open-behind: rewrite of internal logic

There was a critical flaw in the previous implementation of open-behind.

When an open is done in the background, it's necessary to take a
reference on the fd_t object because once we "fake" the open answer,
the fd could be destroyed. However as long as there's a reference,
the release function won't be called. So, if the application closes
the file descriptor without having actually opened it, there will
always remain at least 1 reference, causing a leak.

To avoid this problem, the previous implementation didn't take a
reference on the fd_t, so there were races where the fd could be
destroyed while it was still in use.

To fix this, I've implemented a new xlator cbk that gets called from
fuse when the application closes a file descriptor.

The whole logic of handling background opens have been simplified and
it's more efficient now. Only if the fop needs to be delayed until an
open completes, a stub is created. Otherwise no memory allocations are
needed.

Correctly handling the close request while the open is still pending
has added a bit of complexity, but overall normal operation is simpler.

Change-Id: I6376a5491368e0e1c283cc452849032636261592
Fixes: #1225
Signed-off-by: Xavi Hernandez <xhernandez@redhat.com>

1 files changed, 145 insertions, 0 deletions

diff --git a/tests/basic/open-behind/tester.h b/tests/basic/open-behind/tester.h
new file mode 100644
index 00000000000..64e940c78fc
--- /dev/null
+++ b/tests/basic/open-behind/tester.h
@@ -0,0 +1,145 @@
+/*
+  Copyright (c) 2020 Red Hat, Inc. <http://www.redhat.com>
+  This file is part of GlusterFS.
+
+  This file is licensed to you under your choice of the GNU Lesser
+  General Public License, version 3 or any later version (LGPLv3 or
+  later), or the GNU General Public License, version 2 (GPLv2), in all
+  cases as published by the Free Software Foundation.
+*/
+
+#ifndef __TESTER_H__
+#define __TESTER_H__
+
+#include <stdio.h>
+#include <inttypes.h>
+#include <stdbool.h>
+
+enum _obj_type;
+typedef enum _obj_type obj_type_t;
+
+enum _arg_type;
+typedef enum _arg_type arg_type_t;
+
+struct _buffer;
+typedef struct _buffer buffer_t;
+
+struct _obj;
+typedef struct _obj obj_t;
+
+struct _context;
+typedef struct _context context_t;
+
+struct _arg;
+typedef struct _arg arg_t;
+
+struct _command;
+typedef struct _command command_t;
+
+enum _obj_type { OBJ_TYPE_NONE, OBJ_TYPE_FD };
+
+enum _arg_type { ARG_TYPE_NONE, ARG_TYPE_OBJ, ARG_TYPE_NUM, ARG_TYPE_STR };
+
+struct _buffer {
+    char *base;
+    uint32_t size;
+    uint32_t len;
+    uint32_t pos;
+};
+
+struct _obj {
+    obj_type_t type;
+    union {
+        int32_t fd;
+    };
+};
+
+struct _context {
+    obj_t *objs;
+    buffer_t buffer;
+    uint32_t obj_count;
+    bool active;
+};
+
+struct _arg {
+    arg_type_t type;
+    union {
+        struct {
+            obj_type_t type;
+            obj_t *ref;
+        } obj;
+        struct {
+            uint64_t value;
+            uint64_t min;
+            uint64_t max;
+        } num;
+        struct {
+            uint32_t size;
+            char *data;
+        } str;
+    };
+};
+
+struct _command {
+    const char *name;
+    int32_t (*handler)(context_t *ctx, command_t *cmd);
+    union {
+        arg_t *args;
+        command_t *cmds;
+    };
+};
+
+#define msg(_stream, _fmt, _args...)                                           \
+    do {                                                                       \
+        fprintf(_stream, _fmt "\n", ##_args);                                  \
+        fflush(_stream);                                                       \
+    } while (0)
+
+#define msg_out(_fmt, _args...) msg(stdout, _fmt, ##_args)
+#define msg_err(_err, _fmt, _args...)                                          \
+    ({                                                                         \
+        int32_t __msg_err = (_err);                                            \
+        msg(stderr, "[%4u:%-15s] " _fmt, __LINE__, __FUNCTION__, __msg_err,    \
+            ##_args);                                                          \
+        -__msg_err;                                                            \
+    })
+
+#define error(_err, _fmt, _args...) msg_err(_err, "E(%4d) " _fmt, ##_args)
+#define warn(_err, _fmt, _args...) msg_err(_err, "W(%4d) " _fmt, ##_args)
+#define info(_err, _fmt, _args...) msg_err(_err, "I(%4d) " _fmt, ##_args)
+
+#define out_ok(_args...) msg_out("OK " _args)
+#define out_err(_err) msg_out("ERR %d", _err)
+
+#define ARG_END                                                                \
+    {                                                                          \
+        ARG_TYPE_NONE                                                          \
+    }
+
+#define CMD_ARGS1(_x, _args...)                                                \
+    .args = (arg_t[]) { _args }
+#define CMD_ARGS(_args...) CMD_ARGS1(, ##_args, ARG_END)
+
+#define CMD_SUB(_cmds) .cmds = _cmds
+
+#define CMD_END                                                                \
+    {                                                                          \
+        NULL, NULL, CMD_SUB(NULL)                                              \
+    }
+
+#define ARG_VAL(_type)                                                         \
+    {                                                                          \
+        ARG_TYPE_OBJ, .obj = {.type = _type }                                  \
+    }
+#define ARG_NUM(_min, _max)                                                    \
+    {                                                                          \
+        ARG_TYPE_NUM, .num = {.min = _min, .max = _max }                       \
+    }
+#define ARG_STR(_size)                                                         \
+    {                                                                          \
+        ARG_TYPE_STR, .str = {.size = _size }                                  \
+    }
+
+extern command_t fd_commands[];
+
+#endif /* __TESTER_H__ */
\ No newline at end of file