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um: ubd: Add REQ_FLUSH suppport

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UML's block device driver does not support write barriers,
to support this this patch adds REQ_FLUSH suppport.
Every time the block layer sends a REQ_FLUSH we fsync() now
our backing file to guarantee data consistency.

Reported-and-tested-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Richard Weinberger 2013-08-18 13:30:06 +02:00
parent f75b1b1bed
commit 805f11a0d5
3 changed files with 50 additions and 1 deletions
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41
arch/um/drivers/ubd_kern.c
View file

@ -41,7 +41,7 @@
#include <os.h>
#include "cow.h"
enum ubd_req { UBD_READ, UBD_WRITE };
enum ubd_req { UBD_READ, UBD_WRITE, UBD_FLUSH };
struct io_thread_req {
struct request *req;
@ -866,6 +866,7 @@ static int ubd_add(int n, char **error_out)
goto out;
}
ubd_dev->queue->queuedata = ubd_dev;
blk_queue_flush(ubd_dev->queue, REQ_FLUSH);
blk_queue_max_segments(ubd_dev->queue, MAX_SG);
err = ubd_disk_register(UBD_MAJOR, ubd_dev->size, n, &ubd_gendisk[n]);
@ -1238,6 +1239,19 @@ static void prepare_request(struct request *req, struct io_thread_req *io_req,
}
/* Called with dev->lock held */
static void prepare_flush_request(struct request *req,
struct io_thread_req *io_req)
{
struct gendisk *disk = req->rq_disk;
struct ubd *ubd_dev = disk->private_data;
io_req->req = req;
io_req->fds[0] = (ubd_dev->cow.file != NULL) ? ubd_dev->cow.fd :
ubd_dev->fd;
io_req->op = UBD_FLUSH;
}
/* Called with dev->lock held */
static void do_ubd_request(struct request_queue *q)
{
@ -1259,6 +1273,20 @@ static void do_ubd_request(struct request_queue *q)
}
req = dev->request;
if (req->cmd_flags & REQ_FLUSH) {
io_req = kmalloc(sizeof(struct io_thread_req),
GFP_ATOMIC);
if (io_req == NULL) {
if (list_empty(&dev->restart))
list_add(&dev->restart, &restart);
return;
}
prepare_flush_request(req, io_req);
os_write_file(thread_fd, &io_req,
sizeof(struct io_thread_req *));
}
while(dev->start_sg < dev->end_sg){
struct scatterlist *sg = &dev->sg[dev->start_sg];
@ -1367,6 +1395,17 @@ static void do_io(struct io_thread_req *req)
int err;
__u64 off;
if (req->op == UBD_FLUSH) {
/* fds[0] is always either the rw image or our cow file */
n = os_sync_file(req->fds[0]);
if (n != 0) {
printk("do_io - sync failed err = %d "
"fd = %d\n", -n, req->fds[0]);
req->error = 1;
}
return;
}
nsectors = req->length / req->sectorsize;
start = 0;
do {

1
arch/um/include/shared/os.h
View file

@ -141,6 +141,7 @@ extern int os_seek_file(int fd, unsigned long long offset);
extern int os_open_file(const char *file, struct openflags flags, int mode);
extern int os_read_file(int fd, void *buf, int len);
extern int os_write_file(int fd, const void *buf, int count);
extern int os_sync_file(int fd);
extern int os_file_size(const char *file, unsigned long long *size_out);
extern int os_file_modtime(const char *file, unsigned long *modtime);
extern int os_pipe(int *fd, int stream, int close_on_exec);

9
arch/um/os-Linux/file.c
View file

@ -266,6 +266,15 @@ int os_write_file(int fd, const void *buf, int len)
return n;
}
int os_sync_file(int fd)
{
int n = fsync(fd);
if (n < 0)
return -errno;
return n;
}
int os_file_size(const char *file, unsigned long long *size_out)
{
struct uml_stat buf;