qemu/block/blkverify.c
Stefan Hajnoczi e8b6535533 block: add BDRV_REQ_REGISTERED_BUF request flag
Block drivers may optimize I/O requests accessing buffers previously
registered with bdrv_register_buf(). Checking whether all elements of a
request's QEMUIOVector are within previously registered buffers is
expensive, so we need a hint from the user to avoid costly checks.

Add a BDRV_REQ_REGISTERED_BUF request flag to indicate that all
QEMUIOVector elements in an I/O request are known to be within
previously registered buffers.

Always pass the flag through to driver read/write functions. There is
little harm in passing the flag to a driver that does not use it.
Passing the flag to drivers avoids changes across many block drivers.
Filter drivers would need to explicitly support the flag and pass
through to their children when the children support it. That's a lot of
code changes and it's hard to remember to do that everywhere, leading to
silent reduced performance when the flag is accidentally dropped.

The only problematic scenario with the approach in this patch is when a
driver passes the flag through to internal I/O requests that don't use
the same I/O buffer. In that case the hint may be set when it should
actually be clear. This is a rare case though so the risk is low.

Some drivers have assert(!flags), which no longer works when
BDRV_REQ_REGISTERED_BUF is passed in. These assertions aren't very
useful anyway since the functions are called almost exclusively by
bdrv_driver_preadv/pwritev() so if we get flags handling right there
then the assertion is not needed.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20221013185908.1297568-7-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2022-10-26 14:56:42 -04:00

337 lines
9.9 KiB
C

/*
* Block protocol for block driver correctness testing
*
* Copyright (C) 2010 IBM, Corp.
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu/sockets.h" /* for EINPROGRESS on Windows */
#include "block/block_int.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qmp/qstring.h"
#include "qemu/cutils.h"
#include "qemu/module.h"
#include "qemu/option.h"
#include "qemu/memalign.h"
typedef struct {
BdrvChild *test_file;
} BDRVBlkverifyState;
typedef struct BlkverifyRequest {
Coroutine *co;
BlockDriverState *bs;
/* Request metadata */
bool is_write;
uint64_t offset;
uint64_t bytes;
int flags;
int (*request_fn)(BdrvChild *, int64_t, int64_t, QEMUIOVector *,
BdrvRequestFlags);
int ret; /* test image result */
int raw_ret; /* raw image result */
unsigned int done; /* completion counter */
QEMUIOVector *qiov; /* user I/O vector */
QEMUIOVector *raw_qiov; /* cloned I/O vector for raw file */
} BlkverifyRequest;
static void G_GNUC_PRINTF(2, 3) blkverify_err(BlkverifyRequest *r,
const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
fprintf(stderr, "blkverify: %s offset=%" PRId64 " bytes=%" PRId64 " ",
r->is_write ? "write" : "read", r->offset, r->bytes);
vfprintf(stderr, fmt, ap);
fprintf(stderr, "\n");
va_end(ap);
exit(1);
}
/* Valid blkverify filenames look like blkverify:path/to/raw_image:path/to/image */
static void blkverify_parse_filename(const char *filename, QDict *options,
Error **errp)
{
const char *c;
QString *raw_path;
/* Parse the blkverify: prefix */
if (!strstart(filename, "blkverify:", &filename)) {
/* There was no prefix; therefore, all options have to be already
present in the QDict (except for the filename) */
qdict_put_str(options, "x-image", filename);
return;
}
/* Parse the raw image filename */
c = strchr(filename, ':');
if (c == NULL) {
error_setg(errp, "blkverify requires raw copy and original image path");
return;
}
/* TODO Implement option pass-through and set raw.filename here */
raw_path = qstring_from_substr(filename, 0, c - filename);
qdict_put(options, "x-raw", raw_path);
/* TODO Allow multi-level nesting and set file.filename here */
filename = c + 1;
qdict_put_str(options, "x-image", filename);
}
static QemuOptsList runtime_opts = {
.name = "blkverify",
.head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
.desc = {
{
.name = "x-raw",
.type = QEMU_OPT_STRING,
.help = "[internal use only, will be removed]",
},
{
.name = "x-image",
.type = QEMU_OPT_STRING,
.help = "[internal use only, will be removed]",
},
{ /* end of list */ }
},
};
static int blkverify_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp)
{
BDRVBlkverifyState *s = bs->opaque;
QemuOpts *opts;
int ret;
opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
if (!qemu_opts_absorb_qdict(opts, options, errp)) {
ret = -EINVAL;
goto fail;
}
/* Open the raw file */
bs->file = bdrv_open_child(qemu_opt_get(opts, "x-raw"), options, "raw",
bs, &child_of_bds,
BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
false, errp);
if (!bs->file) {
ret = -EINVAL;
goto fail;
}
/* Open the test file */
s->test_file = bdrv_open_child(qemu_opt_get(opts, "x-image"), options,
"test", bs, &child_of_bds, BDRV_CHILD_DATA,
false, errp);
if (!s->test_file) {
ret = -EINVAL;
goto fail;
}
bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED;
bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED;
ret = 0;
fail:
qemu_opts_del(opts);
return ret;
}
static void blkverify_close(BlockDriverState *bs)
{
BDRVBlkverifyState *s = bs->opaque;
bdrv_unref_child(bs, s->test_file);
s->test_file = NULL;
}
static int64_t blkverify_getlength(BlockDriverState *bs)
{
BDRVBlkverifyState *s = bs->opaque;
return bdrv_getlength(s->test_file->bs);
}
static void coroutine_fn blkverify_do_test_req(void *opaque)
{
BlkverifyRequest *r = opaque;
BDRVBlkverifyState *s = r->bs->opaque;
r->ret = r->request_fn(s->test_file, r->offset, r->bytes, r->qiov,
r->flags);
r->done++;
qemu_coroutine_enter_if_inactive(r->co);
}
static void coroutine_fn blkverify_do_raw_req(void *opaque)
{
BlkverifyRequest *r = opaque;
r->raw_ret = r->request_fn(r->bs->file, r->offset, r->bytes, r->raw_qiov,
r->flags);
r->done++;
qemu_coroutine_enter_if_inactive(r->co);
}
static int coroutine_fn
blkverify_co_prwv(BlockDriverState *bs, BlkverifyRequest *r, uint64_t offset,
uint64_t bytes, QEMUIOVector *qiov, QEMUIOVector *raw_qiov,
int flags, bool is_write)
{
Coroutine *co_a, *co_b;
*r = (BlkverifyRequest) {
.co = qemu_coroutine_self(),
.bs = bs,
.offset = offset,
.bytes = bytes,
.qiov = qiov,
.raw_qiov = raw_qiov,
.flags = flags,
.is_write = is_write,
.request_fn = is_write ? bdrv_co_pwritev : bdrv_co_preadv,
};
co_a = qemu_coroutine_create(blkverify_do_test_req, r);
co_b = qemu_coroutine_create(blkverify_do_raw_req, r);
qemu_coroutine_enter(co_a);
qemu_coroutine_enter(co_b);
while (r->done < 2) {
qemu_coroutine_yield();
}
if (r->ret != r->raw_ret) {
blkverify_err(r, "return value mismatch %d != %d", r->ret, r->raw_ret);
}
return r->ret;
}
static int coroutine_fn
blkverify_co_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes,
QEMUIOVector *qiov, BdrvRequestFlags flags)
{
BlkverifyRequest r;
QEMUIOVector raw_qiov;
void *buf;
ssize_t cmp_offset;
int ret;
buf = qemu_blockalign(bs->file->bs, qiov->size);
qemu_iovec_init(&raw_qiov, qiov->niov);
qemu_iovec_clone(&raw_qiov, qiov, buf);
ret = blkverify_co_prwv(bs, &r, offset, bytes, qiov, &raw_qiov,
flags & ~BDRV_REQ_REGISTERED_BUF, false);
cmp_offset = qemu_iovec_compare(qiov, &raw_qiov);
if (cmp_offset != -1) {
blkverify_err(&r, "contents mismatch at offset %" PRId64,
offset + cmp_offset);
}
qemu_iovec_destroy(&raw_qiov);
qemu_vfree(buf);
return ret;
}
static int coroutine_fn
blkverify_co_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes,
QEMUIOVector *qiov, BdrvRequestFlags flags)
{
BlkverifyRequest r;
return blkverify_co_prwv(bs, &r, offset, bytes, qiov, qiov, flags, true);
}
static int coroutine_fn blkverify_co_flush(BlockDriverState *bs)
{
BDRVBlkverifyState *s = bs->opaque;
/* Only flush test file, the raw file is not important */
return bdrv_co_flush(s->test_file->bs);
}
static bool blkverify_recurse_can_replace(BlockDriverState *bs,
BlockDriverState *to_replace)
{
BDRVBlkverifyState *s = bs->opaque;
/*
* blkverify quits the whole qemu process if there is a mismatch
* between bs->file->bs and s->test_file->bs. Therefore, we know
* know that both must match bs and we can recurse down to either.
*/
return bdrv_recurse_can_replace(bs->file->bs, to_replace) ||
bdrv_recurse_can_replace(s->test_file->bs, to_replace);
}
static void blkverify_refresh_filename(BlockDriverState *bs)
{
BDRVBlkverifyState *s = bs->opaque;
if (bs->file->bs->exact_filename[0]
&& s->test_file->bs->exact_filename[0])
{
int ret = snprintf(bs->exact_filename, sizeof(bs->exact_filename),
"blkverify:%s:%s",
bs->file->bs->exact_filename,
s->test_file->bs->exact_filename);
if (ret >= sizeof(bs->exact_filename)) {
/* An overflow makes the filename unusable, so do not report any */
bs->exact_filename[0] = 0;
}
}
}
static char *blkverify_dirname(BlockDriverState *bs, Error **errp)
{
/* In general, there are two BDSs with different dirnames below this one;
* so there is no unique dirname we could return (unless both are equal by
* chance). Therefore, to be consistent, just always return NULL. */
error_setg(errp, "Cannot generate a base directory for blkverify nodes");
return NULL;
}
static BlockDriver bdrv_blkverify = {
.format_name = "blkverify",
.protocol_name = "blkverify",
.instance_size = sizeof(BDRVBlkverifyState),
.bdrv_parse_filename = blkverify_parse_filename,
.bdrv_file_open = blkverify_open,
.bdrv_close = blkverify_close,
.bdrv_child_perm = bdrv_default_perms,
.bdrv_getlength = blkverify_getlength,
.bdrv_refresh_filename = blkverify_refresh_filename,
.bdrv_dirname = blkverify_dirname,
.bdrv_co_preadv = blkverify_co_preadv,
.bdrv_co_pwritev = blkverify_co_pwritev,
.bdrv_co_flush = blkverify_co_flush,
.is_filter = true,
.bdrv_recurse_can_replace = blkverify_recurse_can_replace,
};
static void bdrv_blkverify_init(void)
{
bdrv_register(&bdrv_blkverify);
}
block_init(bdrv_blkverify_init);