/*
* preallocate filter driver
*
* The driver performs preallocate operation: it is injected above
* some node, and before each write over EOF it does additional preallocating
* write-zeroes request.
*
* Copyright (c) 2020 Virtuozzo International GmbH.
*
* Author:
* Sementsov-Ogievskiy Vladimir <vsementsov@virtuozzo.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu/module.h"
#include "qemu/option.h"
#include "qemu/units.h"
#include "block/block_int.h"
typedef struct PreallocateOpts {
int64_t prealloc_size;
int64_t prealloc_align;
} PreallocateOpts;
typedef struct BDRVPreallocateState {
PreallocateOpts opts;
/*
* Track real data end, to crop preallocation on close. If < 0 the status is
* unknown.
*
* @data_end is a maximum of file size on open (or when we get write/resize
* permissions) and all write request ends after it. So it's safe to
* truncate to data_end if it is valid.
*/
int64_t data_end;
/*
* Start of trailing preallocated area which reads as zero. May be smaller
* than data_end, if user does over-EOF write zero operation. If < 0 the
* status is unknown.
*
* If both @zero_start and @file_end are valid, the region
* [@zero_start, @file_end) is known to be preallocated zeroes. If @file_end
* is not valid, @zero_start doesn't make much sense.
*/
int64_t zero_start;
/*
* Real end of file. Actually the cache for bdrv_getlength(bs->file->bs),
* to avoid extra lseek() calls on each write operation. If < 0 the status
* is unknown.
*/
int64_t file_end;
/*
* All three states @data_end, @zero_start and @file_end are guaranteed to
* be invalid (< 0) when we don't have both exclusive BLK_PERM_RESIZE and
* BLK_PERM_WRITE permissions on file child.
*/
} BDRVPreallocateState;
#define PREALLOCATE_OPT_PREALLOC_ALIGN "prealloc-align"
#define PREALLOCATE_OPT_PREALLOC_SIZE "prealloc-size"
static QemuOptsList runtime_opts = {
.name = "preallocate",
.head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
.desc = {
{
.name = PREALLOCATE_OPT_PREALLOC_ALIGN,
.type = QEMU_OPT_SIZE,
.help = "on preallocation, align file length to this number, "
"default 1M",
},
{
.name = PREALLOCATE_OPT_PREALLOC_SIZE,
.type = QEMU_OPT_SIZE,
.help = "how much to preallocate, default 128M",
},
{ /* end of list */ }
},
};
static bool preallocate_absorb_opts(PreallocateOpts *dest, QDict *options,
BlockDriverState *child_bs, Error **errp)
{
QemuOpts *opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
if (!qemu_opts_absorb_qdict(opts, options, errp)) {
return false;
}
dest->prealloc_align =
qemu_opt_get_size(opts, PREALLOCATE_OPT_PREALLOC_ALIGN, 1 * MiB);
dest->prealloc_size =
qemu_opt_get_size(opts, PREALLOCATE_OPT_PREALLOC_SIZE, 128 * MiB);
qemu_opts_del(opts);
if (!QEMU_IS_ALIGNED(dest->prealloc_align, BDRV_SECTOR_SIZE)) {
error_setg(errp, "prealloc-align parameter of preallocate filter "
"is not aligned to %llu", BDRV_SECTOR_SIZE);
return false;
}
if (!QEMU_IS_ALIGNED(dest->prealloc_align,
child_bs->bl.request_alignment)) {
error_setg(errp, "prealloc-align parameter of preallocate filter "
"is not aligned to underlying node request alignment "
"(%" PRIi32 ")", child_bs->bl.request_alignment);
return false;
}
return true;
}
static int preallocate_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp)
{
BDRVPreallocateState *s = bs->opaque;
/*
* s->data_end and friends should be initialized on permission update.
* For this to work, mark them invalid.
*/
s->file_end = s->zero_start = s->data_end = -EINVAL;
bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
false, errp);
if (!bs->file) {
return -EINVAL;
}
if (!preallocate_absorb_opts(&s->opts, options, bs->file->bs, errp)) {
return -EINVAL;
}
bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
(BDRV_REQ_FUA & bs->file->bs->supported_write_flags);
bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
bs->file->bs->supported_zero_flags);
return 0;
}
static void preallocate_close(BlockDriverState *bs)
{
int ret;
BDRVPreallocateState *s = bs->opaque;
if (s->data_end < 0) {
return;
}
if (s->file_end < 0) {
s->file_end = bdrv_getlength(bs->file->bs);
if (s->file_end < 0) {
return;
}
}
if (s->data_end < s->file_end) {
ret = bdrv_truncate(bs->file, s->data_end, true, PREALLOC_MODE_OFF, 0,
NULL);
s->file_end = ret < 0 ? ret : s->data_end;
}
}
/*
* Handle reopen.
*
* We must implement reopen handlers, otherwise reopen just don't work. Handle
* new options and don't care about preallocation state, as it is handled in
* set/check permission handlers.
*/
static int preallocate_reopen_prepare(BDRVReopenState *reopen_state,
BlockReopenQueue *queue, Error **errp)
{
PreallocateOpts *opts = g_new0(PreallocateOpts, 1);
if (!preallocate_absorb_opts(opts, reopen_state->options,
reopen_state->bs->file->bs, errp)) {
g_free(opts);
return -EINVAL;
}
reopen_state->opaque = opts;
return 0;
}
static void preallocate_reopen_commit(BDRVReopenState *state)
{
BDRVPreallocateState *s = state->bs->opaque;
s->opts = *(PreallocateOpts *)state->opaque;
g_free(state->opaque);
state->opaque = NULL;
}
static void preallocate_reopen_abort(BDRVReopenState *state)
{
g_free(state->opaque);
state->opaque = NULL;
}
static coroutine_fn int preallocate_co_preadv_part(
BlockDriverState *bs, uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, size_t qiov_offset, int flags)
{
return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset,
flags);
}
static int coroutine_fn preallocate_co_pdiscard(BlockDriverState *bs,
int64_t offset, int bytes)
{
return bdrv_co_pdiscard(bs->file, offset, bytes);
}
static bool can_write_resize(uint64_t perm)
{
return (perm & BLK_PERM_WRITE) && (perm & BLK_PERM_RESIZE);
}
static bool has_prealloc_perms(BlockDriverState *bs)
{
BDRVPreallocateState *s = bs->opaque;
if (can_write_resize(bs->file->perm)) {
assert(!(bs->file->shared_perm & BLK_PERM_WRITE));
assert(!(bs->file->shared_perm & BLK_PERM_RESIZE));
return true;
}
assert(s->data_end < 0);
assert(s->zero_start < 0);
assert(s->file_end < 0);
return false;
}
/*
* Call on each write. Returns true if @want_merge_zero is true and the region
* [offset, offset + bytes) is zeroed (as a result of this call or earlier
* preallocation).
*
* want_merge_zero is used to merge write-zero request with preallocation in
* one bdrv_co_pwrite_zeroes() call.
*/
static bool coroutine_fn handle_write(BlockDriverState *bs, int64_t offset,
int64_t bytes, bool want_merge_zero)
{
BDRVPreallocateState *s = bs->opaque;
int64_t end = offset + bytes;
int64_t prealloc_start, prealloc_end;
int ret;
if (!has_prealloc_perms(bs)) {
/* We don't have state neither should try to recover it */
return false;
}
if (s->data_end < 0) {
s->data_end = bdrv_getlength(bs->file->bs);
if (s->data_end < 0) {
return false;
}
if (s->file_end < 0) {
s->file_end = s->data_end;
}
}
if (end <= s->data_end) {
return false;
}
/* We have valid s->data_end, and request writes beyond it. */
s->data_end = end;
if (s->zero_start < 0 || !want_merge_zero) {
s->zero_start = end;
}
if (s->file_end < 0) {
s->file_end = bdrv_getlength(bs->file->bs);
if (s->file_end < 0) {
return false;
}
}
/* Now s->data_end, s->zero_start and s->file_end are valid. */
if (end <= s->file_end) {
/* No preallocation needed. */
return want_merge_zero && offset >= s->zero_start;
}
/* Now we want new preallocation, as request writes beyond s->file_end. */
prealloc_start = want_merge_zero ? MIN(offset, s->file_end) : s->file_end;
prealloc_end = QEMU_ALIGN_UP(end + s->opts.prealloc_size,
s->opts.prealloc_align);
ret = bdrv_co_pwrite_zeroes(
bs->file, prealloc_start, prealloc_end - prealloc_start,
BDRV_REQ_NO_FALLBACK | BDRV_REQ_SERIALISING | BDRV_REQ_NO_WAIT);
if (ret < 0) {
s->file_end = ret;
return false;
}
s->file_end = prealloc_end;
return want_merge_zero;
}
static int coroutine_fn preallocate_co_pwrite_zeroes(BlockDriverState *bs,
int64_t offset, int bytes, BdrvRequestFlags flags)
{
bool want_merge_zero =
!(flags & ~(BDRV_REQ_ZERO_WRITE | BDRV_REQ_NO_FALLBACK));
if (handle_write(bs, offset, bytes, want_merge_zero)) {
return 0;
}
return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
}
static coroutine_fn int preallocate_co_pwritev_part(BlockDriverState *bs,
uint64_t offset,
uint64_t bytes,
QEMUIOVector *qiov,
size_t qiov_offset,
int flags)
{
handle_write(bs, offset, bytes, false);
return bdrv_co_pwritev_part(bs->file, offset, bytes, qiov, qiov_offset,
flags);
}
static int coroutine_fn
preallocate_co_truncate(BlockDriverState *bs, int64_t offset,
bool exact, PreallocMode prealloc,
BdrvRequestFlags flags, Error **errp)
{
ERRP_GUARD();
BDRVPreallocateState *s = bs->opaque;
int ret;
if (s->data_end >= 0 && offset > s->data_end) {
if (s->file_end < 0) {
s->file_end = bdrv_getlength(bs->file->bs);
if (s->file_end < 0) {
error_setg(errp, "failed to get file length");
return s->file_end;
}
}
if (prealloc == PREALLOC_MODE_FALLOC) {
/*
* If offset <= s->file_end, the task is already done, just
* update s->data_end, to move part of "filter preallocation"
* to "preallocation requested by user".
* Otherwise just proceed to preallocate missing part.
*/
if (offset <= s->file_end) {
s->data_end = offset;
return 0;
}
} else {
/*
* We have to drop our preallocation, to
* - avoid "Cannot use preallocation for shrinking files" in
* case of offset < file_end
* - give PREALLOC_MODE_OFF a chance to keep small disk
* usage
* - give PREALLOC_MODE_FULL a chance to actually write the
* whole region as user expects
*/
if (s->file_end > s->data_end) {
ret = bdrv_co_truncate(bs->file, s->data_end, true,
PREALLOC_MODE_OFF, 0, errp);
if (ret < 0) {
s->file_end = ret;
error_prepend(errp, "preallocate-filter: failed to drop "
"write-zero preallocation: ");
return ret;
}
s->file_end = s->data_end;
}
}
s->data_end = offset;
}
ret = bdrv_co_truncate(bs->file, offset, exact, prealloc, flags, errp);
if (ret < 0) {
s->file_end = s->zero_start = s->data_end = ret;
return ret;
}
if (has_prealloc_perms(bs)) {
s->file_end = s->zero_start = s->data_end = offset;
}
return 0;
}
static int coroutine_fn preallocate_co_flush(BlockDriverState *bs)
{
return bdrv_co_flush(bs->file->bs);
}
static int64_t preallocate_getlength(BlockDriverState *bs)
{
int64_t ret;
BDRVPreallocateState *s = bs->opaque;
if (s->data_end >= 0) {
return s->data_end;
}
ret = bdrv_getlength(bs->file->bs);
if (has_prealloc_perms(bs)) {
s->file_end = s->zero_start = s->data_end = ret;
}
return ret;
}
static int preallocate_check_perm(BlockDriverState *bs,
uint64_t perm, uint64_t shared, Error **errp)
{
BDRVPreallocateState *s = bs->opaque;
if (s->data_end >= 0 && !can_write_resize(perm)) {
/*
* Lose permissions.
* We should truncate in check_perm, as in set_perm bs->file->perm will
* be already changed, and we should not violate it.
*/
if (s->file_end < 0) {
s->file_end = bdrv_getlength(bs->file->bs);
if (s->file_end < 0) {
error_setg(errp, "Failed to get file length");
return s->file_end;
}
}
if (s->data_end < s->file_end) {
int ret = bdrv_truncate(bs->file, s->data_end, true,
PREALLOC_MODE_OFF, 0, NULL);
if (ret < 0) {
error_setg(errp, "Failed to drop preallocation");
s->file_end = ret;
return ret;
}
s->file_end = s->data_end;
}
}
return 0;
}
static void preallocate_set_perm(BlockDriverState *bs,
uint64_t perm, uint64_t shared)
{
BDRVPreallocateState *s = bs->opaque;
if (can_write_resize(perm)) {
if (s->data_end < 0) {
s->data_end = s->file_end = s->zero_start =
bdrv_getlength(bs->file->bs);
}
} else {
/*
* We drop our permissions, as well as allow shared
* permissions (see preallocate_child_perm), anyone will be able to
* change the child, so mark all states invalid. We'll regain control if
* get good permissions back.
*/
s->data_end = s->file_end = s->zero_start = -EINVAL;
}
}
static void preallocate_child_perm(BlockDriverState *bs, BdrvChild *c,
BdrvChildRole role, BlockReopenQueue *reopen_queue,
uint64_t perm, uint64_t shared, uint64_t *nperm, uint64_t *nshared)
{
bdrv_default_perms(bs, c, role, reopen_queue, perm, shared, nperm, nshared);
if (can_write_resize(perm)) {
/* This should come by default, but let's enforce: */
*nperm |= BLK_PERM_WRITE | BLK_PERM_RESIZE;
/*
* Don't share, to keep our states s->file_end, s->data_end and
* s->zero_start valid.
*/
*nshared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
}
}
BlockDriver bdrv_preallocate_filter = {
.format_name = "preallocate",
.instance_size = sizeof(BDRVPreallocateState),
.bdrv_getlength = preallocate_getlength,
.bdrv_open = preallocate_open,
.bdrv_close = preallocate_close,
.bdrv_reopen_prepare = preallocate_reopen_prepare,
.bdrv_reopen_commit = preallocate_reopen_commit,
.bdrv_reopen_abort = preallocate_reopen_abort,
.bdrv_co_preadv_part = preallocate_co_preadv_part,
.bdrv_co_pwritev_part = preallocate_co_pwritev_part,
.bdrv_co_pwrite_zeroes = preallocate_co_pwrite_zeroes,
.bdrv_co_pdiscard = preallocate_co_pdiscard,
.bdrv_co_flush = preallocate_co_flush,
.bdrv_co_truncate = preallocate_co_truncate,
.bdrv_check_perm = preallocate_check_perm,
.bdrv_set_perm = preallocate_set_perm,
.bdrv_child_perm = preallocate_child_perm,
.has_variable_length = true,
.is_filter = true,
};
static void bdrv_preallocate_init(void)
{
bdrv_register(&bdrv_preallocate_filter);
}
block_init(bdrv_preallocate_init);
