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Commit 805f11a0 authored by Richard Weinberger's avatar Richard Weinberger
Browse files

um: ubd: Add REQ_FLUSH suppport 



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: default avatarRichard W.M. Jones <rjones@redhat.com>
Signed-off-by: default avatarRichard Weinberger <richard@nod.at>
parent f75b1b1b

arch/um/drivers/ubd_kern.c

+40 −1
Original line number Diff line number Diff line
@@ -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 {

arch/um/include/shared/os.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

arch/um/os-Linux/file.c

+9 −0
Original line number Diff line number Diff line
@@ -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;