system/qemu
system/qemu
1
0
Fork 0
mirror of https://gitlab.com/qemu-project/qemu synced 2024-11-05 20:35:44 +00:00
Code Issues Projects Releases Packages Wiki Activity
qemu/block/io.c
Eric Blake cb2e28780c block: Perform copy-on-read in loop 
Improve our braindead copy-on-read implementation.  Pre-patch,
we have multiple issues:
- we create a bounce buffer and perform a write for the entire
request, even if the active image already has 99% of the
clusters occupied, and really only needs to copy-on-read the
remaining 1% of the clusters
- our bounce buffer was as large as the read request, and can
needlessly exhaust our memory by using double the memory of
the request size (the original request plus our bounce buffer),
rather than a capped maximum overhead beyond the original
- if a driver has a max_transfer limit, we are bypassing the
normal code in bdrv_aligned_preadv() that fragments to that
limit, and instead attempt to read the entire buffer from the
driver in one go, which some drivers may assert on
- a client can request a large request of nearly 2G such that
rounding the request out to cluster boundaries results in a
byte count larger than 2G.  While this cannot exceed 32 bits,
it DOES have some follow-on problems:
-- the call to bdrv_driver_pread() can assert for exceeding
BDRV_REQUEST_MAX_BYTES, if the driver is old and lacks
.bdrv_co_preadv
-- if the buffer is all zeroes, the subsequent call to
bdrv_co_do_pwrite_zeroes is a no-op due to a negative size,
which means we did not actually copy on read

Fix all of these issues by breaking up the action into a loop,
where each iteration is capped to sane limits.  Also, querying
the allocation status allows us to optimize: when data is
already present in the active layer, we don't need to bounce.

Note that the code has a telling comment that copy-on-read
should probably be a filter driver rather than a bolt-on hack
in io.c; but that remains a task for another day.

CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-10-06 16:28:58 +02:00

2637 lines
78 KiB
C
Raw Blame History

/*
* Block layer I/O functions
*
* Copyright (c) 2003 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu/osdep.h"
#include "trace.h"
#include "sysemu/block-backend.h"
#include "block/blockjob.h"
#include "block/blockjob_int.h"
#include "block/block_int.h"
#include "qemu/cutils.h"
#include "qapi/error.h"
#include "qemu/error-report.h"
#define NOT_DONE 0x7fffffff /* used while emulated sync operation in progress */
/* Maximum bounce buffer for copy-on-read and write zeroes, in bytes */
#define MAX_BOUNCE_BUFFER (32768 << BDRV_SECTOR_BITS)
static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
int64_t offset, int bytes, BdrvRequestFlags flags);
void bdrv_parent_drained_begin(BlockDriverState *bs)
{
BdrvChild *c;
QLIST_FOREACH(c, &bs->parents, next_parent) {
if (c->role->drained_begin) {
c->role->drained_begin(c);
}
}
}
void bdrv_parent_drained_end(BlockDriverState *bs)
{
BdrvChild *c;
QLIST_FOREACH(c, &bs->parents, next_parent) {
if (c->role->drained_end) {
c->role->drained_end(c);
}
}
}
static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src)
{
dst->opt_transfer = MAX(dst->opt_transfer, src->opt_transfer);
dst->max_transfer = MIN_NON_ZERO(dst->max_transfer, src->max_transfer);
dst->opt_mem_alignment = MAX(dst->opt_mem_alignment,
src->opt_mem_alignment);
dst->min_mem_alignment = MAX(dst->min_mem_alignment,
src->min_mem_alignment);
dst->max_iov = MIN_NON_ZERO(dst->max_iov, src->max_iov);
}
void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
{
BlockDriver *drv = bs->drv;
Error *local_err = NULL;
memset(&bs->bl, 0, sizeof(bs->bl));
if (!drv) {
return;
}
/* Default alignment based on whether driver has byte interface */
bs->bl.request_alignment = drv->bdrv_co_preadv ? 1 : 512;
/* Take some limits from the children as a default */
if (bs->file) {
bdrv_refresh_limits(bs->file->bs, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
bdrv_merge_limits(&bs->bl, &bs->file->bs->bl);
} else {
bs->bl.min_mem_alignment = 512;
bs->bl.opt_mem_alignment = getpagesize();
/* Safe default since most protocols use readv()/writev()/etc */
bs->bl.max_iov = IOV_MAX;
}
if (bs->backing) {
bdrv_refresh_limits(bs->backing->bs, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
bdrv_merge_limits(&bs->bl, &bs->backing->bs->bl);
}
/* Then let the driver override it */
if (drv->bdrv_refresh_limits) {
drv->bdrv_refresh_limits(bs, errp);
}
}
/**
* The copy-on-read flag is actually a reference count so multiple users may
* use the feature without worrying about clobbering its previous state.
* Copy-on-read stays enabled until all users have called to disable it.
*/
void bdrv_enable_copy_on_read(BlockDriverState *bs)
{
atomic_inc(&bs->copy_on_read);
}
void bdrv_disable_copy_on_read(BlockDriverState *bs)
{
int old = atomic_fetch_dec(&bs->copy_on_read);
assert(old >= 1);
}
/* Check if any requests are in-flight (including throttled requests) */
bool bdrv_requests_pending(BlockDriverState *bs)
{
BdrvChild *child;
if (atomic_read(&bs->in_flight)) {
return true;
}
QLIST_FOREACH(child, &bs->children, next) {
if (bdrv_requests_pending(child->bs)) {
return true;
}
}
return false;
}
typedef struct {
Coroutine *co;
BlockDriverState *bs;
bool done;
} BdrvCoDrainData;
static void coroutine_fn bdrv_drain_invoke_entry(void *opaque)
{
BdrvCoDrainData *data = opaque;
BlockDriverState *bs = data->bs;
bs->drv->bdrv_co_drain(bs);
/* Set data->done before reading bs->wakeup. */
atomic_mb_set(&data->done, true);
bdrv_wakeup(bs);
}
static void bdrv_drain_invoke(BlockDriverState *bs)
{
BdrvCoDrainData data = { .bs = bs, .done = false };
if (!bs->drv || !bs->drv->bdrv_co_drain) {
return;
}
data.co = qemu_coroutine_create(bdrv_drain_invoke_entry, &data);
bdrv_coroutine_enter(bs, data.co);
BDRV_POLL_WHILE(bs, !data.done);
}
static bool bdrv_drain_recurse(BlockDriverState *bs)
{
BdrvChild *child, *tmp;
bool waited;
waited = BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0);
/* Ensure any pending metadata writes are submitted to bs->file. */
bdrv_drain_invoke(bs);
QLIST_FOREACH_SAFE(child, &bs->children, next, tmp) {
BlockDriverState *bs = child->bs;
bool in_main_loop =
qemu_get_current_aio_context() == qemu_get_aio_context();
assert(bs->refcnt > 0);
if (in_main_loop) {
/* In case the recursive bdrv_drain_recurse processes a
* block_job_defer_to_main_loop BH and modifies the graph,
* let's hold a reference to bs until we are done.
*
* IOThread doesn't have such a BH, and it is not safe to call
* bdrv_unref without BQL, so skip doing it there.
*/
bdrv_ref(bs);
}
waited |= bdrv_drain_recurse(bs);
if (in_main_loop) {
bdrv_unref(bs);
}
}
return waited;
}
static void bdrv_co_drain_bh_cb(void *opaque)
{
BdrvCoDrainData *data = opaque;
Coroutine *co = data->co;
BlockDriverState *bs = data->bs;
bdrv_dec_in_flight(bs);
bdrv_drained_begin(bs);
data->done = true;
aio_co_wake(co);
}
static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs)
{
BdrvCoDrainData data;
/* Calling bdrv_drain() from a BH ensures the current coroutine yields and
* other coroutines run if they were queued from
* qemu_co_queue_run_restart(). */
assert(qemu_in_coroutine());
data = (BdrvCoDrainData) {
.co = qemu_coroutine_self(),
.bs = bs,
.done = false,
};
bdrv_inc_in_flight(bs);
aio_bh_schedule_oneshot(bdrv_get_aio_context(bs),
bdrv_co_drain_bh_cb, &data);
qemu_coroutine_yield();
/* If we are resumed from some other event (such as an aio completion or a
* timer callback), it is a bug in the caller that should be fixed. */
assert(data.done);
}
void bdrv_drained_begin(BlockDriverState *bs)
{
if (qemu_in_coroutine()) {
bdrv_co_yield_to_drain(bs);
return;
}
if (atomic_fetch_inc(&bs->quiesce_counter) == 0) {
aio_disable_external(bdrv_get_aio_context(bs));
bdrv_parent_drained_begin(bs);
}
bdrv_drain_recurse(bs);
}
void bdrv_drained_end(BlockDriverState *bs)
{
assert(bs->quiesce_counter > 0);
if (atomic_fetch_dec(&bs->quiesce_counter) > 1) {
return;
}
bdrv_parent_drained_end(bs);
aio_enable_external(bdrv_get_aio_context(bs));
}
/*
* Wait for pending requests to complete on a single BlockDriverState subtree,
* and suspend block driver's internal I/O until next request arrives.
*
* Note that unlike bdrv_drain_all(), the caller must hold the BlockDriverState
* AioContext.
*
* Only this BlockDriverState's AioContext is run, so in-flight requests must
* not depend on events in other AioContexts. In that case, use
* bdrv_drain_all() instead.
*/
void coroutine_fn bdrv_co_drain(BlockDriverState *bs)
{
assert(qemu_in_coroutine());
bdrv_drained_begin(bs);
bdrv_drained_end(bs);
}
void bdrv_drain(BlockDriverState *bs)
{
bdrv_drained_begin(bs);
bdrv_drained_end(bs);
}
/*
* Wait for pending requests to complete across all BlockDriverStates
*
* This function does not flush data to disk, use bdrv_flush_all() for that
* after calling this function.
*
* This pauses all block jobs and disables external clients. It must
* be paired with bdrv_drain_all_end().
*
* NOTE: no new block jobs or BlockDriverStates can be created between
* the bdrv_drain_all_begin() and bdrv_drain_all_end() calls.
*/
void bdrv_drain_all_begin(void)
{
/* Always run first iteration so any pending completion BHs run */
bool waited = true;
BlockDriverState *bs;
BdrvNextIterator it;
GSList *aio_ctxs = NULL, *ctx;
block_job_pause_all();
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
AioContext *aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
bdrv_parent_drained_begin(bs);
aio_disable_external(aio_context);
aio_context_release(aio_context);
if (!g_slist_find(aio_ctxs, aio_context)) {
aio_ctxs = g_slist_prepend(aio_ctxs, aio_context);
}
}
/* Note that completion of an asynchronous I/O operation can trigger any
* number of other I/O operations on other devices---for example a
* coroutine can submit an I/O request to another device in response to
* request completion. Therefore we must keep looping until there was no
* more activity rather than simply draining each device independently.
*/
while (waited) {
waited = false;
for (ctx = aio_ctxs; ctx != NULL; ctx = ctx->next) {
AioContext *aio_context = ctx->data;
aio_context_acquire(aio_context);
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
if (aio_context == bdrv_get_aio_context(bs)) {
waited |= bdrv_drain_recurse(bs);
}
}
aio_context_release(aio_context);
}
}
g_slist_free(aio_ctxs);
}
void bdrv_drain_all_end(void)
{
BlockDriverState *bs;
BdrvNextIterator it;
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
AioContext *aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
aio_enable_external(aio_context);
bdrv_parent_drained_end(bs);
aio_context_release(aio_context);
}
block_job_resume_all();
}
void bdrv_drain_all(void)
{
bdrv_drain_all_begin();
bdrv_drain_all_end();
}
/**
* Remove an active request from the tracked requests list
*
* This function should be called when a tracked request is completing.
*/
static void tracked_request_end(BdrvTrackedRequest *req)
{
if (req->serialising) {
atomic_dec(&req->bs->serialising_in_flight);
}
qemu_co_mutex_lock(&req->bs->reqs_lock);
QLIST_REMOVE(req, list);
qemu_co_queue_restart_all(&req->wait_queue);
qemu_co_mutex_unlock(&req->bs->reqs_lock);
}
/**
* Add an active request to the tracked requests list
*/
static void tracked_request_begin(BdrvTrackedRequest *req,
BlockDriverState *bs,
int64_t offset,
unsigned int bytes,
enum BdrvTrackedRequestType type)
{
*req = (BdrvTrackedRequest){
.bs = bs,
.offset = offset,
.bytes = bytes,
.type = type,
.co = qemu_coroutine_self(),
.serialising = false,
.overlap_offset = offset,
.overlap_bytes = bytes,
};
qemu_co_queue_init(&req->wait_queue);
qemu_co_mutex_lock(&bs->reqs_lock);
QLIST_INSERT_HEAD(&bs->tracked_requests, req, list);
qemu_co_mutex_unlock(&bs->reqs_lock);
}
static void mark_request_serialising(BdrvTrackedRequest *req, uint64_t align)
{
int64_t overlap_offset = req->offset & ~(align - 1);
unsigned int overlap_bytes = ROUND_UP(req->offset + req->bytes, align)
- overlap_offset;
if (!req->serialising) {
atomic_inc(&req->bs->serialising_in_flight);
req->serialising = true;
}
req->overlap_offset = MIN(req->overlap_offset, overlap_offset);
req->overlap_bytes = MAX(req->overlap_bytes, overlap_bytes);
}
/**
* Round a region to cluster boundaries
*/
void bdrv_round_to_clusters(BlockDriverState *bs,
int64_t offset, unsigned int bytes,
int64_t *cluster_offset,
unsigned int *cluster_bytes)
{
BlockDriverInfo bdi;
if (bdrv_get_info(bs, &bdi) < 0 || bdi.cluster_size == 0) {
*cluster_offset = offset;
*cluster_bytes = bytes;
} else {
int64_t c = bdi.cluster_size;
*cluster_offset = QEMU_ALIGN_DOWN(offset, c);
*cluster_bytes = QEMU_ALIGN_UP(offset - *cluster_offset + bytes, c);
}
}
static int bdrv_get_cluster_size(BlockDriverState *bs)
{
BlockDriverInfo bdi;
int ret;
ret = bdrv_get_info(bs, &bdi);
if (ret < 0 || bdi.cluster_size == 0) {
return bs->bl.request_alignment;
} else {
return bdi.cluster_size;
}
}
static bool tracked_request_overlaps(BdrvTrackedRequest *req,
int64_t offset, unsigned int bytes)
{
/* aaaa bbbb */
if (offset >= req->overlap_offset + req->overlap_bytes) {
return false;
}
/* bbbb aaaa */
if (req->overlap_offset >= offset + bytes) {
return false;
}
return true;
}
void bdrv_inc_in_flight(BlockDriverState *bs)
{
atomic_inc(&bs->in_flight);
}
static void dummy_bh_cb(void *opaque)
{
}
void bdrv_wakeup(BlockDriverState *bs)
{
/* The barrier (or an atomic op) is in the caller. */
if (atomic_read(&bs->wakeup)) {
aio_bh_schedule_oneshot(qemu_get_aio_context(), dummy_bh_cb, NULL);
}
}
void bdrv_dec_in_flight(BlockDriverState *bs)
{
atomic_dec(&bs->in_flight);
bdrv_wakeup(bs);
}
static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self)
{
BlockDriverState *bs = self->bs;
BdrvTrackedRequest *req;
bool retry;
bool waited = false;
if (!atomic_read(&bs->serialising_in_flight)) {
return false;
}
do {
retry = false;
qemu_co_mutex_lock(&bs->reqs_lock);
QLIST_FOREACH(req, &bs->tracked_requests, list) {
if (req == self || (!req->serialising && !self->serialising)) {
continue;
}
if (tracked_request_overlaps(req, self->overlap_offset,
self->overlap_bytes))
{
/* Hitting this means there was a reentrant request, for
* example, a block driver issuing nested requests. This must
* never happen since it means deadlock.
*/
assert(qemu_coroutine_self() != req->co);
/* If the request is already (indirectly) waiting for us, or
* will wait for us as soon as it wakes up, then just go on
* (instead of producing a deadlock in the former case). */
if (!req->waiting_for) {
self->waiting_for = req;
qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock);
self->waiting_for = NULL;
retry = true;
waited = true;
break;
}
}
}
qemu_co_mutex_unlock(&bs->reqs_lock);
} while (retry);
return waited;
}
static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset,
size_t size)
{
if (size > BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS) {
return -EIO;
}
if (!bdrv_is_inserted(bs)) {
return -ENOMEDIUM;
}
if (offset < 0) {
return -EIO;
}
return 0;
}
typedef struct RwCo {
BdrvChild *child;
int64_t offset;
QEMUIOVector *qiov;
bool is_write;
int ret;
BdrvRequestFlags flags;
} RwCo;
static void coroutine_fn bdrv_rw_co_entry(void *opaque)
{
RwCo *rwco = opaque;
if (!rwco->is_write) {
rwco->ret = bdrv_co_preadv(rwco->child, rwco->offset,
rwco->qiov->size, rwco->qiov,
rwco->flags);
} else {
rwco->ret = bdrv_co_pwritev(rwco->child, rwco->offset,
rwco->qiov->size, rwco->qiov,
rwco->flags);
}
}
/*
* Process a vectored synchronous request using coroutines
*/
static int bdrv_prwv_co(BdrvChild *child, int64_t offset,
QEMUIOVector *qiov, bool is_write,
BdrvRequestFlags flags)
{
Coroutine *co;
RwCo rwco = {
.child = child,
.offset = offset,
.qiov = qiov,
.is_write = is_write,
.ret = NOT_DONE,
.flags = flags,
};
if (qemu_in_coroutine()) {
/* Fast-path if already in coroutine context */
bdrv_rw_co_entry(&rwco);
} else {
co = qemu_coroutine_create(bdrv_rw_co_entry, &rwco);
bdrv_coroutine_enter(child->bs, co);
BDRV_POLL_WHILE(child->bs, rwco.ret == NOT_DONE);
}
return rwco.ret;
}
/*
* Process a synchronous request using coroutines
*/
static int bdrv_rw_co(BdrvChild *child, int64_t sector_num, uint8_t *buf,
int nb_sectors, bool is_write, BdrvRequestFlags flags)
{
QEMUIOVector qiov;
struct iovec iov = {
.iov_base = (void *)buf,
.iov_len = nb_sectors * BDRV_SECTOR_SIZE,
};
if (nb_sectors < 0 || nb_sectors > BDRV_REQUEST_MAX_SECTORS) {
return -EINVAL;
}
qemu_iovec_init_external(&qiov, &iov, 1);
return bdrv_prwv_co(child, sector_num << BDRV_SECTOR_BITS,
&qiov, is_write, flags);
}
/* return < 0 if error. See bdrv_write() for the return codes */
int bdrv_read(BdrvChild *child, int64_t sector_num,
uint8_t *buf, int nb_sectors)
{
return bdrv_rw_co(child, sector_num, buf, nb_sectors, false, 0);
}
/* Return < 0 if error. Important errors are:
-EIO generic I/O error (may happen for all errors)
-ENOMEDIUM No media inserted.
-EINVAL Invalid sector number or nb_sectors
-EACCES Trying to write a read-only device
*/
int bdrv_write(BdrvChild *child, int64_t sector_num,
const uint8_t *buf, int nb_sectors)
{
return bdrv_rw_co(child, sector_num, (uint8_t *)buf, nb_sectors, true, 0);
}
int bdrv_pwrite_zeroes(BdrvChild *child, int64_t offset,
int bytes, BdrvRequestFlags flags)
{
QEMUIOVector qiov;
struct iovec iov = {
.iov_base = NULL,
.iov_len = bytes,
};
qemu_iovec_init_external(&qiov, &iov, 1);
return bdrv_prwv_co(child, offset, &qiov, true,
BDRV_REQ_ZERO_WRITE | flags);
}
/*
* Completely zero out a block device with the help of bdrv_pwrite_zeroes.
* The operation is sped up by checking the block status and only writing
* zeroes to the device if they currently do not return zeroes. Optional
* flags are passed through to bdrv_pwrite_zeroes (e.g. BDRV_REQ_MAY_UNMAP,
* BDRV_REQ_FUA).
*
* Returns < 0 on error, 0 on success. For error codes see bdrv_write().
*/
int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
{
int64_t target_sectors, ret, nb_sectors, sector_num = 0;
BlockDriverState *bs = child->bs;
BlockDriverState *file;
int n;
target_sectors = bdrv_nb_sectors(bs);
if (target_sectors < 0) {
return target_sectors;
}
for (;;) {
nb_sectors = MIN(target_sectors - sector_num, BDRV_REQUEST_MAX_SECTORS);
if (nb_sectors <= 0) {
return 0;
}
ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n, &file);
if (ret < 0) {
error_report("error getting block status at sector %" PRId64 ": %s",
sector_num, strerror(-ret));
return ret;
}
if (ret & BDRV_BLOCK_ZERO) {
sector_num += n;
continue;
}
ret = bdrv_pwrite_zeroes(child, sector_num << BDRV_SECTOR_BITS,
n << BDRV_SECTOR_BITS, flags);
if (ret < 0) {
error_report("error writing zeroes at sector %" PRId64 ": %s",
sector_num, strerror(-ret));
return ret;
}
sector_num += n;
}
}
int bdrv_preadv(BdrvChild *child, int64_t offset, QEMUIOVector *qiov)
{
int ret;
ret = bdrv_prwv_co(child, offset, qiov, false, 0);
if (ret < 0) {
return ret;
}
return qiov->size;
}
int bdrv_pread(BdrvChild *child, int64_t offset, void *buf, int bytes)
{
QEMUIOVector qiov;
struct iovec iov = {
.iov_base = (void *)buf,
.iov_len = bytes,
};
if (bytes < 0) {
return -EINVAL;
}
qemu_iovec_init_external(&qiov, &iov, 1);
return bdrv_preadv(child, offset, &qiov);
}
int bdrv_pwritev(BdrvChild *child, int64_t offset, QEMUIOVector *qiov)
{
int ret;
ret = bdrv_prwv_co(child, offset, qiov, true, 0);
if (ret < 0) {
return ret;
}
return qiov->size;
}
int bdrv_pwrite(BdrvChild *child, int64_t offset, const void *buf, int bytes)
{
QEMUIOVector qiov;
struct iovec iov = {
.iov_base = (void *) buf,
.iov_len = bytes,
};
if (bytes < 0) {
return -EINVAL;
}
qemu_iovec_init_external(&qiov, &iov, 1);
return bdrv_pwritev(child, offset, &qiov);
}
/*
* Writes to the file and ensures that no writes are reordered across this
* request (acts as a barrier)
*
* Returns 0 on success, -errno in error cases.
*/
int bdrv_pwrite_sync(BdrvChild *child, int64_t offset,
const void *buf, int count)
{
int ret;
ret = bdrv_pwrite(child, offset, buf, count);
if (ret < 0) {
return ret;
}
ret = bdrv_flush(child->bs);
if (ret < 0) {
return ret;
}
return 0;
}
typedef struct CoroutineIOCompletion {
Coroutine *coroutine;
int ret;
} CoroutineIOCompletion;
static void bdrv_co_io_em_complete(void *opaque, int ret)
{
CoroutineIOCompletion *co = opaque;
co->ret = ret;
aio_co_wake(co->coroutine);
}
static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
BlockDriver *drv = bs->drv;
int64_t sector_num;
unsigned int nb_sectors;
assert(!(flags & ~BDRV_REQ_MASK));
if (drv->bdrv_co_preadv) {
return drv->bdrv_co_preadv(bs, offset, bytes, qiov, flags);
}
sector_num = offset >> BDRV_SECTOR_BITS;
nb_sectors = bytes >> BDRV_SECTOR_BITS;
assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS);
if (drv->bdrv_co_readv) {
return drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
} else {
BlockAIOCB *acb;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
acb = bs->drv->bdrv_aio_readv(bs, sector_num, qiov, nb_sectors,
bdrv_co_io_em_complete, &co);
if (acb == NULL) {
return -EIO;
} else {
qemu_coroutine_yield();
return co.ret;
}
}
}
static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
BlockDriver *drv = bs->drv;
int64_t sector_num;
unsigned int nb_sectors;
int ret;
assert(!(flags & ~BDRV_REQ_MASK));
if (drv->bdrv_co_pwritev) {
ret = drv->bdrv_co_pwritev(bs, offset, bytes, qiov,
flags & bs->supported_write_flags);
flags &= ~bs->supported_write_flags;
goto emulate_flags;
}
sector_num = offset >> BDRV_SECTOR_BITS;
nb_sectors = bytes >> BDRV_SECTOR_BITS;
assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS);
if (drv->bdrv_co_writev_flags) {
ret = drv->bdrv_co_writev_flags(bs, sector_num, nb_sectors, qiov,
flags & bs->supported_write_flags);
flags &= ~bs->supported_write_flags;
} else if (drv->bdrv_co_writev) {
assert(!bs->supported_write_flags);
ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov);
} else {
BlockAIOCB *acb;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
acb = bs->drv->bdrv_aio_writev(bs, sector_num, qiov, nb_sectors,
bdrv_co_io_em_complete, &co);
if (acb == NULL) {
ret = -EIO;
} else {
qemu_coroutine_yield();
ret = co.ret;
}
}
emulate_flags:
if (ret == 0 && (flags & BDRV_REQ_FUA)) {
ret = bdrv_co_flush(bs);
}
return ret;
}
static int coroutine_fn
bdrv_driver_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
uint64_t bytes, QEMUIOVector *qiov)
{
BlockDriver *drv = bs->drv;
if (!drv->bdrv_co_pwritev_compressed) {
return -ENOTSUP;
}
return drv->bdrv_co_pwritev_compressed(bs, offset, bytes, qiov);
}
static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
int64_t offset, unsigned int bytes, QEMUIOVector *qiov)
{
BlockDriverState *bs = child->bs;
/* Perform I/O through a temporary buffer so that users who scribble over
* their read buffer while the operation is in progress do not end up
* modifying the image file. This is critical for zero-copy guest I/O
* where anything might happen inside guest memory.
*/
void *bounce_buffer;
BlockDriver *drv = bs->drv;
struct iovec iov;
QEMUIOVector local_qiov;
int64_t cluster_offset;
unsigned int cluster_bytes;
size_t skip_bytes;
int ret;
int max_transfer = MIN_NON_ZERO(bs->bl.max_transfer,
BDRV_REQUEST_MAX_BYTES);
unsigned int progress = 0;
/* FIXME We cannot require callers to have write permissions when all they
* are doing is a read request. If we did things right, write permissions
* would be obtained anyway, but internally by the copy-on-read code. As
* long as it is implemented here rather than in a separate filter driver,
* the copy-on-read code doesn't have its own BdrvChild, however, for which
* it could request permissions. Therefore we have to bypass the permission
* system for the moment. */
// assert(child->perm & (BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE));
/* Cover entire cluster so no additional backing file I/O is required when
* allocating cluster in the image file. Note that this value may exceed
* BDRV_REQUEST_MAX_BYTES (even when the original read did not), which
* is one reason we loop rather than doing it all at once.
*/
bdrv_round_to_clusters(bs, offset, bytes, &cluster_offset, &cluster_bytes);
skip_bytes = offset - cluster_offset;
trace_bdrv_co_do_copy_on_readv(bs, offset, bytes,
cluster_offset, cluster_bytes);
bounce_buffer = qemu_try_blockalign(bs,
MIN(MIN(max_transfer, cluster_bytes),
MAX_BOUNCE_BUFFER));
if (bounce_buffer == NULL) {
ret = -ENOMEM;
goto err;
}
while (cluster_bytes) {
int64_t pnum;
ret = bdrv_is_allocated(bs, cluster_offset,
MIN(cluster_bytes, max_transfer), &pnum);
if (ret < 0) {
/* Safe to treat errors in querying allocation as if
* unallocated; we'll probably fail again soon on the
* read, but at least that will set a decent errno.
*/
pnum = MIN(cluster_bytes, max_transfer);
}
assert(skip_bytes < pnum);
if (ret <= 0) {
/* Must copy-on-read; use the bounce buffer */
iov.iov_base = bounce_buffer;
iov.iov_len = pnum = MIN(pnum, MAX_BOUNCE_BUFFER);
qemu_iovec_init_external(&local_qiov, &iov, 1);
ret = bdrv_driver_preadv(bs, cluster_offset, pnum,
&local_qiov, 0);
if (ret < 0) {
goto err;
}
bdrv_debug_event(bs, BLKDBG_COR_WRITE);
if (drv->bdrv_co_pwrite_zeroes &&
buffer_is_zero(bounce_buffer, pnum)) {
/* FIXME: Should we (perhaps conditionally) be setting
* BDRV_REQ_MAY_UNMAP, if it will allow for a sparser copy
* that still correctly reads as zero? */
ret = bdrv_co_do_pwrite_zeroes(bs, cluster_offset, pnum, 0);
} else {
/* This does not change the data on the disk, it is not
* necessary to flush even in cache=writethrough mode.
*/
ret = bdrv_driver_pwritev(bs, cluster_offset, pnum,
&local_qiov, 0);
}
if (ret < 0) {
/* It might be okay to ignore write errors for guest
* requests. If this is a deliberate copy-on-read
* then we don't want to ignore the error. Simply
* report it in all cases.
*/
goto err;
}
qemu_iovec_from_buf(qiov, progress, bounce_buffer + skip_bytes,
pnum - skip_bytes);
} else {
/* Read directly into the destination */
qemu_iovec_init(&local_qiov, qiov->niov);
qemu_iovec_concat(&local_qiov, qiov, progress, pnum - skip_bytes);
ret = bdrv_driver_preadv(bs, offset + progress, local_qiov.size,
&local_qiov, 0);
qemu_iovec_destroy(&local_qiov);
if (ret < 0) {
goto err;
}
}
cluster_offset += pnum;
cluster_bytes -= pnum;
progress += pnum - skip_bytes;
skip_bytes = 0;
}
ret = 0;
err:
qemu_vfree(bounce_buffer);
return ret;
}
/*
* Forwards an already correctly aligned request to the BlockDriver. This
* handles copy on read, zeroing after EOF, and fragmentation of large
* reads; any other features must be implemented by the caller.
*/
static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
BdrvTrackedRequest *req, int64_t offset, unsigned int bytes,
int64_t align, QEMUIOVector *qiov, int flags)
{
BlockDriverState *bs = child->bs;
int64_t total_bytes, max_bytes;
int ret = 0;
uint64_t bytes_remaining = bytes;
int max_transfer;
assert(is_power_of_2(align));
assert((offset & (align - 1)) == 0);
assert((bytes & (align - 1)) == 0);
assert(!qiov || bytes == qiov->size);
assert((bs->open_flags & BDRV_O_NO_IO) == 0);
max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX),
align);
/* TODO: We would need a per-BDS .supported_read_flags and
* potential fallback support, if we ever implement any read flags
* to pass through to drivers. For now, there aren't any
* passthrough flags. */
assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ)));
/* Handle Copy on Read and associated serialisation */
if (flags & BDRV_REQ_COPY_ON_READ) {
/* If we touch the same cluster it counts as an overlap. This
* guarantees that allocating writes will be serialized and not race
* with each other for the same cluster. For example, in copy-on-read
* it ensures that the CoR read and write operations are atomic and
* guest writes cannot interleave between them. */
mark_request_serialising(req, bdrv_get_cluster_size(bs));
}
if (!(flags & BDRV_REQ_NO_SERIALISING)) {
wait_serialising_requests(req);
}
if (flags & BDRV_REQ_COPY_ON_READ) {
/* TODO: Simplify further once bdrv_is_allocated no longer
* requires sector alignment */
int64_t start = QEMU_ALIGN_DOWN(offset, BDRV_SECTOR_SIZE);
int64_t end = QEMU_ALIGN_UP(offset + bytes, BDRV_SECTOR_SIZE);
int64_t pnum;
ret = bdrv_is_allocated(bs, start, end - start, &pnum);
if (ret < 0) {
goto out;
}
if (!ret || pnum != end - start) {
ret = bdrv_co_do_copy_on_readv(child, offset, bytes, qiov);
goto out;
}
}
/* Forward the request to the BlockDriver, possibly fragmenting it */
total_bytes = bdrv_getlength(bs);
if (total_bytes < 0) {
ret = total_bytes;
goto out;
}
max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
if (bytes <= max_bytes && bytes <= max_transfer) {
ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0);
goto out;
}
while (bytes_remaining) {
int num;
if (max_bytes) {
QEMUIOVector local_qiov;
num = MIN(bytes_remaining, MIN(max_bytes, max_transfer));
assert(num);
qemu_iovec_init(&local_qiov, qiov->niov);
qemu_iovec_concat(&local_qiov, qiov, bytes - bytes_remaining, num);
ret = bdrv_driver_preadv(bs, offset + bytes - bytes_remaining,
num, &local_qiov, 0);
max_bytes -= num;
qemu_iovec_destroy(&local_qiov);
} else {
num = bytes_remaining;
ret = qemu_iovec_memset(qiov, bytes - bytes_remaining, 0,
bytes_remaining);
}
if (ret < 0) {
goto out;
}
bytes_remaining -= num;
}
out:
return ret < 0 ? ret : 0;
}
/*
* Handle a read request in coroutine context
*/
int coroutine_fn bdrv_co_preadv(BdrvChild *child,
int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
BlockDriverState *bs = child->bs;
BlockDriver *drv = bs->drv;
BdrvTrackedRequest req;
uint64_t align = bs->bl.request_alignment;
uint8_t *head_buf = NULL;
uint8_t *tail_buf = NULL;
QEMUIOVector local_qiov;
bool use_local_qiov = false;
int ret;
trace_bdrv_co_preadv(child->bs, offset, bytes, flags);
if (!drv) {
return -ENOMEDIUM;
}
ret = bdrv_check_byte_request(bs, offset, bytes);
if (ret < 0) {
return ret;
}
bdrv_inc_in_flight(bs);
/* Don't do copy-on-read if we read data before write operation */
if (atomic_read(&bs->copy_on_read) && !(flags & BDRV_REQ_NO_SERIALISING)) {
flags |= BDRV_REQ_COPY_ON_READ;
}
/* Align read if necessary by padding qiov */
if (offset & (align - 1)) {
head_buf = qemu_blockalign(bs, align);
qemu_iovec_init(&local_qiov, qiov->niov + 2);
qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));
qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
use_local_qiov = true;
bytes += offset & (align - 1);
offset = offset & ~(align - 1);
}
if ((offset + bytes) & (align - 1)) {
if (!use_local_qiov) {
qemu_iovec_init(&local_qiov, qiov->niov + 1);
qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
use_local_qiov = true;
}
tail_buf = qemu_blockalign(bs, align);
qemu_iovec_add(&local_qiov, tail_buf,
align - ((offset + bytes) & (align - 1)));
bytes = ROUND_UP(bytes, align);
}
tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_READ);
ret = bdrv_aligned_preadv(child, &req, offset, bytes, align,
use_local_qiov ? &local_qiov : qiov,
flags);
tracked_request_end(&req);
bdrv_dec_in_flight(bs);
if (use_local_qiov) {
qemu_iovec_destroy(&local_qiov);
qemu_vfree(head_buf);
qemu_vfree(tail_buf);
}
return ret;
}
static int coroutine_fn bdrv_co_do_readv(BdrvChild *child,
int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
if (nb_sectors < 0 || nb_sectors > BDRV_REQUEST_MAX_SECTORS) {
return -EINVAL;
}
return bdrv_co_preadv(child, sector_num << BDRV_SECTOR_BITS,
nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
}
int coroutine_fn bdrv_co_readv(BdrvChild *child, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
{
return bdrv_co_do_readv(child, sector_num, nb_sectors, qiov, 0);
}
static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
int64_t offset, int bytes, BdrvRequestFlags flags)
{
BlockDriver *drv = bs->drv;
QEMUIOVector qiov;
struct iovec iov = {0};
int ret = 0;
bool need_flush = false;
int head = 0;
int tail = 0;
int max_write_zeroes = MIN_NON_ZERO(bs->bl.max_pwrite_zeroes, INT_MAX);
int alignment = MAX(bs->bl.pwrite_zeroes_alignment,
bs->bl.request_alignment);
int max_transfer = MIN_NON_ZERO(bs->bl.max_transfer, MAX_BOUNCE_BUFFER);
assert(alignment % bs->bl.request_alignment == 0);
head = offset % alignment;
tail = (offset + bytes) % alignment;
max_write_zeroes = QEMU_ALIGN_DOWN(max_write_zeroes, alignment);
assert(max_write_zeroes >= bs->bl.request_alignment);
while (bytes > 0 && !ret) {
int num = bytes;
/* Align request. Block drivers can expect the "bulk" of the request
* to be aligned, and that unaligned requests do not cross cluster
* boundaries.
*/
if (head) {
/* Make a small request up to the first aligned sector. For
* convenience, limit this request to max_transfer even if
* we don't need to fall back to writes. */
num = MIN(MIN(bytes, max_transfer), alignment - head);
head = (head + num) % alignment;
assert(num < max_write_zeroes);
} else if (tail && num > alignment) {
/* Shorten the request to the last aligned sector. */
num -= tail;
}
/* limit request size */
if (num > max_write_zeroes) {
num = max_write_zeroes;
}
ret = -ENOTSUP;
/* First try the efficient write zeroes operation */
if (drv->bdrv_co_pwrite_zeroes) {
ret = drv->bdrv_co_pwrite_zeroes(bs, offset, num,
flags & bs->supported_zero_flags);
if (ret != -ENOTSUP && (flags & BDRV_REQ_FUA) &&
!(bs->supported_zero_flags & BDRV_REQ_FUA)) {
need_flush = true;
}
} else {
assert(!bs->supported_zero_flags);
}
if (ret == -ENOTSUP) {
/* Fall back to bounce buffer if write zeroes is unsupported */
BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE;
if ((flags & BDRV_REQ_FUA) &&
!(bs->supported_write_flags & BDRV_REQ_FUA)) {
/* No need for bdrv_driver_pwrite() to do a fallback
* flush on each chunk; use just one at the end */
write_flags &= ~BDRV_REQ_FUA;
need_flush = true;
}
num = MIN(num, max_transfer);
iov.iov_len = num;
if (iov.iov_base == NULL) {
iov.iov_base = qemu_try_blockalign(bs, num);
if (iov.iov_base == NULL) {
ret = -ENOMEM;
goto fail;
}
memset(iov.iov_base, 0, num);
}
qemu_iovec_init_external(&qiov, &iov, 1);
ret = bdrv_driver_pwritev(bs, offset, num, &qiov, write_flags);
/* Keep bounce buffer around if it is big enough for all
* all future requests.
*/
if (num < max_transfer) {
qemu_vfree(iov.iov_base);
iov.iov_base = NULL;
}
}
offset += num;
bytes -= num;
}
fail:
if (ret == 0 && need_flush) {
ret = bdrv_co_flush(bs);
}
qemu_vfree(iov.iov_base);
return ret;
}
/*
* Forwards an already correctly aligned write request to the BlockDriver,
* after possibly fragmenting it.
*/
static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
BdrvTrackedRequest *req, int64_t offset, unsigned int bytes,
int64_t align, QEMUIOVector *qiov, int flags)
{
BlockDriverState *bs = child->bs;
BlockDriver *drv = bs->drv;
bool waited;
int ret;
int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
uint64_t bytes_remaining = bytes;
int max_transfer;
if (bdrv_has_readonly_bitmaps(bs)) {
return -EPERM;
}
assert(is_power_of_2(align));
assert((offset & (align - 1)) == 0);
assert((bytes & (align - 1)) == 0);
assert(!qiov || bytes == qiov->size);
assert((bs->open_flags & BDRV_O_NO_IO) == 0);
assert(!(flags & ~BDRV_REQ_MASK));
max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX),
align);
waited = wait_serialising_requests(req);
assert(!waited || !req->serialising);
assert(req->overlap_offset <= offset);
assert(offset + bytes <= req->overlap_offset + req->overlap_bytes);
assert(child->perm & BLK_PERM_WRITE);
assert(end_sector <= bs->total_sectors || child->perm & BLK_PERM_RESIZE);
ret = notifier_with_return_list_notify(&bs->before_write_notifiers, req);
if (!ret && bs->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF &&
!(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes &&
qemu_iovec_is_zero(qiov)) {
flags |= BDRV_REQ_ZERO_WRITE;
if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) {
flags |= BDRV_REQ_MAY_UNMAP;
}
}
if (ret < 0) {
/* Do nothing, write notifier decided to fail this request */
} else if (flags & BDRV_REQ_ZERO_WRITE) {
bdrv_debug_event(bs, BLKDBG_PWRITEV_ZERO);
ret = bdrv_co_do_pwrite_zeroes(bs, offset, bytes, flags);
} else if (flags & BDRV_REQ_WRITE_COMPRESSED) {
ret = bdrv_driver_pwritev_compressed(bs, offset, bytes, qiov);
} else if (bytes <= max_transfer) {
bdrv_debug_event(bs, BLKDBG_PWRITEV);
ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, flags);
} else {
bdrv_debug_event(bs, BLKDBG_PWRITEV);
while (bytes_remaining) {
int num = MIN(bytes_remaining, max_transfer);
QEMUIOVector local_qiov;
int local_flags = flags;
assert(num);
if (num < bytes_remaining && (flags & BDRV_REQ_FUA) &&
!(bs->supported_write_flags & BDRV_REQ_FUA)) {
/* If FUA is going to be emulated by flush, we only
* need to flush on the last iteration */
local_flags &= ~BDRV_REQ_FUA;
}
qemu_iovec_init(&local_qiov, qiov->niov);
qemu_iovec_concat(&local_qiov, qiov, bytes - bytes_remaining, num);
ret = bdrv_driver_pwritev(bs, offset + bytes - bytes_remaining,
num, &local_qiov, local_flags);
qemu_iovec_destroy(&local_qiov);
if (ret < 0) {
break;
}
bytes_remaining -= num;
}
}
bdrv_debug_event(bs, BLKDBG_PWRITEV_DONE);
atomic_inc(&bs->write_gen);
bdrv_set_dirty(bs, offset, bytes);
stat64_max(&bs->wr_highest_offset, offset + bytes);
if (ret >= 0) {
bs->total_sectors = MAX(bs->total_sectors, end_sector);
ret = 0;
}
return ret;
}
static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
int64_t offset,
unsigned int bytes,
BdrvRequestFlags flags,
BdrvTrackedRequest *req)
{
BlockDriverState *bs = child->bs;
uint8_t *buf = NULL;
QEMUIOVector local_qiov;
struct iovec iov;
uint64_t align = bs->bl.request_alignment;
unsigned int head_padding_bytes, tail_padding_bytes;
int ret = 0;
head_padding_bytes = offset & (align - 1);
tail_padding_bytes = (align - (offset + bytes)) & (align - 1);
assert(flags & BDRV_REQ_ZERO_WRITE);
if (head_padding_bytes || tail_padding_bytes) {
buf = qemu_blockalign(bs, align);
iov = (struct iovec) {
.iov_base = buf,
.iov_len = align,
};
qemu_iovec_init_external(&local_qiov, &iov, 1);
}
if (head_padding_bytes) {
uint64_t zero_bytes = MIN(bytes, align - head_padding_bytes);
/* RMW the unaligned part before head. */
mark_request_serialising(req, align);
wait_serialising_requests(req);
bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
ret = bdrv_aligned_preadv(child, req, offset & ~(align - 1), align,
align, &local_qiov, 0);
if (ret < 0) {
goto fail;
}
bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
memset(buf + head_padding_bytes, 0, zero_bytes);
ret = bdrv_aligned_pwritev(child, req, offset & ~(align - 1), align,
align, &local_qiov,
flags & ~BDRV_REQ_ZERO_WRITE);
if (ret < 0) {
goto fail;
}
offset += zero_bytes;
bytes -= zero_bytes;
}
assert(!bytes || (offset & (align - 1)) == 0);
if (bytes >= align) {
/* Write the aligned part in the middle. */
uint64_t aligned_bytes = bytes & ~(align - 1);
ret = bdrv_aligned_pwritev(child, req, offset, aligned_bytes, align,
NULL, flags);
if (ret < 0) {
goto fail;
}
bytes -= aligned_bytes;
offset += aligned_bytes;
}
assert(!bytes || (offset & (align - 1)) == 0);
if (bytes) {
assert(align == tail_padding_bytes + bytes);
/* RMW the unaligned part after tail. */
mark_request_serialising(req, align);
wait_serialising_requests(req);
bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
ret = bdrv_aligned_preadv(child, req, offset, align,
align, &local_qiov, 0);
if (ret < 0) {
goto fail;
}
bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
memset(buf, 0, bytes);
ret = bdrv_aligned_pwritev(child, req, offset, align, align,
&local_qiov, flags & ~BDRV_REQ_ZERO_WRITE);
}
fail:
qemu_vfree(buf);
return ret;
}
/*
* Handle a write request in coroutine context
*/
int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
BlockDriverState *bs = child->bs;
BdrvTrackedRequest req;
uint64_t align = bs->bl.request_alignment;
uint8_t *head_buf = NULL;
uint8_t *tail_buf = NULL;
QEMUIOVector local_qiov;
bool use_local_qiov = false;
int ret;
trace_bdrv_co_pwritev(child->bs, offset, bytes, flags);
if (!bs->drv) {
return -ENOMEDIUM;
}
if (bs->read_only) {
return -EPERM;
}
assert(!(bs->open_flags & BDRV_O_INACTIVE));
ret = bdrv_check_byte_request(bs, offset, bytes);
if (ret < 0) {
return ret;
}
bdrv_inc_in_flight(bs);
/*
* Align write if necessary by performing a read-modify-write cycle.
* Pad qiov with the read parts and be sure to have a tracked request not
* only for bdrv_aligned_pwritev, but also for the reads of the RMW cycle.
*/
tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_WRITE);
if (!qiov) {
ret = bdrv_co_do_zero_pwritev(child, offset, bytes, flags, &req);
goto out;
}
if (offset & (align - 1)) {
QEMUIOVector head_qiov;
struct iovec head_iov;
mark_request_serialising(&req, align);
wait_serialising_requests(&req);
head_buf = qemu_blockalign(bs, align);
head_iov = (struct iovec) {
.iov_base = head_buf,
.iov_len = align,
};
qemu_iovec_init_external(&head_qiov, &head_iov, 1);
bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
ret = bdrv_aligned_preadv(child, &req, offset & ~(align - 1), align,
align, &head_qiov, 0);
if (ret < 0) {
goto fail;
}
bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
qemu_iovec_init(&local_qiov, qiov->niov + 2);
qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));
qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
use_local_qiov = true;
bytes += offset & (align - 1);
offset = offset & ~(align - 1);
/* We have read the tail already if the request is smaller
* than one aligned block.
*/
if (bytes < align) {
qemu_iovec_add(&local_qiov, head_buf + bytes, align - bytes);
bytes = align;
}
}
if ((offset + bytes) & (align - 1)) {
QEMUIOVector tail_qiov;
struct iovec tail_iov;
size_t tail_bytes;
bool waited;
mark_request_serialising(&req, align);
waited = wait_serialising_requests(&req);
assert(!waited || !use_local_qiov);
tail_buf = qemu_blockalign(bs, align);
tail_iov = (struct iovec) {
.iov_base = tail_buf,
.iov_len = align,
};
qemu_iovec_init_external(&tail_qiov, &tail_iov, 1);
bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
ret = bdrv_aligned_preadv(child, &req, (offset + bytes) & ~(align - 1),
align, align, &tail_qiov, 0);
if (ret < 0) {
goto fail;
}
bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
if (!use_local_qiov) {
qemu_iovec_init(&local_qiov, qiov->niov + 1);
qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
use_local_qiov = true;
}
tail_bytes = (offset + bytes) & (align - 1);
qemu_iovec_add(&local_qiov, tail_buf + tail_bytes, align - tail_bytes);
bytes = ROUND_UP(bytes, align);
}
ret = bdrv_aligned_pwritev(child, &req, offset, bytes, align,
use_local_qiov ? &local_qiov : qiov,
flags);
fail:
if (use_local_qiov) {
qemu_iovec_destroy(&local_qiov);
}
qemu_vfree(head_buf);
qemu_vfree(tail_buf);
out:
tracked_request_end(&req);
bdrv_dec_in_flight(bs);
return ret;
}
static int coroutine_fn bdrv_co_do_writev(BdrvChild *child,
int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
if (nb_sectors < 0 || nb_sectors > BDRV_REQUEST_MAX_SECTORS) {
return -EINVAL;
}
return bdrv_co_pwritev(child, sector_num << BDRV_SECTOR_BITS,
nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
}
int coroutine_fn bdrv_co_writev(BdrvChild *child, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
{
return bdrv_co_do_writev(child, sector_num, nb_sectors, qiov, 0);
}
int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset,
int bytes, BdrvRequestFlags flags)
{
trace_bdrv_co_pwrite_zeroes(child->bs, offset, bytes, flags);
if (!(child->bs->open_flags & BDRV_O_UNMAP)) {
flags &= ~BDRV_REQ_MAY_UNMAP;
}
return bdrv_co_pwritev(child, offset, bytes, NULL,
BDRV_REQ_ZERO_WRITE | flags);
}
/*
* Flush ALL BDSes regardless of if they are reachable via a BlkBackend or not.
*/
int bdrv_flush_all(void)
{
BdrvNextIterator it;
BlockDriverState *bs = NULL;
int result = 0;
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
AioContext *aio_context = bdrv_get_aio_context(bs);
int ret;
aio_context_acquire(aio_context);
ret = bdrv_flush(bs);
if (ret < 0 && !result) {
result = ret;
}
aio_context_release(aio_context);
}
return result;
}
typedef struct BdrvCoGetBlockStatusData {
BlockDriverState *bs;
BlockDriverState *base;
BlockDriverState **file;
int64_t sector_num;
int nb_sectors;
int *pnum;
int64_t ret;
bool done;
} BdrvCoGetBlockStatusData;
int64_t coroutine_fn bdrv_co_get_block_status_from_file(BlockDriverState *bs,
int64_t sector_num,
int nb_sectors,
int *pnum,
BlockDriverState **file)
{
assert(bs->file && bs->file->bs);
*pnum = nb_sectors;
*file = bs->file->bs;
return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID |
(sector_num << BDRV_SECTOR_BITS);
}
int64_t coroutine_fn bdrv_co_get_block_status_from_backing(BlockDriverState *bs,
int64_t sector_num,
int nb_sectors,
int *pnum,
BlockDriverState **file)
{
assert(bs->backing && bs->backing->bs);
*pnum = nb_sectors;
*file = bs->backing->bs;
return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID |
(sector_num << BDRV_SECTOR_BITS);
}
/*
* Returns the allocation status of the specified sectors.
* Drivers not implementing the functionality are assumed to not support
* backing files, hence all their sectors are reported as allocated.
*
* If 'sector_num' is beyond the end of the disk image the return value is
* BDRV_BLOCK_EOF and 'pnum' is set to 0.
*
* 'pnum' is set to the number of sectors (including and immediately following
* the specified sector) that are known to be in the same
* allocated/unallocated state.
*
* 'nb_sectors' is the max value 'pnum' should be set to. If nb_sectors goes
* beyond the end of the disk image it will be clamped; if 'pnum' is set to
* the end of the image, then the returned value will include BDRV_BLOCK_EOF.
*
* If returned value is positive and BDRV_BLOCK_OFFSET_VALID bit is set, 'file'
* points to the BDS which the sector range is allocated in.
*/
static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
int64_t sector_num,
int nb_sectors, int *pnum,
BlockDriverState **file)
{
int64_t total_sectors;
int64_t n;
int64_t ret, ret2;
*file = NULL;
total_sectors = bdrv_nb_sectors(bs);
if (total_sectors < 0) {
return total_sectors;
}
if (sector_num >= total_sectors) {
*pnum = 0;
return BDRV_BLOCK_EOF;
}
if (!nb_sectors) {
*pnum = 0;
return 0;
}
n = total_sectors - sector_num;
if (n < nb_sectors) {
nb_sectors = n;
}
if (!bs->drv->bdrv_co_get_block_status) {
*pnum = nb_sectors;
ret = BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED;
if (sector_num + nb_sectors == total_sectors) {
ret |= BDRV_BLOCK_EOF;
}
if (bs->drv->protocol_name) {
ret |= BDRV_BLOCK_OFFSET_VALID | (sector_num * BDRV_SECTOR_SIZE);
*file = bs;
}
return ret;
}
bdrv_inc_in_flight(bs);
ret = bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors, pnum,
file);
if (ret < 0) {
*pnum = 0;
goto out;
}
if (ret & BDRV_BLOCK_RAW) {
assert(ret & BDRV_BLOCK_OFFSET_VALID && *file);
ret = bdrv_co_get_block_status(*file, ret >> BDRV_SECTOR_BITS,
*pnum, pnum, file);
goto out;
}
if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) {
ret |= BDRV_BLOCK_ALLOCATED;
} else {
if (bdrv_unallocated_blocks_are_zero(bs)) {
ret |= BDRV_BLOCK_ZERO;
} else if (bs->backing) {
BlockDriverState *bs2 = bs->backing->bs;
int64_t nb_sectors2 = bdrv_nb_sectors(bs2);
if (nb_sectors2 >= 0 && sector_num >= nb_sectors2) {
ret |= BDRV_BLOCK_ZERO;
}
}
}
if (*file && *file != bs &&
(ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
(ret & BDRV_BLOCK_OFFSET_VALID)) {
BlockDriverState *file2;
int file_pnum;
ret2 = bdrv_co_get_block_status(*file, ret >> BDRV_SECTOR_BITS,
*pnum, &file_pnum, &file2);
if (ret2 >= 0) {
/* Ignore errors. This is just providing extra information, it
* is useful but not necessary.
*/
if (ret2 & BDRV_BLOCK_EOF &&
(!file_pnum || ret2 & BDRV_BLOCK_ZERO)) {
/*
* It is valid for the format block driver to read
* beyond the end of the underlying file's current
* size; such areas read as zero.
*/
ret |= BDRV_BLOCK_ZERO;
} else {
/* Limit request to the range reported by the protocol driver */
*pnum = file_pnum;
ret |= (ret2 & BDRV_BLOCK_ZERO);
}
}
}
out:
bdrv_dec_in_flight(bs);
if (ret >= 0 && sector_num + *pnum == total_sectors) {
ret |= BDRV_BLOCK_EOF;
}
return ret;
}
static int64_t coroutine_fn bdrv_co_get_block_status_above(BlockDriverState *bs,
BlockDriverState *base,
int64_t sector_num,
int nb_sectors,
int *pnum,
BlockDriverState **file)
{
BlockDriverState *p;
int64_t ret = 0;
bool first = true;
assert(bs != base);
for (p = bs; p != base; p = backing_bs(p)) {
ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, pnum, file);
if (ret < 0) {
break;
}
if (ret & BDRV_BLOCK_ZERO && ret & BDRV_BLOCK_EOF && !first) {
/*
* Reading beyond the end of the file continues to read
* zeroes, but we can only widen the result to the
* unallocated length we learned from an earlier
* iteration.
*/
*pnum = nb_sectors;
}
if (ret & (BDRV_BLOCK_ZERO | BDRV_BLOCK_DATA)) {
break;
}
/* [sector_num, pnum] unallocated on this layer, which could be only
* the first part of [sector_num, nb_sectors]. */
nb_sectors = MIN(nb_sectors, *pnum);
first = false;
}
return ret;
}
/* Coroutine wrapper for bdrv_get_block_status_above() */
static void coroutine_fn bdrv_get_block_status_above_co_entry(void *opaque)
{
BdrvCoGetBlockStatusData *data = opaque;
data->ret = bdrv_co_get_block_status_above(data->bs, data->base,
data->sector_num,
data->nb_sectors,
data->pnum,
data->file);
data->done = true;
}
/*
* Synchronous wrapper around bdrv_co_get_block_status_above().
*
* See bdrv_co_get_block_status_above() for details.
*/
int64_t bdrv_get_block_status_above(BlockDriverState *bs,
BlockDriverState *base,
int64_t sector_num,
int nb_sectors, int *pnum,
BlockDriverState **file)
{
Coroutine *co;
BdrvCoGetBlockStatusData data = {
.bs = bs,
.base = base,
.file = file,
.sector_num = sector_num,
.nb_sectors = nb_sectors,
.pnum = pnum,
.done = false,
};
if (qemu_in_coroutine()) {
/* Fast-path if already in coroutine context */
bdrv_get_block_status_above_co_entry(&data);
} else {
co = qemu_coroutine_create(bdrv_get_block_status_above_co_entry,
&data);
bdrv_coroutine_enter(bs, co);
BDRV_POLL_WHILE(bs, !data.done);
}
return data.ret;
}
int64_t bdrv_get_block_status(BlockDriverState *bs,
int64_t sector_num,
int nb_sectors, int *pnum,
BlockDriverState **file)
{
return bdrv_get_block_status_above(bs, backing_bs(bs),
sector_num, nb_sectors, pnum, file);
}
int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset,
int64_t bytes, int64_t *pnum)
{
BlockDriverState *file;
int64_t sector_num = offset >> BDRV_SECTOR_BITS;
int nb_sectors = bytes >> BDRV_SECTOR_BITS;
int64_t ret;
int psectors;
assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE) && bytes < INT_MAX);
ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &psectors,
&file);
if (ret < 0) {
return ret;
}
if (pnum) {
*pnum = psectors * BDRV_SECTOR_SIZE;
}
return !!(ret & BDRV_BLOCK_ALLOCATED);
}
/*
* Given an image chain: ... -> [BASE] -> [INTER1] -> [INTER2] -> [TOP]
*
* Return true if (a prefix of) the given range is allocated in any image
* between BASE and TOP (inclusive). BASE can be NULL to check if the given
* offset is allocated in any image of the chain. Return false otherwise,
* or negative errno on failure.
*
* 'pnum' is set to the number of bytes (including and immediately
* following the specified offset) that are known to be in the same
* allocated/unallocated state. Note that a subsequent call starting
* at 'offset + *pnum' may return the same allocation status (in other
* words, the result is not necessarily the maximum possible range);
* but 'pnum' will only be 0 when end of file is reached.
*
*/
int bdrv_is_allocated_above(BlockDriverState *top,
BlockDriverState *base,
int64_t offset, int64_t bytes, int64_t *pnum)
{
BlockDriverState *intermediate;
int ret;
int64_t n = bytes;
intermediate = top;
while (intermediate && intermediate != base) {
int64_t pnum_inter;
int64_t size_inter;
ret = bdrv_is_allocated(intermediate, offset, bytes, &pnum_inter);
if (ret < 0) {
return ret;
}
if (ret) {
*pnum = pnum_inter;
return 1;
}
size_inter = bdrv_getlength(intermediate);
if (size_inter < 0) {
return size_inter;
}
if (n > pnum_inter &&
(intermediate == top || offset + pnum_inter < size_inter)) {
n = pnum_inter;
}
intermediate = backing_bs(intermediate);
}
*pnum = n;
return 0;
}
typedef struct BdrvVmstateCo {
BlockDriverState *bs;
QEMUIOVector *qiov;
int64_t pos;
bool is_read;
int ret;
} BdrvVmstateCo;
static int coroutine_fn
bdrv_co_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
bool is_read)
{
BlockDriver *drv = bs->drv;
int ret = -ENOTSUP;
bdrv_inc_in_flight(bs);
if (!drv) {
ret = -ENOMEDIUM;
} else if (drv->bdrv_load_vmstate) {
if (is_read) {
ret = drv->bdrv_load_vmstate(bs, qiov, pos);
} else {
ret = drv->bdrv_save_vmstate(bs, qiov, pos);
}
} else if (bs->file) {
ret = bdrv_co_rw_vmstate(bs->file->bs, qiov, pos, is_read);
}
bdrv_dec_in_flight(bs);
return ret;
}
static void coroutine_fn bdrv_co_rw_vmstate_entry(void *opaque)
{
BdrvVmstateCo *co = opaque;
co->ret = bdrv_co_rw_vmstate(co->bs, co->qiov, co->pos, co->is_read);
}
static inline int
bdrv_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
bool is_read)
{
if (qemu_in_coroutine()) {
return bdrv_co_rw_vmstate(bs, qiov, pos, is_read);
} else {
BdrvVmstateCo data = {
.bs = bs,
.qiov = qiov,
.pos = pos,
.is_read = is_read,
.ret = -EINPROGRESS,
};
Coroutine *co = qemu_coroutine_create(bdrv_co_rw_vmstate_entry, &data);
bdrv_coroutine_enter(bs, co);
BDRV_POLL_WHILE(bs, data.ret == -EINPROGRESS);
return data.ret;
}
}
int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
int64_t pos, int size)
{
QEMUIOVector qiov;
struct iovec iov = {
.iov_base = (void *) buf,
.iov_len = size,
};
int ret;
qemu_iovec_init_external(&qiov, &iov, 1);
ret = bdrv_writev_vmstate(bs, &qiov, pos);
if (ret < 0) {
return ret;
}
return size;
}
int bdrv_writev_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
{
return bdrv_rw_vmstate(bs, qiov, pos, false);
}
int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf,
int64_t pos, int size)
{
QEMUIOVector qiov;
struct iovec iov = {
.iov_base = buf,
.iov_len = size,
};
int ret;
qemu_iovec_init_external(&qiov, &iov, 1);
ret = bdrv_readv_vmstate(bs, &qiov, pos);
if (ret < 0) {
return ret;
}
return size;
}
int bdrv_readv_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
{
return bdrv_rw_vmstate(bs, qiov, pos, true);
}
/**************************************************************/
/* async I/Os */
void bdrv_aio_cancel(BlockAIOCB *acb)
{
qemu_aio_ref(acb);
bdrv_aio_cancel_async(acb);
while (acb->refcnt > 1) {
if (acb->aiocb_info->get_aio_context) {
aio_poll(acb->aiocb_info->get_aio_context(acb), true);
} else if (acb->bs) {
/* qemu_aio_ref and qemu_aio_unref are not thread-safe, so
* assert that we're not using an I/O thread. Thread-safe
* code should use bdrv_aio_cancel_async exclusively.
*/
assert(bdrv_get_aio_context(acb->bs) == qemu_get_aio_context());
aio_poll(bdrv_get_aio_context(acb->bs), true);
} else {
abort();
}
}
qemu_aio_unref(acb);
}
/* Async version of aio cancel. The caller is not blocked if the acb implements
* cancel_async, otherwise we do nothing and let the request normally complete.
* In either case the completion callback must be called. */
void bdrv_aio_cancel_async(BlockAIOCB *acb)
{
if (acb->aiocb_info->cancel_async) {
acb->aiocb_info->cancel_async(acb);
}
}
/**************************************************************/
/* Coroutine block device emulation */
typedef struct FlushCo {
BlockDriverState *bs;
int ret;
} FlushCo;
static void coroutine_fn bdrv_flush_co_entry(void *opaque)
{
FlushCo *rwco = opaque;
rwco->ret = bdrv_co_flush(rwco->bs);
}
int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
{
int current_gen;
int ret = 0;
bdrv_inc_in_flight(bs);
if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs) ||
bdrv_is_sg(bs)) {
goto early_exit;
}
qemu_co_mutex_lock(&bs->reqs_lock);
current_gen = atomic_read(&bs->write_gen);
/* Wait until any previous flushes are completed */
while (bs->active_flush_req) {
qemu_co_queue_wait(&bs->flush_queue, &bs->reqs_lock);
}
/* Flushes reach this point in nondecreasing current_gen order. */
bs->active_flush_req = true;
qemu_co_mutex_unlock(&bs->reqs_lock);
/* Write back all layers by calling one driver function */
if (bs->drv->bdrv_co_flush) {
ret = bs->drv->bdrv_co_flush(bs);
goto out;
}
/* Write back cached data to the OS even with cache=unsafe */
BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_OS);
if (bs->drv->bdrv_co_flush_to_os) {
ret = bs->drv->bdrv_co_flush_to_os(bs);
if (ret < 0) {
goto out;
}
}
/* But don't actually force it to the disk with cache=unsafe */
if (bs->open_flags & BDRV_O_NO_FLUSH) {
goto flush_parent;
}
/* Check if we really need to flush anything */
if (bs->flushed_gen == current_gen) {
goto flush_parent;
}
BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_DISK);
if (bs->drv->bdrv_co_flush_to_disk) {
ret = bs->drv->bdrv_co_flush_to_disk(bs);
} else if (bs->drv->bdrv_aio_flush) {
BlockAIOCB *acb;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
acb = bs->drv->bdrv_aio_flush(bs, bdrv_co_io_em_complete, &co);
if (acb == NULL) {
ret = -EIO;
} else {
qemu_coroutine_yield();
ret = co.ret;
}
} else {
/*
* Some block drivers always operate in either writethrough or unsafe
* mode and don't support bdrv_flush therefore. Usually qemu doesn't
* know how the server works (because the behaviour is hardcoded or
* depends on server-side configuration), so we can't ensure that
* everything is safe on disk. Returning an error doesn't work because
* that would break guests even if the server operates in writethrough
* mode.
*
* Let's hope the user knows what he's doing.
*/
ret = 0;
}
if (ret < 0) {
goto out;
}
/* Now flush the underlying protocol. It will also have BDRV_O_NO_FLUSH
* in the case of cache=unsafe, so there are no useless flushes.
*/
flush_parent:
ret = bs->file ? bdrv_co_flush(bs->file->bs) : 0;
out:
/* Notify any pending flushes that we have completed */
if (ret == 0) {
bs->flushed_gen = current_gen;
}
qemu_co_mutex_lock(&bs->reqs_lock);
bs->active_flush_req = false;
/* Return value is ignored - it's ok if wait queue is empty */
qemu_co_queue_next(&bs->flush_queue);
qemu_co_mutex_unlock(&bs->reqs_lock);
early_exit:
bdrv_dec_in_flight(bs);
return ret;
}
int bdrv_flush(BlockDriverState *bs)
{
Coroutine *co;
FlushCo flush_co = {
.bs = bs,
.ret = NOT_DONE,
};
if (qemu_in_coroutine()) {
/* Fast-path if already in coroutine context */
bdrv_flush_co_entry(&flush_co);
} else {
co = qemu_coroutine_create(bdrv_flush_co_entry, &flush_co);
bdrv_coroutine_enter(bs, co);
BDRV_POLL_WHILE(bs, flush_co.ret == NOT_DONE);
}
return flush_co.ret;
}
typedef struct DiscardCo {
BlockDriverState *bs;
int64_t offset;
int bytes;
int ret;
} DiscardCo;
static void coroutine_fn bdrv_pdiscard_co_entry(void *opaque)
{
DiscardCo *rwco = opaque;
rwco->ret = bdrv_co_pdiscard(rwco->bs, rwco->offset, rwco->bytes);
}
int coroutine_fn bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset,
int bytes)
{
BdrvTrackedRequest req;
int max_pdiscard, ret;
int head, tail, align;
if (!bs->drv) {
return -ENOMEDIUM;
}
if (bdrv_has_readonly_bitmaps(bs)) {
return -EPERM;
}
ret = bdrv_check_byte_request(bs, offset, bytes);
if (ret < 0) {
return ret;
} else if (bs->read_only) {
return -EPERM;
}
assert(!(bs->open_flags & BDRV_O_INACTIVE));
/* Do nothing if disabled. */
if (!(bs->open_flags & BDRV_O_UNMAP)) {
return 0;
}
if (!bs->drv->bdrv_co_pdiscard && !bs->drv->bdrv_aio_pdiscard) {
return 0;
}
/* Discard is advisory, but some devices track and coalesce
* unaligned requests, so we must pass everything down rather than
* round here. Still, most devices will just silently ignore
* unaligned requests (by returning -ENOTSUP), so we must fragment
* the request accordingly. */
align = MAX(bs->bl.pdiscard_alignment, bs->bl.request_alignment);
assert(align % bs->bl.request_alignment == 0);
head = offset % align;
tail = (offset + bytes) % align;
bdrv_inc_in_flight(bs);
tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_DISCARD);
ret = notifier_with_return_list_notify(&bs->before_write_notifiers, &req);
if (ret < 0) {
goto out;
}
max_pdiscard = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_pdiscard, INT_MAX),
align);
assert(max_pdiscard >= bs->bl.request_alignment);
while (bytes > 0) {
int num = bytes;
if (head) {
/* Make small requests to get to alignment boundaries. */
num = MIN(bytes, align - head);
if (!QEMU_IS_ALIGNED(num, bs->bl.request_alignment)) {
num %= bs->bl.request_alignment;
}
head = (head + num) % align;
assert(num < max_pdiscard);
} else if (tail) {
if (num > align) {
/* Shorten the request to the last aligned cluster. */
num -= tail;
} else if (!QEMU_IS_ALIGNED(tail, bs->bl.request_alignment) &&
tail > bs->bl.request_alignment) {
tail %= bs->bl.request_alignment;
num -= tail;
}
}
/* limit request size */
if (num > max_pdiscard) {
num = max_pdiscard;
}
if (bs->drv->bdrv_co_pdiscard) {
ret = bs->drv->bdrv_co_pdiscard(bs, offset, num);
} else {
BlockAIOCB *acb;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
acb = bs->drv->bdrv_aio_pdiscard(bs, offset, num,
bdrv_co_io_em_complete, &co);
if (acb == NULL) {
ret = -EIO;
goto out;
} else {
qemu_coroutine_yield();
ret = co.ret;
}
}
if (ret && ret != -ENOTSUP) {
goto out;
}
offset += num;
bytes -= num;
}
ret = 0;
out:
atomic_inc(&bs->write_gen);
bdrv_set_dirty(bs, req.offset, req.bytes);
tracked_request_end(&req);
bdrv_dec_in_flight(bs);
return ret;
}
int bdrv_pdiscard(BlockDriverState *bs, int64_t offset, int bytes)
{
Coroutine *co;
DiscardCo rwco = {
.bs = bs,
.offset = offset,
.bytes = bytes,
.ret = NOT_DONE,
};
if (qemu_in_coroutine()) {
/* Fast-path if already in coroutine context */
bdrv_pdiscard_co_entry(&rwco);
} else {
co = qemu_coroutine_create(bdrv_pdiscard_co_entry, &rwco);
bdrv_coroutine_enter(bs, co);
BDRV_POLL_WHILE(bs, rwco.ret == NOT_DONE);
}
return rwco.ret;
}
int bdrv_co_ioctl(BlockDriverState *bs, int req, void *buf)
{
BlockDriver *drv = bs->drv;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
BlockAIOCB *acb;
bdrv_inc_in_flight(bs);
if (!drv || (!drv->bdrv_aio_ioctl && !drv->bdrv_co_ioctl)) {
co.ret = -ENOTSUP;
goto out;
}
if (drv->bdrv_co_ioctl) {
co.ret = drv->bdrv_co_ioctl(bs, req, buf);
} else {
acb = drv->bdrv_aio_ioctl(bs, req, buf, bdrv_co_io_em_complete, &co);
if (!acb) {
co.ret = -ENOTSUP;
goto out;
}
qemu_coroutine_yield();
}
out:
bdrv_dec_in_flight(bs);
return co.ret;
}
void *qemu_blockalign(BlockDriverState *bs, size_t size)
{
return qemu_memalign(bdrv_opt_mem_align(bs), size);
}
void *qemu_blockalign0(BlockDriverState *bs, size_t size)
{
return memset(qemu_blockalign(bs, size), 0, size);
}
void *qemu_try_blockalign(BlockDriverState *bs, size_t size)
{
size_t align = bdrv_opt_mem_align(bs);
/* Ensure that NULL is never returned on success */
assert(align > 0);
if (size == 0) {
size = align;
}
return qemu_try_memalign(align, size);
}
void *qemu_try_blockalign0(BlockDriverState *bs, size_t size)
{
void *mem = qemu_try_blockalign(bs, size);
if (mem) {
memset(mem, 0, size);
}
return mem;
}
/*
* Check if all memory in this vector is sector aligned.
*/
bool bdrv_qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov)
{
int i;
size_t alignment = bdrv_min_mem_align(bs);
for (i = 0; i < qiov->niov; i++) {
if ((uintptr_t) qiov->iov[i].iov_base % alignment) {
return false;
}
if (qiov->iov[i].iov_len % alignment) {
return false;
}
}
return true;
}
void bdrv_add_before_write_notifier(BlockDriverState *bs,
NotifierWithReturn *notifier)
{
notifier_with_return_list_add(&bs->before_write_notifiers, notifier);
}
void bdrv_io_plug(BlockDriverState *bs)
{
BdrvChild *child;
QLIST_FOREACH(child, &bs->children, next) {
bdrv_io_plug(child->bs);
}
if (atomic_fetch_inc(&bs->io_plugged) == 0) {
BlockDriver *drv = bs->drv;
if (drv && drv->bdrv_io_plug) {
drv->bdrv_io_plug(bs);
}
}
}
void bdrv_io_unplug(BlockDriverState *bs)
{
BdrvChild *child;
assert(bs->io_plugged);
if (atomic_fetch_dec(&bs->io_plugged) == 1) {
BlockDriver *drv = bs->drv;
if (drv && drv->bdrv_io_unplug) {
drv->bdrv_io_unplug(bs);
}
}
QLIST_FOREACH(child, &bs->children, next) {
bdrv_io_unplug(child->bs);
}
}
Reference in a new issue View git blame Copy permalink