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Fall back to synchronous io when kernel doesn't support aio.

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Signed-off-by: Brett Holman <bholman.devel@gmail.com>
This commit is contained in:
Brett Holman 2021-10-10 14:13:40 -06:00
parent 2225e9a372
commit ba1dbafc1f
1 changed files with 138 additions and 35 deletions
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173
linux/blkdev.c
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@ -22,6 +22,14 @@
#include "tools-util.h"
struct fops {
void (*init)(void);
void (*cleanup)(void);
void (*read)(struct bio *bio, struct iovec * iov, unsigned i);
void (*write)(struct bio *bio, struct iovec * iov, unsigned i);
};
static struct fops *fops;
static io_context_t aio_ctx;
static atomic_t running_requests;
@ -66,35 +74,12 @@ void generic_make_request(struct bio *bio)
#endif
}
struct iocb iocb = {
.data = bio,
.aio_fildes = bio->bi_opf & REQ_FUA
? bio->bi_bdev->bd_sync_fd
: bio->bi_bdev->bd_fd,
}, *iocbp = &iocb;
switch (bio_op(bio)) {
case REQ_OP_READ:
iocb.aio_lio_opcode = IO_CMD_PREADV;
iocb.u.c.buf = iov;
iocb.u.c.nbytes = i;
iocb.u.c.offset = bio->bi_iter.bi_sector << 9;
atomic_inc(&running_requests);
ret = io_submit(aio_ctx, 1, &iocbp);
if (ret != 1)
die("io_submit err: %s", strerror(-ret));
fops->read(bio, iov, i);
break;
case REQ_OP_WRITE:
iocb.aio_lio_opcode = IO_CMD_PWRITEV;
iocb.u.c.buf = iov;
iocb.u.c.nbytes = i;
iocb.u.c.offset = bio->bi_iter.bi_sector << 9;
atomic_inc(&running_requests);
ret = io_submit(aio_ctx, 1, &iocbp);
if (ret != 1)
die("io_submit err: %s", strerror(-ret));
fops->write(bio, iov, i);
break;
case REQ_OP_FLUSH:
ret = fsync(bio->bi_bdev->bd_fd);
@ -236,6 +221,55 @@ int lookup_bdev(const char *path, dev_t *dev)
return -EINVAL;
}
static void io_fallback(void)
{
fops++;
if (fops->init == NULL)
die("no fallback possible, something is very wrong");
fops->init();
}
static void sync_check(struct bio *bio, int ret)
{
if (ret != bio->bi_iter.bi_size) {
die("IO error: %s\n", strerror(-ret));
}
if (bio->bi_opf & REQ_FUA) {
ret = fdatasync(bio->bi_bdev->bd_fd);
if (ret)
die("fsync error: %s\n", strerror(-ret));
}
bio_endio(bio);
}
static void sync_init(void) {}
static void sync_cleanup(void)
{
/* not necessary? */
sync();
}
static void sync_read(struct bio *bio, struct iovec * iov, unsigned i)
{
int fd = bio->bi_opf & REQ_FUA
? bio->bi_bdev->bd_sync_fd
: bio->bi_bdev->bd_fd;
ssize_t ret = preadv(fd, iov, i, bio->bi_iter.bi_sector << 9);
sync_check(bio, ret);
}
static void sync_write(struct bio *bio, struct iovec * iov, unsigned i)
{
int fd = bio->bi_opf & REQ_FUA
? bio->bi_bdev->bd_sync_fd
: bio->bi_bdev->bd_fd;
ssize_t ret = pwritev(fd, iov, i, bio->bi_iter.bi_sector << 9);
sync_check(bio, ret);
}
static int aio_completion_thread(void *arg)
{
struct io_event events[8], *ev;
@ -274,23 +308,24 @@ static int aio_completion_thread(void *arg)
static struct task_struct *aio_task = NULL;
__attribute__((constructor(102)))
static void blkdev_init(void)
static void aio_init(void)
{
struct task_struct *p;
long err = io_setup(256, &aio_ctx);
if (!err) {
p = kthread_run(aio_completion_thread, NULL, "aio_completion");
BUG_ON(IS_ERR(p));
if (err)
die("io_setup() error: %s", strerror(-err));
aio_task = p;
p = kthread_run(aio_completion_thread, NULL, "aio_completion");
BUG_ON(IS_ERR(p));
aio_task = p;
} else if (err == -ENOSYS) {
io_fallback();
} else {
die("io_setup() error: %s", strerror(err));
}
}
__attribute__((destructor(102)))
static void blkdev_cleanup(void)
static void aio_cleanup(void)
{
struct task_struct *p = NULL;
swap(aio_task, p);
@ -323,3 +358,71 @@ static void blkdev_cleanup(void)
close(fds[0]);
close(fds[1]);
}
static void aio_op(struct bio *bio, struct iovec *iov, unsigned i, int opcode)
{
ssize_t ret;
struct iocb iocb = {
.data = bio,
.aio_fildes = bio->bi_opf & REQ_FUA
? bio->bi_bdev->bd_sync_fd
: bio->bi_bdev->bd_fd,
.aio_lio_opcode = opcode,
.u.v.vec = iov,
.u.v.nr = i,
.u.v.offset = bio->bi_iter.bi_sector << 9,
}, *iocbp = &iocb;
atomic_inc(&running_requests);
ret = io_submit(aio_ctx, 1, &iocbp);
if (ret != 1)
die("io_submit err: %s", strerror(-ret));
}
static void aio_read(struct bio *bio, struct iovec *iov, unsigned i)
{
aio_op(bio, iov, i, IO_CMD_PREADV);
}
static void aio_write(struct bio *bio, struct iovec * iov, unsigned i)
{
aio_op(bio, iov, i, IO_CMD_PWRITEV);
}
/* not implemented */
static void uring_init(void) {
io_fallback();
}
struct fops fops_list[] = {
{
.init = uring_init,
}, {
.init = aio_init,
.cleanup = aio_cleanup,
.read = aio_read,
.write = aio_write,
}, {
.init = sync_init,
.cleanup = sync_cleanup,
.read = sync_read,
.write = sync_write,
}, {
/* NULL */
}
};
__attribute__((constructor(102)))
static void blkdev_init(void)
{
fops = fops_list;
fops->init();
}
__attribute__((destructor(102)))
static void blkdev_cleanup(void)
{
fops->cleanup();
}