8021d00, prev =
0x7fdbe8021d00}, unwinds = {next = 0x7fdbe8021d10, prev =
0x7fdbe8021d10}, wip = {
    next = 0x7fdbe8021d20, prev = 0x7fdbe8021d20}, stub =
0x7fdbe80224dc, write_size = 0, orig_size = 0, total_size = 0, op_ret =
0, op_errno = 0,
  refcount = 1, wb_inode = 0x7fdbe803a5f0, fop = GF_FOP_FLUSH, lk_owner
= {len = 8, data = "W\322T\f\271\367y$", '\000' <repeats 1015 times>},
  iobref = 0x0, gen = 6, fd = 0x7fdbe800f0dc, wind_count = 0, ordering =
{size = 0, off = 0, append = 0, tempted = 0, lied = 0, fulfilled = 0,
    go = 0}}
(gdb) print *((wb_request_t *)0x7fdbe8020200)
$3 = {all = {next = 0x7fdbe8068c30, prev = 0x7fdbe803a608}, todo = {next
= 0x7fdbe8068c40, prev = 0x7fdbe803a618}, lie = {next = 0x7fdbe8068c50,
    prev = 0x7fdbe803a628}, winds = {next = 0x7fdbe8020230, prev =
0x7fdbe8020230}, unwinds = {next = 0x7fdbe8020240, prev =
0x7fdbe8020240}, wip = {
    next = 0x7fdbe8020250, prev = 0x7fdbe8020250}, stub =
0x7fdbe8062c3c, write_size = 131072, orig_size = 4096, total_size = 0,
op_ret = -1,
  op_errno = 116, refcount = 1, wb_inode = 0x7fdbe803a5f0, fop =
GF_FOP_WRITE, lk_owner = {len = 8, data = '\000' <repeats 1023 times>},
  iobref = 0x7fdbe80311a0, gen = 4, fd = 0x7fdbe805c89c, wind_count = 3,
ordering = {size = 131072, off = 1220608, append = 0, tempted = -1,
    lied = -1, fulfilled = 0, go = 0}}
(gdb) print *((wb_request_t *)0x7fdbe8068c30)
$4 = {all = {next = 0x7fdbe8021cd0, prev = 0x7fdbe8020200}, todo = {next
= 0x7fdbe8021ce0, prev = 0x7fdbe8020210}, lie = {next = 0x7fdbe803a628,
    prev = 0x7fdbe8020220}, winds = {next = 0x7fdbe8068c60, prev =
0x7fdbe8068c60}, unwinds = {next = 0x7fdbe8068c70, prev =
0x7fdbe8068c70}, wip = {
    next = 0x7fdbe8068c80, prev = 0x7fdbe8068c80}, stub =
0x7fdbe806746c, write_size = 118784, orig_size = 4096, total_size = 0,
op_ret = -1,
  op_errno = 116, refcount = 1, wb_inode = 0x7fdbe803a5f0, fop =
GF_FOP_WRITE, lk_owner = {len = 8, data = '\000' <repeats 1023 times>},
  iobref = 0x7fdbe8052b10, gen = 5, fd = 0x7fdbe805c89c, wind_count = 2,
ordering = {size = 118784, off = 1351680, append = 0, tempted = -1,
    lied = -1, fulfilled = 0, go = 0}}

you can see they are all on 'todo' queue, and FLUSH op fd is not the
same WRITE op fd.

Change-Id: Id687f9cd3b9f281e1a97c83f1ce981ede272b8ab
BUG: 1372211
Signed-off-by: Ryan Ding <ryan.ding@open-fs.com>
Reviewed-on: http://review.gluster.org/15380
Tested-by: Raghavendra G <rgowdapp@redhat.com>
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/xlators/performance/write-behind/src/write-behind.c b/xlators/performance/write-behind/src/write-behind.c
index 042fbd797bf..9b656069636 100644
--- a/xlators/performance/write-behind/src/write-behind.c
+++ b/xlators/performance/write-behind/src/write-behind.c
@@ -280,6 +280,10 @@ wb_requests_conflict (wb_request_t *lie, wb_request_t *req)
 		   us in the todo list */
 		return _gf_false;
 
+        /* requests from different fd do not conflict with each other. */
+        if (req->fd && (req->fd != lie->fd))
+                return _gf_false;
+
 	if (lie->ordering.append)
 		/* all modifications wait for the completion
 		   of outstanding append */