[Libguestfs] [nbdkit PATCH 3/7] plugins: Move FUA fallback to plugins
Eric Blake
eblake at redhat.com
Tue Jan 16 02:51:43 UTC 2018
As long as the plugins couldn't directly handle Forced Unit Access
(FUA), it made sense to have a common fallback in handle_request().
But upcoming patches will allow plugins to handle FUA, at which
point the fallback is easier to implement on a per-command basis,
via an extra parameter to the plugins wrapper code.
We also add an additional validation to commands sent by the client:
if we did not advertise FUA flag support (because the plugin does
not support flush), then the client should not be requesting FUA;
this in turn means that we can assert that the flush callback is
valid if the plugins layer gets a fua flag.
Signed-off-by: Eric Blake <eblake at redhat.com>
---
src/connections.c | 21 +++++++++------------
src/internal.h | 8 ++++----
src/plugins.c | 42 +++++++++++++++++++++++++++++++-----------
3 files changed, 44 insertions(+), 27 deletions(-)
diff --git a/src/connections.c b/src/connections.c
index 24df4b6..e4a0a82 100644
--- a/src/connections.c
+++ b/src/connections.c
@@ -814,6 +814,11 @@ validate_request (struct connection *conn,
*error = EINVAL;
return false;
}
+ if (!conn->can_flush && (flags & NBD_CMD_FLAG_FUA)) {
+ nbdkit_error ("invalid request: FUA flag not supported");
+ *error = EINVAL;
+ return false;
+ }
/* Refuse over-large read and write requests. */
if ((cmd == NBD_CMD_WRITE || cmd == NBD_CMD_READ) &&
@@ -868,10 +873,7 @@ handle_request (struct connection *conn,
uint16_t cmd, uint16_t flags, uint64_t offset, uint32_t count,
void *buf)
{
- bool flush_after_command;
-
- /* Flush after command performed? */
- flush_after_command = conn->can_flush && (flags & NBD_CMD_FLAG_FUA);
+ bool fua = conn->can_flush && (flags & NBD_CMD_FLAG_FUA);
/* The plugin should call nbdkit_set_error() to request a particular
error, otherwise we fallback to errno or EIO. */
@@ -879,30 +881,28 @@ handle_request (struct connection *conn,
switch (cmd) {
case NBD_CMD_READ:
- flush_after_command = false;
if (plugin_pread (conn, buf, count, offset) == -1)
return get_error (conn);
break;
case NBD_CMD_WRITE:
- if (plugin_pwrite (conn, buf, count, offset) == -1)
+ if (plugin_pwrite (conn, buf, count, offset, fua) == -1)
return get_error (conn);
break;
case NBD_CMD_FLUSH:
- flush_after_command = false;
if (plugin_flush (conn) == -1)
return get_error (conn);
break;
case NBD_CMD_TRIM:
- if (plugin_trim (conn, count, offset) == -1)
+ if (plugin_trim (conn, count, offset, fua) == -1)
return get_error (conn);
break;
case NBD_CMD_WRITE_ZEROES:
if (plugin_zero (conn, count, offset,
- !(flags & NBD_CMD_FLAG_NO_HOLE)) == -1)
+ !(flags & NBD_CMD_FLAG_NO_HOLE), fua) == -1)
return get_error (conn);
break;
@@ -910,9 +910,6 @@ handle_request (struct connection *conn,
abort ();
}
- if (flush_after_command && plugin_flush (conn) == -1)
- return get_error (conn);
-
return 0;
}
diff --git a/src/internal.h b/src/internal.h
index 73bc09e..3ab08d3 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -1,5 +1,5 @@
/* nbdkit
- * Copyright (C) 2013-2017 Red Hat Inc.
+ * Copyright (C) 2013-2018 Red Hat Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -164,10 +164,10 @@ extern int plugin_can_flush (struct connection *conn);
extern int plugin_is_rotational (struct connection *conn);
extern int plugin_can_trim (struct connection *conn);
extern int plugin_pread (struct connection *conn, void *buf, uint32_t count, uint64_t offset);
-extern int plugin_pwrite (struct connection *conn, void *buf, uint32_t count, uint64_t offset);
+extern int plugin_pwrite (struct connection *conn, void *buf, uint32_t count, uint64_t offset, int fua);
extern int plugin_flush (struct connection *conn);
-extern int plugin_trim (struct connection *conn, uint32_t count, uint64_t offset);
-extern int plugin_zero (struct connection *conn, uint32_t count, uint64_t offset, int may_trim);
+extern int plugin_trim (struct connection *conn, uint32_t count, uint64_t offset, int fua);
+extern int plugin_zero (struct connection *conn, uint32_t count, uint64_t offset, int may_trim, int fua);
/* sockets.c */
extern int *bind_unix_socket (size_t *);
diff --git a/src/plugins.c b/src/plugins.c
index 9b5d2d5..61f0cc8 100644
--- a/src/plugins.c
+++ b/src/plugins.c
@@ -1,5 +1,5 @@
/* nbdkit
- * Copyright (C) 2013 Red Hat Inc.
+ * Copyright (C) 2013-2018 Red Hat Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -497,19 +497,26 @@ plugin_pread (struct connection *conn,
int
plugin_pwrite (struct connection *conn,
- void *buf, uint32_t count, uint64_t offset)
+ void *buf, uint32_t count, uint64_t offset, int fua)
{
+ int r;
assert (dl);
assert (connection_get_handle (conn));
- debug ("pwrite count=%" PRIu32 " offset=%" PRIu64, count, offset);
+ debug ("pwrite count=%" PRIu32 " offset=%" PRIu64 " fua=%d", count, offset,
+ fua);
if (plugin.pwrite != NULL)
- return plugin.pwrite (connection_get_handle (conn), buf, count, offset);
+ r = plugin.pwrite (connection_get_handle (conn), buf, count, offset);
else {
errno = EROFS;
return -1;
}
+ if (r == 0 && fua) {
+ assert (plugin.flush);
+ r = plugin_flush (conn);
+ }
+ return r;
}
int
@@ -529,24 +536,31 @@ plugin_flush (struct connection *conn)
}
int
-plugin_trim (struct connection *conn, uint32_t count, uint64_t offset)
+plugin_trim (struct connection *conn, uint32_t count, uint64_t offset, int fua)
{
+ int r;
assert (dl);
assert (connection_get_handle (conn));
- debug ("trim count=%" PRIu32 " offset=%" PRIu64, count, offset);
+ debug ("trim count=%" PRIu32 " offset=%" PRIu64 " fua=%d", count, offset,
+ fua);
if (plugin.trim != NULL)
- return plugin.trim (connection_get_handle (conn), count, offset);
+ r = plugin.trim (connection_get_handle (conn), count, offset);
else {
errno = EINVAL;
return -1;
}
+ if (r == 0 && fua) {
+ assert (plugin.flush);
+ r = plugin_flush (conn);
+ }
+ return r;
}
int
plugin_zero (struct connection *conn,
- uint32_t count, uint64_t offset, int may_trim)
+ uint32_t count, uint64_t offset, int may_trim, int fua)
{
assert (dl);
assert (connection_get_handle (conn));
@@ -555,8 +569,8 @@ plugin_zero (struct connection *conn,
int result;
int err = 0;
- debug ("zero count=%" PRIu32 " offset=%" PRIu64 " may_trim=%d",
- count, offset, may_trim);
+ debug ("zero count=%" PRIu32 " offset=%" PRIu64 " may_trim=%d fua=%d",
+ count, offset, may_trim, fua);
if (!count)
return 0;
@@ -569,7 +583,7 @@ plugin_zero (struct connection *conn,
err = errno;
}
if (result == 0 || err != EOPNOTSUPP)
- return result;
+ goto done;
}
assert (plugin.pwrite);
@@ -593,5 +607,11 @@ plugin_zero (struct connection *conn,
err = errno;
free (buf);
errno = err;
+
+ done:
+ if (!result && fua) {
+ assert (plugin.flush);
+ result = plugin_flush (conn);
+ }
return result;
}
--
2.14.3
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