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file-posix: Make .bdrv_co_truncate asynchronous 

This moves the code to resize an image file to the thread pool to avoid
blocking.

Creating large images with preallocation with blockdev-create is now
actually a background job instead of blocking the monitor (and most
other things) until the preallocation has completed.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2018-06-21 18:23:16 +02:00
parent 1bc5f09f2e
commit 93f4e2ff4b
2 changed files with 154 additions and 116 deletions
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266
block/file-posix.c
View File

@ -188,8 +188,16 @@ typedef struct RawPosixAIOData {
#define aio_ioctl_cmd aio_nbytes /* for QEMU_AIO_IOCTL */
off_t aio_offset;
int aio_type;
int aio_fd2;
off_t aio_offset2;
union {
struct {
int aio_fd2;
off_t aio_offset2;
};
struct {
PreallocMode prealloc;
Error **errp;
};
};
} RawPosixAIOData;
#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
@ -1539,6 +1547,122 @@ static ssize_t handle_aiocb_discard(RawPosixAIOData *aiocb)
return ret;
}
static int handle_aiocb_truncate(RawPosixAIOData *aiocb)
{
int result = 0;
int64_t current_length = 0;
char *buf = NULL;
struct stat st;
int fd = aiocb->aio_fildes;
int64_t offset = aiocb->aio_offset;
Error **errp = aiocb->errp;
if (fstat(fd, &st) < 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not stat file");
return result;
}
current_length = st.st_size;
if (current_length > offset && aiocb->prealloc != PREALLOC_MODE_OFF) {
error_setg(errp, "Cannot use preallocation for shrinking files");
return -ENOTSUP;
}
switch (aiocb->prealloc) {
#ifdef CONFIG_POSIX_FALLOCATE
case PREALLOC_MODE_FALLOC:
/*
* Truncating before posix_fallocate() makes it about twice slower on
* file systems that do not support fallocate(), trying to check if a
* block is allocated before allocating it, so don't do that here.
*/
if (offset != current_length) {
result = -posix_fallocate(fd, current_length,
offset - current_length);
if (result != 0) {
/* posix_fallocate() doesn't set errno. */
error_setg_errno(errp, -result,
"Could not preallocate new data");
}
} else {
result = 0;
}
goto out;
#endif
case PREALLOC_MODE_FULL:
{
int64_t num = 0, left = offset - current_length;
off_t seek_result;
/*
* Knowing the final size from the beginning could allow the file
* system driver to do less allocations and possibly avoid
* fragmentation of the file.
*/
if (ftruncate(fd, offset) != 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not resize file");
goto out;
}
buf = g_malloc0(65536);
seek_result = lseek(fd, current_length, SEEK_SET);
if (seek_result < 0) {
result = -errno;
error_setg_errno(errp, -result,
"Failed to seek to the old end of file");
goto out;
}
while (left > 0) {
num = MIN(left, 65536);
result = write(fd, buf, num);
if (result < 0) {
result = -errno;
error_setg_errno(errp, -result,
"Could not write zeros for preallocation");
goto out;
}
left -= result;
}
if (result >= 0) {
result = fsync(fd);
if (result < 0) {
result = -errno;
error_setg_errno(errp, -result,
"Could not flush file to disk");
goto out;
}
}
goto out;
}
case PREALLOC_MODE_OFF:
if (ftruncate(fd, offset) != 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not resize file");
}
return result;
default:
result = -ENOTSUP;
error_setg(errp, "Unsupported preallocation mode: %s",
PreallocMode_str(aiocb->prealloc));
return result;
}
out:
if (result < 0) {
if (ftruncate(fd, current_length) < 0) {
error_report("Failed to restore old file length: %s",
strerror(errno));
}
}
g_free(buf);
return result;
}
static int aio_worker(void *arg)
{
RawPosixAIOData *aiocb = arg;
@ -1582,6 +1706,9 @@ static int aio_worker(void *arg)
case QEMU_AIO_COPY_RANGE:
ret = handle_aiocb_copy_range(aiocb);
break;
case QEMU_AIO_TRUNCATE:
ret = handle_aiocb_truncate(aiocb);
break;
default:
fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
ret = -EINVAL;
@ -1765,117 +1892,25 @@ static void raw_close(BlockDriverState *bs)
*
* Returns: 0 on success, -errno on failure.
*/
static int raw_regular_truncate(int fd, int64_t offset, PreallocMode prealloc,
Error **errp)
static int coroutine_fn
raw_regular_truncate(BlockDriverState *bs, int fd, int64_t offset,
PreallocMode prealloc, Error **errp)
{
int result = 0;
int64_t current_length = 0;
char *buf = NULL;
struct stat st;
RawPosixAIOData *acb = g_new(RawPosixAIOData, 1);
ThreadPool *pool;
if (fstat(fd, &st) < 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not stat file");
return result;
}
*acb = (RawPosixAIOData) {
.bs = bs,
.aio_fildes = fd,
.aio_type = QEMU_AIO_TRUNCATE,
.aio_offset = offset,
.prealloc = prealloc,
.errp = errp,
};
current_length = st.st_size;
if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
error_setg(errp, "Cannot use preallocation for shrinking files");
return -ENOTSUP;
}
switch (prealloc) {
#ifdef CONFIG_POSIX_FALLOCATE
case PREALLOC_MODE_FALLOC:
/*
* Truncating before posix_fallocate() makes it about twice slower on
* file systems that do not support fallocate(), trying to check if a
* block is allocated before allocating it, so don't do that here.
*/
if (offset != current_length) {
result = -posix_fallocate(fd, current_length, offset - current_length);
if (result != 0) {
/* posix_fallocate() doesn't set errno. */
error_setg_errno(errp, -result,
"Could not preallocate new data");
}
} else {
result = 0;
}
goto out;
#endif
case PREALLOC_MODE_FULL:
{
int64_t num = 0, left = offset - current_length;
off_t seek_result;
/*
* Knowing the final size from the beginning could allow the file
* system driver to do less allocations and possibly avoid
* fragmentation of the file.
*/
if (ftruncate(fd, offset) != 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not resize file");
goto out;
}
buf = g_malloc0(65536);
seek_result = lseek(fd, current_length, SEEK_SET);
if (seek_result < 0) {
result = -errno;
error_setg_errno(errp, -result,
"Failed to seek to the old end of file");
goto out;
}
while (left > 0) {
num = MIN(left, 65536);
result = write(fd, buf, num);
if (result < 0) {
result = -errno;
error_setg_errno(errp, -result,
"Could not write zeros for preallocation");
goto out;
}
left -= result;
}
if (result >= 0) {
result = fsync(fd);
if (result < 0) {
result = -errno;
error_setg_errno(errp, -result,
"Could not flush file to disk");
goto out;
}
}
goto out;
}
case PREALLOC_MODE_OFF:
if (ftruncate(fd, offset) != 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not resize file");
}
return result;
default:
result = -ENOTSUP;
error_setg(errp, "Unsupported preallocation mode: %s",
PreallocMode_str(prealloc));
return result;
}
out:
if (result < 0) {
if (ftruncate(fd, current_length) < 0) {
error_report("Failed to restore old file length: %s",
strerror(errno));
}
}
g_free(buf);
return result;
/* @bs can be NULL, bdrv_get_aio_context() returns the main context then */
pool = aio_get_thread_pool(bdrv_get_aio_context(bs));
return thread_pool_submit_co(pool, aio_worker, acb);
}
static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
@ -1892,7 +1927,7 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
}
if (S_ISREG(st.st_mode)) {
return raw_regular_truncate(s->fd, offset, prealloc, errp);
return raw_regular_truncate(bs, s->fd, offset, prealloc, errp);
}
if (prealloc != PREALLOC_MODE_OFF) {
@ -2094,7 +2129,8 @@ static int64_t raw_get_allocated_file_size(BlockDriverState *bs)
return (int64_t)st.st_blocks * 512;
}
static int raw_co_create(BlockdevCreateOptions *options, Error **errp)
static int coroutine_fn
raw_co_create(BlockdevCreateOptions *options, Error **errp)
{
BlockdevCreateOptionsFile *file_opts;
int fd;
@ -2146,7 +2182,7 @@ static int raw_co_create(BlockdevCreateOptions *options, Error **errp)
}
/* Clear the file by truncating it to 0 */
result = raw_regular_truncate(fd, 0, PREALLOC_MODE_OFF, errp);
result = raw_regular_truncate(NULL, fd, 0, PREALLOC_MODE_OFF, errp);
if (result < 0) {
goto out_close;
}
@ -2168,8 +2204,8 @@ static int raw_co_create(BlockdevCreateOptions *options, Error **errp)
/* Resize and potentially preallocate the file to the desired
* final size */
result = raw_regular_truncate(fd, file_opts->size, file_opts->preallocation,
errp);
result = raw_regular_truncate(NULL, fd, file_opts->size,
file_opts->preallocation, errp);
if (result < 0) {
goto out_close;
}

4
include/block/raw-aio.h
View File

@ -26,6 +26,7 @@
#define QEMU_AIO_DISCARD 0x0010
#define QEMU_AIO_WRITE_ZEROES 0x0020
#define QEMU_AIO_COPY_RANGE 0x0040
#define QEMU_AIO_TRUNCATE 0x0080
#define QEMU_AIO_TYPE_MASK \
(QEMU_AIO_READ | \
QEMU_AIO_WRITE | \
@ -33,7 +34,8 @@
QEMU_AIO_FLUSH | \
QEMU_AIO_DISCARD | \
QEMU_AIO_WRITE_ZEROES | \
QEMU_AIO_COPY_RANGE)
QEMU_AIO_COPY_RANGE | \
QEMU_AIO_TRUNCATE)
/* AIO flags */
#define QEMU_AIO_MISALIGNED 0x1000