cluster/ec: fix fd reopen

Currently EC tries to reopen fd's that have been opened while a brick
was down. This is done as part of regular write operations, just after
having acquired the locks, and it's sent as a sub-fop of the main write
fop.

There were two problems:

1. The reopen was attempted on all UP bricks, even if a previous lock
didn't succeed. This is incorrect because most probably the open will
fail.

2. If reopen is sent and fails, the error is propagated to the main
operation, causing it to fail when it shouldn't.

To fix this, we only attempt reopens on bricks where the current fop
owns a lock, and we prevent any error to be propagated to the main
fop.

To implement this behaviour an argument used to indicate the minimum
number of required answers has overloaded to also include some flags. To
make the change consistent, it has been necessary to rename the
argument, which means that a lot of files have been changed. However
there are no functional changes.

This change has also uncovered a problem in discard code, which didn't
correctely process requests of small sizes because no real discard fop
was being processed, only a write of 0's on some region. In this case
some fields of the fop remained uninitialized or with incorrect values.
To fix this, a new function has been created to simulate success on a
fop and it's used in the discard case.

Thanks to Pranith for providing a test script that has also detected an
issue in this patch. This patch includes a small modification of this
script to force data to be written into bricks before stopping them.

Backport of:
> Change-Id: If272343873369186c2fb8f43c1d9c52c3ea304ec
> BUG: bz#1699866
> Signed-off-by: Xavi Hernandez <xhernandez@redhat.com>

Change-Id: If272343873369186c2fb8f43c1d9c52c3ea304ec
Fixes: bz#1699917
Signed-off-by: Xavi Hernandez <xhernandez@redhat.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/xlators/cluster/ec/src/ec-types.h b/xlators/cluster/ec/src/ec-types.h
index 6ae4a2b970e..1c295c08033 100644
--- a/xlators/cluster/ec/src/ec-types.h
+++ b/xlators/cluster/ec/src/ec-types.h
@@ -308,9 +308,9 @@ struct _ec_fop_data {
     int32_t id; /* ID of the file operation */
     int32_t refs;
     int32_t state;
-    int32_t minimum; /* Minimum number of successful
-                        operation required to conclude a
-                        fop as successful */
+    uint32_t minimum; /* Minimum number of successful
+                         operation required to conclude a
+                         fop as successful */
     int32_t expected;
     int32_t winds;
     int32_t jobs;
@@ -325,11 +325,12 @@ struct _ec_fop_data {
     ec_cbk_data_t *answer;         /* accepted answer */
     int32_t lock_count;
     int32_t locked;
+    gf_lock_t lock;
     ec_lock_link_t locks[2];
     int32_t first_lock;
-    gf_lock_t lock;
 
-    uint32_t flags;
+    uint32_t fop_flags; /* Flags passed by the caller. */
+    uint32_t flags;     /* Internal flags. */
     uint32_t first;
     uintptr_t mask;
     uintptr_t healing; /*Dispatch is done but call is successful only